From 65fe83bb84ce7303ee4f4055e4e3e17b76436612 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Fri, 30 May 1997 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1997-05-30

---
 ip/gre.c | 26 +++++++++++++++++---------
 ip/udp.c | 56 +++++++++++++++++++++++++++++++++-----------------------
 2 files changed, 50 insertions(+), 32 deletions(-)

diff --git a/ip/gre.c b/ip/gre.c
index ec617b422a1662a657ad09cd8a8448181d61021f..1cde43cc415ca76d91916bc318bf518843edecc5 100644
--- a/ip/gre.c
+++ b/ip/gre.c
@@ -11,8 +11,8 @@
 
 enum
 {
-	GRE_IPHDRSIZE	= 20,		/* size of ip header */
-	GRE_HDRSIZE	= 4,		/* minimum size of GRE header */
+	GRE_IPONLY	= 12,		/* size of ip header */
+	GRE_IPPLUSGRE	= 12,		/* minimum size of GRE header */
 	IP_GREPROTO	= 47,
 
 	GRErxms		= 200,
@@ -122,6 +122,7 @@ grekick(Conv *c, int l)
 {
 	GREhdr *ghp;
 	Block *bp;
+	ulong raddr, laddr;
 
 	USED(l);
 
@@ -130,20 +131,27 @@ grekick(Conv *c, int l)
 		return;
 
 	/* Make space to fit ip header (gre header already there) */
-	bp = padblock(bp, GRE_IPHDRSIZE);
+	bp = padblock(bp, GRE_IPONLY);
 	if(bp == nil)
 		return;
 
 	/* make sure the message has a GRE header */
-	bp = pullupblock(bp, GRE_IPHDRSIZE+GRE_HDRSIZE);
+	bp = pullupblock(bp, GRE_IPONLY+GRE_IPPLUSGRE);
 	if(bp == nil)
 		return;
 
 	ghp = (GREhdr *)(bp->rp);
 
+	raddr = nhgetl(ghp->src);
+	laddr = nhgetl(ghp->dst);
+	if(raddr == 0)
+		raddr = c->raddr;
+	if(laddr == 0 || Mediaforme(ghp->dst) <= 0)
+		laddr = c->laddr;
+
 	ghp->proto = IP_GREPROTO;
-	hnputl(ghp->dst, c->raddr);
-	hnputl(ghp->src, c->laddr);
+	hnputl(ghp->dst, raddr);
+	hnputl(ghp->src, laddr);
 	hnputs(ghp->eproto, c->rport);
 	ghp->frag[0] = 0;
 	ghp->frag[1] = 0;
@@ -184,12 +192,12 @@ greiput(Media *m, Block *bp)
 	/*
 	 * Trim the packet down to data size
 	 */
-	len = nhgets(ghp->len) - GRE_IPHDRSIZE;
-	if(len < GRE_HDRSIZE){
+	len = nhgets(ghp->len) - GRE_IPONLY;
+	if(len < GRE_IPPLUSGRE){
 		freeblist(bp);
 		return;
 	}
-	bp = trimblock(bp, GRE_IPHDRSIZE, len);
+	bp = trimblock(bp, GRE_IPONLY, len);
 	if(bp == nil){
 		gre.lenerr++;
 		return;
diff --git a/ip/udp.c b/ip/udp.c
index aec04e5652ff209fc881a51605593be930d37de7..b71975af21b09cb9deebb48e9b634cc245e9af1c 100644
--- a/ip/udp.c
+++ b/ip/udp.c
@@ -15,8 +15,7 @@ enum
 	UDP_HDRSIZE	= 20,
 	UDP_IPHDR	= 8,
 	IP_UDPPROTO	= 17,
-	UDP_USEAD	= 6,
-	UDP_RELSIZE	= 16,
+	UDP_USEAD	= 12,
 
