chiark / gitweb /
site: transport peers: Break out transport_resolve_complete,_tardy
[secnet.git] / site.c
diff --git a/site.c b/site.c
index 1a664ce..afa85e8 100644 (file)
--- a/site.c
+++ b/site.c
@@ -1,17 +1,46 @@
 /* site.c - manage communication with a remote network site */
 
-#include <stdio.h>
-#include <sys/mman.h>
+/* The 'site' code doesn't know anything about the structure of the
+   packets it's transmitting.  In fact, under the new netlink
+   configuration scheme it doesn't need to know anything at all about
+   IP addresses, except how to contact its peer.  This means it could
+   potentially be used to tunnel other protocols too (IPv6, IPX, plain
+   old Ethernet frames) if appropriate netlink code can be written
+   (and that ought not to be too hard, eg. using the TUN/TAP device to
+   pretend to be an Ethernet interface).  */
+
+/* At some point in the future the netlink code will be asked for
+   configuration information to go in the PING/PONG packets at the end
+   of the key exchange. */
 
 #include "secnet.h"
+#include <stdio.h>
+#include <string.h>
+#include <limits.h>
+#include <assert.h>
+#include <sys/socket.h>
+
+#include <sys/mman.h>
 #include "util.h"
+#include "unaligned.h"
+#include "magic.h"
 
 #define SETUP_BUFFER_LEN 2048
 
-#define DEFAULT_KEY_LIFETIME 15000
+#define DEFAULT_KEY_LIFETIME                  (3600*1000) /* [ms] */
+#define DEFAULT_KEY_RENEGOTIATE_GAP           (5*60*1000) /* [ms] */
 #define DEFAULT_SETUP_RETRIES 5
-#define DEFAULT_SETUP_TIMEOUT 500
-#define DEFAULT_WAIT_TIME 10000
+#define DEFAULT_SETUP_RETRY_INTERVAL             (2*1000) /* [ms] */
+#define DEFAULT_WAIT_TIME                       (20*1000) /* [ms] */
+
+#define DEFAULT_MOBILE_KEY_LIFETIME      (2*24*3600*1000) /* [ms] */
+#define DEFAULT_MOBILE_KEY_RENEGOTIATE_GAP (12*3600*1000) /* [ms] */
+#define DEFAULT_MOBILE_SETUP_RETRIES 30
+#define DEFAULT_MOBILE_SETUP_RETRY_INTERVAL      (1*1000) /* [ms] */
+#define DEFAULT_MOBILE_WAIT_TIME                (10*1000) /* [ms] */
+
+#define DEFAULT_MOBILE_PEER_EXPIRY            (2*60)      /* [s] */
+#define DEFAULT_MOBILE_PEERS_MAX 3 /* send at most this many copies (default) */
 
 /* Each site can be in one of several possible states. */
 
 #define SITE_SENTMSG5 7
 #define SITE_WAIT     8
 
-static string_t state_name(uint32_t state)
+int32_t site_max_start_pad = 4*4;
+
+static cstring_t state_name(uint32_t state)
 {
     switch (state) {
-    case 0: return "SITE_STOP";
-    case 1: return "SITE_RUN";
-    case 2: return "SITE_RESOLVE";
-    case 3: return "SITE_SENTMSG1";
-    case 4: return "SITE_SENTMSG2";
-    case 5: return "SITE_SENTMSG3";
-    case 6: return "SITE_SENTMSG4";
-    case 7: return "SITE_SENTMSG5";
-    case 8: return "SITE_WAIT";
+    case 0: return "STOP";
+    case 1: return "RUN";
+    case 2: return "RESOLVE";
+    case 3: return "SENTMSG1";
+    case 4: return "SENTMSG2";
+    case 5: return "SENTMSG3";
+    case 6: return "SENTMSG4";
+    case 7: return "SENTMSG5";
+    case 8: return "WAIT";
     default: return "*bad state*";
     }
 }
 
-#define LABEL_MSG0 0x00020200
-#define LABEL_MSG1 0x01010101
-#define LABEL_MSG2 0x02020202
-#define LABEL_MSG3 0x03030303
-#define LABEL_MSG4 0x04040404
-#define LABEL_MSG5 0x05050505
-#define LABEL_MSG6 0x06060606
-#define LABEL_MSG7 0x07070707
-#define LABEL_MSG8 0x08080808
-#define LABEL_MSG9 0x09090909
-
 #define NONCELEN 8
 
 #define LOG_UNEXPECTED    0x00000001
@@ -94,11 +114,118 @@ static string_t state_name(uint32_t state)
 #define LOG_SETUP_TIMEOUT 0x00000004
 #define LOG_ACTIVATE_KEY  0x00000008
 #define LOG_TIMEOUT_KEY   0x00000010
-#define LOG_SECURITY      0x00000020
+#define LOG_SEC           0x00000020
 #define LOG_STATE         0x00000040
 #define LOG_DROP          0x00000080
 #define LOG_DUMP          0x00000100
 #define LOG_ERROR         0x00000400
+#define LOG_PEER_ADDRS    0x00000800
+
+static struct flagstr log_event_table[]={
+    { "unexpected", LOG_UNEXPECTED },
+    { "setup-init", LOG_SETUP_INIT },
+    { "setup-timeout", LOG_SETUP_TIMEOUT },
+    { "activate-key", LOG_ACTIVATE_KEY },
+    { "timeout-key", LOG_TIMEOUT_KEY },
+    { "security", LOG_SEC },
+    { "state-change", LOG_STATE },
+    { "packet-drop", LOG_DROP },
+    { "dump-packets", LOG_DUMP },
+    { "errors", LOG_ERROR },
+    { "peer-addrs", LOG_PEER_ADDRS },
+    { "default", LOG_SETUP_INIT|LOG_SETUP_TIMEOUT|
+      LOG_ACTIVATE_KEY|LOG_TIMEOUT_KEY|LOG_SEC|LOG_ERROR },
+    { "all", 0xffffffff },
+    { NULL, 0 }
+};
+
+
+/***** TRANSPORT PEERS declarations *****/
+
+/* Details of "mobile peer" semantics:
+   
+   - We record mobile_peers_max peer address/port numbers ("peers")
+     for key setup, and separately mobile_peers_max for data
+     transfer.  If these lists fill up, we retain the newest peers.
+     (For non-mobile peers we only record one of each.)
+
+   - Outgoing packets are sent to every recorded peer in the
+     applicable list.
+
+   - Data transfer peers are straightforward: whenever we successfully
+     process a data packet, we record the peer.  Also, whenever we
+     successfully complete a key setup, we merge the key setup
+     peers into the data transfer peers.
+
+     (For "non-mobile" peers we simply copy the peer used for
+     successful key setup, and don't change the peer otherwise.)
+
+   - Key setup peers are slightly more complicated.
+
+     Whenever we receive and successfully process a key exchange
+     packet, we record the peer.
+
+     Whenever we try to initiate a key setup, we copy the list of data
+     transfer peers and use it for key setup.  But we also look to see
+     if the config supplies an address and port number and if so we
+     add that as a key setup peer (possibly evicting one of the data
+     transfer peers we just copied).
+
+     (For "non-mobile" peers, if we if we have a configured peer
+     address and port, we always use that; otherwise if we have a
+     current data peer address we use that; otherwise we do not
+     attempt to initiate a key setup for lack of a peer address.)
+
+   "Record the peer" means
+    1. expire any peers last seen >120s ("mobile-peer-expiry") ago
+    2. add the peer of the just received packet to the applicable list
+       (possibly evicting older entries)
+   NB that we do not expire peers until an incoming packet arrives.
+
+   */
+
+#define MAX_MOBILE_PEERS_MAX 5 /* send at most this many copies, compiled max */
+
+typedef struct {
+    struct timeval last;
+    struct comm_addr addr;
+} transport_peer;
+
+typedef struct {
+/* configuration information */
+/* runtime information */
+    int npeers;
+    transport_peer peers[MAX_MOBILE_PEERS_MAX];
+} transport_peers;
+
+static void transport_peers_clear(struct site *st, transport_peers *peers);
+static int transport_peers_valid(transport_peers *peers);
+static void transport_peers_copy(struct site *st, transport_peers *dst,
+                                const transport_peers *src);
+
+static void transport_setup_msgok(struct site *st, const struct comm_addr *a);
+static void transport_data_msgok(struct site *st, const struct comm_addr *a);
+static bool_t transport_compute_setupinit_peers(struct site *st,
+        const struct comm_addr *configured_addr /* 0 if none or not found */,
+        const struct comm_addr *prod_hint_addr /* 0 if none */);
+static void transport_resolve_complete(struct site *st,
+                                      const struct comm_addr *a);
+static void transport_resolve_complete_tardy(struct site *st,
+                                            const struct comm_addr *ca_use);
+static void transport_record_peer(struct site *st, transport_peers *peers,
+                                 const struct comm_addr *addr, const char *m);
+
+static void transport_xmit(struct site *st, transport_peers *peers,
+                          struct buffer_if *buf, bool_t candebug);
+
+ /***** END of transport peers declarations *****/
+
+
+struct data_key {
+    struct transform_inst_if *transform;
+    uint64_t key_timeout; /* End of life of current key */
+    uint32_t remote_session_id;
+};
 
 struct site {
     closure_t cl;
@@ -106,30 +233,36 @@ struct site {
 /* configuration information */
     string_t localname;
     string_t remotename;
-    string_t tunname; /* localname<->remotename by default */
+    bool_t local_mobile, peer_mobile; /* Mobile client support */
+    int32_t transport_peers_max;
+    string_t tunname; /* localname<->remotename by default, used in logs */
     string_t address; /* DNS name for bootstrapping, optional */
-    int remoteport;
+    int remoteport; /* Port for bootstrapping, optional */
+    uint32_t mtu_target;
     struct netlink_if *netlink;
-    struct comm_if *comm;
+    struct comm_if **comms;
+    int ncomms;
     struct resolver_if *resolver;
     struct log_if *log;
     struct random_if *random;
     struct rsaprivkey_if *privkey;
-    struct subnet_list remotenets;
     struct rsapubkey_if *pubkey;
-    struct transform_if *transform;
+    struct transform_if **transforms;
+    int ntransforms;
     struct dh_if *dh;
     struct hash_if *hash;
-    void *netlink_cid;
 
-    uint32_t setup_retries; /* How many times to send setup packets */
-    uint32_t setup_timeout; /* Initial timeout for setup packets */
-    uint32_t wait_timeout; /* How long to wait if setup unsuccessful */
-    uint32_t key_lifetime; /* How long a key lasts once set up */
+    uint32_t index; /* Index of this site */
+    uint32_t local_capabilities;
+    int32_t setup_retries; /* How many times to send setup packets */
+    int32_t setup_retry_interval; /* Initial timeout for setup packets */
+    int32_t wait_timeout; /* How long to wait if setup unsuccessful */
+    int32_t mobile_peer_expiry; /* How long to remember 2ary addresses */
+    int32_t key_lifetime; /* How long a key lasts once set up */
+    int32_t key_renegotiate_time; /* If we see traffic (or a keepalive)
+                                     after this time, initiate a new
+                                     key exchange */
 
-    uint8_t *setupsig; /* Expected signature of incoming MSG1 packets */
-    uint32_t setupsiglen; /* Allows us to discard packets quickly if
-                            they are not for us */
     bool_t setup_priority; /* Do we have precedence if both sites emit
                              message 1 simultaneously? */
     uint32_t log_events;
@@ -137,125 +270,351 @@ struct site {
 /* runtime information */
     uint32_t state;
     uint64_t now; /* Most recently seen time */
-
-    uint32_t remote_session_id;
-    struct transform_inst_if *current_transform;
-    bool_t current_valid;
-    uint64_t current_key_timeout; /* End of life of current key */
-    struct sockaddr_in peer; /* Current address of peer */
-    bool_t peer_valid; /* Peer address becomes invalid when key times out,
-                         but only if we have a DNS name for our peer */
-
+    bool_t allow_send_prod;
+    bool_t resolving;
+
+    /* The currently established session */
+    struct data_key current;
+    struct data_key auxiliary_key;
+    bool_t auxiliary_is_new;
+    uint64_t renegotiate_key_time; /* When we can negotiate a new key */
+    uint64_t auxiliary_renegotiate_key_time;
+    transport_peers peers; /* Current address(es) of peer for data traffic */
+
+    /* The current key setup protocol exchange.  We can only be
+       involved in one of these at a time.  There's a potential for
+       denial of service here (the attacker keeps sending a setup
+       packet; we keep trying to continue the exchange, and have to
+       timeout before we can listen for another setup packet); perhaps
+       we should keep a list of 'bad' sources for setup packets. */
+    uint32_t remote_capabilities;
+    uint16_t remote_adv_mtu;
+    struct transform_if *chosen_transform;
     uint32_t setup_session_id;
-    struct sockaddr_in setup_peer;
+    transport_peers setup_peers;
     uint8_t localN[NONCELEN]; /* Nonces for key exchange */
     uint8_t remoteN[NONCELEN];
     struct buffer_if buffer; /* Current outgoing key exchange packet */
-    uint32_t retries; /* Number of retries remaining */
+    struct buffer_if scratch;
+    int32_t retries; /* Number of retries remaining */
     uint64_t timeout; /* Timeout for current state */
     uint8_t *dhsecret;
     uint8_t *sharedsecret;
-
+    uint32_t sharedsecretlen, sharedsecretallocd;
     struct transform_inst_if *new_transform; /* For key setup/verify */
 };
 
