chiark / gitweb /
comm: Introduce comm_addr_to_string
[secnet.git] / site.c
diff --git a/site.c b/site.c
index f65051fca9a4009467384e6f9f1f0b6a8f81b0b4..1d8c77788d532968f8cae245450fa16e2be46f3f 100644 (file)
--- a/site.c
+++ b/site.c
@@ -89,6 +89,8 @@
 #define SITE_SENTMSG5 7
 #define SITE_WAIT     8
 
+int32_t site_max_start_pad = 4*4;
+
 static cstring_t state_name(uint32_t state)
 {
     switch (state) {
@@ -204,7 +206,8 @@ static void transport_peers_copy(struct site *st, transport_peers *dst,
 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 *configured_addr /* 0 if none or not found */,
+        const struct comm_addr *prod_hint_addr /* 0 if none */);
 static void transport_record_peer(struct site *st, transport_peers *peers,
                                  const struct comm_addr *addr, const char *m);
 
@@ -214,6 +217,12 @@ static void transport_xmit(struct site *st, transport_peers *peers,
  /***** 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;
     struct site_if ops;
@@ -225,6 +234,7 @@ struct site {
     string_t tunname; /* localname<->remotename by default, used in logs */
     string_t address; /* DNS name for bootstrapping, optional */
     int remoteport; /* Port for bootstrapping, optional */
+    uint32_t mtu_target;
     struct netlink_if *netlink;
     struct comm_if **comms;
     int ncomms;
@@ -233,11 +243,13 @@ struct site {
     struct random_if *random;
     struct rsaprivkey_if *privkey;
     struct rsapubkey_if *pubkey;
-    struct transform_if *transform;
+    struct transform_if **transforms;
+    int ntransforms;
     struct dh_if *dh;
     struct hash_if *hash;
 
     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 */
@@ -247,9 +259,6 @@ struct site {
                                      after this time, initiate a new
                                      key exchange */
 
-    uint8_t *setupsig; /* Expected signature of incoming MSG1 packets */
-    int32_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;
@@ -257,13 +266,14 @@ struct site {
 /* runtime information */
     uint32_t state;
     uint64_t now; /* Most recently seen time */
+    bool_t allow_send_prod;
 
     /* The currently established session */
-    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 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
@@ -272,55 +282,126 @@ struct site {
        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;
     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 */
+    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, cstring_t msg, ...)
+static uint32_t event_log_priority(struct site *st, uint32_t event)
+{
+    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)
 {
-    va_list ap;
-    char buf[240];
     uint32_t class;
 
-    va_start(ap,msg);
+    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");
+    }
+}
 
-    if (event&st->log_events) {
-       switch(event) {
-       case LOG_UNEXPECTED: class=M_INFO; break;
-       case LOG_SETUP_INIT: class=M_INFO; break;
-       case LOG_SETUP_TIMEOUT: class=M_NOTICE; break;
-       case LOG_ACTIVATE_KEY: class=M_INFO; break;
-       case LOG_TIMEOUT_KEY: class=M_INFO; break;
-       case LOG_SEC: class=M_SECURITY; break;
-       case LOG_STATE: class=M_DEBUG; break;
-       case LOG_DROP: class=M_DEBUG; break;
-       case LOG_DUMP: class=M_DEBUG; break;
-       case LOG_ERROR: class=M_ERR; break;
-       case LOG_PEER_ADDRS: class=M_DEBUG; break;
-       default: class=M_ERR; break;
-       }
+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);
+}
 
-       vsnprintf(buf,sizeof(buf),msg,ap);
-       st->log->log(st->log->st,class,"%s: %s",st->tunname,buf);
-    }
+static void logtimeout(struct site *st, const char *fmt, ...)
+FORMAT(printf,2,3);
+static void logtimeout(struct site *st, const char *fmt, ...)
+{
+    va_list ap;
+    va_start(ap,fmt);
+    vslog(st,LOG_SETUP_TIMEOUT,fmt,ap);
     va_end(ap);
 }
 
 static void set_link_quality(struct site *st);
-static void delete_key(struct site *st, cstring_t reason, uint32_t loglevel);
-static bool_t initiate_key_setup(struct site *st, cstring_t reason);
+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_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)
@@ -329,14 +410,29 @@ static void enter_state_wait(struct site *st);
     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;
-    int32_t remlen;
-    uint8_t *remote;
-    int32_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;
     int32_t pklen;
@@ -346,6 +442,63 @@ struct msg {
     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 of config data supplied by netlink */
 static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
@@ -361,7 +514,17 @@ static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
        (type==LABEL_MSG1?0:st->setup_session_id));
     buf_append_uint32(&st->buffer,st->index);
     buf_append_uint32(&st->buffer,type);
-    buf_append_string(&st->buffer,st->localname);
+
+    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;
@@ -370,6 +533,9 @@ static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
 
