[PATCH 5/6] site: Clearer processing for name-addressed packets

[Ian Jackson]

Ian Jackson writes ("[PATCH 5/6] site: Clearer processing for name-addressed packets"):
> We are going to introduce a new packet which (like MSG1) is addressed
> by name rather than the site id.  To make this easier:

The diff here is inflated by a reindent.

Here is a copy of it prepared with "diff -b":

diff --git a/NOTES b/NOTES
index 09c083e..477104f 100644
--- a/NOTES
+++ b/NOTES
@@ -202,6 +202,9 @@ Messages:
 
 1) A->B: *,iA,msg1,A,B,protorange-A,nA
 
+i* must be encoded as 0.  (However, it is permitted for a site to use
+zero as its "index" for another site.)
+
 2) B->A: iA,iB,msg2,B,A,chosen-protocol,nB,nA
 
 (The order of B and A reverses in alternate messages so that the same
diff --git a/site.c b/site.c
index 5c73533..aecd64d 100644
--- a/site.c
+++ b/site.c
@@ -253,9 +253,9 @@ 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 */
+    uint8_t *namedsig; /* Names section of MSG1 packets */
+    int32_t namedsiglen; /* Allows us to discard name-addressed 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;
@@ -1220,6 +1220,18 @@ static void site_outgoing(void *sst, struct buffer_if *buf)
     initiate_key_setup(st,"outgoing packet");
 }
 
+static bool_t named_for_us(struct site *st, struct buffer_if *buf,
+			   int extralen)
+    /* 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. */
+{
+    if (buf->size<(st->namedsiglen+12+extralen))
+	return False;
+    if (memcmp(buf->start+12,st->namedsig,st->namedsiglen))
+	return False;
+    return True;
+}
+
 /* This function is called by the communication device to deliver
    packets from our peers. */
 static bool_t site_incoming(void *sst, struct buffer_if *buf,
@@ -1230,14 +1242,11 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
 
     if (buf->size < 12) return False;
 
+    uint32_t msgtype=ntohl(get_uint32(buf->start+8));
     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. */
+    if (msgtype==LABEL_MSG1 && named_for_us(st,buf,NONCELEN)) {
+	/* 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) {
@@ -1279,11 +1288,8 @@ static bool_t site_incoming(void *sst, struct buffer_if *buf,
 	    BUF_FREE(buf);
 	    return True;
 	}
-	return False; /* Not for us. */
-    }
     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 LABEL_NAK:
@@ -1532,13 +1538,12 @@ 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,
+    st->namedsiglen=strlen(st->remotename)+strlen(st->localname)+4;
+    st->namedsig=safe_malloc(st->namedsiglen,"site_apply");
+    put_uint16(st->namedsig+0,strlen(st->remotename));
+    memcpy(&st->namedsig[2],st->remotename,strlen(st->remotename));
+    put_uint16(st->namedsig+(2+strlen(st->remotename)),strlen(st->localname));
+    memcpy(&st->namedsig[4+strlen(st->remotename)],st->localname,
 	   strlen(st->localname));
     st->setup_priority=(strcmp(st->localname,st->remotename)>0);