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Re: [PATCH net-next v3 02/15] net: skbuff: add skb_checksum_full() that reports failure
- To: Josef Bacik <josef@xxxxxxxxxxxxxx>
- From: Mina Almasry <almasrymina@xxxxxxxxxx>
- Date: Mon, 2 Nov 2026 18:44:46 -0800
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- Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>, Eric Dumazet <edumazet@xxxxxxxxxx>, Jakub Kicinski <kuba@xxxxxxxxxx>, Paolo Abeni <pabeni@xxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxx>, Andrew Lunn <andrew+netdev@xxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx>, Fernando Fernandez Mancera <fmancera@xxxxxxx>, David Laight <david.laight.linux@xxxxxxxxx>, netdev@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 03 Nov 2026 02:45:05 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Mon, Nov 2, 2026 at 6:28 PM Josef Bacik <josef@xxxxxxxxxxxxxx> wrote:
>
> skb_checksum() can't fail. When the range runs into unreadable frags or
> past the end of the skb, skb_checksum() returns 0, which is also a valid
> checksum, so its callers can't tell a sum from a failure.
>
> Add skb_checksum_full(), which adds the range's sum to *@csump and
> returns 0. On failure it leaves *@csump alone and returns -EFAULT, or
> -EINVAL for a negative length. It is __must_check. Its frag_list loop
> sits in a noinline function so that taking the address of a local
> doesn't give skb_checksum_full() a stack protector.
>
> skb_checksum() becomes a wrapper for the callers that aren't converted
> yet, and still returns 0 on failure. Three things change for them:
>
Hmm, but do we really want this intermediate state where skb_checksum
and skb_checksum_full exist? Why not fix it in one go rather than
little by little?
--
Thanks,
Mina
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