| Message ID | 1406064838-21782-1-git-send-email-christoph.paasch@uclouvain.be |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
Hello David, On 22/07/14 - 23:33:58, Christoph Paasch wrote: > In veno we do a multiplication of the cwnd and the rtt. This > may overflow and thus their result is stored in a u64. However, we first > need to cast the cwnd so that actually 64-bit arithmetic is done. > > A first attempt at fixing 76f1017757aa0 ([TCP]: TCP Veno congestion > control) was made by 159131149c2 (tcp: Overflow bug in Vegas), but it > failed to add the required cast in tcp_veno_cong_avoid(). > > Fixes: 76f1017757aa0 ([TCP]: TCP Veno congestion control) > Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be> > --- > net/ipv4/tcp_veno.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) I see you marked this one also as "Changes Requested" on patchwork. But the story here is a bit different than for vegas, because in veno the do_div is already present. Do you want me to remove the do_div for -net and try to do a similar calculation as in vegas? Because, my proposed veno-patch already fixes the overflow-issues in veno, while a modification to the do_div would be more of a (small) performance improvement. Cheers, Christoph > > diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c > index 27b9825753d1..8276977d2c85 100644 > --- a/net/ipv4/tcp_veno.c > +++ b/net/ipv4/tcp_veno.c > @@ -144,7 +144,7 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked) > > rtt = veno->minrtt; > > - target_cwnd = (tp->snd_cwnd * veno->basertt); > + target_cwnd = (u64)tp->snd_cwnd * veno->basertt; > target_cwnd <<= V_PARAM_SHIFT; > do_div(target_cwnd, rtt); > > -- > 1.9.3 > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c index 27b9825753d1..8276977d2c85 100644 --- a/net/ipv4/tcp_veno.c +++ b/net/ipv4/tcp_veno.c @@ -144,7 +144,7 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked) rtt = veno->minrtt; - target_cwnd = (tp->snd_cwnd * veno->basertt); + target_cwnd = (u64)tp->snd_cwnd * veno->basertt; target_cwnd <<= V_PARAM_SHIFT; do_div(target_cwnd, rtt);
In veno we do a multiplication of the cwnd and the rtt. This may overflow and thus their result is stored in a u64. However, we first need to cast the cwnd so that actually 64-bit arithmetic is done. A first attempt at fixing 76f1017757aa0 ([TCP]: TCP Veno congestion control) was made by 159131149c2 (tcp: Overflow bug in Vegas), but it failed to add the required cast in tcp_veno_cong_avoid(). Fixes: 76f1017757aa0 ([TCP]: TCP Veno congestion control) Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be> --- net/ipv4/tcp_veno.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)