-static void slog(struct site *st, uint32_t event, string_t msg, ...)
+static uint32_t event_log_priority(struct site *st, uint32_t event)
 {
-    va_list ap;
-    uint8_t buf[240];
+    if (!(event&st->log_events))
+       return 0;
+    switch(event) {
+    case LOG_UNEXPECTED:    return M_INFO;
+    case LOG_SETUP_INIT:    return M_INFO;
+    case LOG_SETUP_TIMEOUT: return M_NOTICE;
+    case LOG_ACTIVATE_KEY:  return M_INFO;
+    case LOG_TIMEOUT_KEY:   return M_INFO;
+    case LOG_SEC:           return M_SECURITY;
+    case LOG_STATE:         return M_DEBUG;
+    case LOG_DROP:          return M_DEBUG;
+    case LOG_DUMP:          return M_DEBUG;
+    case LOG_ERROR:         return M_ERR;
+    case LOG_PEER_ADDRS:    return M_DEBUG;
+    default:                return M_ERR;
+    }
+}
+
+static void vslog(struct site *st, uint32_t event, cstring_t msg, va_list ap)
+FORMAT(printf,3,0);
+static void vslog(struct site *st, uint32_t event, cstring_t msg, va_list ap)
+{
+    uint32_t class;
+
+    class=event_log_priority(st, event);
+    if (class) {
+       slilog_part(st->log,class,"%s: ",st->tunname);
+       vslilog_part(st->log,class,msg,ap);
+       slilog_part(st->log,class,"\n");
+    }
+}
 
+static void slog(struct site *st, uint32_t event, cstring_t msg, ...)
+FORMAT(printf,3,4);
+static void slog(struct site *st, uint32_t event, cstring_t msg, ...)
+{
+    va_list ap;
     va_start(ap,msg);
+    vslog(st,event,msg,ap);
+    va_end(ap);
+}
+
+static void logtimeout(struct site *st, const char *fmt, ...)
+FORMAT(printf,2,3);
+static void logtimeout(struct site *st, const char *fmt, ...)
+{
+    uint32_t class=event_log_priority(st,LOG_SETUP_TIMEOUT);
+    if (!class)
+       return;
 
-    if (event&st->log_events) {
-       vsnprintf(buf,240,msg,ap);
-       st->log->log(st->log->st,0,"%s: %s",st->tunname,buf);
+    va_list ap;
+    va_start(ap,fmt);
+
+    slilog_part(st->log,class,"%s: ",st->tunname);
+    vslilog_part(st->log,class,fmt,ap);
+
+    const char *delim;
+    int i;
+    for (i=0, delim=" (tried ";
+        i<st->setup_peers.npeers;
+        i++, delim=", ") {
+       transport_peer *peer=&st->setup_peers.peers[i];
+       const char *s=comm_addr_to_string(&peer->addr);
+       slilog_part(st->log,class,"%s%s",delim,s);
     }
+
+    slilog_part(st->log,class,")\n");
     va_end(ap);
 }
 
+static void set_link_quality(struct site *st);
+static void delete_keys(struct site *st, cstring_t reason, uint32_t loglevel);
+static void delete_one_key(struct site *st, struct data_key *key,
+                          const char *reason /* may be 0 meaning don't log*/,
+                          const char *which /* ignored if !reasonn */,
+                          uint32_t loglevel /* ignored if !reasonn */);
+static bool_t initiate_key_setup(struct site *st, cstring_t reason,
+                                const struct comm_addr *prod_hint);
 static void enter_state_run(struct site *st);
 static bool_t enter_state_resolve(struct site *st);
-static bool_t enter_state_sentmsg1(struct site *st);
-static bool_t enter_state_sentmsg2(struct site *st);
-static bool_t enter_state_sentmsg3(struct site *st);
-static bool_t enter_state_sentmsg4(struct site *st);
-static bool_t enter_state_sentmsg5(struct site *st);
+static bool_t enter_new_state(struct site *st,uint32_t next);
 static void enter_state_wait(struct site *st);
+static void activate_new_key(struct site *st);
+
+static bool_t is_transform_valid(struct transform_inst_if *transform)
+{
+    return transform && transform->valid(transform->st);
+}
+
+static bool_t current_valid(struct site *st)
+{
+    return is_transform_valid(st->current.transform);
+}
+
+#define DEFINE_CALL_TRANSFORM(fwdrev)                                  \
+static int call_transform_##fwdrev(struct site *st,                    \
+                                  struct transform_inst_if *transform, \
+                                  struct buffer_if *buf,               \
+                                  const char **errmsg)                 \
+{                                                                      \
+    if (!is_transform_valid(transform)) {                              \
+       *errmsg="transform not set up";                                 \
+       return 1;                                                       \
+    }                                                                  \
+    return transform->fwdrev(transform->st,buf,errmsg);                        \
+}
+
+DEFINE_CALL_TRANSFORM(forwards)
+DEFINE_CALL_TRANSFORM(reverse)
+
+static void dispose_transform(struct transform_inst_if **transform_var)
+{
+    struct transform_inst_if *transform=*transform_var;
+    if (transform) {
+       transform->delkey(transform->st);
+       transform->destroy(transform->st);
+    }
+    *transform_var = 0;
+}    
 
 #define CHECK_AVAIL(b,l) do { if ((b)->size<(l)) return False; } while(0)
 #define CHECK_EMPTY(b) do { if ((b)->size!=0) return False; } while(0)
 #define CHECK_TYPE(b,t) do { uint32_t type; \
     CHECK_AVAIL((b),4); \
-    type=*(uint32_t *)buf_unprepend((b),4); \
+    type=buf_unprepend_uint32((b)); \
     if (type!=(t)) return False; } while(0)
 
+static _Bool type_is_msg34(uint32_t type)
+{
+    return
+       type == LABEL_MSG3 ||
+       type == LABEL_MSG3BIS ||
+       type == LABEL_MSG4;
+}
+
+struct parsedname {
+    int32_t len;
+    uint8_t *name;
+    struct buffer_if extrainfo;
+};
+
 struct msg {
     uint8_t *hashstart;
     uint32_t dest;
     uint32_t source;
-    uint32_t remlen;
-    uint8_t *remote;
-    uint32_t loclen;
-    uint8_t *local;
+    struct parsedname remote;
+    struct parsedname local;
+    uint32_t remote_capabilities;
+    uint16_t remote_mtu;
+    int capab_transformnum;
     uint8_t *nR;
     uint8_t *nL;
-    uint32_t pklen;
-    uint8_t *pk;
-    uint32_t hashlen;
-    uint32_t siglen;
-    uint8_t *sig;
+    int32_t pklen;
+    char *pk;
+    int32_t hashlen;
+    int32_t siglen;
+    char *sig;
+};
+
+static void set_new_transform(struct site *st, char *pk)
+{
+    /* Make room for the shared key */
+    st->sharedsecretlen=st->chosen_transform->keylen?:st->dh->ceil_len;
+    assert(st->sharedsecretlen);
+    if (st->sharedsecretlen > st->sharedsecretallocd) {
+       st->sharedsecretallocd=st->sharedsecretlen;
+       st->sharedsecret=realloc(st->sharedsecret,st->sharedsecretallocd);
+    }
+    if (!st->sharedsecret) fatal_perror("site:sharedsecret");
+
+    /* Generate the shared key */
+    st->dh->makeshared(st->dh->st,st->dhsecret,st->dh->len,pk,
+                      st->sharedsecret,st->sharedsecretlen);
+
+    /* Set up the transform */
+    struct transform_if *generator=st->chosen_transform;
+    struct transform_inst_if *generated=generator->create(generator->st);
+    generated->setkey(generated->st,st->sharedsecret,
+                     st->sharedsecretlen,st->setup_priority);
+    dispose_transform(&st->new_transform);
+    st->new_transform=generated;
+
+    slog(st,LOG_SETUP_INIT,"key exchange negotiated transform"
+        " %d (capabilities ours=%#"PRIx32" theirs=%#"PRIx32")",
+        st->chosen_transform->capab_transformnum,
+        st->local_capabilities, st->remote_capabilities);
+}
+
+struct xinfoadd {
+    int32_t lenpos, afternul;
 };
+static void append_string_xinfo_start(struct buffer_if *buf,
+                                     struct xinfoadd *xia,
+                                     const char *str)
+    /* Helps construct one of the names with additional info as found
+     * in MSG1..4.  Call this function first, then append all the
+     * desired extra info (not including the nul byte) to the buffer,
+     * then call append_string_xinfo_done. */
+{
+    xia->lenpos = buf->size;
+    buf_append_string(buf,str);
+    buf_append_uint8(buf,0);
+    xia->afternul = buf->size;
+}
+static void append_string_xinfo_done(struct buffer_if *buf,
+                                    struct xinfoadd *xia)
+{
+    /* we just need to adjust the string length */
+    if (buf->size == xia->afternul) {
+       /* no extra info, strip the nul too */
+       buf_unappend_uint8(buf);
+    } else {
+       put_uint16(buf->start+xia->lenpos, buf->size-(xia->lenpos+2));
+    }
+}
 
-/* Build any of msg1 to msg4. msg5 and msg6 are built from the inside out
-   using a transform. */
-static bool_t generate_msg(struct site *st, uint32_t type, string_t what)
+/* Build any of msg1 to msg4. msg5 and msg6 are built from the inside
+   out using a transform of config data supplied by netlink */
+static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
 {
     void *hst;
-    uint8_t *hash=alloca(st->hash->len);
+    uint8_t *hash;
     string_t dhpub, sig;
 
     st->retries=st->setup_retries;
     BUF_ALLOC(&st->buffer,what);
     buffer_init(&st->buffer,0);
-    *(uint32_t *)buf_append(&st->buffer,4)=
-       (type==LABEL_MSG1?0:st->setup_session_id);
-    *(uint32_t *)buf_append(&st->buffer,4)=(uint32_t)st;
-    *(uint32_t *)buf_append(&st->buffer,4)=type;
-    buf_append_string(&st->buffer,st->localname);
+    buf_append_uint32(&st->buffer,
+       (type==LABEL_MSG1?0:st->setup_session_id));
+    buf_append_uint32(&st->buffer,st->index);
+    buf_append_uint32(&st->buffer,type);
+
+    struct xinfoadd xia;
+    append_string_xinfo_start(&st->buffer,&xia,st->localname);
+    if ((st->local_capabilities & CAPAB_EARLY) || (type != LABEL_MSG1)) {
+       buf_append_uint32(&st->buffer,st->local_capabilities);
+    }
+    if (type_is_msg34(type)) {
+       buf_append_uint16(&st->buffer,st->mtu_target);
+    }
+    append_string_xinfo_done(&st->buffer,&xia);
+
     buf_append_string(&st->buffer,st->remotename);
     memcpy(buf_append(&st->buffer,NONCELEN),st->localN,NONCELEN);
     if (type==LABEL_MSG1) return True;
     memcpy(buf_append(&st->buffer,NONCELEN),st->remoteN,NONCELEN);
     if (type==LABEL_MSG2) return True;
+
+    if (hacky_par_mid_failnow()) return False;
+
+    if (type==LABEL_MSG3BIS)
+       buf_append_uint8(&st->buffer,st->chosen_transform->capab_transformnum);
+
     dhpub=st->dh->makepublic(st->dh->st,st->dhsecret,st->dh->len);
     buf_append_string(&st->buffer,dhpub);
     free(dhpub);
+    hash=safe_malloc(st->hash->len, "generate_msg");
     hst=st->hash->init();
     st->hash->update(hst,st->buffer.start,st->buffer.size);
     st->hash->final(hst,hash);
     sig=st->privkey->sign(st->privkey->st,hash,st->hash->len);
     buf_append_string(&st->buffer,sig);
     free(sig);
+    free(hash);
+    return True;
+}
+
+static bool_t unpick_name(struct buffer_if *msg, struct parsedname *nm)
+{
+    CHECK_AVAIL(msg,2);
+    nm->len=buf_unprepend_uint16(msg);
+    CHECK_AVAIL(msg,nm->len);
+    nm->name=buf_unprepend(msg,nm->len);
+    uint8_t *nul=memchr(nm->name,0,nm->len);
+    if (!nul) {
+       buffer_readonly_view(&nm->extrainfo,0,0);
+    } else {
+       buffer_readonly_view(&nm->extrainfo, nul+1, msg->start-(nul+1));
+       nm->len=nul-nm->name;
+    }
     return True;
 }
 
 static bool_t unpick_msg(struct site *st, uint32_t type,
                         struct buffer_if *msg, struct msg *m)
 {
+    m->capab_transformnum=-1;
     m->hashstart=msg->start;
     CHECK_AVAIL(msg,4);
-    m->dest=*(uint32_t *)buf_unprepend(msg,4);
+    m->dest=buf_unprepend_uint32(msg);
     CHECK_AVAIL(msg,4);
-    m->source=*(uint32_t *)buf_unprepend(msg,4);
+    m->source=buf_unprepend_uint32(msg);
     CHECK_TYPE(msg,type);
-    CHECK_AVAIL(msg,2);
-    m->remlen=ntohs(*(uint16_t *)buf_unprepend(msg,2));
-    CHECK_AVAIL(msg,m->remlen);
-    m->remote=buf_unprepend(msg,m->remlen);
-    CHECK_AVAIL(msg,2);
-    m->loclen=ntohs(*(uint16_t *)buf_unprepend(msg,2));
-    CHECK_AVAIL(msg,m->loclen);
-    m->local=buf_unprepend(msg,m->loclen);
+    if (!unpick_name(msg,&m->remote)) return False;
+    m->remote_capabilities=0;
+    m->remote_mtu=0;
+    if (m->remote.extrainfo.size) {
+       CHECK_AVAIL(&m->remote.extrainfo,4);
+       m->remote_capabilities=buf_unprepend_uint32(&m->remote.extrainfo);
+    }
+    if (type_is_msg34(type) && m->remote.extrainfo.size) {
+       CHECK_AVAIL(&m->remote.extrainfo,2);
+       m->remote_mtu=buf_unprepend_uint16(&m->remote.extrainfo);
+    }
+    if (!unpick_name(msg,&m->local)) return False;
+    if (type==LABEL_PROD) {
+       CHECK_EMPTY(msg);
+       return True;
+    }
     CHECK_AVAIL(msg,NONCELEN);
     m->nR=buf_unprepend(msg,NONCELEN);
     if (type==LABEL_MSG1) {
@@ -268,19 +627,69 @@ static bool_t unpick_msg(struct site *st, uint32_t type,
        CHECK_EMPTY(msg);
        return True;
     }
+    if (type==LABEL_MSG3BIS) {
+       CHECK_AVAIL(msg,1);
+       m->capab_transformnum = buf_unprepend_uint8(msg);
+    } else {
+       m->capab_transformnum = CAPAB_TRANSFORMNUM_ANCIENT;
+    }
     CHECK_AVAIL(msg,2);
-    m->pklen=ntohs(*(uint16_t *)buf_unprepend(msg,2));
+    m->pklen=buf_unprepend_uint16(msg);
     CHECK_AVAIL(msg,m->pklen);
     m->pk=buf_unprepend(msg,m->pklen);
     m->hashlen=msg->start-m->hashstart;
     CHECK_AVAIL(msg,2);
-    m->siglen=ntohs(*(uint16_t *)buf_unprepend(msg,2));
+    m->siglen=buf_unprepend_uint16(msg);
     CHECK_AVAIL(msg,m->siglen);
     m->sig=buf_unprepend(msg,m->siglen);
     CHECK_EMPTY(msg);
     return True;
 }
 
