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Date: Mon, 18 Apr 2016 15:46:04 -0700 From: Martin KaFai Lau <kafai@...com> To: <netdev@...r.kernel.org> CC: Eric Dumazet <edumazet@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, Soheil Hassas Yeganeh <soheil.kdev@...il.com>, Willem de Bruijn <willemb@...gle.com>, Yuchung Cheng <ycheng@...gle.com>, Kernel Team <kernel-team@...com> Subject: [RFC PATCH v2 net-next 2/7] tcp: Merge tx_flags/tskey/txstamp_ack in tcp_collapse_retrans If two skbs are merged/collapsed during retransmission, the current logic does not merge the tx_flags, tskey and txstamp_ack. The end result is the SCM_TSTAMP_ACK timestamp could be missing for a packet that the end-user has specifically turned on SOF_TIMESTAMPING_TX_ACK (e.g. by cmsg). The patch: 1. Merge the tx_flags and txstamp_ack 2. Overwrite the tskey with the later skb (next_skb) BPF Output Before: ~~~~~~ <no-output-due-to-missing-tstamp-event> 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 <mss 1460,sackOK,nop,nop,nop,wscale 7> 0.100 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 7> 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 0.200 > 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 <sack 1461:2921,nop,nop> 0.300 < . 1:1(0) ack 1 win 257 <sack 1461:4381,nop,nop> 0.300 < . 1:1(0) ack 1 win 257 <sack 1461:5841,nop,nop> 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 <kafai@...com> Cc: Eric Dumazet <edumazet@...gle.com> Cc: Neal Cardwell <ncardwell@...gle.com> Cc: Soheil Hassas Yeganeh <soheil.kdev@...il.com> Cc: Willem de Bruijn <willemb@...gle.com> Cc: Yuchung Cheng <ycheng@...gle.com> --- net/ipv4/tcp_output.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 0527ce9..889ed96 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2443,6 +2443,22 @@ 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); + + if (unlikely(next_shinfo->tx_flags & SKBTX_ANY_TSTAMP)) { + struct skb_shared_info *shinfo = skb_shinfo(skb); + u8 tsflags = next_shinfo->tx_flags & SKBTX_ANY_TSTAMP; + + shinfo->tx_flags |= tsflags; + shinfo->tskey = next_shinfo->tskey; + TCP_SKB_CB(skb)->txstamp_ack = + !!(shinfo->tx_flags & SKBTX_ACK_TSTAMP); + } +} + /* Collapses two adjacent SKB's during retransmission. */ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) { @@ -2486,6 +2502,8 @@ 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
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