ipv6: Fix getsockopt() for sockets with default IPV6_AUTOFLOWLABEL

Commit 513674b5a2c9 ("net: reevalulate autoflowlabel setting after
sysctl setting") removed the initialisation of
ipv6_pinfo::autoflowlabel and added a second flag to indicate
whether this field or the net namespace default should be used.

The getsockopt() handling for this case was not updated, so it
currently returns 0 for all sockets for which IPV6_AUTOFLOWLABEL is
not explicitly enabled.  Fix it to return the effective value, whether
that has been set at the socket or net namespace level.

Fixes: 513674b5a2c9 ("net: reevalulate autoflowlabel setting after sysctl ...")
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ipv6.h

@@ -331,6 +331,7 @@ int ipv6_flowlabel_opt_get(struct sock *sk, struct in6_flowlabel_req *freq,
 			   int flags);
 int ip6_flowlabel_init(void);
 void ip6_flowlabel_cleanup(void);
+bool ip6_autoflowlabel(struct net *net, const struct ipv6_pinfo *np);
 
 static inline void fl6_sock_release(struct ip6_flowlabel *fl)
 {

net/ipv6/ip6_output.c

@@ -166,7 +166,7 @@ int ip6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 			    !(IP6CB(skb)->flags & IP6SKB_REROUTED));
 }
 
-static bool ip6_autoflowlabel(struct net *net, const struct ipv6_pinfo *np)
+bool ip6_autoflowlabel(struct net *net, const struct ipv6_pinfo *np)
 {
 	if (!np->autoflowlabel_set)
 		return ip6_default_np_autolabel(net);

net/ipv6/ipv6_sockglue.c

@@ -1336,7 +1336,7 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case IPV6_AUTOFLOWLABEL:
-		val = np->autoflowlabel;
+		val = ip6_autoflowlabel(sock_net(sk), np);
 		break;
 
 	case IPV6_RECVFRAGSIZE: