https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=6194
Eric Travis <eric.dot.travis@xxxxxxxxx> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
CC| |eric.dot.travis@xxxxxxxxx
Resolution|FIXED |
--- Comment #3 from Eric Travis <eric.dot.travis@xxxxxxxxx> 2011-11-11 18:15:49 PST ---
See Bug 6562 for more detailed explanation and corrective patches
The modifications made are incorrect in function;
Wireshark *was* properly handling the included pcap file regarding
the malformed TCP Options.
I can easily modify any random TCP implementation to include 2-octet SACK
options on every TCP segment, but that doesn't mean Wireshark should be
altered so that they don't get flagged as malformed.
SCPS(TCP Option 20) is:
- a variable length option with a minimum length of 4, NOT 2.
- As a negotiated option, it is legal only on segments where
the SYN flag is set, NOT during an established connection flow.
If SCPS capabilities are not successfully negotiated during
connection handshake, no SCPS-related options are legitimate
and wireshark's flagging occurrences as illegal helps developers
debug implementations (such as the source of the triggering
implementation)
The on-the-wire bit specification of the three reserved bits was
correct (read: as specified) prior to modification.
If unfamiliar with the specification of the SCPS TCP enhancements,
please refer to (http://public.ccsds.org/publications/archive/714x0b2.pdf)
Specifically Section 3.2.4 & Section 3.2.5 for this bug.
Wireshark is an invaluable tool for developers, even more so when it can be
depended on to parse correctly.
Rather than simply trusting the contents of a packet trace (regardless of
the source), it is best to verify the CORRECTNESS of observed behavior (per
protocol specification) prior to altering Wireshark behavior so it conforms
to the illustrative trace.
Sorry if this comes off harsh, but the existing comments in the pre-patched
packet-tcp.c should have *at least* prompted a slight pause prior to
committing the patch. This bug took less than 12-hours from submission to
resolution...
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