Re: [PATCH] checksum: Fix calculation for ICMP checksum on IPv4

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Oct 25, 2022 at 06:07:13PM +0200, Stefano Brivio wrote:
> We need to zero out the checksum field before calculating the
> checksum, of course. I have no idea how this passed the "icmp" test
> set, looking into it.
> 
> Reported-by: Paul Holzinger <pholzing@redhat.com>
> Fixes: 67ab6171729c ("Add csum_icmp4() helper for calculating ICMP checksums")
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Oops, that's embarrassing.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  checksum.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/checksum.c b/checksum.c
> index 09d2c7c..c59869c 100644
> --- a/checksum.c
> +++ b/checksum.c
> @@ -160,10 +160,13 @@ void csum_udp4(struct udphdr *udp4hr, in_addr_t saddr, in_addr_t daddr,
>   */
>  void csum_icmp4(struct icmphdr *icmp4hr, const void *payload, size_t len)
>  {
> -	/* Partial checksum for ICMP header alone */
> -	uint32_t psum = sum_16b(icmp4hr, sizeof(*icmp4hr));
> +	uint32_t psum;
>  
>  	icmp4hr->checksum = 0;
> +
> +	/* Partial checksum for ICMP header alone */
> +	psum = sum_16b(icmp4hr, sizeof(*icmp4hr));
> +
>  	icmp4hr->checksum = csum_unaligned(payload, len, psum);
>  }
>  

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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