Subject: Re: [UDP6]: Restore sk_filter optimisation

From: Mitsuru Chinen <[email-masked]>
Date: Mon, 29 Oct 2007 15:33:20 +0900

Hello Herbert,

Let me ask a question about this patch.
After this patch was applied, 2 of the protocol stack behaviors were
changed when it receives a UDP datagram with broken checksum:

 1. udp6InDatagrams is incremented instead of udpInErrors
 2. In userland, recvfrom() replies an error with EAGAIN.
    recvfrom() wasn't aware of such a packet before.

Are these changes intentional?

Best Regards,
----
Mitsuru Chinen <[email-masked]>

On Tue, 6 Mar 2007 12:20:10 +1100
Herbert Xu <[email-masked]> wrote:

> Hi Dave:
> 
> [UDP6]: Restore sk_filter optimisation
> 
> This reverts the changeset
> 
>     [IPV6]: UDPv6 checksum.
> 
>     We always need to check UDPv6 checksum because it is mandatory.
> 
> The sk_filter optimisation has nothing to do whether we verify the
> checksum.  It simply postpones it to the point when the user calls
> recv or poll.
> 
> Signed-off-by: Herbert Xu <[email-masked]>
> 
> Cheers,
> -- 
> Visit Openswan at http://www.openswan.org/
> Email: Herbert Xu ~{PmV>HI~} <[email-masked]>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
> --
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index 0ad4719..4474480 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -279,8 +279,10 @@ int udpv6_queue_rcv_skb(struct sock * sk, struct sk_buff *skb)
>  		}
>  	}
> 
> -	if (udp_lib_checksum_complete(skb))
> -		goto drop;
> +	if (sk->sk_filter) {
> +		if (udp_lib_checksum_complete(skb))
> +			goto drop;
> +	}
> 
>  	if ((rc = sock_queue_rcv_skb(sk,skb)) < 0) {
>  		/* Note that an ENOMEM error is charged twice */