From: Shan Wei <shanwei@cn•fujitsu.com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: David Miller <davem@davemloft•net>,
"Ronciak, John" <john.ronciak@intel•com>,
netdev@vger•kernel.org
Subject: Re: [RFC][BUG-FIX] the problem of checksum checking in UDP protocol
Date: Mon, 28 Jun 2010 18:49:36 +0800 [thread overview]
Message-ID: <4C287E40.40906@cn.fujitsu.com> (raw)
In-Reply-To: <1277530086.2481.15.camel@edumazet-laptop>
Eric Dumazet wrote, at 06/26/2010 01:28 PM:
>> (This patch is not complete, it's just for my idea.)
>> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
>> index 1dd1aff..47f7e86 100644
>> --- a/net/ipv6/udp.c
>> +++ b/net/ipv6/udp.c
>> @@ -723,6 +723,10 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
>> if (ulen < skb->len) {
>> if (pskb_trim_rcsum(skb, ulen))
>> goto short_packet;
>> +
>> + if (skb_csum_unnecessary(skb))
>> + skb->ip_summed = CHECKSUM_NONE;
>> +
>> saddr = &ipv6_hdr(skb)->saddr;
>> daddr = &ipv6_hdr(skb)->daddr;
>> uh = udp_hdr(skb);
>>
>
> I really dont know if this fix is the right one.
>
> pskb_trim_rcsum() already contains a check. Should this check be changed
> to include yours ?
Oh..... I don't think so.
pskb_trim_rcsum() is also used when IPv4/IPv6 protocol receiving packets
and reassembling fragments. IP protocol does the right check and should
trust CHECKSUM_UNNECESSARY flag that drivers set, So we no need to
change IP protocol.
If we add the skb_csum_unnecessary(skb) check into pskb_trim_rcsum() and
reset ip_summed with CHECKSUM_NONE, the checksum check that NIC hardward
has done is wasted.
Only for UDP protocol over IPv4/IPv6, and length parameter is lower than
skb->len, We reset ip_summed with CHECKSUM_NONE.
--
Best Regards
-----
Shan Wei
next prev parent reply other threads:[~2010-06-28 10:51 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-17 9:09 [RFC][BUG-FIX] the problem of checksum checking in UDP protocol Shan Wei
2010-06-26 5:28 ` Eric Dumazet
2010-06-28 10:49 ` Shan Wei [this message]
2010-06-28 20:38 ` Eric Dumazet
2010-06-29 6:39 ` Shan Wei
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