+static bool_t name_matches(const struct parsedname *nm, const char *expected)
+{
+    int expected_len=strlen(expected);
+    return
+       nm->len == expected_len &&
+       !memcmp(nm->name, expected, expected_len);
+}    
+
+static bool_t check_msg(struct site *st, uint32_t type, struct msg *m,
+                       cstring_t *error)
+{
+    if (type==LABEL_MSG1) return True;
+
+    /* Check that the site names and our nonce have been sent
+       back correctly, and then store our peer's nonce. */ 
+    if (!name_matches(&m->remote,st->remotename)) {
+       *error="wrong remote site name";
+       return False;
+    }
+    if (!name_matches(&m->local,st->localname)) {
+       *error="wrong local site name";
+       return False;
+    }
+    if (memcmp(m->nL,st->localN,NONCELEN)!=0) {
+       *error="wrong locally-generated nonce";
+       return False;
+    }
+    if (type==LABEL_MSG2) return True;
+    if (!consttime_memeq(m->nR,st->remoteN,NONCELEN)!=0) {
+       *error="wrong remotely-generated nonce";
+       return False;
+    }
+    /* MSG3 has complicated rules about capabilities, which are
+     * handled in process_msg3. */
+    if (type==LABEL_MSG3 || type==LABEL_MSG3BIS) return True;
+    if (m->remote_capabilities!=st->remote_capabilities) {
+       *error="remote capabilities changed";
+       return False;
+    }
+    if (type==LABEL_MSG4) return True;
+    *error="unknown message type";
+    return False;
+}
+
 static bool_t generate_msg1(struct site *st)
 {
     st->random->generate(st->random->st,NONCELEN,st->localN);
@@ -288,21 +697,15 @@ static bool_t generate_msg1(struct site *st)
 }
 
 static bool_t process_msg1(struct site *st, struct buffer_if *msg1,
-                          struct sockaddr_in *src)
+                          const struct comm_addr *src, struct msg *m)
 {
-    struct msg m;
-
     /* We've already determined we're in an appropriate state to
        process an incoming MSG1, and that the MSG1 has correct values
        of A and B. */
 
-    if (!unpick_msg(st,LABEL_MSG1,msg1,&m)) return False;
-
-    /* XXX save src as our peer address here? */
-    st->setup_peer=*src;
-
-    st->setup_session_id=m.source;
-    memcpy(st->remoteN,m.nR,NONCELEN);
+    st->setup_session_id=m->source;
+    st->remote_capabilities=m->remote_capabilities;
+    memcpy(st->remoteN,m->nR,NONCELEN);
     return True;
 }
 
@@ -313,27 +716,41 @@ static bool_t generate_msg2(struct site *st)
 }
 
 static bool_t process_msg2(struct site *st, struct buffer_if *msg2,
-                          struct sockaddr_in *src)
+                          const struct comm_addr *src)
 {
     struct msg m;
+    cstring_t err;
 
     if (!unpick_msg(st,LABEL_MSG2,msg2,&m)) return False;
-
-    /* Check that the site names and our nonce have been sent
-       back correctly, and then store our peer's nonce. */ 
-    if (memcmp(m.remote,st->remotename,strlen(st->remotename)!=0)) {
-       slog(st,LOG_SECURITY,"msg2: bad B (remote site name)");
-       return False;
-    }
-    if (memcmp(m.local,st->localname,strlen(st->localname)!=0)) {
-       slog(st,LOG_SECURITY,"msg2: bad A (local site name)");
-       return False;
-    }
-    if (memcmp(m.nL,st->localN,NONCELEN)!=0) {
-       slog(st,LOG_SECURITY,"msg2: bad nA (locally generated nonce)");
+    if (!check_msg(st,LABEL_MSG2,&m,&err)) {
+       slog(st,LOG_SEC,"msg2: %s",err);
        return False;
     }
     st->setup_session_id=m.source;
+    st->remote_capabilities=m.remote_capabilities;
+
+    /* Select the transform to use */
+
+    uint32_t remote_transforms = st->remote_capabilities & CAPAB_TRANSFORM_MASK;
+    if (!remote_transforms)
+       /* old secnets only had this one transform */
+       remote_transforms = 1UL << CAPAB_TRANSFORMNUM_ANCIENT;
+
+    struct transform_if *ti;
+    int i;
+    for (i=0; i<st->ntransforms; i++) {
+       ti=st->transforms[i];
+       if ((1UL << ti->capab_transformnum) & remote_transforms)
+           goto transform_found;
+    }
+    slog(st,LOG_ERROR,"no transforms in common"
+        " (us %#"PRIx32"; them: %#"PRIx32")",
+        st->local_capabilities & CAPAB_TRANSFORM_MASK,
+        remote_transforms);
+    return False;
+ transform_found:
+    st->chosen_transform=ti;
+
     memcpy(st->remoteN,m.nR,NONCELEN);
     return True;
 }
@@ -343,60 +760,82 @@ static bool_t generate_msg3(struct site *st)
     /* Now we have our nonce and their nonce. Think of a secret key,
        and create message number 3. */
     st->random->generate(st->random->st,st->dh->len,st->dhsecret);
-    return generate_msg(st,LABEL_MSG3,"site:MSG3");
+    return generate_msg(st,
+                       (st->remote_capabilities & CAPAB_TRANSFORM_MASK
+                        ? LABEL_MSG3BIS : LABEL_MSG3),
+                       "site:MSG3");
 }
 
-static bool_t process_msg3(struct site *st, struct buffer_if *msg3,
-                          struct sockaddr_in *src)
+static bool_t process_msg3_msg4(struct site *st, struct msg *m)
 {
-    struct msg m;
-    uint8_t *hash=alloca(st->hash->len);
+    uint8_t *hash;
     void *hst;
 
-    if (!unpick_msg(st,LABEL_MSG3,msg3,&m)) return False;
-
-    /* Check that the site names and nonces have been sent back
-       correctly */
-    if (memcmp(m.remote,st->remotename,strlen(st->remotename)!=0)) {
-       slog(st,LOG_SECURITY,"msg3: bad A (remote site name)");
+    /* Check signature and store g^x mod m */
+    hash=safe_malloc(st->hash->len, "process_msg3_msg4");
+    hst=st->hash->init();
+    st->hash->update(hst,m->hashstart,m->hashlen);
+    st->hash->final(hst,hash);
+    /* Terminate signature with a '0' - cheating, but should be ok */
+    m->sig[m->siglen]=0;
+    if (!st->pubkey->check(st->pubkey->st,hash,st->hash->len,m->sig)) {
+       slog(st,LOG_SEC,"msg3/msg4 signature failed check!");
+       free(hash);
        return False;
     }
-    if (memcmp(m.local,st->localname,strlen(st->localname)!=0)) {
-       slog(st,LOG_SECURITY,"msg3: bad B (local site name)");
+    free(hash);
+
+    st->remote_adv_mtu=m->remote_mtu;
+
+    return True;
+}
+
+static bool_t process_msg3(struct site *st, struct buffer_if *msg3,
+                          const struct comm_addr *src, uint32_t msgtype)
+{
+    struct msg m;
+    cstring_t err;
+
+    assert(msgtype==LABEL_MSG3 || msgtype==LABEL_MSG3BIS);
+
+    if (!unpick_msg(st,msgtype,msg3,&m)) return False;
+    if (!check_msg(st,msgtype,&m,&err)) {
+       slog(st,LOG_SEC,"msg3: %s",err);
        return False;
     }
-    if (memcmp(m.nR,st->remoteN,NONCELEN)!=0) {
-       slog(st,LOG_SECURITY,"msg3: bad nA (remotely generated nonce)");
+    uint32_t capab_adv_late = m.remote_capabilities
+       & ~st->remote_capabilities & CAPAB_EARLY;
+    if (capab_adv_late) {
+       slog(st,LOG_SEC,"msg3 impermissibly adds early capability flag(s)"
+            " %#"PRIx32" (was %#"PRIx32", now %#"PRIx32")",
+            capab_adv_late, st->remote_capabilities, m.remote_capabilities);
        return False;
     }
-    if (memcmp(m.nL,st->localN,NONCELEN)!=0) {
-       slog(st,LOG_SECURITY,"msg3: bad nB (locally generated nonce)");
-       return False;
+    st->remote_capabilities|=m.remote_capabilities;
+
+    struct transform_if *ti;
+    int i;
+    for (i=0; i<st->ntransforms; i++) {
+       ti=st->transforms[i];
+       if (ti->capab_transformnum == m.capab_transformnum)
+           goto transform_found;
     }
-    
-    /* Check signature and store g^x mod m */
-    hst=st->hash->init();
-    st->hash->update(hst,m.hashstart,m.hashlen);
-    st->hash->final(hst,hash);
-    /* Terminate signature with a '0' - cheating, but should be ok */
-    m.sig[m.siglen]=0;
-    if (!st->pubkey->check(st->pubkey->st,hash,st->hash->len,m.sig)) {
-       slog(st,LOG_SECURITY,"msg3 signature failed check!");
+    slog(st,LOG_SEC,"peer chose unknown-to-us transform %d!",
+        m.capab_transformnum);
+    return False;
+ transform_found:
+    st->chosen_transform=ti;
+
+    if (!process_msg3_msg4(st,&m))
        return False;
-    }
 
     /* Terminate their DH public key with a '0' */
     m.pk[m.pklen]=0;
     /* Invent our DH secret key */
     st->random->generate(st->random->st,st->dh->len,st->dhsecret);
 
-    /* Generate the shared key */
-    st->dh->makeshared(st->dh->st,st->dhsecret,st->dh->len,m.pk,
-                      st->sharedsecret,st->transform->keylen);
-
-    /* Set up the transform */
-    st->new_transform->setkey(st->new_transform->st,st->sharedsecret,
-                             st->transform->keylen);
+    /* Generate the shared key and set up the transform */
+    set_new_transform(st,m.pk);
 
     return True;
 }
@@ -409,71 +848,26 @@ static bool_t generate_msg4(struct site *st)
 }
 
 static bool_t process_msg4(struct site *st, struct buffer_if *msg4,
-                          struct sockaddr_in *src)
+                          const struct comm_addr *src)
 {
     struct msg m;
-    uint8_t *hash=alloca(st->hash->len);
-    void *hst;
+    cstring_t err;
 
     if (!unpick_msg(st,LABEL_MSG4,msg4,&m)) return False;
-
-    /* Check that the site names and nonces have been sent back
-       correctly */
-    if (memcmp(m.remote,st->remotename,strlen(st->remotename)!=0)) {
-       slog(st,LOG_SECURITY,"msg4: bad B (remote site name)");
-       return False;
-    }
-    if (memcmp(m.local,st->localname,strlen(st->localname)!=0)) {
-       slog(st,LOG_SECURITY,"msg4: bad A (local site name)");
-       return False;
-    }
-    if (memcmp(m.nR,st->remoteN,NONCELEN)!=0) {
-       slog(st,LOG_SECURITY,"msg4: bad nB (remotely generated nonce)");
-       return False;
-    }
-    if (memcmp(m.nL,st->localN,NONCELEN)!=0) {
-       slog(st,LOG_SECURITY,"msg4: bad nA (locally generated nonce)");
+    if (!check_msg(st,LABEL_MSG4,&m,&err)) {
+       slog(st,LOG_SEC,"msg4: %s",err);
        return False;
     }
     
-    /* Check signature and store g^x mod m */
-    hst=st->hash->init();
-    st->hash->update(hst,m.hashstart,m.hashlen);
-    st->hash->final(hst,hash);
-    /* Terminate signature with a '0' - cheating, but should be ok */
-    m.sig[m.siglen]=0;
-    if (!st->pubkey->check(st->pubkey->st,hash,st->hash->len,m.sig)) {
-       slog(st,LOG_SECURITY,"msg4 signature failed check!");
+    if (!process_msg3_msg4(st,&m))
        return False;
-    }
 
     /* Terminate their DH public key with a '0' */
     m.pk[m.pklen]=0;
-    /* Generate the shared key */
-    st->dh->makeshared(st->dh->st,st->dhsecret,st->dh->len,m.pk,
-                      st->sharedsecret,st->transform->keylen);
-    /* Set up the transform */
-    st->new_transform->setkey(st->new_transform->st,st->sharedsecret,
-                             st->transform->keylen);
 
