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authorPetr Tesarik <ptesarik@suse.cz>2008-11-21 19:42:58 -0500
committerDavid S. Miller <davem@davemloft.net>2008-11-21 19:42:58 -0500
commit33cf71cee14743185305c61625c4544885055733 (patch)
treed05c9fb2fd12d8eede22c261c2db57d30f96a73a /net
parent38ae07e44bb2dc86770555a1acafcb937ec74478 (diff)
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>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_output.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ba85d8831893..85b07eba1879 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)
722static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, 722static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb,
723 unsigned int mss_now) 723 unsigned int mss_now)
724{ 724{
725 if (skb->len <= mss_now || !sk_can_gso(sk)) { 725 if (skb->len <= mss_now || !sk_can_gso(sk) ||
726 tcp_urg_mode(tcp_sk(sk))) {
726 /* Avoid the costly divide in the normal 727 /* Avoid the costly divide in the normal
727 * non-TSO case. 728 * non-TSO case.
728 */ 729 */
@@ -1163,7 +1164,9 @@ static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb,
1163{ 1164{
1164 int tso_segs = tcp_skb_pcount(skb); 1165 int tso_segs = tcp_skb_pcount(skb);
1165 1166
1166 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) { 1167 if (!tso_segs ||
1168 (tso_segs > 1 && (tcp_skb_mss(skb) != mss_now ||
1169 tcp_urg_mode(tcp_sk(sk))))) {
1167 tcp_set_skb_tso_segs(sk, skb, mss_now); 1170 tcp_set_skb_tso_segs(sk, skb, mss_now);
1168 tso_segs = tcp_skb_pcount(skb); 1171 tso_segs = tcp_skb_pcount(skb);
1169 } 1172 }