[lwip-devel] RE: [bug #20075] A problem with keep-alive timer and TCP flags

[Gollakota, Srinivas]

I checked few related documents in the net. The below document it
appears like linux kernel uses ACK flag set for keep alive probes.
Please see section 2.1 in the below link.

http://www.linux.org/docs/ldp/howto/TCP-Keepalive-HOWTO/index.html

But in RFC1122 (Requirements for Internet Hosts -- Communication Layers
)
section 4.2.3.6 talks about keep-alive probes and TCP sequence number
but not about TCP flags.

http://www.faqs.org/rfcs/rfc1122.html

-Srinivas.

-----Original Message-----
From: Oleg Tyshev [mailto:address@hidden 
Sent: Wednesday, June 06, 2007 6:10 AM
To: Kieran Mansley; Srinivas Gollakota; Oleg Tyshev;
address@hidden
Subject: [bug #20075] A problem with keep-alive timer and TCP flags



Follow-up Comment #2, bug #20075 (project lwip):

I think keep-alive packets should not send ACK flag.
Data are already acknowledged.
We need acknowledge only as reply to keep-alive packet.
So, it will be better TCPH_FLAGS_SET( tcphdr, 0);

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