From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin KaFai Lau Subject: [PATCH net 1/2] tcp: Merge tx_flags and tskey in tcp_collapse_retrans Date: Tue, 19 Apr 2016 22:39:28 -0700 Message-ID: <1461130769-1442865-2-git-send-email-kafai@fb.com> References: <1461130769-1442865-1-git-send-email-kafai@fb.com> Mime-Version: 1.0 Content-Type: text/plain Cc: Eric Dumazet , Neal Cardwell , Soheil Hassas Yeganeh , Willem de Bruijn , Yuchung Cheng , Kernel Team To: Return-path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:56431 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751881AbcDTFj4 (ORCPT ); Wed, 20 Apr 2016 01:39:56 -0400 Received: from pps.filterd (m0044008.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u3K5acXb017693 for ; Tue, 19 Apr 2016 22:39:55 -0700 Received: from mail.thefacebook.com ([199.201.64.23]) by mx0a-00082601.pphosted.com with ESMTP id 22e2gs0axc-2 (version=TLSv1 cipher=AES128-SHA bits=128 verify=NOT) for ; Tue, 19 Apr 2016 22:39:55 -0700 Received: from facebook.com (2401:db00:11:d0a6:face:0:33:0) by mx-out.facebook.com (10.212.236.87) with ESMTP id 4df3791006ba11e688910002c9521c9e-a85cdc50 for ; Tue, 19 Apr 2016 22:39:52 -0700 In-Reply-To: <1461130769-1442865-1-git-send-email-kafai@fb.com> Sender: netdev-owner@vger.kernel.org List-ID: If two skbs are merged/collapsed during retransmission, the current logic does not merge the tx_flags and tskey. The end result is the SCM_TSTAMP_ACK timestamp could be missing for a packet. The patch: 1. Merge the tx_flags 2. Overwrite the prev_skb's tskey with the next_skb's tskey BPF Output Before: ~~~~~~ BPF Output After: ~~~~~~ packetdrill-2092 [001] d.s. 453.998486: : ee_data:1459 Packetdrill Script: ~~~~~~ +0 `sysctl -q -w net.ipv4.tcp_min_tso_segs=10` +0 `sysctl -q -w net.ipv4.tcp_no_metrics_save=1` +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 +0 bind(3, ..., ...) = 0 +0 listen(3, 1) = 0 0.100 < S 0:0(0) win 32792 0.100 > S. 0:0(0) ack 1 0.200 < . 1:1(0) ack 1 win 257 0.200 accept(3, ..., ...) = 4 +0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0 0.200 write(4, ..., 730) = 730 +0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0 0.200 write(4, ..., 730) = 730 +0 setsockopt(4, SOL_SOCKET, 37, [2176], 4) = 0 0.200 write(4, ..., 11680) = 11680 +0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0 0.200 > P. 1:731(730) ack 1 0.200 > P. 731:1461(730) ack 1 0.200 > . 1461:8761(7300) ack 1 0.200 > P. 8761:13141(4380) ack 1 0.300 < . 1:1(0) ack 1 win 257 0.300 < . 1:1(0) ack 1 win 257 0.300 < . 1:1(0) ack 1 win 257 0.300 > P. 1:1461(1460) ack 1 0.400 < . 1:1(0) ack 13141 win 257 0.400 close(4) = 0 0.400 > F. 13141:13141(0) ack 1 0.500 < F. 1:1(0) ack 13142 win 257 0.500 > . 13142:13142(0) ack 2 Signed-off-by: Martin KaFai Lau Cc: Eric Dumazet Cc: Neal Cardwell Cc: Soheil Hassas Yeganeh Cc: Willem de Bruijn Cc: Yuchung Cheng --- net/ipv4/tcp_output.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 7d2dc01..5bc3c30 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2441,6 +2441,20 @@ u32 __tcp_select_window(struct sock *sk) return window; } +static void tcp_skb_collapse_tstamp(struct sk_buff *skb, + const struct sk_buff *next_skb) +{ + const struct skb_shared_info *next_shinfo = skb_shinfo(next_skb); + u8 tsflags = next_shinfo->tx_flags & SKBTX_ANY_TSTAMP; + + if (unlikely(tsflags)) { + struct skb_shared_info *shinfo = skb_shinfo(skb); + + shinfo->tx_flags |= tsflags; + shinfo->tskey = next_shinfo->tskey; + } +} + /* Collapses two adjacent SKB's during retransmission. */ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) { @@ -2484,6 +2498,8 @@ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb)); + tcp_skb_collapse_tstamp(skb, next_skb); + sk_wmem_free_skb(sk, next_skb); } -- 2.5.1