Resolve source address selection in presense of CARP. Add a couple

of helper functions:

- carp_master()   - boolean function which is true if an address
		    is in the MASTER state.
- ifa_preferred() - boolean function that compares two addresses,
		    and is aware of CARP.

  Utilize ifa_preferred() in ifa_ifwithnet().

  The previous version of patch also changed source address selection
logic in jails using carp_master(), but we failed to negotiate this part
with Bjoern. May be we will approach this problem again later.

Reported & tested by:	Anton Yuzhaninov <citrin citrin.ru>
Sponsored by:		Nginx, Inc

2 files changed, 22 insertions, 4 deletions

diff --git a/sys/net/if.c b/sys/net/if.c
index 1c887cb..57bd4e1 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -130,6 +130,7 @@ void	(*lagg_linkstate_p)(struct ifnet *ifp, int state);
 /* These are external hooks for CARP. */
 void	(*carp_linkstate_p)(struct ifnet *ifp);
 void	(*carp_demote_adj_p)(int, char *);
+int	(*carp_master_p)(struct ifaddr *);
 #if defined(INET) || defined(INET6)
 int	(*carp_forus_p)(struct ifnet *ifp, u_char *dhost);
 int	(*carp_output_p)(struct ifnet *ifp, struct mbuf *m,
@@ -1706,11 +1707,13 @@ next:				continue;
 				/*
 				 * If the netmask of what we just found
 				 * is more specific than what we had before
-				 * (if we had one) then remember the new one
-				 * before continuing to search
-				 * for an even better one.
+				 * (if we had one), or if the virtual status
+				 * of new prefix is better than of the old one,
+				 * then remember the new one before continuing
+				 * to search for an even better one.
 				 */
 				if (ifa_maybe == NULL ||
+				    ifa_preferred(ifa_maybe, ifa) ||
 				    rn_refines((caddr_t)ifa->ifa_netmask,
 				    (caddr_t)ifa_maybe->ifa_netmask)) {
 					if (ifa_maybe != NULL)
@@ -1782,6 +1785,21 @@ done:
 	return (ifa);
 }
 
+/*
+ * See whether new ifa is better than current one:
+ * 1) A non-virtual one is preferred over virtual.
+ * 2) A virtual in master state preferred over any other state.
+ *
+ * Used in several address selecting functions.
+ */
+int
+ifa_preferred(struct ifaddr *cur, struct ifaddr *next)
+{
+
+	return (cur->ifa_carp && (!next->ifa_carp ||
+	    ((*carp_master_p)(next) && !(*carp_master_p)(cur))));
+}
+
 #include <net/if_llatbl.h>
 
 /*
diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 7fcbd38..6ccf364 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -939,8 +939,8 @@ struct	ifaddr *ifa_ifwithdstaddr(struct sockaddr *);
 struct	ifaddr *ifa_ifwithnet(struct sockaddr *, int);
 struct	ifaddr *ifa_ifwithroute(int, struct sockaddr *, struct sockaddr *);
 struct	ifaddr *ifa_ifwithroute_fib(int, struct sockaddr *, struct sockaddr *, u_int);
-
 struct	ifaddr *ifaof_ifpforaddr(struct sockaddr *, struct ifnet *);
+int	ifa_preferred(struct ifaddr *, struct ifaddr *);
 
 int	if_simloop(struct ifnet *ifp, struct mbuf *m, int af, int hlen);