[AH6]: Get things working again.

Re: [AH6] Disable mutable bits after AH header

Unfortunately I broke ah6_input() in that patch.  Thanks to Miyazawa-san
for notifying me of the problem.

In that patch I removed the nh_offset parameter to ipv6_clear_mutable_options.
That broke ah6_input() because it relies on that variable to set the nexthdr.

The following patch fixes this by moving this work out to the caller
xfrm6_rcv() where the information is already available.  It also removes
an unnecessary call to ip6_find_1stfragopt() in xfrm6_rcv() since nhoffp
already points to the nexthdr preceding the current header.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@redhat.com>

net/ipv6/ah6.c

@@ -246,9 +246,7 @@ int ah6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_bu
 	unsigned char *tmp_hdr = NULL;
 	u16 hdr_len;
 	u16 ah_hlen;
-	u16 nh_offset = 0;
-	u8 nexthdr = 0;
-	u8 *prevhdr;
+	int nexthdr;
 
 	if (!pskb_may_pull(skb, sizeof(struct ip_auth_hdr)))
 		goto out;
@@ -301,8 +299,6 @@ int ah6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_bu
 
 	skb->nh.raw = skb_pull(skb, ah_hlen);
 	memcpy(skb->nh.raw, tmp_hdr, hdr_len);
-	prevhdr = (u8*)(skb->nh.raw + nh_offset);
-	*prevhdr = nexthdr;
 	skb->nh.ipv6h->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 	skb_pull(skb, hdr_len);
 	skb->h.raw = skb->data;

net/ipv6/esp6.c

@@ -258,7 +258,6 @@ int esp6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_b
 		u8 nexthdr[2];
 		struct scatterlist *sg = &esp->sgbuf[0];
 		u8 padlen;
-		u8 *prevhdr;
 
 		if (unlikely(nfrags > ESP_NUM_FAST_SG)) {
 			sg = kmalloc(sizeof(struct scatterlist)*nfrags, GFP_ATOMIC);
@@ -289,8 +288,7 @@ int esp6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, struct sk_b
 		skb->nh.raw += sizeof(struct ipv6_esp_hdr) + esp->conf.ivlen;
 		memcpy(skb->nh.raw, tmp_hdr, hdr_len);
 		skb->nh.ipv6h->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
-		ip6_find_1stfragopt(skb, &prevhdr);
-		ret = *prevhdr = nexthdr[1];
+		ret = nexthdr[1];
 	}
 
 out:

net/ipv6/ipcomp6.c

@@ -49,7 +49,6 @@ static int ipcomp6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, s
 {
 	int err = 0;
 	u8 nexthdr = 0;
-	u8 *prevhdr;
 	int hdr_len = skb->h.raw - skb->nh.raw;
 	unsigned char *tmp_hdr = NULL;
 	struct ipv6hdr *iph;
@@ -106,8 +105,6 @@ static int ipcomp6_input(struct xfrm_state *x, struct xfrm_decap_state *decap, s
 	iph = skb->nh.ipv6h;
 	iph->payload_len = htons(skb->len);
 	
-	ip6_find_1stfragopt(skb, &prevhdr);
-	*prevhdr = nexthdr;
 out:
 	if (tmp_hdr)
 		kfree(tmp_hdr);

net/ipv6/xfrm6_input.c

@@ -34,12 +34,11 @@ int xfrm6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
 	struct xfrm_state *x;
 	int xfrm_nr = 0;
 	int decaps = 0;
-	int nexthdr = 0;
-	u8 *prevhdr = NULL;
+	int nexthdr;
+	unsigned int nhoff;
 
-	ip6_find_1stfragopt(skb, &prevhdr);
-	nexthdr = *prevhdr;
-	*nhoffp = prevhdr - skb->nh.raw;
+	nhoff = *nhoffp;
+	nexthdr = skb->nh.raw[nhoff];
 
 	if ((err = xfrm_parse_spi(skb, nexthdr, &spi, &seq)) != 0)
 		goto drop;
@@ -67,6 +66,8 @@ int xfrm6_rcv(struct sk_buff **pskb, unsigned int *nhoffp)
 		if (nexthdr <= 0)
 			goto drop_unlock;
 
+		skb->nh.raw[nhoff] = nexthdr;
+
 		if (x->props.replay_window)
 			xfrm_replay_advance(x, seq);