Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1d464c26b5625215c4b35fb336c8f3c57d248c2e
Commit: 1d464c26b5625215c4b35fb336c8f3c57d248c2e
Parent: ba755f8ec80fdbf2b5212622eabf7355464c6327
Author: Dave Johnson <[EMAIL PROTECTED]>
AuthorDate: Wed Apr 18 10:39:41 2007 -0400
Committer: Ralf Baechle <[EMAIL PROTECTED]>
CommitDate: Fri Apr 20 14:58:37 2007 +0100
[MIPS] Fix wrong checksum for split TCP packets on 64-bit MIPS
I've traced down an off-by-one TCP checksum calculation error under
the following conditions:
1) The TCP code needs to split a full-sized packet due to a reduced
MSS (typically due to the addition of TCP options mid-stream like
SACK).
_AND_
2) The checksum of the 2nd fragment is larger than the checksum of the
original packet. After subtraction this results in a checksum for
the 1st fragment with bits 16..31 set to 1. (this is ok)
_AND_
3) The checksum of the 1st fragment's TCP header plus the previously
32bit checksum of the 1st fragment DOES NOT cause a 32bit overflow
when added together. This results in a checksum of the TCP header
plus TCP data that still has the upper 16 bits as 1's.
_THEN_
4) The TCP+data checksum is added to the checksum of the pseudo IP
header with csum_tcpudp_nofold() incorrectly (the bug).
The problem is the checksum of the TCP+data is passed to
csum_tcpudp_nofold() as an 32bit unsigned value, however the assembly
code acts on it as if it is a 64bit unsigned value.
This causes an incorrect 32->64bit extension if the sum has bit 31
set. The resulting checksum is off by one.
This problems is data and TCP header dependent due to #2 and #3
above so it doesn't occur on every TCP packet split.
Signed-off-by: Dave Johnson <[EMAIL PROTECTED]>
Signed-off-by: Ralf Baechle <[EMAIL PROTECTED]>
---
include/asm-mips/checksum.h | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/include/asm-mips/checksum.h b/include/asm-mips/checksum.h
index 20a81e1..290485a 100644
--- a/include/asm-mips/checksum.h
+++ b/include/asm-mips/checksum.h
@@ -166,7 +166,7 @@ static inline __wsum csum_tcpudp_nofold(__be32 saddr,
#else
"r" (proto + len),
#endif
- "r" (sum));
+ "r" ((__force unsigned long)sum));
return sum;
}
-
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