Messages in this thread | | | Subject | Re: [PATCH] tcp: Modify the condition for the first skb to collapse | From | Eric Dumazet <> | Date | Mon, 17 Jun 2013 01:15:35 -0700 |
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On Mon, 2013-06-17 at 10:18 -0400, Jun Chen wrote: > When search the first skb to collapse,the condition of overlap to the next one have been > reached,but the start is less than TCP_SKB_CB(skb)->seq at this time, then followed process > will trigger the BUG_ON of the offset(start - TCP_SKB_CB(skb)->seq). > So this patch add one check (! before(start,TCP_SKB_CB(skb)->seq)) to avoid this ipanic. > > Signed-off-by: Chen Jun <jun.d.chen@intel.com> > --- > net/ipv4/tcp_input.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c > index 9c62257..4c745c5 100644 > --- a/net/ipv4/tcp_input.c > +++ b/net/ipv4/tcp_input.c > @@ -4465,7 +4465,8 @@ restart: > * overlaps to the next one. > */ > if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && > - (tcp_win_from_space(skb->truesize) > skb->len || > + ((tcp_win_from_space(skb->truesize) > skb->len && > + !before(start, TCP_SKB_CB(skb)->seq)) || > before(TCP_SKB_CB(skb)->seq, start))) { > end_of_skbs = false; > break;
Hmm... I must say I do not understand this patch.
If we find a skb with before(TCP_SKB_CB(skb)->seq, start), then the final condition will be true.
Let's rewrite your code to equivalent one :
if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && (before(TCP_SKB_CB(skb)->seq, start) || tcp_win_from_space(skb->truesize) > skb->len)) {
So it seems your patch would not solve the problem for all possible skbs (aka not bloated) ?
Please tell us how you trigger this bug, and send the stack trace.
Thanks
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