From dfe62ca27cb9ef628b5f2be1d7d51fe1697fd27b Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 3 Sep 1997 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1997-09-03

---
 ip/icmp.c | 21 +++++++++++++++++++++
 ip/ip.h   |  1 +
 ip/udp.c  |  1 +
 3 files changed, 23 insertions(+)

diff --git a/ip/icmp.c b/ip/icmp.c
index 8863dfee25b900f30f196afe3bb23d4265791b8a..57c25fb3a84e6cc6a34168182300660751bc4014 100644
--- a/ip/icmp.c
+++ b/ip/icmp.c
@@ -121,6 +121,27 @@ icmpkick(Conv *c, int l)
 	ipoput(bp, 0, MAXTTL);
 }
 
+extern void
+icmpnoconv(Block *bp)
+{
+	Block	*nbp;
+	Icmp	*p, *np;
+
+	p = (Icmp *)bp->rp;
+	nbp = allocb(ICMP_IPSIZE + ICMP_HDRSIZE + ICMP_IPSIZE + 8);
+	nbp->wp += ICMP_IPSIZE + ICMP_HDRSIZE + ICMP_IPSIZE + 8;
+	np = (Icmp *)nbp->rp;
+	memmove(np->dst, p->src, sizeof(np->dst));
+	memmove(np->src, p->dst, sizeof(np->src));
+	memmove(np->data, bp->rp, ICMP_IPSIZE + 8);
+	np->type = Unreachable;
+	np->code = 3;
+	p->proto = IP_ICMPPROTO;
+	hnputs(p->icmpid, 0);
+	memset(p->cksum, 0, sizeof(p->cksum));
+	hnputs(p->cksum, ptclcsum(bp, ICMP_IPSIZE, blocklen(bp) - ICMP_IPSIZE));
+	ipoput(nbp, 0, MAXTTL);
+}
 
 static void
 goticmpkt(Block *bp)
diff --git a/ip/ip.h b/ip/ip.h
index af6ff5ca2311a60800f439e54cf2333a8af3eb71..955d93e655bf904e75716406c27b9bbed194446d 100644
--- a/ip/ip.h
+++ b/ip/ip.h
@@ -250,6 +250,7 @@ int	equivip(byte*, byte*);
 void	fatal(byte*, ...);
 void	hnputl(byte*, ulong);
 void	hnputs(byte*, ushort);
+void	icmpnoconv(Block*);
 void	initfrag(int);
 ushort	ipcsum(byte*);
 void	(*ipextprotoiput)(Block*);
diff --git a/ip/udp.c b/ip/udp.c
index a42bf23402b93a47aaf603de4a8db2ba6706bc3b..ae23a86bcc6e09c29f4034e8998a7aa08443149c 100644
--- a/ip/udp.c
+++ b/ip/udp.c
@@ -244,6 +244,7 @@ udpiput(Media *m, Block *bp)
 	if(*p == nil) {
 		netlog(Logudp, "udp: no conv %I.%d -> %I.%d\n", src, rport,
 			dst, lport);
+		icmpnoconv(bp);
 		freeblist(bp);
 		return;
 	}