leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

tcp: add accessors to read/set tp->snd_cwnd

Browse Source 
We had various bugs over the years with code
breaking the assumption that tp->snd_cwnd is greater
than zero.

Lately, syzbot reported the WARN_ON_ONCE(!tp->prior_cwnd) added
in commit 8b8a321ff7 ("tcp: fix zero cwnd in tcp_cwnd_reduction")
can trigger, and without a repro we would have to spend
considerable time finding the bug.

Instead of complaining too late, we want to catch where
and when tp->snd_cwnd is set to an illegal value.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Link: https://lore.kernel.org/r/20220405233538.947344-1-eric.dumazet@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet
2022-04-05 16:35:38 -07:00
committed by Jakub Kicinski
parent 487dc3ca60
commit 4057037535
27 changed files with 208 additions and 192 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
net/ipv4/tcp_veno.c
View File

@@ -146,11 +146,11 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
rtt = veno->minrtt;
target_cwnd = (u64)tp->snd_cwnd * veno->basertt;
target_cwnd = (u64)tcp_snd_cwnd(tp) * veno->basertt;
target_cwnd <<= V_PARAM_SHIFT;
do_div(target_cwnd, rtt);
veno->diff = (tp->snd_cwnd << V_PARAM_SHIFT) - target_cwnd;
veno->diff = (tcp_snd_cwnd(tp) << V_PARAM_SHIFT) - target_cwnd;
if (tcp_in_slow_start(tp)) {
/* Slow start. */
@@ -164,15 +164,15 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
/* In the "non-congestive state", increase cwnd
* every rtt.
*/
tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
tcp_cong_avoid_ai(tp, tcp_snd_cwnd(tp), acked);
} else {
/* In the "congestive state", increase cwnd
* every other rtt.
*/
if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
if (tp->snd_cwnd_cnt >= tcp_snd_cwnd(tp)) {
if (veno->inc &&
tp->snd_cwnd < tp->snd_cwnd_clamp) {
tp->snd_cwnd++;
tcp_snd_cwnd(tp) < tp->snd_cwnd_clamp) {
tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
veno->inc = 0;
} else
veno->inc = 1;
@@ -181,10 +181,10 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
tp->snd_cwnd_cnt += acked;
}
done:
if (tp->snd_cwnd < 2)
tp->snd_cwnd = 2;
else if (tp->snd_cwnd > tp->snd_cwnd_clamp)
tp->snd_cwnd = tp->snd_cwnd_clamp;
if (tcp_snd_cwnd(tp) < 2)
tcp_snd_cwnd_set(tp, 2);
else if (tcp_snd_cwnd(tp) > tp->snd_cwnd_clamp)
tcp_snd_cwnd_set(tp, tp->snd_cwnd_clamp);
}
/* Wipe the slate clean for the next rtt. */
/* veno->cntrtt = 0; */
@@ -199,10 +199,10 @@ static u32 tcp_veno_ssthresh(struct sock *sk)
if (veno->diff < beta)
/* in "non-congestive state", cut cwnd by 1/5 */
return max(tp->snd_cwnd * 4 / 5, 2U);
return max(tcp_snd_cwnd(tp) * 4 / 5, 2U);
else
/* in "congestive state", cut cwnd by 1/2 */
return max(tp->snd_cwnd >> 1U, 2U);
return max(tcp_snd_cwnd(tp) >> 1U, 2U);
}
static struct tcp_congestion_ops tcp_veno __read_mostly = {