From e7d0c88586a66cf03e70750a8119d984fdedf2aa Mon Sep 17 00:00:00 2001 From: Stephen Hemminger Date: Wed, 25 Jul 2007 23:50:06 -0700 Subject: [PATCH] [TCP]: cubic - eliminate use of receive time stamp Remove use of received timestamp option value from RTT calculation in Cubic. A hostile receiver may be returning a larger timestamp option than the original value. This would cause the sender to believe the malevolent receiver had a larger RTT and because Cubic tries to provide some RTT friendliness, the sender would then favor the liar. Instead, use the jiffie resolutionRTT value already computed and passed back after ack. Signed-off-by: Stephen Hemminger Signed-off-by: David S. Miller --- net/ipv4/tcp_cubic.c | 46 +++++++++++++++++--------------------------- 1 file changed, 18 insertions(+), 28 deletions(-) diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c index 0c44bb67a671..485d7ea35f75 100644 --- a/net/ipv4/tcp_cubic.c +++ b/net/ipv4/tcp_cubic.c @@ -246,38 +246,12 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd) ca->cnt = 1; } - -/* Keep track of minimum rtt */ -static inline void measure_delay(struct sock *sk) -{ - const struct tcp_sock *tp = tcp_sk(sk); - struct bictcp *ca = inet_csk_ca(sk); - u32 delay; - - /* No time stamp */ - if (!(tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) || - /* Discard delay samples right after fast recovery */ - (s32)(tcp_time_stamp - ca->epoch_start) < HZ) - return; - - delay = (tcp_time_stamp - tp->rx_opt.rcv_tsecr)<<3; - if (delay == 0) - delay = 1; - - /* first time call or link delay decreases */ - if (ca->delay_min == 0 || ca->delay_min > delay) - ca->delay_min = delay; -} - static void bictcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight, int data_acked) { struct tcp_sock *tp = tcp_sk(sk); struct bictcp *ca = inet_csk_ca(sk); - if (data_acked) - measure_delay(sk); - if (!tcp_is_cwnd_limited(sk, in_flight)) return; @@ -337,14 +311,30 @@ static void bictcp_state(struct sock *sk, u8 new_state) static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us) { const struct inet_connection_sock *icsk = inet_csk(sk); + struct bictcp *ca = inet_csk_ca(sk); + u32 delay; if (cnt > 0 && icsk->icsk_ca_state == TCP_CA_Open) { - struct bictcp *ca = inet_csk_ca(sk); cnt -= ca->delayed_ack >> ACK_RATIO_SHIFT; ca->delayed_ack += cnt; } -} + /* Some calls are for duplicates without timetamps */ + if (rtt_us < 0) + return; + + /* Discard delay samples right after fast recovery */ + if ((s32)(tcp_time_stamp - ca->epoch_start) < HZ) + return; + + delay = usecs_to_jiffies(rtt_us) << 3; + if (delay == 0) + delay = 1; + + /* first time call or link delay decreases */ + if (ca->delay_min == 0 || ca->delay_min > delay) + ca->delay_min = delay; +} static struct tcp_congestion_ops cubictcp = { .init = bictcp_init, -- 2.39.2