diff options
Diffstat (limited to 'net/ipv4/tcp_input.c')
| -rw-r--r-- | net/ipv4/tcp_input.c | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index ff71b18d9682..2c6797134553 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -97,6 +97,7 @@ int sysctl_tcp_max_orphans __read_mostly = NR_FILE; #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */ #define FLAG_NO_CHALLENGE_ACK 0x8000 /* do not call tcp_send_challenge_ack() */ +#define FLAG_ACK_MAYBE_DELAYED 0x10000 /* Likely a delayed ACK */ #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) @@ -2857,11 +2858,18 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una, *rexmit = REXMIT_LOST; } -static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us) +static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us, const int flag) { u32 wlen = sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen * HZ; struct tcp_sock *tp = tcp_sk(sk); + if ((flag & FLAG_ACK_MAYBE_DELAYED) && rtt_us > tcp_min_rtt(tp)) { + /* If the remote keeps returning delayed ACKs, eventually + * the min filter would pick it up and overestimate the + * prop. delay when it expires. Skip suspected delayed ACKs. + */ + return; + } minmax_running_min(&tp->rtt_min, wlen, tcp_jiffies32, rtt_us ? : jiffies_to_usecs(1)); } @@ -2901,7 +2909,7 @@ static bool tcp_ack_update_rtt(struct sock *sk, const int flag, * always taken together with ACK, SACK, or TS-opts. Any negative * values will be skipped with the seq_rtt_us < 0 check above. */ - tcp_update_rtt_min(sk, ca_rtt_us); + tcp_update_rtt_min(sk, ca_rtt_us, flag); tcp_rtt_estimator(sk, seq_rtt_us); tcp_set_rto(sk); @@ -3125,6 +3133,17 @@ static int tcp_clean_rtx_queue(struct sock *sk, u32 prior_fack, if (likely(first_ackt) && !(flag & FLAG_RETRANS_DATA_ACKED)) { seq_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, first_ackt); ca_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, last_ackt); + + if (pkts_acked == 1 && last_in_flight < tp->mss_cache && + last_in_flight && !prior_sacked && fully_acked && + sack->rate->prior_delivered + 1 == tp->delivered && + !(flag & (FLAG_CA_ALERT | FLAG_SYN_ACKED))) { + /* Conservatively mark a delayed ACK. It's typically + * from a lone runt packet over the round trip to + * a receiver w/o out-of-order or CE events. + */ + flag |= FLAG_ACK_MAYBE_DELAYED; + } } if (sack->first_sackt) { sack_rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, sack->first_sackt); |