From patchwork Mon Jul 11 07:49:00 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: YonglongLi X-Patchwork-Id: 12913042 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18D9BC433EF for ; Mon, 11 Jul 2022 07:50:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230206AbiGKHuD (ORCPT ); Mon, 11 Jul 2022 03:50:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33516 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230203AbiGKHuC (ORCPT ); Mon, 11 Jul 2022 03:50:02 -0400 Received: from chinatelecom.cn (prt-mail.chinatelecom.cn [42.123.76.226]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 27ADA1BEAC for ; Mon, 11 Jul 2022 00:49:57 -0700 (PDT) HMM_SOURCE_IP: 172.18.0.218:50322.580737606 HMM_ATTACHE_NUM: 0000 HMM_SOURCE_TYPE: SMTP Received: from clientip-36.111.140.9 (unknown [172.18.0.218]) by chinatelecom.cn (HERMES) with SMTP id 11A3D2800D5; Mon, 11 Jul 2022 15:49:52 +0800 (CST) X-189-SAVE-TO-SEND: +liyonglong@chinatelecom.cn Received: from ([172.18.0.218]) by app0025 with ESMTP id 409ce89312494811bcd672b3e0318c7a for netdev@vger.kernel.org; Mon, 11 Jul 2022 15:49:54 CST X-Transaction-ID: 409ce89312494811bcd672b3e0318c7a X-Real-From: liyonglong@chinatelecom.cn X-Receive-IP: 172.18.0.218 X-MEDUSA-Status: 0 Sender: liyonglong@chinatelecom.cn From: Yonglong Li To: netdev@vger.kernel.org Cc: davem@davemloft.net, dsahern@kernel.org, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, liyonglong@chinatelecom.cn Subject: [PATCH v3] tcp: make retransmitted SKB fit into the send window Date: Mon, 11 Jul 2022 15:49:00 +0800 Message-Id: <1657525740-7585-1-git-send-email-liyonglong@chinatelecom.cn> X-Mailer: git-send-email 1.8.3.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window. If receiver has shrunk his window, and skb is out of new window, it should retransmit a smaller portion of the payload. test packetdrill script: 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR) +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress) +0 > S 0:0(0) win 65535 +.05 < S. 0:0(0) ack 1 win 6000 +0 > . 1:1(0) ack 1 +0 write(3, ..., 10000) = 10000 +0 > . 1:2001(2000) ack 1 win 65535 +0 > . 2001:4001(2000) ack 1 win 65535 +0 > . 4001:6001(2000) ack 1 win 65535 +.05 < . 1:1(0) ack 4001 win 1001 and tcpdump show: 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 1:2001, ack 1, win 65535, length 2000 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 2001:4001, ack 1, win 65535, length 2000 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000 192.0.2.1.8080 > 192.168.226.67.55: Flags [.], ack 4001, win 1001, length 0 192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000 192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000 when cient retract window to 1001, send window is [4001,5002], but TLP send 5001-6001 packet which is out of send window. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Yonglong Li --- net/ipv4/tcp_output.c | 36 ++++++++++++++++++++++++------------ 1 file changed, 24 insertions(+), 12 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 18c913a..efd0f05 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -3100,7 +3100,6 @@ static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb) static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to, int space) { - struct tcp_sock *tp = tcp_sk(sk); struct sk_buff *skb = to, *tmp; bool first = true; @@ -3123,14 +3122,18 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to, continue; } - if (space < 0) - break; - - if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp))) + if (space < 0) { + if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, + skb, space + skb->len, + tcp_current_mss(sk), GFP_ATOMIC))) + break; + tcp_collapse_retrans(sk, to); break; + } if (!tcp_collapse_retrans(sk, to)) break; + } } @@ -3144,7 +3147,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) struct tcp_sock *tp = tcp_sk(sk); unsigned int cur_mss; int diff, len, err; - + int avail_wnd; /* Inconclusive MTU probe */ if (icsk->icsk_mtup.probe_size) @@ -3166,17 +3169,25 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) return -EHOSTUNREACH; /* Routing failure or similar. */ cur_mss = tcp_current_mss(sk); + avail_wnd = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; /* If receiver has shrunk his window, and skb is out of * new window, do not retransmit it. The exception is the * case, when window is shrunk to zero. In this case - * our retransmit serves as a zero window probe. + * our retransmit of one segment serves as a zero window probe. */ - if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) && - TCP_SKB_CB(skb)->seq != tp->snd_una) - return -EAGAIN; + if (avail_wnd <= 0) { + if (TCP_SKB_CB(skb)->seq != tp->snd_una) + return -EAGAIN; + avail_wnd = cur_mss; + } len = cur_mss * segs; + if (len > avail_wnd) { + len = rounddown(avail_wnd, cur_mss); + if (!len) + len = avail_wnd; + } if (skb->len > len) { if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len, cur_mss, GFP_ATOMIC)) @@ -3190,8 +3201,9 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) diff -= tcp_skb_pcount(skb); if (diff) tcp_adjust_pcount(sk, skb, diff); - if (skb->len < cur_mss) - tcp_retrans_try_collapse(sk, skb, cur_mss); + avail_wnd = min_t(int, avail_wnd, cur_mss); + if (skb->len < avail_wnd) + tcp_retrans_try_collapse(sk, skb, avail_wnd); } /* RFC3168, section 6.1.1.1. ECN fallback */