Hello,
David Miller wrote:
>> diff -pruN net-2.6/net/ipv4/ip_output.c
>> net-2.6-udp-take11a1-p1/net/ipv4/ip_output.c
>> --- net-2.6/net/ipv4/ip_output.c 2007-12-11 10:54:55.000000000 -0500
>> +++ net-2.6-udp-take11a1-p1/net/ipv4/ip_output.c 2007-12-17
>> 14:42:31.000000000 -0500
>> @@ -1004,6 +1004,11 @@ alloc_new_skb:
>> frag = &skb_shinfo(skb)->frags[i];
>> }
>> } else if (i < MAX_SKB_FRAGS) {
>> + if (atomic_read(&sk->sk_wmem_alloc) + PAGE_SIZE
>> + > 2 * sk->sk_sndbuf) {
>> + err = -ENOBUFS;
>> + goto error;
>> + }
>> if (copy > PAGE_SIZE)
>> copy = PAGE_SIZE;
>> page = alloc_pages(sk->sk_allocation, 0);
>
> If we are going to do this, we need to add the same check to
> skb_append_datato_frags() which is invoked via ip_ufo_append_data().
>
> We also have to be very careful in this area. One problem we had a
> long time ago was that we would socket account when fragmenting an
> outgoing frame. This was bogus because even if the socket had enough
> space for one full sized frame, the packet send would fail because it
> could not fit the space for both the original frame and the
> fragmented copy of it.
>
> This situation was cured by simply not enforcing accounting for the
> fragmented copy. It is valid because after we fragment, we keep
> the fragmented copy but free the original.
>
> This doesn't apply directly to this specific patch, but it is
> something to keep in mind when doing these changes.
Hello,
Thank you for sharing your experience.
Let me investigate this code and skb_append_datato_frags().
I'll include the check code in next patch set if it is really needed.
Regards,
Hideo
--
Hitachi Computer Products (America) Inc.
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