 	Udprxms		= 200,
 	Udptickms	= 100,
@@ -123,8 +122,8 @@ void
 udpkick(Conv *c, int l)
 {
 	Udphdr *uh;
-	ushort port;
-	Ipaddr addr;
+	ushort rport;
+	Ipaddr laddr, raddr;
 	Block *bp, *f;
 	Udpcb *ucb;
 	int dlen, ptcllen;
@@ -143,13 +142,20 @@ udpkick(Conv *c, int l)
 			freeblist(bp);
 			return;
 		}
-		addr = nhgetl(bp->rp);
+		raddr = nhgetl(bp->rp);
 		bp->rp += 4;
-		port = nhgets(bp->rp);
+		laddr = nhgetl(bp->rp);
+		if(laddr != 0 && Mediaforme(bp->rp) <= 0)
+			laddr = 0;
+		bp->rp += 4;
+		rport = nhgets(bp->rp);
+		bp->rp += 2;
+		/* ignore local port number */
 		bp->rp += 2;
 	} else {
-		addr = 0;
-		port = 0;
+		raddr = 0;
+		rport = 0;
+		laddr = 0;
 	}
 
 	/* Round packet up to even number of bytes */
@@ -179,11 +185,12 @@ udpkick(Conv *c, int l)
 	uh->frag[1] = 0;
 	hnputs(uh->udpplen, ptcllen);
 	if(ucb->headers) {
-		hnputl(uh->udpdst, addr);
-		hnputs(uh->udpdport, port);
-
-		/* pick the closest source address (best we can do) */
-		hnputl(uh->udpsrc, Mediagetsrc(uh->udpdst));
+		hnputl(uh->udpdst, raddr);
+		hnputs(uh->udpdport, rport);
+		if(laddr)
+			hnputl(uh->udpsrc, laddr);
+		else
+			hnputl(uh->udpsrc, Mediagetsrc(uh->udpdst));
 	} else {
 		hnputl(uh->udpdst, c->raddr);
 		hnputs(uh->udpdport, c->rport);
@@ -204,10 +211,10 @@ udpiput(Media *m, Block *bp)
 {
 	int len;
 	Udphdr *uh;
-	Ipaddr addr;
 	Conv *c, **p;
 	Udpcb *ucb;
-	ushort dport, sport;
+	Ipaddr raddr, laddr;
+	ushort rport, lport;
 
 	USED(m);
 	uh = (Udphdr*)(bp->rp);
@@ -217,7 +224,8 @@ udpiput(Media *m, Block *bp)
 	len = nhgets(uh->udplen);
 	hnputs(uh->udpplen, len);
 
-	addr = nhgetl(uh->udpsrc);
+	raddr = nhgetl(uh->udpsrc);
+	laddr = nhgetl(uh->udpdst);
 
 	if(udpsum && nhgets(uh->udpcksum)) {
 		if(ptclcsum(bp, UDP_IPHDR, len+UDP_PHDRSIZE)) {
@@ -228,8 +236,8 @@ udpiput(Media *m, Block *bp)
 		}
 	}
 
-	dport = nhgets(uh->udpdport);
-	sport = nhgets(uh->udpsport);
+	lport = nhgets(uh->udpdport);
+	rport = nhgets(uh->udpsport);
 
 	/* Look for a conversation structure for this port */
 	c = nil;
@@ -237,7 +245,7 @@ udpiput(Media *m, Block *bp)
 		c = *p;
 		if(c->inuse == 0)
 			continue;
-		if(c->lport == dport && (c->rport == 0 || c->rport == sport))
+		if(c->lport == lport && (c->rport == 0 || c->rport == rport))
 			break;
 	}
 
@@ -261,14 +269,16 @@ udpiput(Media *m, Block *bp)
 	if(ucb->headers) {
 		/* pass the src address */
 		bp = padblock(bp, UDP_USEAD);
-		hnputl(bp->rp, addr);
-		hnputs(bp->rp+4, sport);
+		hnputl(bp->rp, raddr);
+		hnputl(bp->rp+4, laddr);
+		hnputs(bp->rp+8, rport);
+		hnputs(bp->rp+10, lport);
 	} else {
 		/* connection oriented udp */
 		if(c->raddr == 0){
 			/* save the src address in the conversation */
-		 	c->raddr = addr;
-			c->rport = sport;
+		 	c->raddr = raddr;
+			c->rport = rport;
 
 			/* reply with the same ip address (if not broadcast) */
 			if(Mediaforme(uh->udpdst) > 0)