From 91cc17c0e5e5ada156a8d5787a2509d263ea6bbf Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ilpo=20J=C3=A4rvinen?= Date: Fri, 23 Nov 2007 19:08:16 +0800 Subject: [PATCH] [TCP]: MTUprobe: receiver window & data available checks fixed MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit It seems that the checked range for receiver window check should begin from the first rather than from the last skb that is going to be included to the probe. And that can be achieved without reference to skbs at all, snd_nxt and write_seq provides the correct seqno already. Plus, it SHOULD account packets that are necessary to trigger fast retransmit [RFC4821]. Location of snd_wnd < probe_size/size_needed check is bogus because it will cause the other if() match as well (due to snd_nxt >= snd_una invariant). Removed dead obvious comment. Signed-off-by: Ilpo Järvinen Signed-off-by: Herbert Xu --- net/ipv4/tcp_output.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index e48e28e7d539..4f8a8a17891a 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1295,6 +1295,7 @@ static int tcp_mtu_probe(struct sock *sk) struct sk_buff *skb, *nskb, *next; int len; int probe_size; + int size_needed; unsigned int pif; int copy; int mss_now; @@ -1313,6 +1314,7 @@ static int tcp_mtu_probe(struct sock *sk) /* Very simple search strategy: just double the MSS. */ mss_now = tcp_current_mss(sk, 0); probe_size = 2*tp->mss_cache; + size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache; if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) { /* TODO: set timer for probe_converge_event */ return -1; @@ -1322,18 +1324,15 @@ static int tcp_mtu_probe(struct sock *sk) len = 0; if ((skb = tcp_send_head(sk)) == NULL) return -1; - while ((len += skb->len) < probe_size && !tcp_skb_is_last(sk, skb)) + while ((len += skb->len) < size_needed && !tcp_skb_is_last(sk, skb)) skb = tcp_write_queue_next(sk, skb); - if (len < probe_size) + if (len < size_needed) return -1; - /* Receive window check. */ - if (after(TCP_SKB_CB(skb)->seq + probe_size, tp->snd_una + tp->snd_wnd)) { - if (tp->snd_wnd < probe_size) - return -1; - else - return 0; - } + if (tp->snd_wnd < size_needed) + return -1; + if (after(tp->snd_nxt + size_needed, tp->snd_una + tp->snd_wnd)) + return 0; /* Do we need to wait to drain cwnd? */ pif = tcp_packets_in_flight(tp); -- 2.20.1