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| author | Eric Dumazet <edumazet@google.com> | 2013-02-02 05:23:16 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2013-02-03 16:00:25 -0500 |
| commit | 973ec449bb4f2b8c514bacbcb4d9506fc31c8ce3 (patch) | |
| tree | 29d7b5de18aeff078f265f75a2a94be22254b851 /net | |
| parent | 59fa534874e6779082275d12d950e26c67c86498 (diff) | |
| download | linux-stable-973ec449bb4f2b8c514bacbcb4d9506fc31c8ce3.tar.gz linux-stable-973ec449bb4f2b8c514bacbcb4d9506fc31c8ce3.tar.bz2 linux-stable-973ec449bb4f2b8c514bacbcb4d9506fc31c8ce3.zip | |
tcp: fix an infinite loop in tcp_slow_start()
Since commit 9dc274151a548 (tcp: fix ABC in tcp_slow_start()),
a nul snd_cwnd triggers an infinite loop in tcp_slow_start()
Avoid this infinite loop and log a one time error for further
analysis. FRTO code is suspected to cause this bug.
Reported-by: Pasi Kärkkäinen <pasik@iki.fi>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/tcp_cong.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index 291f2ed7cc31..cdf2e707bb10 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -310,6 +310,12 @@ void tcp_slow_start(struct tcp_sock *tp) { int cnt; /* increase in packets */ unsigned int delta = 0; + u32 snd_cwnd = tp->snd_cwnd; + + if (unlikely(!snd_cwnd)) { + pr_err_once("snd_cwnd is nul, please report this bug.\n"); + snd_cwnd = 1U; + } /* RFC3465: ABC Slow start * Increase only after a full MSS of bytes is acked @@ -324,7 +330,7 @@ void tcp_slow_start(struct tcp_sock *tp) if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh) cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */ else - cnt = tp->snd_cwnd; /* exponential increase */ + cnt = snd_cwnd; /* exponential increase */ /* RFC3465: ABC * We MAY increase by 2 if discovered delayed ack @@ -334,11 +340,11 @@ void tcp_slow_start(struct tcp_sock *tp) tp->bytes_acked = 0; tp->snd_cwnd_cnt += cnt; - while (tp->snd_cwnd_cnt >= tp->snd_cwnd) { - tp->snd_cwnd_cnt -= tp->snd_cwnd; + while (tp->snd_cwnd_cnt >= snd_cwnd) { + tp->snd_cwnd_cnt -= snd_cwnd; delta++; } - tp->snd_cwnd = min(tp->snd_cwnd + delta, tp->snd_cwnd_clamp); + tp->snd_cwnd = min(snd_cwnd + delta, tp->snd_cwnd_clamp); } EXPORT_SYMBOL_GPL(tcp_slow_start); |