linux-kernel - [PATCH] metag: checksum.h: fix carry in csum_tcpudp

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Date:	Tue, 9 Jul 2013 10:57:05 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
CC:	James <james.hogan@...tec.com>
Subject: [PATCH] metag: checksum.h: fix carry in csum_tcpudp_nofold

In csum_tcpudp_nofold, add 1 if the carry bit is set after adding the
destination IP address (32 bits) to the checksum (16 bits).

The lack of carry handling for this particular addition meant that a
destination address of *.*.255.255 (e.g. certain broadcasts) sometimes
resulted in an incorrect checksum. This bug has been present in the Meta
port since the code was written in the 2.4 days.

Reported-by: Marcin Nowakowski <Marcin.Nowakowski@...e.com>
Signed-off-by: James Hogan <james.hogan@...tec.com>
---
I'll add this patch to my arch/metag fixes branch for v3.11.

 arch/metag/include/asm/checksum.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/metag/include/asm/checksum.h b/arch/metag/include/asm/checksum.h
index 999bf76..08dd1cc 100644
--- a/arch/metag/include/asm/checksum.h
+++ b/arch/metag/include/asm/checksum.h
@@ -64,7 +64,8 @@ static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
 					__wsum sum)
 {
 	unsigned long len_proto = (proto + len) << 8;
-	asm ("ADD    %0, %0, %1\n"
+	asm ("ADDS   %0, %0, %1\n"
+	     "ADDCS  %0, %0, #1\n"
 	     "ADDS   %0, %0, %2\n"
 	     "ADDCS  %0, %0, #1\n"
 	     "ADDS   %0, %0, %3\n"
-- 
1.8.1.2

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