CVS commit: syssrc/sys/netinet

[Bill Sommerfeld <sommerfeld%netbsd.org@localhost>]

Module Name:    syssrc
Committed By:   sommerfeld
Date:           Tue Sep 24 14:14:26 UTC 2002

Modified Files:
        syssrc/sys/netinet: ip_nat.c

Log Message:
Relax overly-conservative TCP option parsing used by ipnat when
hunting for an MSS option to clamp.  The previous code assumed that at least
one more byte of options (such as a TCPOPT_EOL) would follow the MSS
option; now, we allow the MSS option to end on the last byte of the
TCP header.

Packets have been observed "in the wild" with a TCP header length of
'6' (24 bytes.. 20 bytes fixed header, 4 bytes options) with a 4-byte
MSS option exactly filling the 4 bytes of options payload and no
following TCPOPT_EOL.

RFC793 is quite explicit that the EOL byte:

        " .. need only be used if the end of the options would not
        otherwise coincide with the end of the TCP header."


To generate a diff of this commit:
cvs rdiff -r1.53 -r1.54 syssrc/sys/netinet/ip_nat.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.