{IPv4,xfrm} Add ESN support for AH ingress part

This patch add esn support for AH input stage by attaching upper 32bits
sequence number right after packet payload as specified by RFC 4302.

Then the ICV value will guard upper 32bits sequence number as well when
packet getting in.

Signed-off-by: Fan Du <fan.du@windriver.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/ipv4/ah4.c

@@ -309,6 +309,10 @@ static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 	struct ip_auth_hdr *ah;
 	struct ah_data *ahp;
 	int err = -ENOMEM;
+	int seqhi_len = 0;
+	__be32 *seqhi;
+	int sglists = 0;
+	struct scatterlist *seqhisg;
 
 	if (!pskb_may_pull(skb, sizeof(*ah)))
 		goto out;
@@ -349,14 +353,22 @@ static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 	iph = ip_hdr(skb);
 	ihl = ip_hdrlen(skb);
 
-	work_iph = ah_alloc_tmp(ahash, nfrags, ihl + ahp->icv_trunc_len);
+	if (x->props.flags & XFRM_STATE_ESN) {
+		sglists = 1;
+		seqhi_len = sizeof(*seqhi);
+	}
+
+	work_iph = ah_alloc_tmp(ahash, nfrags + sglists, ihl +
+				ahp->icv_trunc_len + seqhi_len);
 	if (!work_iph)
 		goto out;
 
-	auth_data = ah_tmp_auth(work_iph, ihl);
+	seqhi = (__be32 *)((char *)work_iph + ihl);
+	auth_data = ah_tmp_auth(seqhi, seqhi_len);
 	icv = ah_tmp_icv(ahash, auth_data, ahp->icv_trunc_len);
 	req = ah_tmp_req(ahash, icv);
 	sg = ah_req_sg(ahash, req);
+	seqhisg = sg + nfrags;
 
 	memcpy(work_iph, iph, ihl);
 	memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
@@ -375,10 +387,15 @@ static int ah_input(struct xfrm_state *x, struct sk_buff *skb)
 
 	skb_push(skb, ihl);
 
-	sg_init_table(sg, nfrags);
-	skb_to_sgvec(skb, sg, 0, skb->len);
+	sg_init_table(sg, nfrags + sglists);
+	skb_to_sgvec_nomark(skb, sg, 0, skb->len);
 
-	ahash_request_set_crypt(req, sg, icv, skb->len);
+	if (x->props.flags & XFRM_STATE_ESN) {
+		/* Attach seqhi sg right after packet payload */
+		*seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
+		sg_set_buf(seqhisg, seqhi, seqhi_len);
+	}
+	ahash_request_set_crypt(req, sg, icv, skb->len + seqhi_len);
 	ahash_request_set_callback(req, 0, ah_input_done, skb);
 
 	AH_SKB_CB(skb)->tmp = work_iph;