path: root/net/ipv4/tcp_input.c
diff options
authorWei Wang <weiwan@google.com>2018-06-19 21:42:50 -0700
committerDavid S. Miller <davem@davemloft.net>2018-06-22 13:45:01 +0900
commit3f6c65d6255a872846c44182c82c78d3dc6239f5 (patch)
tree7dabd565296b1e797140820da5205e4c0f60aae2 /net/ipv4/tcp_input.c
parentMerge branch 'rhashtables-cleanups' (diff)
tcp: ignore rcv_rtt sample with old ts ecr value
When receiving multiple packets with the same ts ecr value, only try to compute rcv_rtt sample with the earliest received packet. This is because the rcv_rtt calculated by later received packets could possibly include long idle time or other types of delay. For example: (1) server sends last packet of reply with TS val V1 (2) client ACKs last packet of reply with TS ecr V1 (3) long idle time passes (4) client sends next request data packet with TS ecr V1 (again!) At this time, the rcv_rtt computed on server with TS ecr V1 will be inflated with the idle time and should get ignored. Signed-off-by: Wei Wang <weiwan@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_input.c')
1 files changed, 11 insertions, 3 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 355d3dffd021..76ca88f63b70 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -582,9 +582,12 @@ static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
struct tcp_sock *tp = tcp_sk(sk);
- if (tp->rx_opt.rcv_tsecr &&
- (TCP_SKB_CB(skb)->end_seq -
- TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) {
+ if (tp->rx_opt.rcv_tsecr == tp->rcv_rtt_last_tsecr)
+ return;
+ tp->rcv_rtt_last_tsecr = tp->rx_opt.rcv_tsecr;
+ if (TCP_SKB_CB(skb)->end_seq -
+ TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss) {
u32 delta = tcp_time_stamp(tp) - tp->rx_opt.rcv_tsecr;
u32 delta_us;
@@ -5475,6 +5478,11 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
tcp_ack(sk, skb, 0);
+ /* When receiving pure ack in fast path, update
+ * last ts ecr directly instead of calling
+ * tcp_rcv_rtt_measure_ts()
+ */
+ tp->rcv_rtt_last_tsecr = tp->rx_opt.rcv_tsecr;
} else { /* Header too small */