devip: fix icmp bugs

icmpdontfrag() was not working properly, need to pass the
gating source interface. in fact, we now always pass the source
interface to all icmp*() functions, which is used to
determine source ip address of the icmp reply.

also dont generate a icmp response for packets going to
non-unicast addresses (such as broadcast).

increase the amount of icmp response payload, but keep
icmp responses below the minimum ipv4 mtu (68 bytes).

regularize icmpv6 function names.

move icmp unreachable codes to icmpv6.c.

provide the mtu value for icmppkttoobig6().

dont advise announced udp connections.

avoid code duplication in icmp.c and icmpv6.c,
by having single send function with type, code and arg
parameters.

maintain statistics for sent ipv4 icmp types.

avoid route lookup in ipout*() by passing Routehint* to
icmpnohost*().

iladvise()... more like ill advice.

1 files changed, 50 insertions, 57 deletions

diff --git a/sys/src/9/ip/icmp.c b/sys/src/9/ip/icmp.c
index c4168605b..2b8218a51 100644
--- a/sys/src/9/ip/icmp.c
+++ b/sys/src/9/ip/icmp.c
@@ -66,7 +66,7 @@ enum {
 	ICMP_IPSIZE	= 20,
 	ICMP_HDRSIZE	= 8,
 
-	MinAdvise	= ICMP_IPSIZE+4,	/* minimum needed for us to advise another protocol */ 
+	MinAdvise	= IP4HDR+4,	/* minimum needed for us to advise another protocol */
 };
 
 enum
@@ -212,93 +212,86 @@ ip4me(Fs *f, uchar ip4[4])
 	return ipforme(f, addr) == Runi;
 }
 
-void
-icmpttlexceeded(Fs *f, Ipifc *ifc, Block *bp)
+/*
+ *  Send a ICMP packet back of type/code/arg in response to packet bp
+ *  which was received on ifc. The route hint rh is valid for the
+ *  reverse route.
+ */
+static void
+icmpsend(Fs *f, Ipifc *ifc, Block *bp, int type, int code, int arg, Routehint *rh)
 {
-	Block	*nbp;
-	Icmp	*p, *np;
+	Proto	*icmp;
 	uchar	ia[IPv4addrlen];
+	Block	*nbp;
+	Icmp	*np, *p;
+	int	sz, osz;
+
+	osz = BLEN(bp);
+	if(osz < IP4HDR)
+		return;
 
 	p = (Icmp *)bp->rp;
-	if(isv4mcast(p->dst) || !ip4reply(f, p->src) || !ipv4local(ifc, ia, 0, p->src))
+	if(!ip4reply(f, p->dst) || !ip4reply(f, p->src) || !ipv4local(ifc, ia, 0, p->src))
 		return;
 
-	netlog(f, Logicmp, "sending icmpttlexceeded %V -> src %V dst %V\n",
-		ia, p->src, p->dst);
+	netlog(f, Logicmp, "icmpsend %s (%d) %d ia %V -> src %V dst %V\n",
+		icmpnames[type], type, code, ia, p->src, p->dst);
 
-	nbp = allocb(ICMP_IPSIZE + ICMP_HDRSIZE + ICMP_IPSIZE + 8);
-	nbp->wp += ICMP_IPSIZE + ICMP_HDRSIZE + ICMP_IPSIZE + 8;
+	sz = MIN(ICMP_IPSIZE + ICMP_HDRSIZE + osz, v4MINTU);
+	nbp = allocb(sz);
+	nbp->wp += sz;
+	memset(nbp->rp, 0, sz);
 	np = (Icmp *)nbp->rp;
 	np->vihl = IP_VER4;
 	memmove(np->src, ia, sizeof(np->src));
 	memmove(np->dst, p->src, sizeof(np->dst));
-	memmove(np->data, bp->rp, ICMP_IPSIZE + 8);
-	np->type = TimeExceed;
-	np->code = 0;
+	memmove(np->data, bp->rp, sz - ICMP_IPSIZE - ICMP_HDRSIZE);
+	np->type = type;
+	np->code = code;
 	np->proto = IP_ICMPPROTO;
 	hnputs(np->icmpid, 0);
-	hnputs(np->seq, 0);
+	hnputs(np->seq, arg);
 	memset(np->cksum, 0, sizeof(np->cksum));
 	hnputs(np->cksum, ptclcsum(nbp, ICMP_IPSIZE, blocklen(nbp) - ICMP_IPSIZE));
-	ipoput4(f, nbp, nil, MAXTTL, DFLTTOS, nil);
-}
 
