Subject: Re: [PATCH net v2 2/4] ipv4: add defensive check for CHECKSUM_PARTIAL skbs in ip_fragment

From: Sergei Shtylyov <[email-masked]>
Date: Tue, 27 Oct 2015 22:01:44 +0300

Hello.

On 10/27/2015 06:02 PM, Hannes Frederic Sowa wrote:

> CHECKSUM_PARTIAL skbs should never arrive in ip_fragment. If we get one
> of those warn about them once and handle them gracefully by recalculating
> the checksum.
>
> Cc: Eric Dumazet <[email-masked]>
> Cc: Vlad Yasevich <[email-masked]>
> Cc: Benjamin Coddington <[email-masked]>
> Cc: Tom Herbert <[email-masked]>
> Signed-off-by: Hannes Frederic Sowa <[email-masked]>
> ---
>   net/ipv4/ip_output.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index 0b02417..3f94a3b 100644
> --- a/net/ipv4/ip_output.c
> +++ b/net/ipv4/ip_output.c
> @@ -533,6 +533,11 @@ int ip_do_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
>
>   	dev = rt->dst.dev;
>
> +	/* for offloaded checksums cleanup checksum before fragmentation */
> +	if (WARN_ON_ONCE(skb->ip_summed == CHECKSUM_PARTIAL) &&
> +	    (err = skb_checksum_help(skb)))

    scripts/checkpatch.pl shou;d have complained about using = in the *if* 
expression.

> +		goto fail;
> +
>   	/*
>   	 *	Point into the IP datagram header.
>   	 */
[...]

MBR, Sergei