tcpdump manpage has incomplete docs on TCP headers

[guyharris]

Converted from SourceForge issue 753399, submitted by arach

I got this reported to us and I think it belongs upstream.

reporter:rindolf@snappydsl.net
http://bugs.gentoo.org/show_bug.cgi?id=21312
Regards,
Spider@gentoo.org

---

There are two TCP headers, ECN Echo and ECN Cwnd
Reduced, that tcpdump
recognizes and outputs the existence of, but aren't
listed in the manpage. The
relevant section of tcpdump.1, near the top of the TCP
Packets section, line 743:

   Flags  are some combination of S (SYN), F (FIN),

P (PUSH) or R (RST) or
a single `.' (no flags). Data-seqno describes
the portion of sequence

The part of print-tcp.c that produces the header flag
output, inside the
function tcp_print, line 274:

if ((flags = tp->th_flags) &
(TH_SYN|TH_FIN|TH_RST|TH_PUSH|
TH_ECNECHO|TH_CWR)) {
if (flags & TH_SYN)
putchar('S');
if (flags & TH_FIN)
putchar('F');
if (flags & TH_RST)
putchar('R');
if (flags & TH_PUSH)
putchar('P');
if (flags & TH_CWR)
putchar('W');/* congestion _W_indow reduced (ECN) /
if (flags & TH_ECNECHO)
putchar('E');/ ecn _E_cho sent (ECN) */
} else
putchar('.');

W and E are not documented in the manpage.

Reproducible: Always
Steps to Reproduce:
1.Run tcpdump
2.Receive a packet with the W or E header flags set
3.Wonder what W and E mean, as they aren't in the manpage.

[guyharris]

Submitted by guy_harris

Logged In: YES
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An update to the man page has been checked in.