-static void
-icmpunreachable(Fs *f, Ipifc *ifc, Block *bp, int code, int seq)
-{
-	Block	*nbp;
-	Icmp	*p, *np;
-	uchar	ia[IPv4addrlen];
+	icmp = f->t2p[IP_ICMPPROTO];
+	((Icmppriv*)icmp->priv)->out[type]++;
 
-	p = (Icmp *)bp->rp;
-	if(isv4mcast(p->dst) || !ip4reply(f, p->src))
-		return;
+	if(rh != nil && rh->r != nil && (rh->r->type & Runi) != 0){
+		np = (Icmp *)nbp->rp;
+		np->vihl = IP_VER4|IP_HLEN4;
+		np->tos = DFLTTOS;
+		np->ttl = MAXTTL;
 
-	if(ifc == nil){
-		if(!ipforme(f, p->dst))
-			return;
-		memmove(ia, p->dst, sizeof(p->dst));
-	} else {
-		if(!ipv4local(ifc, ia, 0, p->src))
-			return;
+		(*icmp->rcv)(icmp, ifc, nbp);
+		return;
 	}
 
-	netlog(f, Logicmp, "sending icmpunreachable %V -> src %V dst %V\n",
-		ia, p->src, p->dst);
+	ipoput4(f, nbp, nil, MAXTTL, DFLTTOS, rh);
+}
 
-	nbp = allocb(ICMP_IPSIZE + ICMP_HDRSIZE + ICMP_IPSIZE + 8);
-	nbp->wp += ICMP_IPSIZE + ICMP_HDRSIZE + ICMP_IPSIZE + 8;
-	np = (Icmp *)nbp->rp;
-	np->vihl = IP_VER4;
-	memmove(np->src, ia, sizeof(np->src));
-	memmove(np->dst, p->src, sizeof(np->dst));
-	memmove(np->data, bp->rp, ICMP_IPSIZE + 8);
-	np->type = Unreachable;
-	np->code = code;
-	np->proto = IP_ICMPPROTO;
-	hnputs(np->icmpid, 0);
-	hnputs(np->seq, seq);
-	memset(np->cksum, 0, sizeof(np->cksum));
-	hnputs(np->cksum, ptclcsum(nbp, ICMP_IPSIZE, blocklen(nbp) - ICMP_IPSIZE));
-	ipoput4(f, nbp, nil, MAXTTL, DFLTTOS, nil);
+void
+icmpnohost(Fs *f, Ipifc *ifc, Block *bp, Routehint *rh)
+{
+	icmpsend(f, ifc, bp, Unreachable, 1, 0, rh);
 }
 
 void
-icmpnohost(Fs *f, Ipifc *ifc, Block *bp)
+icmpnoconv(Fs *f, Ipifc *ifc, Block *bp)
 {
-	icmpunreachable(f, ifc, bp, 1, 0);
+	icmpsend(f, ifc, bp, Unreachable, 3, 0, nil);
 }
 
 void
-icmpnoconv(Fs *f, Block *bp)
+icmpcantfrag(Fs *f, Ipifc *ifc, Block *bp, int mtu)
 {
-	icmpunreachable(f, nil, bp, 3, 0);
+	icmpsend(f, ifc, bp, Unreachable, 4, mtu, nil);
 }
 
 void
-icmpcantfrag(Fs *f, Block *bp, int mtu)
+icmpttlexceeded(Fs *f, Ipifc *ifc, Block *bp)
 {
-	icmpunreachable(f, nil, bp, 4, mtu);
+	icmpsend(f, ifc, bp, TimeExceed, 0, 0, nil);
 }
 
 static void
@@ -479,7 +472,7 @@ raise:
  * and send the advice to ip4.
  */
 void
-icmpproxyadvice(Fs *f, Block *bp, Ipifc *ifc, uchar *ip4)
+icmpproxyadvice(Fs *f, Ipifc *ifc, Block *bp, uchar *ip4)
 {
 	Icmp	*p;
 	int	hop;
@@ -543,7 +536,7 @@ icmpadvise(Proto *icmp, Block *bp, Ipifc *ifc, char *msg)
 		hnputs_csum(p->icmpid, q->forward.rport, p->cksum);
 		qunlock(icmp);
 
-		icmpproxyadvice(icmp->f, bp, ifc, p->src);
+		icmpproxyadvice(icmp->f, ifc, bp, p->src);
 		return;
 	}
 	for(c = icmp->conv; (s = *c) != nil; c++){