ipsec: Don't update the pmtu on ICMPV6_DEST_UNREACH

Currently we update the pmtu in the IPsec protocol error handlers
if icmpv6 message type is either ICMPV6_DEST_UNREACH or
ICMPV6_PKT_TOOBIG. Updating the pmtu on ICMPV6_DEST_UNREACH
is wrong in any case, it causes strangely fragmented packets.
Only ICMPV6_PKT_TOOBIG signalizes pmtu discovery, so remove the
ICMPV6_DEST_UNREACH check in the IPsec protocol error handlers.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/ipv6/ah6.c

@@ -618,8 +618,7 @@ static void ah6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	struct ip_auth_hdr *ah = (struct ip_auth_hdr*)(skb->data+offset);
 	struct xfrm_state *x;
 
-	if (type != ICMPV6_DEST_UNREACH &&
-	    type != ICMPV6_PKT_TOOBIG &&
+	if (type != ICMPV6_PKT_TOOBIG &&
 	    type != NDISC_REDIRECT)
 		return;
 

net/ipv6/esp6.c

@@ -436,8 +436,7 @@ static void esp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	struct ip_esp_hdr *esph = (struct ip_esp_hdr *)(skb->data + offset);
 	struct xfrm_state *x;
 
-	if (type != ICMPV6_DEST_UNREACH &&
-	    type != ICMPV6_PKT_TOOBIG &&
+	if (type != ICMPV6_PKT_TOOBIG &&
 	    type != NDISC_REDIRECT)
 		return;
 

net/ipv6/ipcomp6.c

@@ -64,8 +64,7 @@ static void ipcomp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 		(struct ip_comp_hdr *)(skb->data + offset);
 	struct xfrm_state *x;
 
-	if (type != ICMPV6_DEST_UNREACH &&
-	    type != ICMPV6_PKT_TOOBIG &&
+	if (type != ICMPV6_PKT_TOOBIG &&
 	    type != NDISC_REDIRECT)
 		return;