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| author | Lachlan Andrew <lachlan.andrew@gmail.com> | 2008-04-30 01:04:03 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2008-04-30 01:04:03 -0700 |
| commit | 159131149c2f56c1da5ae5e23ab9d5acef4916d1 (patch) | |
| tree | 7ad3fc498c27fd8dfdf4a1fcf506b1220919f715 /net/ipv4/tcp_vegas.c | |
| parent | be9164e769d57aa10b2bbe15d103edc041b9e7de (diff) | |
| download | lwn-159131149c2f56c1da5ae5e23ab9d5acef4916d1.tar.gz lwn-159131149c2f56c1da5ae5e23ab9d5acef4916d1.zip | |
tcp: Overflow bug in Vegas
From: Lachlan Andrew <lachlan.andrew@gmail.com>
There is an overflow bug in net/ipv4/tcp_vegas.c for large BDPs
(e.g. 400Mbit/s, 400ms). The multiplication (old_wnd *
vegas->baseRTT) << V_PARAM_SHIFT overflows a u32.
[ Fix tcp_veno.c too, it has similar calculations. -DaveM ]
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_vegas.c')
| -rw-r--r-- | net/ipv4/tcp_vegas.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c index be24d6ee34bd..0e1a8c91f78e 100644 --- a/net/ipv4/tcp_vegas.c +++ b/net/ipv4/tcp_vegas.c @@ -229,7 +229,8 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) */ tcp_reno_cong_avoid(sk, ack, in_flight); } else { - u32 rtt, target_cwnd, diff; + u32 rtt, diff; + u64 target_cwnd; /* We have enough RTT samples, so, using the Vegas * algorithm, we determine if we should increase or @@ -252,8 +253,9 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) * We keep it as a fixed point number with * V_PARAM_SHIFT bits to the right of the binary point. */ - target_cwnd = ((old_wnd * vegas->baseRTT) - << V_PARAM_SHIFT) / rtt; + target_cwnd = ((u64)old_wnd * vegas->baseRTT); + target_cwnd <<= V_PARAM_SHIFT; + do_div(target_cwnd, rtt); /* Calculate the difference between the window we had, * and the window we would like to have. This quantity @@ -279,7 +281,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) * utilization. */ tp->snd_cwnd = min(tp->snd_cwnd, - (target_cwnd >> + ((u32)target_cwnd >> V_PARAM_SHIFT)+1); } else if (tp->snd_cwnd <= tp->snd_ssthresh) { |