[IPV6]: Fix routing by fwmark

Fix mark comparison, also dump the mask to userspace when the mask is
zero, but the mark is not (in which case the mark is dumped, so the
mask is needed to make sense of it).

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

net/ipv6/fib6_rules.c

@@ -129,7 +129,7 @@ static int fib6_rule_match(struct fib_rule *rule, struct flowi *fl, int flags)
 		return 0;
 
 #ifdef CONFIG_IPV6_ROUTE_FWMARK
-	if ((r->fwmark ^ fl->fl6_fwmark) / r->fwmask)
+	if ((r->fwmark ^ fl->fl6_fwmark) & r->fwmask)
 		return 0;
 #endif
 
@@ -256,7 +256,7 @@ static int fib6_rule_fill(struct fib_rule *rule, struct sk_buff *skb,
 	if (rule6->fwmark)
 		NLA_PUT_U32(skb, FRA_FWMARK, rule6->fwmark);
 
-	if (rule6->fwmask)
+	if (rule6->fwmask || rule6->fwmark)
 		NLA_PUT_U32(skb, FRA_FWMASK, rule6->fwmask);
 #endif