xfrm: Skip redundant replay recheck for the hardware offload path

The xfrm_replay_recheck() function was introduced to handle the issues
arising from asynchronous crypto algorithms.

The crypto offload path is now effectively synchronous, as it holds
the state lock throughout its operation. This eliminates the race
condition, making the recheck an unnecessary overhead. This patch
improves performance by skipping the redundant call when
crypto_done is true.

Additionally, the sequence number assignment is moved to an earlier
point in the function. This improves performance by reducing lock
contention and places the logic at a more appropriate point, as the
full sequence number (including the higher-order bits) can be
determined as soon as the packet is received.

Signed-off-by: Jianbo Liu <[e-mail]>
Reviewed-by: Cosmin Ratiu <[e-mail]>
Signed-off-by: Steffen Klassert <[e-mail]>

net/xfrm/xfrm_input.c

···
 			nexthdr = x->type_offload->input_tail(x, skb);
 		}
 
-		goto lock;
+		goto process;
 	}
 
 	family = XFRM_SPI_SKB_CB(skb)->family;
···
 			goto drop;
 		}
 
-lock:
+process:
+		seq_hi = htonl(xfrm_replay_seqhi(x, seq));
+
+		XFRM_SKB_CB(skb)->seq.input.low = seq;
+		XFRM_SKB_CB(skb)->seq.input.hi = seq_hi;
+
 		spin_lock(&x->lock);
 
 		if (unlikely(x->km.state != XFRM_STATE_VALID)) {
···
 			goto drop_unlock;
 		}
 
-		seq_hi = htonl(xfrm_replay_seqhi(x, seq));
-
-		XFRM_SKB_CB(skb)->seq.input.low = seq;
-		XFRM_SKB_CB(skb)->seq.input.hi = seq_hi;
-
 		if (!crypto_done) {
 			spin_unlock(&x->lock);
 			dev_hold(skb->dev);
···
 		/* only the first xfrm gets the encap type */
 		encap_type = 0;
 
-		if (xfrm_replay_recheck(x, skb, seq)) {
+		if (!crypto_done && xfrm_replay_recheck(x, skb, seq)) {
 			XFRM_INC_STATS(net, LINUX_MIB_XFRMINSTATESEQERROR);
 			goto drop_unlock;
 		}