Petr Tesarik 33cf71cee1 tcp: Do not use TSO/GSO when there is urgent data
This patch fixes http://bugzilla.kernel.org/show_bug.cgi?id=12014

Since most (if not all) implementations of TSO and even the in-kernel
software GSO do not update the urgent pointer when splitting a large
segment, it is necessary to turn off TSO/GSO for all outgoing traffic
with the URG pointer set.

Looking at tcp_current_mss (and the preceding comment) I even think
this was the original intention. However, this approach is insufficient,
because TSO/GSO is turned off only for newly created frames, not for
frames which were already pending at the arrival of a message with
MSG_OOB set. These frames were created when TSO/GSO was enabled,
so they may be large, and they will have the urgent pointer set
in tcp_transmit_skb().

With this patch, such large packets will be fragmented again before
going to the transmit routine.

As a side note, at least the following NICs are known to screw up
the urgent pointer in the TCP header when doing TSO:

	Intel 82566MM (PCI ID 8086:1049)
	Intel 82566DC (PCI ID 8086:104b)
	Intel 82541GI (PCI ID 8086:1076)
	Broadcom NetXtreme II BCM5708 (PCI ID 14e4:164c)

Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-11-21 16:42:58 -08:00
..
2008-07-16 20:20:11 -07:00
2008-08-06 02:39:30 -07:00
2008-06-11 21:00:38 -07:00
2008-07-16 20:20:11 -07:00
2008-11-12 23:23:51 -08:00
2008-11-19 14:07:41 -08:00
2008-10-07 08:38:24 +11:00
2008-10-07 08:38:24 +11:00
2008-06-11 21:00:38 -07:00
2008-07-16 20:19:49 -07:00
2008-10-16 11:21:47 -07:00
2008-05-01 08:03:58 -07:00
2008-06-11 21:00:38 -07:00
2008-11-12 01:41:09 -08:00
2008-10-07 14:43:06 -07:00
2008-07-10 16:51:32 -07:00
2008-10-07 14:18:42 -07:00