From aaf0177750d55669d64e54cdb59e4f6872e9a295 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Thu, 13 Feb 2003 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2003-02-13

---
 ip/ip.c        |  2 +-
 ip/tcp.c       | 16 +++++++++++++++-
 port/portdat.h | 10 ++++++++--
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/ip/ip.c b/ip/ip.c
index 5467af7b09ec900d4ebff65427f434608c9189c4..213c5911395da1108b04a13473371b9b03dff2f4 100644
--- a/ip/ip.c
+++ b/ip/ip.c
@@ -441,7 +441,7 @@ ipiput4(Fs *f, Ipifc *ifc, Block *bp)
 	h = (Ip4hdr*)(bp->rp);
 
 	/* dump anything that whose header doesn't checksum */
-	if(ipcsum(&h->vihl)) {
+	if((bp->flag & Bipck) == 0 && ipcsum(&h->vihl)) {
 		ip->stats[InHdrErrors]++;
 		netlog(f, Logip, "ip: checksum error %V\n", h->src);
 		freeblist(bp);
diff --git a/ip/tcp.c b/ip/tcp.c
index fab8dcf1d86d82e34cb1da86141cef7cd2d05e83..31069fdb2c7d137413811ea2aa694b6524a9df48 100644
--- a/ip/tcp.c
+++ b/ip/tcp.c
@@ -361,7 +361,7 @@ struct Tcppriv
  *  it that number gets acked by the other end, we shut down the connection.
  *  Look for tcpporthogedefense in the code.
  */
-int tcpporthogdefense = 1;
+int tcpporthogdefense = 0;
 
 int	addreseq(Tcpctl*, Tcppriv*, Tcp*, Block*, ushort);
 void	getreseq(Tcpctl*, Tcp*, Block**, ushort*);
@@ -3013,6 +3013,18 @@ tcpadvise(Proto *tcp, Block *bp, char *msg)
 	freeblist(bp);
 }
 
+static char*
+tcpporthogdefensectl(char *val)
+{
+	if(strcmp(val, "on") == 0)
+		tcpporthogdefense = 1;
+	else if(strcmp(val, "off") == 0)
+		tcpporthogdefense = 0;
+	else
+		return "unknown value for tcpporthogdefense";
+	return nil;
+}
+
 /* called with c qlocked */
 char*
 tcpctl(Conv* c, char** f, int n)
@@ -3023,6 +3035,8 @@ tcpctl(Conv* c, char** f, int n)
 		return tcpstartka(c, f, n);
 	if(n >= 1 && strcmp(f[0], "checksum") == 0)
 		return tcpsetchecksum(c, f, n);
+	if(n >= 1 && strcmp(f[0], "tcpporthogdefense") == 0)
+		return tcpporthogdefensectl(f[1]);
 	return "unknown control request";
 }
 
diff --git a/port/portdat.h b/port/portdat.h
index 07cd7530698d315fea22c2325bd537dc41d71bd1..e4440ed61cf2e33890899c43a8db7e74faf1c3fe 100644
--- a/port/portdat.h
+++ b/port/portdat.h
@@ -124,10 +124,15 @@ enum
 	CCACHE	= 0x0080,		/* client cache */
 };
 
+/* flag values */
 enum
 {
 	BINTR	=	(1<<0),
 	BFREE	=	(1<<1),
+	Bipck	=	(1<<2),		/* ip checksum */
+	Budpck	=	(1<<3),		/* udp checksum */
+	Btcpck	=	(1<<4),		/* tcp checksum */
+	Bpktck	=	(1<<5),		/* packet checksum */
 };
 
 struct Block
@@ -137,9 +142,10 @@ struct Block
 	uchar*	rp;			/* first unconsumed byte */
 	uchar*	wp;			/* first empty byte */
 	uchar*	lim;			/* 1 past the end of the buffer */
-	uchar*	base;		/* start of the buffer */
+	uchar*	base;			/* start of the buffer */
 	void	(*free)(Block*);
-	ulong	flag;
+	ushort	flag;
+	ushort	checksum;		/* IP checksum of complete packet (minus media header) */
 };
 #define BLEN(s)	((s)->wp - (s)->rp)
 #define BALLOC(s) ((s)->lim - (s)->base)