-    return True;
-}
-
-static bool_t generate_msg5(struct site *st)
-{
-    string_t transform_err;
-
-    BUF_ALLOC(&st->buffer,"site:MSG5");
-    /* We are going to add three words to the transformed message */
-    buffer_init(&st->buffer,st->transform->max_start_pad+(4*3));
-    *(uint32_t *)buf_append(&st->buffer,4)=LABEL_MSG5;
-    st->new_transform->forwards(st->new_transform->st,&st->buffer,
-                               &transform_err);
-    *(uint32_t *)buf_prepend(&st->buffer,4)=LABEL_MSG5;
-    *(uint32_t *)buf_prepend(&st->buffer,4)=(uint32_t)st;
-    *(uint32_t *)buf_prepend(&st->buffer,4)=st->setup_session_id;
+    /* Generate the shared key and set up the transform */
+    set_new_transform(st,m.pk);
 
-    st->retries=st->setup_retries;
     return True;
 }
 
@@ -487,132 +881,231 @@ static bool_t unpick_msg0(struct site *st, struct buffer_if *msg0,
                          struct msg0 *m)
 {
     CHECK_AVAIL(msg0,4);
-    m->dest=*(uint32_t *)buf_unprepend(msg0,4);
+    m->dest=buf_unprepend_uint32(msg0);
     CHECK_AVAIL(msg0,4);
-    m->source=*(uint32_t *)buf_unprepend(msg0,4);
+    m->source=buf_unprepend_uint32(msg0);
     CHECK_AVAIL(msg0,4);
-    m->type=*(uint32_t *)buf_unprepend(msg0,4);
+    m->type=buf_unprepend_uint32(msg0);
     return True;
     /* Leaves transformed part of buffer untouched */
 }
 
+static bool_t generate_msg5(struct site *st)
+{
+    cstring_t transform_err;
+
+    BUF_ALLOC(&st->buffer,"site:MSG5");
+    /* We are going to add four words to the message */
+    buffer_init(&st->buffer,calculate_max_start_pad());
+    /* Give the netlink code an opportunity to put its own stuff in the
+       message (configuration information, etc.) */
+    buf_prepend_uint32(&st->buffer,LABEL_MSG5);
+    if (call_transform_forwards(st,st->new_transform,
+                               &st->buffer,&transform_err))
+       return False;
+    buf_prepend_uint32(&st->buffer,LABEL_MSG5);
+    buf_prepend_uint32(&st->buffer,st->index);
+    buf_prepend_uint32(&st->buffer,st->setup_session_id);
+
+    st->retries=st->setup_retries;
+    return True;
+}
+
 static bool_t process_msg5(struct site *st, struct buffer_if *msg5,
-                          struct sockaddr_in *src)
+                          const struct comm_addr *src,
+                          struct transform_inst_if *transform)
 {
     struct msg0 m;
-    string_t transform_err;
+    cstring_t transform_err;
 
     if (!unpick_msg0(st,msg5,&m)) return False;
 
-    if (st->new_transform->reverse(st->new_transform->st,
-                                  msg5,&transform_err)) {
+    if (call_transform_reverse(st,transform,msg5,&transform_err)) {
        /* There's a problem */
-       slog(st,LOG_SECURITY,"process_msg5: transform: %s",transform_err);
+       slog(st,LOG_SEC,"process_msg5: transform: %s",transform_err);
        return False;
     }
     /* Buffer should now contain untransformed PING packet data */
     CHECK_AVAIL(msg5,4);
-    if ((*(uint32_t *)buf_unprepend(msg5,4))!=LABEL_MSG5) {
-       slog(st,LOG_SECURITY,"MSG5/PING packet contained invalid data");
+    if (buf_unprepend_uint32(msg5)!=LABEL_MSG5) {
+       slog(st,LOG_SEC,"MSG5/PING packet contained wrong label");
        return False;
     }
-    CHECK_EMPTY(msg5);
+    /* Older versions of secnet used to write some config data here
+     * which we ignore.  So we don't CHECK_EMPTY */
     return True;
 }
 
-static bool_t generate_msg6(struct site *st)
+static void create_msg6(struct site *st, struct transform_inst_if *transform,
+                       uint32_t session_id)
 {
-    string_t transform_err;
+    cstring_t transform_err;
 
     BUF_ALLOC(&st->buffer,"site:MSG6");
-    /* We are going to add three words to the transformed message */
-    buffer_init(&st->buffer,st->transform->max_start_pad+(4*3));
-    *(uint32_t *)buf_append(&st->buffer,4)=LABEL_MSG6;
-    st->new_transform->forwards(st->new_transform->st,&st->buffer,
-                               &transform_err);
-    *(uint32_t *)buf_prepend(&st->buffer,4)=LABEL_MSG6;
-    *(uint32_t *)buf_prepend(&st->buffer,4)=(uint32_t)st;
-    *(uint32_t *)buf_prepend(&st->buffer,4)=st->setup_session_id;
-
-    st->retries=1; /* Peer will retransmit MSG5 if necessary */
+    /* We are going to add four words to the message */
+    buffer_init(&st->buffer,calculate_max_start_pad());
+    /* Give the netlink code an opportunity to put its own stuff in the
+       message (configuration information, etc.) */
+    buf_prepend_uint32(&st->buffer,LABEL_MSG6);
+    int problem = call_transform_forwards(st,transform,
+                                         &st->buffer,&transform_err);
+    assert(!problem);
+    buf_prepend_uint32(&st->buffer,LABEL_MSG6);
+    buf_prepend_uint32(&st->buffer,st->index);
+    buf_prepend_uint32(&st->buffer,session_id);
+}
+
+static bool_t generate_msg6(struct site *st)
+{
+    if (!is_transform_valid(st->new_transform))
+       return False;
+    create_msg6(st,st->new_transform,st->setup_session_id);
+    st->retries=1; /* Peer will retransmit MSG5 if this packet gets lost */
     return True;
 }
 
 static bool_t process_msg6(struct site *st, struct buffer_if *msg6,
-                          struct sockaddr_in *src)
+                          const struct comm_addr *src)
 {
     struct msg0 m;
-    string_t transform_err;
+    cstring_t transform_err;
 
     if (!unpick_msg0(st,msg6,&m)) return False;
 
-    if (st->new_transform->reverse(st->new_transform->st,
-                                  msg6,&transform_err)) {
+    if (call_transform_reverse(st,st->new_transform,msg6,&transform_err)) {
        /* There's a problem */
-       slog(st,LOG_SECURITY,"process_msg6: transform: %s",transform_err);
+       slog(st,LOG_SEC,"process_msg6: transform: %s",transform_err);
        return False;
     }
     /* Buffer should now contain untransformed PING packet data */
     CHECK_AVAIL(msg6,4);
-    if ((*(uint32_t *)buf_unprepend(msg6,4))!=LABEL_MSG6) {
-       slog(st,LOG_SECURITY,"MSG6/PONG packet contained invalid data");
+    if (buf_unprepend_uint32(msg6)!=LABEL_MSG6) {
+       slog(st,LOG_SEC,"MSG6/PONG packet contained invalid data");
        return False;
     }
-    CHECK_EMPTY(msg6);
+    /* Older versions of secnet used to write some config data here
+     * which we ignore.  So we don't CHECK_EMPTY */
     return True;
 }
 
-static bool_t process_msg0(struct site *st, struct buffer_if *msg0,
-                          struct sockaddr_in *src)
+static bool_t decrypt_msg0(struct site *st, struct buffer_if *msg0,
+                          const struct comm_addr *src)
 {
+    cstring_t transform_err, auxkey_err, newkey_err="n/a";
     struct msg0 m;
-    string_t transform_err;
-    uint32_t type;
+    uint32_t problem;
+
+    if (!unpick_msg0(st,msg0,&m)) return False;
 
-    if (!st->current_valid) {
-       slog(st,LOG_DROP,"incoming message but no current key -> dropping");
-       if (st->state==SITE_RUN) {
-           slog(st,LOG_SETUP_INIT|LOG_STATE,
-                "now initiating setup of new key");
-           return enter_state_resolve(st);
+    /* Keep a copy so we can try decrypting it with multiple keys */
+    buffer_copy(&st->scratch, msg0);
+
+    problem = call_transform_reverse(st,st->current.transform,
+                                    msg0,&transform_err);
+    if (!problem) {
+       if (!st->auxiliary_is_new)
+           delete_one_key(st,&st->auxiliary_key,
+                          "peer has used new key","auxiliary key",LOG_SEC);
+       return True;
+    }
+    if (problem==2)
+       goto skew;
+
+    buffer_copy(msg0, &st->scratch);
+    problem = call_transform_reverse(st,st->auxiliary_key.transform,
+                                    msg0,&auxkey_err);
+    if (problem==0) {
+       slog(st,LOG_DROP,"processing packet which uses auxiliary key");
+       if (st->auxiliary_is_new) {
+           /* We previously timed out in state SENTMSG5 but it turns
+            * out that our peer did in fact get our MSG5 and is
+            * using the new key.  So we should switch to it too. */
+           /* This is a bit like activate_new_key. */
+           struct data_key t;
+           t=st->current;
+           st->current=st->auxiliary_key;
+           st->auxiliary_key=t;
+
+           delete_one_key(st,&st->auxiliary_key,"peer has used new key",
+                          "previous key",LOG_SEC);
+           st->auxiliary_is_new=0;
+           st->renegotiate_key_time=st->auxiliary_renegotiate_key_time;
        }
-       return False;
+       return True;
+    }
+    if (problem==2)
+       goto skew;
+
+    if (st->state==SITE_SENTMSG5) {
+       buffer_copy(msg0, &st->scratch);
+       problem = call_transform_reverse(st,st->new_transform,
+                                        msg0,&newkey_err);
+       if (!problem) {
+           /* It looks like we didn't get the peer's MSG6 */
+           /* This is like a cut-down enter_new_state(SITE_RUN) */
+           slog(st,LOG_STATE,"will enter state RUN (MSG0 with new key)");
+           BUF_FREE(&st->buffer);
+           st->timeout=0;
+           activate_new_key(st);
+           return True; /* do process the data in this packet */
+       }
+       if (problem==2)
+           goto skew;
     }
 
-    if (!unpick_msg0(st,msg0,&m)) return False;
+    slog(st,LOG_SEC,"transform: %s (aux: %s, new: %s)",
+        transform_err,auxkey_err,newkey_err);
+    initiate_key_setup(st,"incoming message would not decrypt",0);
+    send_nak(src,m.dest,m.source,m.type,msg0,"message would not decrypt");
+    return False;
 
-    if (st->current_transform->reverse(st->current_transform->st,
-                                      msg0,&transform_err)) {
-       /* There's a problem */
-       slog(st,LOG_SECURITY,"transform: %s",transform_err);
+ skew:
+    slog(st,LOG_DROP,"transform: %s (merely skew)",transform_err);
+    return False;
+}
+
+static bool_t process_msg0(struct site *st, struct buffer_if *msg0,
+                          const struct comm_addr *src)
+{
+    uint32_t type;
+
+    if (!decrypt_msg0(st,msg0,src))
        return False;
-    }
+
     CHECK_AVAIL(msg0,4);
-    type=*(uint32_t *)buf_unprepend(msg0,4);
+    type=buf_unprepend_uint32(msg0);
     switch(type) {
+    case LABEL_MSG7:
+       /* We must forget about the current session. */
+       delete_keys(st,"request from peer",LOG_SEC);
+       return True;
     case LABEL_MSG9:
        /* Deliver to netlink layer */
-       st->netlink->deliver(st->netlink->st,st->netlink_cid,msg0);
+       st->netlink->deliver(st->netlink->st,msg0);
+       transport_data_msgok(st,src);
+       /* See whether we should start negotiating a new key */
+       if (st->now > st->renegotiate_key_time)
+           initiate_key_setup(st,"incoming packet in renegotiation window",0);
        return True;
-       break;
     default:
-       slog(st,LOG_SECURITY,"incoming message of type %08x (unknown)",type);
+       slog(st,LOG_SEC,"incoming encrypted message of type %08x "
+            "(unknown)",type);
        break;
     }
     return False;
 }
 
 static void dump_packet(struct site *st, struct buffer_if *buf,
-                       struct sockaddr_in *addr, bool_t incoming)
+                       const struct comm_addr *addr, bool_t incoming)
 {
-    uint32_t dest=*(uint32_t *)buf->start;
-    uint32_t source=*(uint32_t *)(buf->start+4);
-    uint32_t msgtype=*(uint32_t *)(buf->start+8);
+    uint32_t dest=get_uint32(buf->start);
+    uint32_t source=get_uint32(buf->start+4);
+    uint32_t msgtype=get_uint32(buf->start+8);
 
     if (st->log_events & LOG_DUMP)
-       log(st->log,0,"(%s,%s): %s: %08x<-%08x: %08x:",
-           st->localname,st->remotename,incoming?"incoming":"outgoing",
-           dest,source,msgtype);
+       slilog(st->log,M_DEBUG,"%s: %s: %08x<-%08x: %08x:",
+              st->tunname,incoming?"incoming":"outgoing",
+              dest,source,msgtype);
 }
 
 static uint32_t site_status(void *st)
@@ -623,13 +1116,31 @@ static uint32_t site_status(void *st)
 static bool_t send_msg(struct site *st)
 {
     if (st->retries>0) {
-       dump_packet(st,&st->buffer,&st->setup_peer,False);
-       st->comm->sendmsg(st->comm->st,&st->buffer,&st->setup_peer);
-       st->timeout=st->now+st->setup_timeout;
+       transport_xmit(st, &st->setup_peers, &st->buffer, True);
+       st->timeout=st->now+st->setup_retry_interval;
        st->retries--;
        return True;
+    } else if (st->state==SITE_SENTMSG5) {
+       logtimeout(st,"timed out sending MSG5, stashing new key");
+       /* We stash the key we have produced, in case it turns out that
+        * our peer did see our MSG5 after all and starts using it. */
+       /* This is a bit like some of activate_new_key */
+       struct transform_inst_if *t;
+       t=st->auxiliary_key.transform;
+       st->auxiliary_key.transform=st->new_transform;
+       st->new_transform=t;
+       dispose_transform(&st->new_transform);
+
+       st->auxiliary_is_new=1;
+       st->auxiliary_key.key_timeout=st->now+st->key_lifetime;
+       st->auxiliary_renegotiate_key_time=st->now+st->key_renegotiate_time;
+       st->auxiliary_key.remote_session_id=st->setup_session_id;
+
+       enter_state_wait(st);
+       return False;
     } else {
-       slog(st,LOG_SETUP_TIMEOUT,"timed out sending key setup packet");
+       logtimeout(st,"timed out sending key setup packet "
+           "(in state %s)",state_name(st->state));
        enter_state_wait(st);
        return False;
     }
@@ -638,60 +1149,175 @@ static bool_t send_msg(struct site *st)
 static void site_resolve_callback(void *sst, struct in_addr *address)
 {
     struct site *st=sst;
+    struct comm_addr ca_buf, *ca_use;
+
+    st->resolving=False;
 
