From b68e9f857271189bd7a59b74c99890de9195b0e1 Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Thu, 4 Aug 2005 19:52:02 -0700 Subject: [PATCH] [PATCH] tcp: fix TSO cwnd caching bug tcp_write_xmit caches the cwnd value indirectly in cwnd_quota. When tcp_transmit_skb reduces the cwnd because of tcp_enter_cwr, the cached value becomes invalid. This patch ensures that the cwnd value is always reread after each tcp_transmit_skb call. Signed-off-by: Herbert Xu Cc: "David S. Miller" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- net/ipv4/tcp_output.c | 34 +++++++++------------------------- 1 file changed, 9 insertions(+), 25 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index e118b4b5b326..7d076f0db100 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -972,19 +972,18 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle) if (unlikely(sk->sk_state == TCP_CLOSE)) return 0; - skb = sk->sk_send_head; - if (unlikely(!skb)) - return 0; - - tso_segs = tcp_init_tso_segs(sk, skb, mss_now); - cwnd_quota = tcp_cwnd_test(tp, skb); - if (unlikely(!cwnd_quota)) - goto out; - sent_pkts = 0; - while (likely(tcp_snd_wnd_test(tp, skb, mss_now))) { + while ((skb = sk->sk_send_head)) { + tso_segs = tcp_init_tso_segs(sk, skb, mss_now); BUG_ON(!tso_segs); + cwnd_quota = tcp_cwnd_test(tp, skb); + if (!cwnd_quota) + break; + + if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) + break; + if (tso_segs == 1) { if (unlikely(!tcp_nagle_test(tp, skb, mss_now, (tcp_skb_is_last(sk, skb) ? @@ -1026,27 +1025,12 @@ static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle) tcp_minshall_update(tp, mss_now, skb); sent_pkts++; - - /* Do not optimize this to use tso_segs. If we chopped up - * the packet above, tso_segs will no longer be valid. - */ - cwnd_quota -= tcp_skb_pcount(skb); - - BUG_ON(cwnd_quota < 0); - if (!cwnd_quota) - break; - - skb = sk->sk_send_head; - if (!skb) - break; - tso_segs = tcp_init_tso_segs(sk, skb, mss_now); } if (likely(sent_pkts)) { tcp_cwnd_validate(sk, tp); return 0; } -out: return !tp->packets_out && sk->sk_send_head; } -- 2.20.1