     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);
@@ -384,23 +550,48 @@ static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
     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=buf_unprepend_uint32(msg);
     CHECK_AVAIL(msg,4);
     m->source=buf_unprepend_uint32(msg);
     CHECK_TYPE(msg,type);
-    CHECK_AVAIL(msg,2);
-    m->remlen=buf_unprepend_uint16(msg);
-    CHECK_AVAIL(msg,m->remlen);
-    m->remote=buf_unprepend(msg,m->remlen);
-    CHECK_AVAIL(msg,2);
-    m->loclen=buf_unprepend_uint16(msg);
-    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) {
@@ -413,6 +604,12 @@ 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=buf_unprepend_uint16(msg);
     CHECK_AVAIL(msg,m->pklen);
@@ -426,6 +623,14 @@ static bool_t unpick_msg(struct site *st, uint32_t type,
     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)
 {
@@ -433,11 +638,11 @@ static bool_t check_msg(struct site *st, uint32_t type, struct msg *m,
 
     /* 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)) {
+    if (!name_matches(&m->remote,st->remotename)) {
        *error="wrong remote site name";
        return False;
     }
-    if (memcmp(m->local,st->localname,strlen(st->localname)!=0)) {
+    if (!name_matches(&m->local,st->localname)) {
        *error="wrong local site name";
        return False;
     }
@@ -446,11 +651,17 @@ static bool_t check_msg(struct site *st, uint32_t type, struct msg *m,
        return False;
     }
     if (type==LABEL_MSG2) return True;
-    if (memcmp(m->nR,st->remoteN,NONCELEN)!=0) {
+    if (!consttime_memeq(m->nR,st->remoteN,NONCELEN)!=0) {
        *error="wrong remotely-generated nonce";
        return False;
     }
-    if (type==LABEL_MSG3) return True;
+    /* 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;
@@ -463,19 +674,16 @@ static bool_t generate_msg1(struct site *st)
 }
 
 static bool_t process_msg1(struct site *st, struct buffer_if *msg1,
-                          const struct comm_addr *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;
-
     transport_record_peer(st,&st->setup_peers,src,"msg1");
-    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;
 }
 
@@ -497,6 +705,30 @@ static bool_t process_msg2(struct site *st, struct buffer_if *msg2,
        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;
 }
@@ -506,49 +738,82 @@ 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,
-                          const struct comm_addr *src)
+static bool_t process_msg3_msg4(struct site *st, struct msg *m)
 {
-    struct msg m;
     uint8_t *hash;
     void *hst;
-    cstring_t err;
-
-    if (!unpick_msg(st,LABEL_MSG3,msg3,&m)) return False;
-    if (!check_msg(st,LABEL_MSG3,&m,&err)) {
-       slog(st,LOG_SEC,"msg3: %s",err);
-       return False;
-    }
 
     /* Check signature and store g^x mod m */
-    hash=safe_malloc(st->hash->len, "process_msg3");
+    hash=safe_malloc(st->hash->len, "process_msg3_msg4");
     hst=st->hash->init();
-    st->hash->update(hst,m.hashstart,m.hashlen);
+    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 signature failed check!");
+    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;
     }
     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;
+    }
+    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;
+    }
+    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;
+    }
+    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;
 }
@@ -564,8 +829,6 @@ static bool_t process_msg4(struct site *st, struct buffer_if *msg4,
                           const struct comm_addr *src)
 {
     struct msg m;
-    uint8_t *hash;
-    void *hst;
     cstring_t err;
 
     if (!unpick_msg(st,LABEL_MSG4,msg4,&m)) return False;
@@ -574,28 +837,14 @@ static bool_t process_msg4(struct site *st, struct buffer_if *msg4,
        return False;
     }
     
