On Fri, Sep 27, 2024 at 03:53:47PM +0200, Laurent Vivier wrote:
> The offset allows any headers that are not part of the data
> to checksum to be skipped.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

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

> ---
> 
> Notes:
>     v5:
>       - correctly set the length for the partial csum_unfolded()
>     v3:
>       - reorder @offset and @init
>     v2:
>       - check iov_skip_bytes() return value
> 
>  checksum.c | 16 ++++++++++++++--
>  checksum.h |  3 ++-
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/checksum.c b/checksum.c
> index 006614fcbb28..05d002ab0c25 100644
> --- a/checksum.c
> +++ b/checksum.c
> @@ -59,6 +59,7 @@
>  #include "util.h"
>  #include "ip.h"
>  #include "checksum.h"
> +#include "iov.h"
>  
>  /* Checksums are optional for UDP over IPv4, so we usually just set
>   * them to 0.  Change this to 1 to calculate real UDP over IPv4
> @@ -497,16 +498,27 @@ uint16_t csum(const void *buf, size_t len, uint32_t init)
>   *
>   * @iov		Pointer to the array of IO vectors
>   * @n		Length of the array
> + * @offset:	Offset of the data to checksum within the full data length
>   * @init	Initial 32-bit checksum, 0 for no pre-computed checksum
>   *
>   * Return: 16-bit folded, complemented checksum
>   */
>  /* cppcheck-suppress unusedFunction */
> -uint16_t csum_iov(const struct iovec *iov, size_t n, uint32_t init)
> +uint16_t csum_iov(const struct iovec *iov, size_t n, size_t offset,
> +		  uint32_t init)
>  {
>  	unsigned int i;
> +	size_t first;
>  
> -	for (i = 0; i < n; i++)
> +	i = iov_skip_bytes(iov, n, offset, &first);
> +	if (i >= n)
> +		return (uint16_t)~csum_fold(init);
> +
> +	init = csum_unfolded((char *)iov[i].iov_base + first,
> +			     iov[i].iov_len - first, init);
> +	i++;
> +
> +	for (; i < n; i++)
>  		init = csum_unfolded(iov[i].iov_base, iov[i].iov_len, init);
>  
>  	return (uint16_t)~csum_fold(init);
> diff --git a/checksum.h b/checksum.h
> index c5964ac78921..49f7472dd1b6 100644
> --- a/checksum.h
> +++ b/checksum.h
> @@ -32,6 +32,7 @@ void csum_icmp6(struct icmp6hdr *icmp6hr,
>  		const void *payload, size_t dlen);
>  uint32_t csum_unfolded(const void *buf, size_t len, uint32_t init);
>  uint16_t csum(const void *buf, size_t len, uint32_t init);
> -uint16_t csum_iov(const struct iovec *iov, size_t n, uint32_t init);
> +uint16_t csum_iov(const struct iovec *iov, size_t n, size_t offset,
> +		  uint32_t init);
>  
>  #endif /* CHECKSUM_H */

-- 
David Gibson (he or they)	| 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