-    if (st->state!=SITE_RESOLVE) {
-       slog(st,LOG_UNEXPECTED,"site_resolve_callback called unexpectedly");
-       return;
-    }
     if (address) {
-       memset(&st->setup_peer,0,sizeof(st->setup_peer));
-       st->setup_peer.sin_family=AF_INET;
-       st->setup_peer.sin_port=htons(st->remoteport);
-       st->setup_peer.sin_addr=*address;
-       enter_state_sentmsg1(st);
+       FILLZERO(ca_buf);
+       ca_buf.comm=st->comms[0];
+       ca_buf.sin.sin_family=AF_INET;
+       ca_buf.sin.sin_port=htons(st->remoteport);
+       ca_buf.sin.sin_addr=*address;
+       ca_use=&ca_buf;
+       slog(st,LOG_STATE,"resolution of %s completed: %s",
+            st->address, comm_addr_to_string(ca_use));;
     } else {
-       /* Resolution failed */
        slog(st,LOG_ERROR,"resolution of %s failed",st->address);
-       enter_state_run(st);
+       ca_use=0;
+    }
+
+    switch (st->state) {
+    case SITE_RESOLVE:
+        if (transport_compute_setupinit_peers(st,ca_use,0)) {
+           enter_new_state(st,SITE_SENTMSG1);
+       } else {
+           /* Can't figure out who to try to to talk to */
+           slog(st,LOG_SETUP_INIT,
+                "key exchange failed: cannot find peer address");
+           enter_state_run(st);
+       }
+       break;
+    case SITE_SENTMSG1: case SITE_SENTMSG2:
+    case SITE_SENTMSG3: case SITE_SENTMSG4:
+    case SITE_SENTMSG5:
+       if (ca_use) {
+           /* We start using the address immediately for data too.
+            * It's best to store it in st->peers now because we might
+            * go via SENTMSG5, WAIT, and a MSG0, straight into using
+            * the new key (without updating the data peer addrs). */
+           transport_resolve_complete(st,ca_use);
+       } else if (st->local_mobile) {
+           /* We can't let this rest because we may have a peer
+            * address which will break in the future. */
+           slog(st,LOG_SETUP_INIT,"resolution of %s failed: "
+                "abandoning key exchange",st->address);
+           enter_state_wait(st);
+       } else {
+           slog(st,LOG_SETUP_INIT,"resolution of %s failed: "
+                " continuing to use source address of peer's packets"
+                " for key exchange and ultimately data",
+                st->address);
+       }
+       break;
+    case SITE_RUN:
+       if (ca_use) {
+           slog(st,LOG_SETUP_INIT,"resolution of %s completed tardily,"
+                " updating peer address(es)",st->address);
+           transport_resolve_complete_tardy(st,ca_use);
+       } else if (st->local_mobile) {
+           /* Not very good.  We should queue (another) renegotiation
+            * so that we can update the peer address. */
+           st->key_renegotiate_time=st->now+st->wait_timeout;
+       } else {
+           slog(st,LOG_SETUP_INIT,"resolution of %s failed: "
+                " continuing to use source address of peer's packets",
+                st->address);
+       }
+       break;
+    case SITE_WAIT:
+    case SITE_STOP:
+       /* oh well */
+       break;
+    }
+}
+
+static bool_t initiate_key_setup(struct site *st, cstring_t reason,
+                                const struct comm_addr *prod_hint)
+{
+    /* Reentrancy hazard: can call enter_new_state/enter_state_* */
+    if (st->state!=SITE_RUN) return False;
+    slog(st,LOG_SETUP_INIT,"initiating key exchange (%s)",reason);
+    if (st->address) {
+       slog(st,LOG_SETUP_INIT,"resolving peer address");
+       return enter_state_resolve(st);
+    } else if (transport_compute_setupinit_peers(st,0,prod_hint)) {
+       return enter_new_state(st,SITE_SENTMSG1);
     }
+    slog(st,LOG_SETUP_INIT,"key exchange failed: no address for peer");
+    return False;
 }
 
 static void activate_new_key(struct site *st)
 {
     struct transform_inst_if *t;
 
-    t=st->current_transform;
-    st->current_transform=st->new_transform;
+    /* We have three transform instances, which we swap between old,
+       active and setup */
+    t=st->auxiliary_key.transform;
+    st->auxiliary_key.transform=st->current.transform;
+    st->current.transform=st->new_transform;
     st->new_transform=t;
+    dispose_transform(&st->new_transform);
 
-    t->delkey(t->st);
-    st->state=SITE_RUN;
     st->timeout=0;
-    st->current_valid=True;
-    st->current_key_timeout=st->now+st->key_lifetime;
-    st->peer=st->setup_peer;
-    st->peer_valid=True;
-    st->remote_session_id=st->setup_session_id;
+    st->auxiliary_is_new=0;
+    st->auxiliary_key.key_timeout=st->current.key_timeout;
+    st->current.key_timeout=st->now+st->key_lifetime;
+    st->renegotiate_key_time=st->now+st->key_renegotiate_time;
+    transport_peers_copy(st,&st->peers,&st->setup_peers);
+    st->current.remote_session_id=st->setup_session_id;
+
+    /* Compute the inter-site MTU.  This is min( our_mtu, their_mtu ).
+     * But their mtu be unspecified, in which case we just use ours. */
+    uint32_t intersite_mtu=
+       MIN(st->mtu_target, st->remote_adv_mtu ?: ~(uint32_t)0);
+    st->netlink->set_mtu(st->netlink->st,intersite_mtu);
+
+    slog(st,LOG_ACTIVATE_KEY,"new key activated"
+        " (mtu ours=%"PRId32" theirs=%"PRId32" intersite=%"PRId32")",
+        st->mtu_target, st->remote_adv_mtu, intersite_mtu);
+    enter_state_run(st);
+}
+
+static void delete_one_key(struct site *st, struct data_key *key,
+                          cstring_t reason, cstring_t which, uint32_t loglevel)
+{
+    if (!is_transform_valid(key->transform)) return;
+    if (reason) slog(st,loglevel,"%s deleted (%s)",which,reason);
+    dispose_transform(&key->transform);
+    key->key_timeout=0;
+}
+
+static void delete_keys(struct site *st, cstring_t reason, uint32_t loglevel)
+{
+    if (current_valid(st)) {
+       slog(st,loglevel,"session closed (%s)",reason);
 
-    slog(st,LOG_ACTIVATE_KEY,"new key activated");
+       delete_one_key(st,&st->current,0,0,0);
+       set_link_quality(st);
+    }
+    delete_one_key(st,&st->auxiliary_key,0,0,0);
 }
 
 static void state_assert(struct site *st, bool_t ok)
 {
-    if (!ok) fatal("state_assert\n");
+    if (!ok) fatal("site:state_assert");
 }
 
 static void enter_state_stop(struct site *st)
 {
     st->state=SITE_STOP;
     st->timeout=0;
-    st->current_transform->delkey(st->current_transform->st);
-    st->current_valid=False;
-    st->current_key_timeout=0;
-    
-    st->peer_valid=False;
-    
-    st->new_transform->delkey(st->new_transform->st);
+    delete_keys(st,"entering state STOP",LOG_TIMEOUT_KEY);
+    dispose_transform(&st->new_transform);
+}
+
+static void set_link_quality(struct site *st)
+{
+    uint32_t quality;
+    if (current_valid(st))
+       quality=LINK_QUALITY_UP;
+    else if (st->state==SITE_WAIT || st->state==SITE_STOP)
+       quality=LINK_QUALITY_DOWN;
+    else if (st->address)
+       quality=LINK_QUALITY_DOWN_CURRENT_ADDRESS;
+    else if (transport_peers_valid(&st->peers))
+       quality=LINK_QUALITY_DOWN_STALE_ADDRESS;
+    else
+       quality=LINK_QUALITY_DOWN;
+
+    st->netlink->set_quality(st->netlink->st,quality);
 }
 
 static void enter_state_run(struct site *st)
@@ -699,111 +1325,137 @@ static void enter_state_run(struct site *st)
     slog(st,LOG_STATE,"entering state RUN");
     st->state=SITE_RUN;
     st->timeout=0;
-    st->netlink->set_delivery(st->netlink->st,st->netlink_cid,True);
-    /* XXX get rid of key setup data */
-}
 
-static bool_t enter_state_resolve(struct site *st)
-{
-    state_assert(st,st->state==SITE_RUN);
-    slog(st,LOG_STATE,"entering state RESOLVE");
-    st->state=SITE_RESOLVE;
-    st->resolver->request(st->resolver->st,st->address,
-                         site_resolve_callback,st);
-    return True;
+    st->setup_session_id=0;
+    transport_peers_clear(st,&st->setup_peers);
+    memset(st->localN,0,NONCELEN);
+    memset(st->remoteN,0,NONCELEN);
+    dispose_transform(&st->new_transform);
+    memset(st->dhsecret,0,st->dh->len);
+    memset(st->sharedsecret,0,st->sharedsecretlen);
+    set_link_quality(st);
 }
 
-static bool_t enter_state_sentmsg1(struct site *st)
+static bool_t ensure_resolving(struct site *st)
 {
-    state_assert(st,st->state==SITE_RUN || st->state==SITE_RESOLVE);
-    slog(st,LOG_STATE,"entering state SENTMSG1");
-    if (generate_msg1(st) && send_msg(st)) {
-       st->state=SITE_SENTMSG1;
-       return True;
-    }
-    slog(st,LOG_ERROR,"error entering state SENTMSG1");
-    st->buffer.free=False; /* Can't tell which it was, but enter_state_wait()
-                             will do a BUF_FREE() */
-    enter_state_wait(st);
-    return False;
+    /* Reentrancy hazard: may call site_resolve_callback and hence
+     * enter_new_state, enter_state_* and generate_msg*. */
+    if (st->resolving)
+        return True;
+
+    assert(st->address);
+
+    /* resolver->request might reentrantly call site_resolve_callback
+     * which will clear st->resolving, so we need to set it beforehand
+     * rather than afterwards; also, it might return False, in which
+     * case we have to clear ->resolving again. */
+    st->resolving=True;
+    bool_t ok = st->resolver->request(st->resolver->st,st->address,
+                                     site_resolve_callback,st);
+    if (!ok)
+       st->resolving=False;
+
+    return ok;
 }
 
-static bool_t enter_state_sentmsg2(struct site *st)
+static bool_t enter_state_resolve(struct site *st)
 {
-    state_assert(st,st->state==SITE_RUN || st->state==SITE_RESOLVE ||
-                st->state==SITE_SENTMSG1 || st->state==SITE_WAIT);
-    slog(st,LOG_STATE,"entering state SENTMSG2");
-    if (generate_msg2(st) && send_msg(st)) {
-       st->state=SITE_SENTMSG2;
-       return True;
-    }
-    slog(st,LOG_ERROR,"error entering state SENTMSG2");
-    st->buffer.free=False;
-    enter_state_wait(st);
-    return False;
+    /* Reentrancy hazard!  See ensure_resolving. */
+    state_assert(st,st->state==SITE_RUN);
+    slog(st,LOG_STATE,"entering state RESOLVE");
+    st->state=SITE_RESOLVE;
+    return ensure_resolving(st);
 }
 
-static bool_t enter_state_sentmsg3(struct site *st)
+static bool_t enter_new_state(struct site *st, uint32_t next)
 {
-    state_assert(st,st->state==SITE_SENTMSG1);
-    slog(st,LOG_STATE,"entering state SENTMSG3");
-    BUF_FREE(&st->buffer); /* Free message 1 */
-    if (generate_msg3(st) && send_msg(st)) {
-       st->state=SITE_SENTMSG3;
-       return True;
+    bool_t (*gen)(struct site *st);
+    int r;
+
+    slog(st,LOG_STATE,"entering state %s",state_name(next));
+    switch(next) {
+    case SITE_SENTMSG1:
+       state_assert(st,st->state==SITE_RUN || st->state==SITE_RESOLVE);
+       gen=generate_msg1;
+       break;
+    case SITE_SENTMSG2:
+       state_assert(st,st->state==SITE_RUN || st->state==SITE_RESOLVE ||
+                    st->state==SITE_SENTMSG1 || st->state==SITE_WAIT);
+       gen=generate_msg2;
+       break;
+    case SITE_SENTMSG3:
+       state_assert(st,st->state==SITE_SENTMSG1);
+       BUF_FREE(&st->buffer);
+       gen=generate_msg3;
+       break;
+    case SITE_SENTMSG4:
+       state_assert(st,st->state==SITE_SENTMSG2);
+       BUF_FREE(&st->buffer);
+       gen=generate_msg4;
+       break;
+    case SITE_SENTMSG5:
+       state_assert(st,st->state==SITE_SENTMSG3);
+       BUF_FREE(&st->buffer);
+       gen=generate_msg5;
+       break;
+    case SITE_RUN:
+       state_assert(st,st->state==SITE_SENTMSG4);
+       BUF_FREE(&st->buffer);
+       gen=generate_msg6;
+       break;
+    default:
+       gen=NULL;
+       fatal("enter_new_state(%s): invalid new state",state_name(next));
+       break;
     }
-    slog(st,LOG_ERROR,"error entering state SENTMSG3");
-    st->buffer.free=False;
-    enter_state_wait(st);
-    return False;
-}
 
