From: Eric Dumazet Date: Wed, 15 May 2013 15:38:01 +0000 (+0000) Subject: tcp: gso: do not generate out of order packets X-Git-Tag: MMI-PSA29.97-13-9~14343^2~37 X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=6ff50cd55545d922f5c62776fe1feb38a9846168;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git tcp: gso: do not generate out of order packets GSO TCP handler has following issues : 1) ooo_okay from original GSO packet is duplicated to all segments 2) segments (but the last one) are orphaned, so transmit path can not get transmit queue number from the socket. This happens if GSO segmentation is done before stacked device for example. Result is we can send packets from a given TCP flow to different TX queues (if using multiqueue NICS). This generates OOO problems and spurious SACK & retransmits. Fix this by keeping socket pointer set for all segments. This means that every segment must also have a destructor, and the original gso skb truesize must be split on all segments, to keep precise sk->sk_wmem_alloc accounting. Signed-off-by: Eric Dumazet Cc: Maciej Żenczykowski Cc: Tom Herbert Cc: Neal Cardwell Cc: Yuchung Cheng Signed-off-by: David S. Miller --- diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 10c93930abda..ab450c099aa4 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2887,6 +2887,7 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, unsigned int mss; struct sk_buff *gso_skb = skb; __sum16 newcheck; + bool ooo_okay, copy_destructor; if (!pskb_may_pull(skb, sizeof(*th))) goto out; @@ -2927,10 +2928,18 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, goto out; } + copy_destructor = gso_skb->destructor == tcp_wfree; + ooo_okay = gso_skb->ooo_okay; + /* All segments but the first should have ooo_okay cleared */ + skb->ooo_okay = 0; + segs = skb_segment(skb, features); if (IS_ERR(segs)) goto out; + /* Only first segment might have ooo_okay set */ + segs->ooo_okay = ooo_okay; + delta = htonl(oldlen + (thlen + mss)); skb = segs; @@ -2950,6 +2959,17 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, thlen, skb->csum)); seq += mss; + if (copy_destructor) { + skb->destructor = gso_skb->destructor; + skb->sk = gso_skb->sk; + /* {tcp|sock}_wfree() use exact truesize accounting : + * sum(skb->truesize) MUST be exactly be gso_skb->truesize + * So we account mss bytes of 'true size' for each segment. + * The last segment will contain the remaining. + */ + skb->truesize = mss; + gso_skb->truesize -= mss; + } skb = skb->next; th = tcp_hdr(skb); @@ -2962,7 +2982,7 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, * is freed at TX completion, and not right now when gso_skb * is freed by GSO engine */ - if (gso_skb->destructor == tcp_wfree) { + if (copy_destructor) { swap(gso_skb->sk, skb->sk); swap(gso_skb->destructor, skb->destructor); swap(gso_skb->truesize, skb->truesize);