From 33cf71cee14743185305c61625c4544885055733 Mon Sep 17 00:00:00 2001 From: Petr Tesarik Date: Fri, 21 Nov 2008 16:42:58 -0800 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- net/ipv4/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 index ba85d883189..85b07eba187 100644 --- 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); } -- 2.41.1