-static bool_t enter_state_sentmsg4(struct site *st)
-{
-    state_assert(st,st->state==SITE_SENTMSG2);
-    slog(st,LOG_STATE,"entering state SENTMSG4");
-    BUF_FREE(&st->buffer); /* Free message 2 */
-    if (generate_msg4(st) && send_msg(st)) {
-       st->state=SITE_SENTMSG4;
-       return True;
-    }
-    slog(st,LOG_ERROR,"error entering state SENTMSG4");
-    st->buffer.free=False;
-    enter_state_wait(st);
-    return False;
-}
+    if (hacky_par_start_failnow()) return False;
 
-static bool_t enter_state_sentmsg5(struct site *st)
-{
-    state_assert(st,st->state==SITE_SENTMSG3);
-    slog(st,LOG_STATE,"entering state SENTMSG5");
-    BUF_FREE(&st->buffer); /* Free message 3 */
+    r= gen(st) && send_msg(st);
 
-    if (generate_msg5(st) && send_msg(st)) {
-       st->state=SITE_SENTMSG5;
+    hacky_par_end(&r,
+                 st->setup_retries, st->setup_retry_interval,
+                 send_msg, st);
+    
+    if (r) {
+       st->state=next;
+       if (next==SITE_RUN) {
+           BUF_FREE(&st->buffer); /* Never reused */
+           st->timeout=0; /* Never retransmit */
+           activate_new_key(st);
+       }
        return True;
     }
-    slog(st,LOG_ERROR,"error entering state SENTMSG5");
-    st->buffer.free=False;
+    slog(st,LOG_ERROR,"error entering state %s",state_name(next));
+    st->buffer.free=False; /* Unconditionally use the buffer; it may be
+                             in either state, and enter_state_wait() will
+                             do a BUF_FREE() */
     enter_state_wait(st);
-    
     return False;
 }
 
-static bool_t send_msg6(struct site *st)
+/* msg7 tells our peer that we're about to forget our key */
+static bool_t send_msg7(struct site *st, cstring_t reason)
 {
-    state_assert(st,st->state==SITE_SENTMSG4);
-    slog(st,LOG_STATE,"entering state RUN after sending msg6");
-    BUF_FREE(&st->buffer); /* Free message 4 */
-    if (generate_msg6(st) && send_msg(st)) {
-       BUF_FREE(&st->buffer); /* Never reused */
-       st->timeout=0; /* Never retransmit */
-       activate_new_key(st);
+    cstring_t transform_err;
+
+    if (current_valid(st) && st->buffer.free
+       && transport_peers_valid(&st->peers)) {
+       BUF_ALLOC(&st->buffer,"site:MSG7");
+       buffer_init(&st->buffer,calculate_max_start_pad());
+       buf_append_uint32(&st->buffer,LABEL_MSG7);
+       buf_append_string(&st->buffer,reason);
+       if (call_transform_forwards(st, st->current.transform,
+                                   &st->buffer, &transform_err))
+           goto free_out;
+       buf_prepend_uint32(&st->buffer,LABEL_MSG0);
+       buf_prepend_uint32(&st->buffer,st->index);
+       buf_prepend_uint32(&st->buffer,st->current.remote_session_id);
+       transport_xmit(st,&st->peers,&st->buffer,True);
+       BUF_FREE(&st->buffer);
+    free_out:
        return True;
     }
-    slog(st,LOG_ERROR,"error entering state RUN after sending msg6");
-    st->buffer.free=False;
-    enter_state_wait(st);
     return False;
 }
 
@@ -815,15 +1467,48 @@ static void enter_state_wait(struct site *st)
     slog(st,LOG_STATE,"entering state WAIT");
     st->timeout=st->now+st->wait_timeout;
     st->state=SITE_WAIT;
-    st->peer_valid=False;
-    st->netlink->set_delivery(st->netlink->st,st->netlink_cid,False);
+    set_link_quality(st);
     BUF_FREE(&st->buffer); /* will have had an outgoing packet in it */
     /* XXX Erase keys etc. */
 }
 
+static void generate_prod(struct site *st, struct buffer_if *buf)
+{
+    buffer_init(buf,0);
+    buf_append_uint32(buf,0);
+    buf_append_uint32(buf,0);
+    buf_append_uint32(buf,LABEL_PROD);
+    buf_append_string(buf,st->localname);
+    buf_append_string(buf,st->remotename);
+}
+
+static void generate_send_prod(struct site *st,
+                              const struct comm_addr *source)
+{
+    if (!st->allow_send_prod) return; /* too soon */
+    if (!(st->state==SITE_RUN || st->state==SITE_RESOLVE ||
+         st->state==SITE_WAIT)) return; /* we'd ignore peer's MSG1 */
+
+    slog(st,LOG_SETUP_INIT,"prodding peer for key exchange");
+    st->allow_send_prod=0;
+    generate_prod(st,&st->scratch);
+    dump_packet(st,&st->scratch,source,False);
+    source->comm->sendmsg(source->comm->st, &st->scratch, source);
+}
+
+static inline void site_settimeout(uint64_t timeout, int *timeout_io)
+{
+    if (timeout) {
+       int64_t offset=timeout-*now;
+       if (offset<0) offset=0;
+       if (offset>INT_MAX) offset=INT_MAX;
+       if (*timeout_io<0 || offset<*timeout_io)
+           *timeout_io=offset;
+    }
+}
+
 static int site_beforepoll(void *sst, struct pollfd *fds, int *nfds_io,
-                          int *timeout_io, const struct timeval *tv_now,
-                          uint64_t *now)
+                          int *timeout_io)
 {
     struct site *st=sst;
 
@@ -831,201 +1516,261 @@ static int site_beforepoll(void *sst, struct pollfd *fds, int *nfds_io,
     st->now=*now;
 
     /* Work out when our next timeout is. The earlier of 'timeout' or
-       'current_key_timeout'. A stored value of '0' indicates no timeout
+       'current.key_timeout'. A stored value of '0' indicates no timeout
        active. */
-    if (st->timeout && st->timeout-*now < *timeout_io) {
-       *timeout_io=st->timeout-*now;
-    }
-
-    if (st->current_key_timeout && st->current_key_timeout-*now < *timeout_io)
-       *timeout_io=st->current_key_timeout-*now;
+    site_settimeout(st->timeout, timeout_io);
+    site_settimeout(st->current.key_timeout, timeout_io);
+    site_settimeout(st->auxiliary_key.key_timeout, timeout_io);
 
     return 0; /* success */
 }
 
+static void check_expiry(struct site *st, struct data_key *key,
+                        const char *which)
+{
+    if (key->key_timeout && *now>key->key_timeout) {
+       delete_one_key(st,key,"maximum life exceeded",which,LOG_TIMEOUT_KEY);
+    }
+}
+
 /* NB site_afterpoll will be called before site_beforepoll is ever called */
-static void site_afterpoll(void *sst, struct pollfd *fds, int nfds,
-                          const struct timeval *tv_now, uint64_t *now)
+static void site_afterpoll(void *sst, struct pollfd *fds, int nfds)
 {
     struct site *st=sst;
 
     st->now=*now;
     if (st->timeout && *now>st->timeout) {
-       /* Do stuff */
        st->timeout=0;
-       if (st->state>=SITE_SENTMSG1 && st->state<=SITE_SENTMSG5)
-           send_msg(st);
-       else if (st->state==SITE_WAIT) {
+       if (st->state>=SITE_SENTMSG1 && st->state<=SITE_SENTMSG5) {
+           if (!hacky_par_start_failnow())
+               send_msg(st);
+       } else if (st->state==SITE_WAIT) {
            enter_state_run(st);
        } else {
            slog(st,LOG_ERROR,"site_afterpoll: unexpected timeout, state=%d",
                 st->state);
        }
     }
-    if (st->current_key_timeout && *now>st->current_key_timeout) {
-       slog(st,LOG_TIMEOUT_KEY,"maximum key life exceeded; session closed");
-       st->current_valid=False;
-       st->current_transform->delkey(st->current_transform->st);
-       st->current_key_timeout=0;
-    }
+    check_expiry(st,&st->current,"current key");
+    check_expiry(st,&st->auxiliary_key,"auxiliary key");
 }
 
 /* This function is called by the netlink device to deliver packets
    intended for the remote network. The packet is in "raw" wire
    format, but is guaranteed to be word-aligned. */
-static void site_outgoing(void *sst, void *cid, struct buffer_if *buf)
+static void site_outgoing(void *sst, struct buffer_if *buf)
 {
     struct site *st=sst;
-    string_t transform_err;
+    cstring_t transform_err;
     
     if (st->state==SITE_STOP) {
        BUF_FREE(buf);
        return;
     }
 
+    st->allow_send_prod=1;
+
     /* In all other states we consider delivering the packet if we have
        a valid key and a valid address to send it to. */
-    if (st->current_valid && st->peer_valid) {
+    if (current_valid(st) && transport_peers_valid(&st->peers)) {
        /* Transform it and send it */
-       *(uint32_t *)buf_prepend(buf,4)=LABEL_MSG9;
-       st->current_transform->forwards(st->current_transform->st,
-                                       buf, &transform_err);
-       *(uint32_t *)buf_prepend(buf,4)=LABEL_MSG0;
-       *(uint32_t *)buf_prepend(buf,4)=(uint32_t)st;
-       *(uint32_t *)buf_prepend(buf,4)=st->remote_session_id;
-       st->comm->sendmsg(st->comm->st,buf,&st->peer);
+       if (buf->size>0) {
+           buf_prepend_uint32(buf,LABEL_MSG9);
+           if (call_transform_forwards(st, st->current.transform,
+                                       buf, &transform_err))
+               goto free_out;
+           buf_prepend_uint32(buf,LABEL_MSG0);
+           buf_prepend_uint32(buf,st->index);
+           buf_prepend_uint32(buf,st->current.remote_session_id);
+           transport_xmit(st,&st->peers,buf,False);
+       }
+    free_out:
        BUF_FREE(buf);
        return;
     }
 
-    if (st->state==SITE_RUN) {
-       BUF_FREE(buf); /* We throw the outgoing packet away */
-       slog(st,LOG_SETUP_INIT,"initiating key exchange");
-       enter_state_resolve(st);
-       return;
-    }
-
-    /* Otherwise we're in the middle of key setup or a wait - just
-       throw the outgoing packet away */
-    slog(st,LOG_DROP,"discarding outgoing packet");
+    slog(st,LOG_DROP,"discarding outgoing packet of size %d",buf->size);
     BUF_FREE(buf);
-    return;
+    initiate_key_setup(st,"outgoing packet",0);
+}
+
+static bool_t named_for_us(struct site *st, const struct buffer_if *buf_in,
+                          uint32_t type, struct msg *m)
+    /* For packets which are identified by the local and remote names.
+     * If it has our name and our peer's name in it it's for us. */
+{
+    struct buffer_if buf[1];
+    buffer_readonly_clone(buf,buf_in);
+    return unpick_msg(st,type,buf,m)
+       && name_matches(&m->remote,st->remotename)
+       && name_matches(&m->local,st->localname);
 }
 
