netdev - querying TOS/DSCP at accept() time?

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Date:	Sun, 27 Dec 2009 09:57:32 -0500
From:	Jeremy Jackson <jerj@...lanar.net>
To:	netdev@...r.kernel.org
Subject: querying TOS/DSCP at accept() time?

I would like to allow clients connecting to webserver to choose TOS/DSCP
value they want in reply packets, based on TOS setting received by
webserver in initial SYN-SYN/ACK-ACK exchange.  Linux samples the TOS
byte of the ACK that moves the state to CONNECTED, presumably to use for
later ECN processing, but I cannot find a way to get this from
userspace.

net/ipv4/tcp_ipv4.c:1645
    TCP_SKB_CB(skb)->flags   = iph->tos;

Am I missing something in getsockopt(TCP_INFO perhaps?) or accept(), or
is this currently not possible?

-- 
Jeremy Jackson
Coplanar Networks
(519)489-4903
http://www.coplanar.net
jerj@...lanar.net

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