Re: [PATCH ipsec 5/7] net/mlx5e: Use the packet sequence number for the IPsec IV

[Tariq Toukan <tariqt@nvidia.com>]

On 30/09/2026 17:45, Jérémy Jean wrote:
> mlx5e_ipsec_set_iv_esn() may decrement xo->seq.hi for a GSO skb based
> on the SA's current output counter. The metadata already contains the
> high word for the first packet, so this can produce the wrong IV.
> 
> For a three-segment GSO skb starting at (H, 0), oseq is 2 and
> oseq - gso_segs wraps to 0xffffffff. The helper then uses (H-1, 0)
> for the IV instead of (H, 0). This can create a situation where GCM
> reuses a nonce.
> 
> Remove the high-word adjustment and use xo->seq directly to generate
> the IV.
> 
> Fixes: cb01008390bb ("net/mlx5: IPSec, Add support for ESN")
> Cc: stable@vger.kernel.org
> Assisted-by: LLM
> Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
> ---
>   .../mellanox/mlx5/core/en_accel/ipsec_rxtx.c         | 12 +-----------
>   1 file changed, 1 insertion(+), 11 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.c
> index 6056106edcc6..4aa9f9c52f57 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.c
> @@ -153,21 +153,11 @@ static void mlx5e_ipsec_set_swp(struct sk_buff *skb,
>   void mlx5e_ipsec_set_iv_esn(struct sk_buff *skb, struct xfrm_state *x,
>   			    struct xfrm_offload *xo)
>   {
> -	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
> -	__u32 oseq = replay_esn->oseq;
>   	int iv_offset;
>   	__be64 seqno;
> -	u32 seq_hi;
> -
> -	if (unlikely(skb_is_gso(skb) && oseq < MLX5E_IPSEC_ESN_SCOPE_MID &&
> -		     MLX5E_IPSEC_ESN_SCOPE_MID < (oseq - skb_shinfo(skb)->gso_segs))) {
> -		seq_hi = xo->seq.hi - 1;
> -	} else {
> -		seq_hi = xo->seq.hi;
> -	}
>   
>   	/* Place the SN in the IV field */
> -	seqno = cpu_to_be64(xo->seq.low + ((u64)seq_hi << 32));
> +	seqno = cpu_to_be64(xo->seq.low + ((u64)xo->seq.hi << 32));
>   	iv_offset = skb_transport_offset(skb) + sizeof(struct ip_esp_hdr);
>   	skb_store_bits(skb, iv_offset, &seqno, 8);
>   }

Thanks for your patch.

Doesn't this make mlx5e_ipsec_set_iv_esn() identical to 
mlx5e_ipsec_set_iv()?

I wouldn't keep both copies then..