 /* This function is called by the communication device to deliver
-   packets from our peers. */
+   packets from our peers.
+   It should return True if the packet is recognised as being for
+   this current site instance (and should therefore not be processed
+   by other sites), even if the packet was otherwise ignored. */
 static bool_t site_incoming(void *sst, struct buffer_if *buf,
-                           struct sockaddr_in *source)
+                           const struct comm_addr *source)
 {
     struct site *st=sst;
-    uint32_t dest=*(uint32_t *)buf->start;
-
-    if (dest==0) {
-       if (buf->size<(st->setupsiglen+8+NONCELEN)) return False;
-       /* It could be for any site - it should have LABEL_MSG1 and
-          might have our name and our peer's name in it */
-       if (memcmp(buf->start+8,st->setupsig,st->setupsiglen)==0) {
-           dump_packet(st,buf,source,True);
-           /* It's addressed to us. Decide what to do about it. */
-           if (st->state==SITE_RUN || st->state==SITE_RESOLVE ||
-               st->state==SITE_WAIT) {
-               /* We should definitely process it */
-               if (process_msg1(st,buf,source)) {
-                   slog(st,LOG_SETUP_INIT,"key setup initiated by peer");
-                   enter_state_sentmsg2(st);
-               } else {
-                   slog(st,LOG_ERROR,"failed to process incoming msg1");
-               }
+
+    if (buf->size < 12) return False;
+
+    uint32_t dest=get_uint32(buf->start);
+    uint32_t msgtype=get_uint32(buf->start+8);
+    struct msg named_msg;
+
+    if (msgtype==LABEL_MSG1) {
+       if (!named_for_us(st,buf,msgtype,&named_msg))
+           return False;
+       /* It's a MSG1 addressed to us. Decide what to do about it. */
+       dump_packet(st,buf,source,True);
+       if (st->state==SITE_RUN || st->state==SITE_RESOLVE ||
+           st->state==SITE_WAIT) {
+           /* We should definitely process it */
+           transport_record_peer(st,&st->setup_peers,source,"msg1");
+           if (process_msg1(st,buf,source,&named_msg)) {
+               slog(st,LOG_SETUP_INIT,"key setup initiated by peer");
+               bool_t entered=enter_new_state(st,SITE_SENTMSG2);
+               if (entered && st->address && st->local_mobile)
+                   /* We must do this as the very last thing, because
+                      the resolver callback might reenter us. */
+                   ensure_resolving(st);
+           } else {
+               slog(st,LOG_ERROR,"failed to process incoming msg1");
+           }
+           BUF_FREE(buf);
+           return True;
+       } else if (st->state==SITE_SENTMSG1) {
+           /* We've just sent a message 1! They may have crossed on
+              the wire. If we have priority then we ignore the
+              incoming one, otherwise we process it as usual. */
+           if (st->setup_priority) {
                BUF_FREE(buf);
+               slog(st,LOG_DUMP,"crossed msg1s; we are higher "
+                    "priority => ignore incoming msg1");
                return True;
-           }
-           if (st->state==SITE_SENTMSG1) {
-               /* We've just sent a message 1! They may have crossed on
-                  the wire. If we have priority then we ignore the
-                  incoming one, otherwise we process it as usual. */
-               if (st->setup_priority) {
-                   BUF_FREE(buf);
-                   slog(st,LOG_DUMP,"crossed msg1s; we are higher "
-                        "priority => ignore incoming msg1");
-                   return True;
+           } else {
+               slog(st,LOG_DUMP,"crossed msg1s; we are lower "
+                    "priority => use incoming msg1");
+               if (process_msg1(st,buf,source,&named_msg)) {
+                   BUF_FREE(&st->buffer); /* Free our old message 1 */
+                   transport_setup_msgok(st,source);
+                   enter_new_state(st,SITE_SENTMSG2);
                } else {
-                   slog(st,LOG_DUMP,"crossed msg1s; we are lower "
-                        "priority => use incoming msg1");
-                   if (process_msg1(st,buf,source)) {
-                       BUF_FREE(&st->buffer); /* Free our old message 1 */
-                       enter_state_sentmsg2(st);
-                   } else {
-                       slog(st,LOG_ERROR,"failed to process an incoming "
-                            "crossed msg1 (we have low priority)");
-                   }
-                   BUF_FREE(buf);
-                   return True;
+                   slog(st,LOG_ERROR,"failed to process an incoming "
+                        "crossed msg1 (we have low priority)");
                }
+               BUF_FREE(buf);
+               return True;
            }
-           /* The message 1 was received at an unexpected stage of the
-              key setup. XXX POLICY - what do we do? */
-           slog(st,LOG_UNEXPECTED,"unexpected incoming message 1");
-           BUF_FREE(buf);
-           return True;
        }
-       return False; /* Not for us. */
+       /* The message 1 was received at an unexpected stage of the
+          key setup. XXX POLICY - what do we do? */
+       slog(st,LOG_UNEXPECTED,"unexpected incoming message 1");
+       BUF_FREE(buf);
+       return True;
+    }
+    if (msgtype==LABEL_PROD) {
+       if (!named_for_us(st,buf,msgtype,&named_msg))
+           return False;
+       dump_packet(st,buf,source,True);
+       if (st->state!=SITE_RUN) {
+           slog(st,LOG_DROP,"ignoring PROD when not in state RUN");
+       } else if (current_valid(st)) {
+           slog(st,LOG_DROP,"ignoring PROD when we think we have a key");
+       } else {
+           initiate_key_setup(st,"peer sent PROD packet",source);
+       }
+       BUF_FREE(buf);
+       return True;
     }
-    if (dest==(uint32_t)st) {
-       uint32_t msgtype=*(uint32_t *)(buf->start+8);
+    if (dest==st->index) {
        /* Explicitly addressed to us */
        if (msgtype!=LABEL_MSG0) dump_packet(st,buf,source,True);
        switch (msgtype) {
+       case LABEL_NAK:
+           /* If the source is our current peer then initiate a key setup,
+              because our peer's forgotten the key */
+           if (get_uint32(buf->start+4)==st->current.remote_session_id) {
+               bool_t initiated;
+               initiated = initiate_key_setup(st,"received a NAK",0);
+               if (!initiated) generate_send_prod(st,source);
+           } else {
+               slog(st,LOG_SEC,"bad incoming NAK");
+           }
+           break;
        case LABEL_MSG0:
            process_msg0(st,buf,source);
            break;
        case LABEL_MSG1:
            /* Setup packet: should not have been explicitly addressed
               to us */
-           slog(st,LOG_SECURITY,"incoming explicitly addressed msg1");
+           slog(st,LOG_SEC,"incoming explicitly addressed msg1");
            break;
        case LABEL_MSG2:
            /* Setup packet: expected only in state SENTMSG1 */
            if (st->state!=SITE_SENTMSG1) {
                slog(st,LOG_UNEXPECTED,"unexpected MSG2");
-           } else if (process_msg2(st,buf,source))
-               enter_state_sentmsg3(st);
-           else {
-               slog(st,LOG_SECURITY,"invalid MSG2");
+           } else if (process_msg2(st,buf,source)) {
+               transport_setup_msgok(st,source);
+               enter_new_state(st,SITE_SENTMSG3);
+           } else {
+               slog(st,LOG_SEC,"invalid MSG2");
            }
            break;
        case LABEL_MSG3:
+       case LABEL_MSG3BIS:
            /* Setup packet: expected only in state SENTMSG2 */
            if (st->state!=SITE_SENTMSG2) {
                slog(st,LOG_UNEXPECTED,"unexpected MSG3");
-           } else if (process_msg3(st,buf,source))
-               enter_state_sentmsg4(st);
-           else {
-               slog(st,LOG_SECURITY,"invalid MSG3");
+           } else if (process_msg3(st,buf,source,msgtype)) {
+               transport_setup_msgok(st,source);
+               enter_new_state(st,SITE_SENTMSG4);
+           } else {
+               slog(st,LOG_SEC,"invalid MSG3");
            }
            break;
        case LABEL_MSG4:
            /* Setup packet: expected only in state SENTMSG3 */
            if (st->state!=SITE_SENTMSG3) {
                slog(st,LOG_UNEXPECTED,"unexpected MSG4");
-           } else if (process_msg4(st,buf,source))
-               enter_state_sentmsg5(st);
-           else {
-               slog(st,LOG_SECURITY,"invalid MSG4");
+           } else if (process_msg4(st,buf,source)) {
+               transport_setup_msgok(st,source);
+               enter_new_state(st,SITE_SENTMSG5);
+           } else {
+               slog(st,LOG_SEC,"invalid MSG4");
            }
            break;
        case LABEL_MSG5:
            /* Setup packet: expected only in state SENTMSG4 */
            /* (may turn up in state RUN if our return MSG6 was lost
               and the new key has already been activated. In that
-              case we should treat it as an ordinary PING packet. We
-              can't pass it to process_msg5() because the
-              new_transform will now be null. XXX) */
-           if (st->state!=SITE_SENTMSG4) {
-               slog(st,LOG_UNEXPECTED,"unexpected MSG5");
-           } else if (process_msg5(st,buf,source)) {
-               send_msg6(st);
+              case we discard it. The peer will realise that we
+              are using the new key when they see our data packets.
+              Until then the peer's data packets to us get discarded. */
+           if (st->state==SITE_SENTMSG4) {
+               if (process_msg5(st,buf,source,st->new_transform)) {
+                   transport_setup_msgok(st,source);
+                   enter_new_state(st,SITE_RUN);
+               } else {
+                   slog(st,LOG_SEC,"invalid MSG5");
+               }
+           } else if (st->state==SITE_RUN) {
+               if (process_msg5(st,buf,source,st->current.transform)) {
+                   slog(st,LOG_DROP,"got MSG5, retransmitting MSG6");
+                   transport_setup_msgok(st,source);
+                   create_msg6(st,st->current.transform,
+                               st->current.remote_session_id);
+                   transport_xmit(st,&st->peers,&st->buffer,True);
+                   BUF_FREE(&st->buffer);
+               } else {
+                   slog(st,LOG_SEC,"invalid MSG5 (in state RUN)");
+               }
            } else {
-               slog(st,LOG_SECURITY,"invalid MSG5");
+               slog(st,LOG_UNEXPECTED,"unexpected MSG5");
            }
            break;
        case LABEL_MSG6:
@@ -1034,17 +1779,14 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
                slog(st,LOG_UNEXPECTED,"unexpected MSG6");
            } else if (process_msg6(st,buf,source)) {
                BUF_FREE(&st->buffer); /* Free message 5 */
+               transport_setup_msgok(st,source);
                activate_new_key(st);
            } else {
-               slog(st,LOG_SECURITY,"invalid MSG6");
+               slog(st,LOG_SEC,"invalid MSG6");
            }
            break;
-       case LABEL_MSG8:
-           /* NAK packet: enter state where we ping and check for response */
-           slog(st,LOG_ERROR,"received a NAK");
-           break;
        default:
-           slog(st,LOG_SECURITY,"received message of unknown type 0x%08x",
+           slog(st,LOG_SEC,"received message of unknown type 0x%08x",
                 msgtype);
            break;
        }
@@ -1062,12 +1804,22 @@ static void site_control(void *vst, bool_t run)
     else enter_state_stop(st);
 }
 
+static void site_phase_hook(void *sst, uint32_t newphase)
+{
+    struct site *st=sst;
+
+    /* The program is shutting down; tell our peer */
+    send_msg7(st,"shutting down");
+}
+
 static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
                          list_t *args)
 {
+    static uint32_t index_sequence;
     struct site *st;
     item_t *item;
     dict_t *dict;
+    int i;
 
     st=safe_malloc(sizeof(*st),"site_apply");
 
@@ -1085,89 +1837,338 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
        cfgfatal(loc,"site","parameter must be a dictionary\n");
     
     dict=item->data.dict;
-    st->netlink=find_cl_if(dict,"netlink",CL_NETLINK,True,"site",loc);
-    st->comm=find_cl_if(dict,"comm",CL_COMM,True,"site",loc);
+    st->localname=dict_read_string(dict, "local-name", True, "site", loc);
+    st->remotename=dict_read_string(dict, "name", True, "site", loc);
+
+    st->peer_mobile=dict_read_bool(dict,"mobile",False,"site",loc,False);
+    st->local_mobile=
+       dict_read_bool(dict,"local-mobile",False,"site",loc,False);
+
+    /* Sanity check (which also allows the 'sites' file to include
+       site() closures for all sites including our own): refuse to
+       talk to ourselves */
+    if (strcmp(st->localname,st->remotename)==0) {
+       Message(M_DEBUG,"site %s: local-name==name -> ignoring this site\n",
+               st->localname);
+       if (st->peer_mobile != st->local_mobile)
+           cfgfatal(loc,"site","site %s's peer-mobile=%d"
+                   " but our local-mobile=%d\n",
+                   st->localname, st->peer_mobile, st->local_mobile);
+       free(st);
+       return NULL;
+    }
+    if (st->peer_mobile && st->local_mobile) {
+       Message(M_WARNING,"site %s: site is mobile but so are we"
+               " -> ignoring this site\n", st->remotename);
+       free(st);
+       return NULL;
+    }
+
+    assert(index_sequence < 0xffffffffUL);
+    st->index = ++index_sequence;
+    st->local_capabilities = 0;
+    st->netlink=find_cl_if(dict,"link",CL_NETLINK,True,"site",loc);
+
+#define GET_CLOSURE_LIST(dictkey,things,nthings,CL_TYPE) do{           \
+    list_t *things##_cfg=dict_lookup(dict,dictkey);                    \
+    if (!things##_cfg)                                                 \
+       cfgfatal(loc,"site","closure list \"%s\" not found\n",dictkey); \
+    st->nthings=list_length(things##_cfg);                             \
+    st->things=safe_malloc_ary(sizeof(*st->things),st->nthings,dictkey "s"); \
+    assert(st->nthings);                                               \
+    for (i=0; i<st->nthings; i++) {                                    \
+       item_t *item=list_elem(things##_cfg,i);                         \
+       if (item->type!=t_closure)                                      \
+           cfgfatal(loc,"site","%s is not a closure\n",dictkey);       \
+       closure_t *cl=item->data.closure;                               \
+       if (cl->type!=CL_TYPE)                                          \
+           cfgfatal(loc,"site","%s closure wrong type\n",dictkey);     \
+       st->things[i]=cl->interface;                                    \
+    }                                                                  \
+}while(0)
+
+    GET_CLOSURE_LIST("comm",comms,ncomms,CL_COMM);
+
     st->resolver=find_cl_if(dict,"resolver",CL_RESOLVER,True,"site",loc);
     st->log=find_cl_if(dict,"log",CL_LOG,True,"site",loc);
     st->random=find_cl_if(dict,"random",CL_RANDOMSRC,True,"site",loc);
 
-    st->localname=dict_read_string(dict, "local-name", True, "site", loc);
     st->privkey=find_cl_if(dict,"local-key",CL_RSAPRIVKEY,True,"site",loc);
-    st->remoteport=dict_read_number(dict,"port",True,"site",loc,0);
-
-    st->remotename=dict_read_string(dict, "name", True, "site", loc);
     st->address=dict_read_string(dict, "address", False, "site", loc);
-    dict_read_subnet_list(dict, "networks", True, "site", loc,
-                         &st->remotenets);
+    if (st->address)
+       st->remoteport=dict_read_number(dict,"port",True,"site",loc,0);
+    else st->remoteport=0;
     st->pubkey=find_cl_if(dict,"key",CL_RSAPUBKEY,True,"site",loc);
 
-    st->transform=
-       find_cl_if(dict,"transform",CL_TRANSFORM,True,"site",loc);
+    GET_CLOSURE_LIST("transform",transforms,ntransforms,CL_TRANSFORM);
 
     st->dh=find_cl_if(dict,"dh",CL_DH,True,"site",loc);
     st->hash=find_cl_if(dict,"hash",CL_HASH,True,"site",loc);
 
