Messages in this thread Patch in this message | | | From | Petr Tesarik <> | Subject | [PATCH] Do not use TSO/GSO when there is urgent data | Date | Fri, 21 Nov 2008 13:19:45 +0100 |
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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> CC: Jan Sembera <jsembera@suse.cz> CC: Ilpo Jarvinen <ilpo.jarvinen@helsinki.fi>
-- tcp_output.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -722,7 +722,8 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now) { - if (skb->len <= mss_now || !sk_can_gso(sk)) { + if (skb->len <= mss_now || !sk_can_gso(sk) || + tcp_urg_mode(tcp_sk(sk))) { /* Avoid the costly divide in the normal * non-TSO case. */ @@ -1163,7 +1164,9 @@ static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, { int tso_segs = tcp_skb_pcount(skb); - if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) { + if (!tso_segs || + (tso_segs > 1 && (tcp_skb_mss(skb) != mss_now || + tcp_urg_mode(tcp_sk(sk))))) { tcp_set_skb_tso_segs(sk, skb, mss_now); tso_segs = tcp_skb_pcount(skb); }
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