-    /* Check signature and store g^x mod m */
-    hash=safe_malloc(st->hash->len, "process_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,"msg4 signature failed check!");
-       free(hash);
+    if (!process_msg3_msg4(st,&m))
        return False;
-    }
-    free(hash);
 
     /* 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);
+
+    /* Generate the shared key and set up the transform */
+    set_new_transform(st,m.pk);
 
     return True;
 }
@@ -625,12 +874,13 @@ static bool_t generate_msg5(struct site *st)
 
     BUF_ALLOC(&st->buffer,"site:MSG5");
     /* We are going to add four words to the message */
-    buffer_init(&st->buffer,st->transform->max_start_pad+(4*4));
+    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);
-    st->new_transform->forwards(st->new_transform->st,&st->buffer,
-                               &transform_err);
+    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);
@@ -640,15 +890,15 @@ static bool_t generate_msg5(struct site *st)
 }
 
 static bool_t process_msg5(struct site *st, struct buffer_if *msg5,
-                          const struct comm_addr *src)
+                          const struct comm_addr *src,
+                          struct transform_inst_if *transform)
 {
     struct msg0 m;
     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_SEC,"process_msg5: transform: %s",transform_err);
        return False;
@@ -664,22 +914,30 @@ static bool_t process_msg5(struct site *st, struct buffer_if *msg5,
     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)
 {
     cstring_t transform_err;
 
     BUF_ALLOC(&st->buffer,"site:MSG6");
     /* We are going to add four words to the message */
-    buffer_init(&st->buffer,st->transform->max_start_pad+(4*4));
+    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);
-    st->new_transform->forwards(st->new_transform->st,&st->buffer,
-                               &transform_err);
+    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,st->setup_session_id);
+    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;
 }
@@ -692,8 +950,7 @@ static bool_t process_msg6(struct site *st, struct buffer_if *msg6,
 
     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_SEC,"process_msg6: transform: %s",transform_err);
        return False;
@@ -709,26 +966,79 @@ static bool_t process_msg6(struct site *st, struct buffer_if *msg6,
     return True;
 }
 
-static bool_t decrypt_msg0(struct site *st, struct buffer_if *msg0)
+static bool_t decrypt_msg0(struct site *st, struct buffer_if *msg0,
+                          const struct comm_addr *src)
 {
-    cstring_t transform_err;
+    cstring_t transform_err, auxkey_err, newkey_err="n/a";
     struct msg0 m;
     uint32_t problem;
 
-    if (!st->current_valid) {
-       slog(st,LOG_DROP,"incoming message but no current key -> dropping");
-       initiate_key_setup(st,"incoming message but no current key");
-       return False;
-    }
-
     if (!unpick_msg0(st,msg0,&m)) return False;
 
-    problem = st->current_transform->reverse(st->current_transform->st,
-                                            msg0,&transform_err);
-    if (!problem) return True;
+    /* 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 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;
+    }
+
+    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;
 
-    slog(st,LOG_SEC,"transform: %s",transform_err);
-    initiate_key_setup(st,"incoming message would not decrypt");
+ skew:
+    slog(st,LOG_DROP,"transform: %s (merely skew)",transform_err);
     return False;
 }
 
@@ -737,7 +1047,7 @@ static bool_t process_msg0(struct site *st, struct buffer_if *msg0,
 {
     uint32_t type;
 
-    if (!decrypt_msg0(st,msg0))
+    if (!decrypt_msg0(st,msg0,src))
        return False;
 
