tcp_tso_should_defer() last step tries to check if the probable
next ACK packet is coming in less than half rtt.
Problem is that the head->tstamp might be in the future,
so we need to use signed arithmetics to avoid overflows.
Signed-off-by: Eric Dumazet <eduma...@google.com>
Acked-by: Soheil Hassas Yeganeh <soh...@google.com>
---
net/ipv4/tcp_output.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index
35feadf480300cd061411d65257f06ee658daa3c..78a56cef7e397c65ad18897d550f3800e8fe8f41
100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1907,10 +1907,11 @@ static bool tcp_tso_should_defer(struct sock *sk,
struct sk_buff *skb,
bool *is_cwnd_limited, u32 max_segs)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
- u32 age, send_win, cong_win, limit, in_flight;
+ u32 send_win, cong_win, limit, in_flight;
struct tcp_sock *tp = tcp_sk(sk);
struct sk_buff *head;
int win_divisor;
+ s64 delta;
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
goto send_now;
@@ -1972,9 +1973,9 @@ static bool tcp_tso_should_defer(struct sock *sk, struct
sk_buff *skb,
head = tcp_rtx_queue_head(sk);
if (!head)
goto send_now;
- age = tcp_stamp_us_delta(tp->tcp_mstamp, tcp_skb_timestamp_us(head));
+ delta = tp->tcp_clock_cache - head->tstamp;
/* If next ACK is likely to come too late (half srtt), do not defer */
- if (age < (tp->srtt_us >> 4))
+ if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0)
goto send_now;
/* Ok, it looks like it is advisable to defer. */
--
2.19.1.930.g4563a0d9d0-goog
