From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <shemminger@vyatta.com>
Subject: Re: DSCP values in TCP handshake
Date: Mon, 18 Apr 2011 08:38:27 -0700
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Cc: Joe Buehler <aspam@cox.net>, netdev@vger.kernel.org
To: Eric Dumazet <eric.dumazet@gmail.com>
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On Mon, 18 Apr 2011 16:05:12 +0200
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> Le lundi 18 avril 2011 =C3=A0 13:48 +0000, Joe Buehler a =C3=A9crit :
> > What does the LINUX network code put in the DSCP field of TCP SYN-A=
CK packets
> > that are replies to a SYN connection request?  I have a customer se=
nding SYN
> > with 0x2e in the DSCP field but apparently getting DSCP 0x0 in the =
reply.
>=20
> The other way (server->client) is depending on application and listen=
er
> only.
>=20
> If it uses a standard socket, standard bind() + listen(), TOS is 0

If you want to set DSCP in the response, the application needs to apply
set it on the listening socket.=20
   dscp =3D 0x2e;
   setsockopt(s, IPPROTO_IP, IP_TOS, &dscp, sizeof(dscp));