diff options
author | Yuchung Cheng <ycheng@google.com> | 2019-01-17 00:05:30 +0100 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2019-01-18 00:12:26 +0100 |
commit | 7ae189759cc48cf8b54beebff566e9fd2d4e7d7c (patch) | |
tree | 352db05710fad943494d48107a6fb4d7555d0a70 /net/ipv4/tcp_timer.c | |
parent | tcp: always timestamp on every skb transmission (diff) | |
download | linux-7ae189759cc48cf8b54beebff566e9fd2d4e7d7c.tar.xz linux-7ae189759cc48cf8b54beebff566e9fd2d4e7d7c.zip |
tcp: always set retrans_stamp on recovery
Previously TCP socket's retrans_stamp is not set if the
retransmission has failed to send. As a result if a socket is
experiencing local issues to retransmit packets, determining when
to abort a socket is complicated w/o knowning the starting time of
the recovery since retrans_stamp may remain zero.
This complication causes sub-optimal behavior that TCP may use the
latest, instead of the first, retransmission time to compute the
elapsed time of a stalling connection due to local issues. Then TCP
may disrecard TCP retries settings and keep retrying until it finally
succeed: not a good idea when the local host is already strained.
The simple fix is to always timestamp the start of a recovery.
It's worth noting that retrans_stamp is also used to compare echo
timestamp values to detect spurious recovery. This patch does
not break that because retrans_stamp is still later than when the
original packet was sent.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_timer.c')
-rw-r--r-- | net/ipv4/tcp_timer.c | 23 |
1 files changed, 3 insertions, 20 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index e7d09e3705b8..1e61f0bd6e24 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -22,28 +22,14 @@ #include <linux/gfp.h> #include <net/tcp.h> -static u32 tcp_retransmit_stamp(const struct sock *sk) -{ - u32 start_ts = tcp_sk(sk)->retrans_stamp; - - if (unlikely(!start_ts)) { - struct sk_buff *head = tcp_rtx_queue_head(sk); - - if (!head) - return 0; - start_ts = tcp_skb_timestamp(head); - } - return start_ts; -} - static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk); u32 elapsed, start_ts; s32 remaining; - start_ts = tcp_retransmit_stamp(sk); - if (!icsk->icsk_user_timeout || !start_ts) + start_ts = tcp_sk(sk)->retrans_stamp; + if (!icsk->icsk_user_timeout) return icsk->icsk_rto; elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts; remaining = icsk->icsk_user_timeout - elapsed; @@ -197,10 +183,7 @@ static bool retransmits_timed_out(struct sock *sk, if (!inet_csk(sk)->icsk_retransmits) return false; - start_ts = tcp_retransmit_stamp(sk); - if (!start_ts) - return false; - + start_ts = tcp_sk(sk)->retrans_stamp; if (likely(timeout == 0)) { linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base); |