[PATCH net 2/2] tcp: Merge tx_flags and tskey in tcp_shifted_skb

[Martin KaFai Lau]

After receiving sacks, tcp_shifted_skb() will collapse
skbs if possible.  tx_flags and tskey also have to be
merged.

This patch reuses the tcp_skb_collapse_tstamp() to handle
them.

BPF Output Before:
~~~~~
<no-output-due-to-missing-tstamp-event>

BPF Output After:
~~~~~
<...>-2024  [007] d.s.    88.644374: : ee_data:14599

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, ..., 1460) = 1460
+0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0
0.200 write(4, ..., 13140) = 13140

0.200 > P. 1:1461(1460) ack 1
0.200 > . 1461:8761(7300) ack 1
0.200 > P. 8761:14601(5840) ack 1

0.300 < . 1:1(0) ack 1 win 257 <sack 1461:14601,nop,nop>
0.300 > P. 1:1461(1460) ack 1
0.400 < . 1:1(0) ack 14601 win 257

0.400 close(4) = 0
0.400 > F. 14601:14601(0) ack 1
0.500 < F. 1:1(0) ack 14602 win 257
0.500 > . 14602:14602(0) ack 2

Signed-off-by: Martin KaFai Lau <ka...@fb.com>
Cc: Eric Dumazet <eduma...@google.com>
Cc: Neal Cardwell <ncardw...@google.com>
Cc: Soheil Hassas Yeganeh <soh...@google.com>
Cc: Willem de Bruijn <will...@google.com>
Cc: Yuchung Cheng <ych...@google.com>
---
 include/net/tcp.h     | 2 ++
 net/ipv4/tcp_input.c  | 1 +
 net/ipv4/tcp_output.c | 4 ++--
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index b91370f..6db1022 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -552,6 +552,8 @@ void tcp_send_ack(struct sock *sk);
 void tcp_send_delayed_ack(struct sock *sk);
 void tcp_send_loss_probe(struct sock *sk);
 bool tcp_schedule_loss_probe(struct sock *sk);
+void tcp_skb_collapse_tstamp(struct sk_buff *skb,
+                            const struct sk_buff *next_skb);
 
 /* tcp_input.c */
 void tcp_resume_early_retransmit(struct sock *sk);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0edb071..c124c3c 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1309,6 +1309,7 @@ static bool tcp_shifted_skb(struct sock *sk, struct 
sk_buff *skb,
        if (skb == tcp_highest_sack(sk))
                tcp_advance_highest_sack(sk, skb);
 
+       tcp_skb_collapse_tstamp(prev, skb);
        tcp_unlink_write_queue(skb, sk);
        sk_wmem_free_skb(sk, skb);
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 5bc3c30..441ae9d 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2441,8 +2441,8 @@ 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)
+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;
-- 
2.5.1