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Date: Wed, 30 Apr 2014 07:18:18 -0700 From: Eric Dumazet <eric.dumazet@...il.com> To: Liu Yu <allanliuyu@...il.com> Cc: ncardwell@...gle.com, shemminger@...tta.com, "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org Subject: Re: [PATCH] tcp_cubic: fix the range of delayed_ack On Wed, 2014-04-30 at 17:34 +0800, Liu Yu wrote: > From: Liu Yu <allanyuliu@...cent.com> > > commit b9f47a3aaeab (tcp_cubic: limit delayed_ack ratio to prevent > divide error) try to prevent divide error, but there is still a little > chance that delayed_ack can reach zero. In case the param cnt get > negative value, then ratio+cnt would overflow and may happen to be zero. > As a result, min(ratio, ACK_RATIO_LIMIT) will calculate to be zero. > > In some old kernels, such as 2.6.32, there is a bug that would > pass negative param, which then ultimately leads to this divide error. > > commit 5b35e1e6e9c (tcp: fix tcp_trim_head() to adjust segment count > with skb MSS) fixed the negative param issue. However, > it's safe that we fix the range of delayed_ack as well, > to make sure we do not hit a divide by zero. > > CC: Stephen Hemminger <shemminger@...tta.com> > Signed-off-by: Liu Yu <allanyuliu@...cent.com> > --- > net/ipv4/tcp_cubic.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) Signed-off-by: Eric Dumazet <edumazet@...gle.com> Thanks ! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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