     CHECK_AVAIL(msg0,4);
@@ -745,7 +1055,7 @@ static bool_t process_msg0(struct site *st, struct buffer_if *msg0,
     switch(type) {
     case LABEL_MSG7:
        /* We must forget about the current session. */
-       delete_key(st,"request from peer",LOG_SEC);
+       delete_keys(st,"request from peer",LOG_SEC);
        return True;
     case LABEL_MSG9:
        /* Deliver to netlink layer */
@@ -753,7 +1063,7 @@ static bool_t process_msg0(struct site *st, struct buffer_if *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");
+           initiate_key_setup(st,"incoming packet in renegotiation window",0);
        return True;
     default:
        slog(st,LOG_SEC,"incoming encrypted message of type %08x "
@@ -766,9 +1076,9 @@ static bool_t process_msg0(struct site *st, struct buffer_if *msg0,
 static void dump_packet(struct site *st, struct buffer_if *buf,
                        const struct comm_addr *addr, bool_t incoming)
 {
-    uint32_t dest=ntohl(*(uint32_t *)buf->start);
-    uint32_t source=ntohl(*(uint32_t *)(buf->start+4));
-    uint32_t msgtype=ntohl(*(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)
        slilog(st->log,M_DEBUG,"%s: %s: %08x<-%08x: %08x:",
@@ -788,8 +1098,26 @@ static bool_t send_msg(struct site *st)
        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;
@@ -816,7 +1144,7 @@ static void site_resolve_callback(void *sst, struct in_addr *address)
        slog(st,LOG_ERROR,"resolution of %s failed",st->address);
        ca_use=0;
     }
-    if (transport_compute_setupinit_peers(st,ca_use)) {
+    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 */
@@ -825,14 +1153,15 @@ static void site_resolve_callback(void *sst, struct in_addr *address)
     }
 }
 
-static bool_t initiate_key_setup(struct site *st, cstring_t reason)
+static bool_t initiate_key_setup(struct site *st, cstring_t reason,
+                                const struct comm_addr *prod_hint)
 {
     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)) {
+    } 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");
@@ -843,34 +1172,52 @@ static void activate_new_key(struct site *st)
 {
     struct transform_inst_if *t;
 
-    /* We have two transform instances, which we swap between active
-       and setup */
-    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->timeout=0;
-    st->current_valid=True;
-    st->current_key_timeout=st->now+st->key_lifetime;
+    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->remote_session_id=st->setup_session_id;
+    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");
+    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_key(struct site *st, cstring_t reason, uint32_t loglevel)
+static void delete_one_key(struct site *st, struct data_key *key,
+                          cstring_t reason, cstring_t which, uint32_t loglevel)
 {
-    if (st->current_valid) {
+    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);
 
-       st->current_valid=False;
-       st->current_transform->delkey(st->current_transform->st);
-       st->current_key_timeout=0;
+       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)
@@ -882,14 +1229,14 @@ static void enter_state_stop(struct site *st)
 {
     st->state=SITE_STOP;
     st->timeout=0;
-    delete_key(st,"entering state STOP",LOG_TIMEOUT_KEY);
-    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 (st->current_valid)
+    if (current_valid(st))
        quality=LINK_QUALITY_UP;
     else if (st->state==SITE_WAIT || st->state==SITE_STOP)
        quality=LINK_QUALITY_DOWN;
@@ -913,9 +1260,9 @@ static void enter_state_run(struct site *st)
     transport_peers_clear(st,&st->setup_peers);
     memset(st->localN,0,NONCELEN);
     memset(st->remoteN,0,NONCELEN);
-    st->new_transform->delkey(st->new_transform->st);
+    dispose_transform(&st->new_transform);
     memset(st->dhsecret,0,st->dh->len);
-    memset(st->sharedsecret,0,st->transform->keylen);
+    memset(st->sharedsecret,0,st->sharedsecretlen);
     set_link_quality(st);
 }
 
@@ -1001,19 +1348,21 @@ static bool_t send_msg7(struct site *st, cstring_t reason)
 {
     cstring_t transform_err;
 
