diff options
Diffstat (limited to 'include/net/tcp.h')
| -rw-r--r-- | include/net/tcp.h | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 163d2b467d78..a9fe7bc4f4bb 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -974,7 +974,27 @@ static inline u32 tcp_wnd_end(const struct tcp_sock *tp) { return tp->snd_una + tp->snd_wnd; } -bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight); + +/* We follow the spirit of RFC2861 to validate cwnd but implement a more + * flexible approach. The RFC suggests cwnd should not be raised unless + * it was fully used previously. But we allow cwnd to grow as long as the + * application has used half the cwnd. + * Example : + * cwnd is 10 (IW10), but application sends 9 frames. + * We allow cwnd to reach 18 when all frames are ACKed. + * This check is safe because it's as aggressive as slow start which already + * risks 100% overshoot. The advantage is that we discourage application to + * either send more filler packets or data to artificially blow up the cwnd + * usage, and allow application-limited process to probe bw more aggressively. + * + * TODO: remove in_flight once we can fix all callers, and their callers... + */ +static inline bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + return tp->snd_cwnd < 2 * tp->lsnd_pending; +} static inline void tcp_check_probe_timer(struct sock *sk) { |