ipv6: unify logic evaluating inet6_dev's accept_ra property

As of 026359b [ipv6: Send ICMPv6 RSes only when RAs are accepted], the
logic determining whether to send Router Solicitations is identical
to the logic determining whether kernel accepts Router Advertisements.

However the condition itself is repeated in several code locations.

Unify it by introducing 'ipv6_accept_ra()' accessor.

Also, simplify the condition expression, making it more readable.
No semantic change.

Signed-off-by: Shmulik Ladkani <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/ipv6.h

···
 
 extern bool ipv6_opt_accepted(const struct sock *sk, const struct sk_buff *skb);
 
+static inline bool ipv6_accept_ra(struct inet6_dev *idev)
+{
+	/* If forwarding is enabled, RA are not accepted unless the special
+	 * hybrid mode (accept_ra=2) is enabled.
+	 */
+	return idev->cnf.forwarding ? idev->cnf.accept_ra == 2 :
+	    idev->cnf.accept_ra;
+}
+
 #if IS_ENABLED(CONFIG_IPV6)
 static inline int ip6_frag_nqueues(struct net *net)
 {

net/ipv6/addrconf.c

···
 	   router advertisements, start sending router solicitations.
 	 */
 
-	if (((ifp->idev->cnf.accept_ra == 1 && !ifp->idev->cnf.forwarding) ||
-	     ifp->idev->cnf.accept_ra == 2) &&
+	if (ipv6_accept_ra(ifp->idev) &&
 	    ifp->idev->cnf.rtr_solicits > 0 &&
 	    (dev->flags&IFF_LOOPBACK) == 0 &&
 	    (ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL)) {

net/ipv6/ndisc.c

···
 	rtnl_set_sk_err(net, RTNLGRP_ND_USEROPT, err);
 }
 
-static inline int accept_ra(struct inet6_dev *in6_dev)
-{
-	/*
-	 * If forwarding is enabled, RA are not accepted unless the special
-	 * hybrid mode (accept_ra=2) is enabled.
-	 */
-	if (in6_dev->cnf.forwarding && in6_dev->cnf.accept_ra < 2)
-		return 0;
-
-	return in6_dev->cnf.accept_ra;
-}
-
 static void ndisc_router_discovery(struct sk_buff *skb)
 {
 	struct ra_msg *ra_msg = (struct ra_msg *)skb_transport_header(skb);
···
 		return;
 	}
 
-	if (!accept_ra(in6_dev))
+	if (!ipv6_accept_ra(in6_dev))
 		goto skip_linkparms;
 
 #ifdef CONFIG_IPV6_NDISC_NODETYPE
···
 			     NEIGH_UPDATE_F_ISROUTER);
 	}
 
-	if (!accept_ra(in6_dev))
+	if (!ipv6_accept_ra(in6_dev))
 		goto out;
 
 #ifdef CONFIG_IPV6_ROUTE_INFO