-    if (st->current_valid && st->buffer.free
+    if (current_valid(st) && st->buffer.free
        && transport_peers_valid(&st->peers)) {
        BUF_ALLOC(&st->buffer,"site:MSG7");
-       buffer_init(&st->buffer,st->transform->max_start_pad+(4*3));
+       buffer_init(&st->buffer,calculate_max_start_pad());
        buf_append_uint32(&st->buffer,LABEL_MSG7);
        buf_append_string(&st->buffer,reason);
-       st->current_transform->forwards(st->current_transform->st,
-                                       &st->buffer, &transform_err);
+       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->remote_session_id);
+       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;
     }
     return False;
@@ -1032,6 +1381,30 @@ static void enter_state_wait(struct site *st)
     /* 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) {
@@ -1052,14 +1425,23 @@ 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. */
     site_settimeout(st->timeout, timeout_io);
-    site_settimeout(st->current_key_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)
 {
@@ -1078,9 +1460,8 @@ static void site_afterpoll(void *sst, struct pollfd *fds, int nfds)
                 st->state);
        }
     }
-    if (st->current_key_timeout && *now>st->current_key_timeout) {
-       delete_key(st,"maximum key life exceeded",LOG_TIMEOUT_KEY);
-    }
+    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
@@ -1096,30 +1477,49 @@ static void site_outgoing(void *sst, struct buffer_if *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 && transport_peers_valid(&st->peers)) {
+    if (current_valid(st) && transport_peers_valid(&st->peers)) {
        /* Transform it and send it */
        if (buf->size>0) {
            buf_prepend_uint32(buf,LABEL_MSG9);
-           st->current_transform->forwards(st->current_transform->st,
-                                           buf, &transform_err);
+           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->remote_session_id);
+           buf_prepend_uint32(buf,st->current.remote_session_id);
            transport_xmit(st,&st->peers,buf,False);
        }
+    free_out:
        BUF_FREE(buf);
        return;
     }
 
     slog(st,LOG_DROP,"discarding outgoing packet of size %d",buf->size);
     BUF_FREE(buf);
-    initiate_key_setup(st,"outgoing packet");
+    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,
                            const struct comm_addr *source)
 {
@@ -1127,67 +1527,80 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
 
     if (buf->size < 12) return False;
 
-    uint32_t dest=ntohl(*(uint32_t *)buf->start);
-
-    if (dest==0) {
-       /* It could be for any site - it should have LABEL_MSG1 and
-          might have our name and our peer's name in it */
-       if (buf->size<(st->setupsiglen+8+NONCELEN)) return False;
-       if (memcmp(buf->start+8,st->setupsig,st->setupsiglen)==0) {
-           /* It's 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 */
-               if (process_msg1(st,buf,source)) {
-                   slog(st,LOG_SETUP_INIT,"key setup initiated by peer");
+    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 */
+           if (process_msg1(st,buf,source,&named_msg)) {
+               slog(st,LOG_SETUP_INIT,"key setup initiated by peer");
+               enter_new_state(st,SITE_SENTMSG2);
+           } 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;
+           } 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 */
                    enter_new_state(st,SITE_SENTMSG2);
                } else {
-                   slog(st,LOG_ERROR,"failed to process incoming msg1");
+                   slog(st,LOG_ERROR,"failed to process an incoming "
+                        "crossed msg1 (we have low priority)");
                }
                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;
-               } 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_new_state(st,SITE_SENTMSG2);
-                   } else {
-                       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==st->index) {
        /* Explicitly addressed to us */
-       uint32_t msgtype=ntohl(get_uint32(buf->start+8));
        if (msgtype!=LABEL_MSG0) dump_packet(st,buf,source,True);
        switch (msgtype) {
-       case 0: /* NAK */
+       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->remote_session_id) {
-               initiate_key_setup(st,"received a NAK");
+           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");
            }
@@ -1212,10 +1625,11 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
            }
            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)) {
+           } else if (process_msg3(st,buf,source,msgtype)) {
                transport_setup_msgok(st,source);
                enter_new_state(st,SITE_SENTMSG4);
            } else {
@@ -1237,16 +1651,29 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
            /* 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 unkeyed. XXX) */
-           if (st->state!=SITE_SENTMSG4) {
-               slog(st,LOG_UNEXPECTED,"unexpected MSG5");
-           } else if (process_msg5(st,buf,source)) {
-               transport_setup_msgok(st,source);
-               enter_new_state(st,SITE_RUN);
+              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_SEC,"invalid MSG5");
+               slog(st,LOG_UNEXPECTED,"unexpected MSG5");
            }
            break;
        case LABEL_MSG6:
@@ -1342,21 +1769,28 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
 
     assert(index_sequence < 0xffffffffUL);
     st->index = ++index_sequence;
+    st->local_capabilities = 0;
     st->netlink=find_cl_if(dict,"link",CL_NETLINK,True,"site",loc);
 
