diff options
author | Dave Johnson <djohnson+linux-mips@sw.starentnetworks.com> | 2007-04-18 10:39:41 -0400 |
---|---|---|
committer | Ralf Baechle <ralf@linux-mips.org> | 2007-04-20 14:58:37 +0100 |
commit | 1d464c26b5625215c4b35fb336c8f3c57d248c2e (patch) | |
tree | 88316e8149c4125dbdb55ff90a4e8d45a024940b /include/asm-ia64/sn/tiocp.h | |
parent | ba755f8ec80fdbf2b5212622eabf7355464c6327 (diff) |
[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 <djohnson+linux-mips@sw.starentnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'include/asm-ia64/sn/tiocp.h')
0 files changed, 0 insertions, 0 deletions