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Subject[PATCH] [46/139] tcp: Increase TCP_MAXSEG socket option minimum.
Date
2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: David S. Miller <davem@davemloft.net>

[ Upstream commit 7a1abd08d52fdeddb3e9a5a33f2f15cc6a5674d2 ]

As noted by Steve Chen, since commit
f5fff5dc8a7a3f395b0525c02ba92c95d42b7390 ("tcp: advertise MSS
requested by user") we can end up with a situation where
tcp_select_initial_window() does a divide by a zero (or
even negative) mss value.

The problem is that sometimes we effectively subtract
TCPOLEN_TSTAMP_ALIGNED and/or TCPOLEN_MD5SIG_ALIGNED from the mss.

Fix this by increasing the minimum from 8 to 64.

Reported-by: Steve Chen <schen@mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
net/ipv4/tcp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6.35.y/net/ipv4/tcp.c
===================================================================
--- linux-2.6.35.y.orig/net/ipv4/tcp.c
+++ linux-2.6.35.y/net/ipv4/tcp.c
@@ -2235,7 +2235,7 @@ static int do_tcp_setsockopt(struct sock
/* Values greater than interface MTU won't take effect. However
* at the point when this call is done we typically don't yet
* know which interface is going to be used */
- if (val < 8 || val > MAX_TCP_WINDOW) {
+ if (val < 64 || val > MAX_TCP_WINDOW) {
err = -EINVAL;
break;
}

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