-    st->key_lifetime=dict_read_number(dict,"key-lifetime",
-                                     False,"site",loc,DEFAULT_KEY_LIFETIME);
-    st->setup_retries=dict_read_number(dict,"setup-retries",
-                                      False,"site",loc,DEFAULT_SETUP_RETRIES);
-    st->setup_timeout=dict_read_number(dict,"setup-timeout",
-                                      False,"site",loc,DEFAULT_SETUP_TIMEOUT);
-    st->wait_timeout=dict_read_number(dict,"wait-time",
-                                     False,"site",loc,DEFAULT_WAIT_TIME);
-    /* XXX should be configurable */
-    st->log_events=LOG_SECURITY|LOG_ERROR|
-       LOG_ACTIVATE_KEY|LOG_TIMEOUT_KEY|LOG_SETUP_INIT|LOG_SETUP_TIMEOUT;
+#define DEFAULT(D) (st->peer_mobile || st->local_mobile        \
+                    ? DEFAULT_MOBILE_##D : DEFAULT_##D)
+#define CFG_NUMBER(k,D) dict_read_number(dict,(k),False,"site",loc,DEFAULT(D));
+
+    st->key_lifetime=         CFG_NUMBER("key-lifetime",  KEY_LIFETIME);
+    st->setup_retries=        CFG_NUMBER("setup-retries", SETUP_RETRIES);
+    st->setup_retry_interval= CFG_NUMBER("setup-timeout", SETUP_RETRY_INTERVAL);
+    st->wait_timeout=         CFG_NUMBER("wait-time",     WAIT_TIME);
+    st->mtu_target= dict_read_number(dict,"mtu-target",False,"site",loc,0);
+
+    st->mobile_peer_expiry= dict_read_number(
+       dict,"mobile-peer-expiry",False,"site",loc,DEFAULT_MOBILE_PEER_EXPIRY);
+
+    st->transport_peers_max= !st->peer_mobile ? 1 : dict_read_number(
+       dict,"mobile-peers-max",False,"site",loc,DEFAULT_MOBILE_PEERS_MAX);
+    if (st->transport_peers_max<1 ||
+       st->transport_peers_max>=MAX_MOBILE_PEERS_MAX) {
+       cfgfatal(loc,"site","mobile-peers-max must be in range 1.."
+                STRING(MAX_MOBILE_PEERS_MAX) "\n");
+    }
+
+    if (st->key_lifetime < DEFAULT(KEY_RENEGOTIATE_GAP)*2)
+       st->key_renegotiate_time=st->key_lifetime/2;
+    else
+       st->key_renegotiate_time=st->key_lifetime-DEFAULT(KEY_RENEGOTIATE_GAP);
+    st->key_renegotiate_time=dict_read_number(
+       dict,"renegotiate-time",False,"site",loc,st->key_renegotiate_time);
+    if (st->key_renegotiate_time > st->key_lifetime) {
+       cfgfatal(loc,"site",
+                "renegotiate-time must be less than key-lifetime\n");
+    }
+
+    st->log_events=string_list_to_word(dict_lookup(dict,"log-events"),
+                                      log_event_table,"site");
+
+    st->resolving=False;
+    st->allow_send_prod=0;
 
     st->tunname=safe_malloc(strlen(st->localname)+strlen(st->remotename)+5,
                            "site_apply");
     sprintf(st->tunname,"%s<->%s",st->localname,st->remotename);
 
     /* The information we expect to see in incoming messages of type 1 */
-    st->setupsiglen=strlen(st->remotename)+strlen(st->localname)+8;
-    st->setupsig=safe_malloc(st->setupsiglen,"site_apply");
-    *(uint32_t *)&(st->setupsig[0])=LABEL_MSG1;
-    *(uint16_t *)&(st->setupsig[4])=htons(strlen(st->remotename));
-    memcpy(&st->setupsig[6],st->remotename,strlen(st->remotename));
-    *(uint16_t *)&(st->setupsig[6+strlen(st->remotename)])=
-       htons(strlen(st->localname));
-    memcpy(&st->setupsig[8+strlen(st->remotename)],st->localname,
-          strlen(st->localname));
+    /* fixme: lots of unchecked overflows here, but the results are only
+       corrupted packets rather than undefined behaviour */
     st->setup_priority=(strcmp(st->localname,st->remotename)>0);
 
     buffer_new(&st->buffer,SETUP_BUFFER_LEN);
 
+    buffer_new(&st->scratch,SETUP_BUFFER_LEN);
+    BUF_ALLOC(&st->scratch,"site:scratch");
+
     /* We are interested in poll(), but only for timeouts. We don't have
        any fds of our own. */
     register_for_poll(st, site_beforepoll, site_afterpoll, 0, "site");
     st->timeout=0;
 
-    st->current_valid=False;
-    st->current_key_timeout=0;
-    st->peer_valid=False;
+    st->remote_capabilities=0;
+    st->chosen_transform=0;
+    st->current.key_timeout=0;
+    st->auxiliary_key.key_timeout=0;
+    transport_peers_clear(st,&st->peers);
+    transport_peers_clear(st,&st->setup_peers);
     /* XXX mlock these */
     st->dhsecret=safe_malloc(st->dh->len,"site:dhsecret");
-    st->sharedsecret=safe_malloc(st->transform->keylen,"site:sharedsecret");
+    st->sharedsecretlen=st->sharedsecretallocd=0;
+    st->sharedsecret=0;
+
+    for (i=0; i<st->ntransforms; i++) {
+       struct transform_if *ti=st->transforms[i];
+       uint32_t capbit = 1UL << ti->capab_transformnum;
+       if (st->local_capabilities & capbit)
+           slog(st,LOG_ERROR,"transformnum capability bit"
+                " %d (%#"PRIx32") reused", ti->capab_transformnum, capbit);
+       st->local_capabilities |= capbit;
+    }
 
     /* We need to register the remote networks with the netlink device */
-    st->netlink_cid=st->netlink->regnets(st->netlink->st, &st->remotenets,
-                                        site_outgoing, st,
-                                        st->transform->max_start_pad+(4*4),
-                                        st->transform->max_end_pad,
-                                        st->tunname);
-
-    st->comm->request_notify(st->comm->st, st, site_incoming);
+    uint32_t netlink_mtu; /* local virtual interface mtu */
+    st->netlink->reg(st->netlink->st, site_outgoing, st, &netlink_mtu);
+    if (!st->mtu_target)
+       st->mtu_target=netlink_mtu;
+    
+    for (i=0; i<st->ncomms; i++)
+       st->comms[i]->request_notify(st->comms[i]->st, st, site_incoming);
 
-    st->current_transform=st->transform->create(st->transform->st);
-    st->new_transform=st->transform->create(st->transform->st);
+    st->current.transform=0;
+    st->auxiliary_key.transform=0;
+    st->new_transform=0;
+    st->auxiliary_is_new=0;
 
     enter_state_stop(st);
 
+    add_hook(PHASE_SHUTDOWN,site_phase_hook,st);
+
     return new_closure(&st->cl);
 }
 
-init_module site_module;
 void site_module(dict_t *dict)
 {
     add_closure(dict,"site",site_apply);
 }
+
+
+/***** TRANSPORT PEERS definitions *****/
+
+static void transport_peers_debug(struct site *st, transport_peers *dst,
+                                 const char *didwhat,
+                                 int nargs, const struct comm_addr *args,
+                                 size_t stride) {
+    int i;
+    char *argp;
+
+    if (!(st->log_events & LOG_PEER_ADDRS))
+       return; /* an optimisation */
+
+    slog(st, LOG_PEER_ADDRS, "peers (%s) %s nargs=%d => npeers=%d",
+        (dst==&st->peers ? "data" :
+         dst==&st->setup_peers ? "setup" : "UNKNOWN"),
+        didwhat, nargs, dst->npeers);
+
+    for (i=0, argp=(void*)args;
+        i<nargs;
+        i++, (argp+=stride?stride:sizeof(*args))) {
+       const struct comm_addr *ca=(void*)argp;
+       slog(st, LOG_PEER_ADDRS, " args: addrs[%d]=%s",
+            i, comm_addr_to_string(ca));
+    }
+    for (i=0; i<dst->npeers; i++) {
+       struct timeval diff;
+       timersub(tv_now,&dst->peers[i].last,&diff);
+       const struct comm_addr *ca=&dst->peers[i].addr;
+       slog(st, LOG_PEER_ADDRS, " peers: addrs[%d]=%s T-%ld.%06ld",
+            i, comm_addr_to_string(ca),
+            (unsigned long)diff.tv_sec, (unsigned long)diff.tv_usec);
+    }
+}
+
+static int transport_peer_compar(const void *av, const void *bv) {
+    const transport_peer *a=av;
+    const transport_peer *b=bv;
+    /* put most recent first in the array */
+    if (timercmp(&a->last, &b->last, <)) return +1;
+    if (timercmp(&a->last, &b->last, >)) return -11;
+    return 0;
+}
+
+static void transport_peers_expire(struct site *st, transport_peers *peers) {
+    /* peers must be sorted first */
+    int previous_peers=peers->npeers;
+    struct timeval oldest;
+    oldest.tv_sec  = tv_now->tv_sec - st->mobile_peer_expiry;
+    oldest.tv_usec = tv_now->tv_usec;
+    while (peers->npeers>1 &&
+          timercmp(&peers->peers[peers->npeers-1].last, &oldest, <))
+       peers->npeers--;
+    if (peers->npeers != previous_peers)
+       transport_peers_debug(st,peers,"expire", 0,0,0);
+}
+
+static void transport_record_peer(struct site *st, transport_peers *peers,
+                                 const struct comm_addr *addr, const char *m) {
+    int slot, changed=0;
+
+    for (slot=0; slot<peers->npeers; slot++)
+       if (!memcmp(&peers->peers[slot].addr, addr, sizeof(*addr)))
+           goto found;
+
+    changed=1;
+    if (peers->npeers==st->transport_peers_max)
+       slot=st->transport_peers_max-1;
+    else
+       slot=peers->npeers++;
+
+ found:
+    peers->peers[slot].addr=*addr;
+    peers->peers[slot].last=*tv_now;
+
+    if (peers->npeers>1)
+       qsort(peers->peers, peers->npeers,
+             sizeof(*peers->peers), transport_peer_compar);
+
+    if (changed || peers->npeers!=1)
+       transport_peers_debug(st,peers,m, 1,addr,0);
+    transport_peers_expire(st, peers);
+}
+
+static bool_t transport_compute_setupinit_peers(struct site *st,
+        const struct comm_addr *configured_addr /* 0 if none or not found */,
+        const struct comm_addr *prod_hint_addr /* 0 if none */) {
+
+    if (!configured_addr && !prod_hint_addr &&
+       !transport_peers_valid(&st->peers))
+       return False;
+
+    slog(st,LOG_SETUP_INIT,
+        "using:%s%s %d old peer address(es)",
+        configured_addr ? " configured address;" : "",
+        prod_hint_addr ? " PROD hint address;" : "",
+        st->peers.npeers);
+
+    /* Non-mobile peers have st->peers.npeers==0 or ==1, since they
+     * have transport_peers_max==1.  The effect is that this code
+     * always uses the configured address if supplied, or otherwise
+     * the address of the incoming PROD, or the existing data peer if
+     * one exists; this is as desired. */
+
+    transport_peers_copy(st,&st->setup_peers,&st->peers);
+
+    if (prod_hint_addr)
+       transport_record_peer(st,&st->setup_peers,prod_hint_addr,"prod");
+
+    if (configured_addr)
+       transport_record_peer(st,&st->setup_peers,configured_addr,"setupinit");
+
+    assert(transport_peers_valid(&st->setup_peers));
+    return True;
+}
+
+static void transport_setup_msgok(struct site *st, const struct comm_addr *a) {
+    if (st->peer_mobile)
+       transport_record_peer(st,&st->setup_peers,a,"setupmsg");
+}
+static void transport_data_msgok(struct site *st, const struct comm_addr *a) {
+    if (st->peer_mobile)
+       transport_record_peer(st,&st->peers,a,"datamsg");
+}
+
+static int transport_peers_valid(transport_peers *peers) {
+    return peers->npeers;
+}
+static void transport_peers_clear(struct site *st, transport_peers *peers) {
+    peers->npeers= 0;
+    transport_peers_debug(st,peers,"clear",0,0,0);
+}
+static void transport_peers_copy(struct site *st, transport_peers *dst,
+                                const transport_peers *src) {
+    dst->npeers=src->npeers;
+    memcpy(dst->peers, src->peers, sizeof(*dst->peers) * dst->npeers);
+    transport_peers_debug(st,dst,"copy",
+                         src->npeers, &src->peers->addr, sizeof(*src->peers));
+}
+
+static void transport_resolve_complete(struct site *st,
+                                      const struct comm_addr *ca_use) {
+    transport_record_peer(st,&st->peers,ca_use,"resolved data");
+    transport_record_peer(st,&st->setup_peers,ca_use,"resolved setup");
+}
+
+static void transport_resolve_complete_tardy(struct site *st,
+                                            const struct comm_addr *ca_use) {
+    transport_record_peer(st,&st->peers,ca_use,"resolved tardily");
+}
+
+void transport_xmit(struct site *st, transport_peers *peers,
+                   struct buffer_if *buf, bool_t candebug) {
+    int slot;
+    transport_peers_expire(st, peers);
+    for (slot=0; slot<peers->npeers; slot++) {
+       transport_peer *peer=&peers->peers[slot];
+       if (candebug)
+           dump_packet(st, buf, &peer->addr, False);
+       peer->addr.comm->sendmsg(peer->addr.comm->st, buf, &peer->addr);
+    }
+}
+
+/***** END of transport peers declarations *****/