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

Hello Tariq,

On 2026-10-05 15:06, Tariq Toukan wrote:

On 30/09/2026 17:45, Jérémy Jean wrote:

quoted

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 <redacted>
---
  .../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..

Good point: after a quick check, indeed you are probably right.
I will look to simplify this in a new version of the patch series.

Jérémy