tcp: fix tcp_rearm_rto()

skbs in (re)transmit queue no longer have a copy of jiffies
at the time of the transmit : skb->skb_mstamp is now in usec unit,
with no correlation to tcp_jiffies32.

We have to convert rto from jiffies to usec, compute a time difference
in usec, then convert the delta to HZ units.

Fixes: 9a568de4818d ("tcp: switch TCP TS option (RFC 7323) to 1ms clock")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 6 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9a5a9e8eda89..aa1eef150dc4 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3002,14 +3002,14 @@ void tcp_rearm_rto(struct sock *sk)
                 if (icsk->icsk_pending == ICSK_TIME_REO_TIMEOUT ||
                     icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
                         struct sk_buff *skb = tcp_write_queue_head(sk);
-                        const u32 rto_time_stamp =
-                                tcp_skb_timestamp(skb) + rto;
-                        s32 delta = (s32)(rto_time_stamp - tcp_jiffies32);
-                        /* delta may not be positive if the socket is locked
+                        u64 rto_time_stamp = skb->skb_mstamp +
+                                             jiffies_to_usecs(rto);
+                        s64 delta_us = rto_time_stamp - tp->tcp_mstamp;
+                        /* delta_us may not be positive if the socket is locked
                          * when the retrans timer fires and is rescheduled.
                          */
-                        if (delta > 0)
-                                rto = delta;
+                        if (delta_us > 0)
+                                rto = usecs_to_jiffies(delta_us);
                 }
                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto,
                                           TCP_RTO_MAX);