From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sergei Trofimovich <slyfox@gentoo.org>
Subject: [BUG?] tcp regression in v4.7-r1:
 c14ac9451c34832554db33386a4393be8bba3a7b breaks pulseaudio over TCP
Date: Sun, 10 Jul 2016 12:42:40 +0100
Message-ID: <20160710124240.7d484f44@sf>
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Cc: Willem de Bruijn <willemb@google.com>, Tanu Kaskinen <tanuk@iki.fi>
To: Soheil Hassas Yeganeh <soheil@google.com>,
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Hi netdev folk!

Commit c14ac9451c34832554db33386a4393be8bba3a7b
broke pulseaudio (PA) over TCP.

PA does unusual thing: it calls
    sendmsg(cmsg_type=3DSCM_CREDENTIALS)
on a TCP socket. It's not a new PA behaviour though.

Originally reported as PA bug (has more details)
    https://bugs.freedesktop.org/show_bug.cgi?id=3D96873

It looks like kernel used to ignore control messages
but now it does not:
    http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/diff/net=
/ipv4/tcp.c?id=3Dc14ac9451c34832554db33386a4393be8bba3a7b

+	if (msg->msg_controllen) {
+		err =3D sock_cmsg_send(sk, msg, &sockc);
+		if (unlikely(err)) {
+			err =3D -EINVAL;
+			goto out_err;
+		}
+	}

This change breaks streaming of pulse clients.

Pulseaudio will be fixed at some point.

But kernel change does not look like intentional
breakage of old behaviour.

Perhaps kernel should have a grace period and only
warn about unsupported control messages for a socket?

Last working kernel: v4.6

Thanks!

--=20

  Sergei

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