-    list_t *comms_cfg=dict_lookup(dict,"comm");
-    if (!comms_cfg) cfgfatal(loc,"site","closure list \"comm\" not found\n");
-    st->ncomms=list_length(comms_cfg);
-    st->comms=safe_malloc_ary(sizeof(*st->comms),st->ncomms,"comms");
-    assert(st->ncomms);
-    for (i=0; i<st->ncomms; i++) {
-       item_t *item=list_elem(comms_cfg,i);
-       if (item->type!=t_closure)
-           cfgfatal(loc,"site","comm is not a closure\n");
-       closure_t *cl=item->data.closure;
-       if (cl->type!=CL_COMM) cfgfatal(loc,"site","comm closure wrong type\n");
-       st->comms[i]=cl->interface;
-    }
+#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);
@@ -1369,8 +1803,7 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
     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);
@@ -1383,6 +1816,7 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
     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);
@@ -1409,6 +1843,8 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
     st->log_events=string_list_to_word(dict_lookup(dict,"log-events"),
                                       log_event_table,"site");
 
+    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);
@@ -1416,53 +1852,51 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
     /* The information we expect to see in incoming messages of type 1 */
     /* fixme: lots of unchecked overflows here, but the results are only
        corrupted packets rather than undefined behaviour */
-    st->setupsiglen=strlen(st->remotename)+strlen(st->localname)+8;
-    st->setupsig=safe_malloc(st->setupsiglen,"site_apply");
-    put_uint32(st->setupsig+0,LABEL_MSG1);
-    put_uint16(st->setupsig+4,strlen(st->remotename));
-    memcpy(&st->setupsig[6],st->remotename,strlen(st->remotename));
-    put_uint16(st->setupsig+(6+strlen(st->remotename)),strlen(st->localname));
-    memcpy(&st->setupsig[8+strlen(st->remotename)],st->localname,
-          strlen(st->localname));
     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->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");
-
-    /* We need to compute some properties of our comms */
-#define COMPUTE_WORST(pad)                     \
-    int worst_##pad=0;                         \
-    for (i=0; i<st->ncomms; i++) {             \
-       int thispad=st->comms[i]->pad;          \
-       if (thispad > worst_##pad)              \
-           worst_##pad=thispad;                \
+    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;
     }
-    COMPUTE_WORST(min_start_pad)
-    COMPUTE_WORST(min_end_pad)
 
     /* We need to register the remote networks with the netlink device */
-    st->netlink->reg(st->netlink->st, site_outgoing, st,
-                    st->transform->max_start_pad+(4*4)+
-                    worst_min_start_pad,
-                    st->transform->max_end_pad+worst_min_end_pad);
+    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);
 
@@ -1499,14 +1933,14 @@ static void transport_peers_debug(struct site *st, transport_peers *dst,
         i++, (argp+=stride?stride:sizeof(*args))) {
        const struct comm_addr *ca=(void*)argp;
        slog(st, LOG_PEER_ADDRS, " args: addrs[%d]=%s",
-            i, ca->comm->addr_to_string(ca->comm->st,ca));
+            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, ca->comm->addr_to_string(ca->comm->st,ca),
+            i, comm_addr_to_string(ca),
             (unsigned long)diff.tv_sec, (unsigned long)diff.tv_usec);
     }
 }
@@ -1543,7 +1977,7 @@ static void transport_record_peer(struct site *st, transport_peers *peers,
 
     changed=1;
     if (peers->npeers==st->transport_peers_max)
-       slot=st->transport_peers_max;
+       slot=st->transport_peers_max-1;
     else
        slot=peers->npeers++;
 
@@ -1561,23 +1995,30 @@ static void transport_record_peer(struct site *st, transport_peers *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 *configured_addr /* 0 if none or not found */,
+        const struct comm_addr *prod_hint_addr /* 0 if none */) {
 
-    if (!configured_addr && !transport_peers_valid(&st->peers))
+    if (!configured_addr && !prod_hint_addr &&
+       !transport_peers_valid(&st->peers))
        return False;
 
     slog(st,LOG_SETUP_INIT,
-        (!configured_addr ? "using only %d old peer address(es)"
-         : "using configured address, and/or perhaps %d old peer address(es)"),
-        st->peers);
+        "using:%s%s %d old peer address(es)",
+        configured_addr ? " configured address;" : "",
+        prod_hint_addr ? " PROD hint address;" : "",
+        st->peers.npeers);
 
     /* Non-mobile peers havve 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 existing data peer if one exists; this is as desired. */
+     * 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");