X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=blobdiff_plain;f=site.c;h=f9c2f087823d191f2b056032ff4c5a28b3c90eef;hb=5c19b79c7c817a28a1582970b2685c98e05b2de5;hp=20f9507cee7782c2f801dba295e9a82421855e88;hpb=779837e133a4740798015a1d7de6fbf6b4b1720f;p=secnet.git

diff --git a/site.c b/site.c
index 20f9507..f9c2f08 100644
--- 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);
 
@@ -231,6 +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;
@@ -262,6 +266,8 @@ struct site {
 /* runtime information */
     uint32_t state;
     uint64_t now; /* Most recently seen time */
+    bool_t allow_send_prod;
+    bool_t resolving;
 
     /* The currently established session */
     struct data_key current;
@@ -278,6 +284,7 @@ struct site {
        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;
@@ -293,35 +300,75 @@ struct site {
     struct transform_inst_if *new_transform; /* For key setup/verify */
 };
 
+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)
+{
+    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;
-    char buf[240];
-    uint32_t class;
-
     va_start(ap,msg);
+    vslog(st,event,msg,ap);
+    va_end(ap);
+}
 
-    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 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;
 
-	vsnprintf(buf,sizeof(buf),msg,ap);
-	slilog(st->log,class,"%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);
 }
 
@@ -331,7 +378,8 @@ 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);
+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);
@@ -381,6 +429,14 @@ static void dispose_transform(struct transform_inst_if **transform_var)
     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;
@@ -394,6 +450,7 @@ struct msg {
     struct parsedname remote;
     struct parsedname local;
     uint32_t remote_capabilities;
+    uint16_t remote_mtu;
     int capab_transformnum;
     uint8_t *nR;
     uint8_t *nL;
@@ -482,6 +539,9 @@ static bool_t generate_msg(struct site *st, uint32_t type, cstring_t what)
     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);
@@ -537,11 +597,20 @@ static bool_t unpick_msg(struct site *st, uint32_t type,
     CHECK_TYPE(msg,type);
     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) {
@@ -694,12 +763,34 @@ static bool_t generate_msg3(struct site *st)
 			"site:MSG3");
 }
 
+static bool_t process_msg3_msg4(struct site *st, struct msg *m)
+{
+    uint8_t *hash;
+    void *hst;
+
+    /* 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;
+    }
+    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;
-    uint8_t *hash;
-    void *hst;
     cstring_t err;
 
     assert(msgtype==LABEL_MSG3 || msgtype==LABEL_MSG3BIS);
@@ -732,19 +823,8 @@ static bool_t process_msg3(struct site *st, struct buffer_if *msg3,
  transform_found:
     st->chosen_transform=ti;
 
-    /* Check signature and store g^x mod m */
-    hash=safe_malloc(st->hash->len, "process_msg3");
-    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 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;
@@ -768,8 +848,6 @@ 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;
@@ -778,19 +856,8 @@ 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;
@@ -826,7 +893,7 @@ 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->new_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);
@@ -873,7 +940,7 @@ static void create_msg6(struct site *st, struct transform_inst_if *transform,
 
     BUF_ALLOC(&st->buffer,"site:MSG6");
     /* We are going to add four words to the message */
-    buffer_init(&st->buffer,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);
@@ -985,7 +1052,7 @@ static bool_t decrypt_msg0(struct site *st, struct buffer_if *msg0,
 
     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");
+    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;
 
@@ -1015,7 +1082,7 @@ 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 "
@@ -1051,7 +1118,7 @@ static bool_t send_msg(struct site *st)
 	st->retries--;
 	return True;
     } else if (st->state==SITE_SENTMSG5) {
-	slog(st,LOG_SETUP_TIMEOUT,"timed out sending MSG5, stashing new key");
+	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 */
@@ -1069,7 +1136,7 @@ static bool_t send_msg(struct site *st)
 	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;
@@ -1081,6 +1148,8 @@ 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;
@@ -1096,7 +1165,7 @@ 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 */
@@ -1105,14 +1174,16 @@ 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)
 {
+    /* 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)) {
+    } 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");
@@ -1139,7 +1210,15 @@ static void activate_new_key(struct site *st)
     transport_peers_copy(st,&st->peers,&st->setup_peers);
     st->current.remote_session_id=st->setup_session_id;
 
