[IPV6]: Fix raw socket hardware checksum failures

When packets hit raw sockets the csum update isn't done yet, do it manually.
Packets can also reach rawv6_rcv on the output path through
ip6_call_ra_chain, in this case skb->ip_summed is CHECKSUM_NONE and this
codepath isn't executed.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/raw.c

@@ -328,6 +328,8 @@ int rawv6_rcv(struct sock *sk, struct sk_buff *skb)
 
 	if (skb->ip_summed != CHECKSUM_UNNECESSARY) {
 		if (skb->ip_summed == CHECKSUM_HW) {
+			skb_postpull_rcsum(skb, skb->nh.raw,
+			                   skb->h.raw - skb->nh.raw);
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
 			if (csum_ipv6_magic(&skb->nh.ipv6h->saddr,
 					    &skb->nh.ipv6h->daddr,