netdev - TCP socket receives strange packet

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Message-ID: <543D2EB2.4000009@oktetlabs.ru>
Date:	Tue, 14 Oct 2014 18:09:54 +0400
From:	"Yurij M. Plotnikov" <Yurij.Plotnikov@...etlabs.ru>
To:	netdev@...r.kernel.org
CC:	"Alexandra N. Kossovsky" <Alexandra.Kossovsky@...etlabs.ru>
Subject: TCP socket receives strange packet

Connected TCP socket receives packet without timestamps option which 
exists in SYN, SYNACK and ACK. It is packet 4 in attached tcpdump output.

tcpdump output description: The host has address 10.208.10.1 (server) 
and the peer host has address 10.208.10.2 (client).

Establishing connection: Timestamps option exists in SYN, SYNACK and ACK 
(packets 1, 2 and 3 in attached file), so accepted socket should receive 
packets only with timestamps option.

Sending packet: the socket receives the packet without timestamps option 
(packet 4 in attached file), i.e. recv() function called on the socket 
receives the data from the packet. The "strange" packet is generated 
using PCAP.

I see this behaviour on 2.6.26 and on 3.14 kernels.

Download attachment "pcap_with_bad_packet" of type "application/octet-stream" (866 bytes)