-    slog(st,LOG_ACTIVATE_KEY,"new key activated");
+    /* 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);
 }
 
@@ -1209,14 +1288,33 @@ static void enter_state_run(struct site *st)
     set_link_quality(st);
 }
 
+static bool_t ensure_resolving(struct site *st)
+{
+    /* Reentrancy hazard: may call site_resolve_callback and hence
+     * enter_new_state, enter_state_* and generate_msg*. */
+    if (st->resolving)
+        return True;
+
+    /* 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_resolve(struct site *st)
 {
+    /* Reentrancy hazard!  See ensure_resolving. */
     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;
+    return ensure_resolving(st);
 }
 
 static bool_t enter_new_state(struct site *st, uint32_t next)
@@ -1294,7 +1392,7 @@ static bool_t send_msg7(struct site *st, cstring_t reason)
     if (current_valid(st) && st->buffer.free
 	&& transport_peers_valid(&st->peers)) {
 	BUF_ALLOC(&st->buffer,"site:MSG7");
-	buffer_init(&st->buffer,st->current.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);
 	if (call_transform_forwards(st, st->current.transform,
@@ -1324,6 +1422,30 @@ 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) {
@@ -1396,6 +1518,8 @@ 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 (current_valid(st) && transport_peers_valid(&st->peers)) {
@@ -1417,7 +1541,7 @@ static void site_outgoing(void *sst, struct buffer_if *buf)
 
     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,
@@ -1433,7 +1557,10 @@ static bool_t named_for_us(struct site *st, const struct buffer_if *buf_in,
 }
 
 /* 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)
 {
@@ -1490,6 +1617,20 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
 	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 */
 	if (msgtype!=LABEL_MSG0) dump_packet(st,buf,source,True);
@@ -1498,7 +1639,9 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
 	    /* 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) {
-		initiate_key_setup(st,"received a NAK");
+		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");
 	    }
@@ -1714,6 +1857,7 @@ 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);
@@ -1740,6 +1884,9 @@ 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->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);
@@ -1751,7 +1898,7 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
 
     buffer_new(&st->buffer,SETUP_BUFFER_LEN);
 
-    buffer_new(&st->scratch,0);
+    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
@@ -1770,17 +1917,6 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
     st->sharedsecretlen=st->sharedsecretallocd=0;
     st->sharedsecret=0;
 
-    /* We need to compute some properties of our comms and transports */
-#define COMPUTE_WORST(things,pad)		\
-    int things##_worst_##pad=0;			\
-    for (i=0; i<st->n##things; i++) {		\
-	int thispad=st->things[i]->pad;		\
-	if (thispad > things##_worst_##pad)	\
-	    things##_worst_##pad=thispad;	\
-    }
-    COMPUTE_WORST(comms,min_start_pad)
-    COMPUTE_WORST(transforms,max_start_pad)
-
     for (i=0; i<st->ntransforms; i++) {
 	struct transform_if *ti=st->transforms[i];
 	uint32_t capbit = 1UL << ti->capab_transformnum;
@@ -1791,9 +1927,10 @@ static list_t *site_apply(closure_t *self, struct cloc loc, dict_t *context,
     }
 
     /* We need to register the remote networks with the netlink device */
-    st->netlink->reg(st->netlink->st, site_outgoing, st,
-		     transforms_worst_max_start_pad+(4*4)+
-		     comms_worst_min_start_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);
@@ -1838,14 +1975,14 @@ 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);
     }
 }
@@ -1882,7 +2019,7 @@ 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++;
 
@@ -1900,23 +2037,30 @@ 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)"),
+	 "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");