Add no_prefer_iface option.

It stops treating the address on the interface as special by source
address selection rule even when the interface is outgoing interface.
This is desired in some situation.

Requested by:	hrs
Reviewed by:	IHANet folks including hrs
MFC after:	1 week

sbin/ifconfig/af_inet6.c

@@ -473,6 +473,8 @@ static struct cmd inet6_cmds[] = {
 	DEF_CMD("-nud",		-ND6_IFF_PERFORMNUD,	setnd6flags),
 	DEF_CMD("auto_linklocal",ND6_IFF_AUTO_LINKLOCAL,setnd6flags),
 	DEF_CMD("-auto_linklocal",-ND6_IFF_AUTO_LINKLOCAL,setnd6flags),
+	DEF_CMD("no_prefer_iface",ND6_IFF_NO_PREFER_IFACE,setnd6flags),
+	DEF_CMD("-no_prefer_iface",-ND6_IFF_NO_PREFER_IFACE,setnd6flags),
 	DEF_CMD_ARG("pltime",        			setip6pltime),
 	DEF_CMD_ARG("vltime",        			setip6vltime),
 	DEF_CMD("eui64",	0,			setip6eui64),

sbin/ifconfig/af_nd6.c

@@ -58,7 +58,7 @@ static const char rcsid[] =
 #define	MAX_SYSCTL_TRY	5
 #define	ND6BITS	"\020\001PERFORMNUD\002ACCEPT_RTADV\003PREFER_SOURCE" \
 		"\004IFDISABLED\005DONT_SET_IFROUTE\006AUTO_LINKLOCAL" \
-		"\007NO_RADR\020DEFAULTIF"
+		"\007NO_RADR\010NO_PREFER_IFACE\020DEFAULTIF"
 
 static int isnd6defif(int);
 void setnd6flags(const char *, int, int, const struct afswtch *);

sbin/ifconfig/ifconfig.8

@@ -28,7 +28,7 @@
 .\"     From: @(#)ifconfig.8	8.3 (Berkeley) 1/5/94
 .\" $FreeBSD$
 .\"
-.Dd November 7, 2012
+.Dd January 10, 2013
 .Dt IFCONFIG 8
 .Os
 .Sh NAME
@@ -716,6 +716,13 @@ Set a flag to enable Neighbor Unreachability Detection.
 .It Cm -nud
 Clear a flag
 .Cm nud .
+.It Cm no_prefer_iface
+Set a flag to not prefer address on the interface as candidates of the
+source address for outgoing packets, even when the interface is
+outgoing interface.
+.It Cm -no_prefer_iface
+Clear a flag
+.Cm no_prefer_iface .
 .El
 .Pp
 The following parameters are specific to cloning

sys/netinet6/in6_src.c

@@ -383,10 +383,12 @@ in6_selectsrc(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
 		 */
 
 		/* Rule 5: Prefer outgoing interface */
-		if (ia_best->ia_ifp == ifp && ia->ia_ifp != ifp)
-			NEXT(5);
-		if (ia_best->ia_ifp != ifp && ia->ia_ifp == ifp)
-			REPLACE(5);
+		if (!(ND_IFINFO(ifp)->flags & ND6_IFF_NO_PREFER_IFACE)) {
+			if (ia_best->ia_ifp == ifp && ia->ia_ifp != ifp)
+				NEXT(5);
+			if (ia_best->ia_ifp != ifp && ia->ia_ifp == ifp)
+				REPLACE(5);
+		}
 
 		/*
 		 * Rule 6: Prefer matching label

sys/netinet6/nd6.h

@@ -86,6 +86,7 @@ struct nd_ifinfo {
 #define ND6_IFF_DONT_SET_IFROUTE	0x10
 #define ND6_IFF_AUTO_LINKLOCAL	0x20
 #define	ND6_IFF_NO_RADR		0x40
+#define ND6_IFF_NO_PREFER_IFACE	0x80 /* XXX: not related to ND. */
 
 #define	ND6_CREATE		LLE_CREATE
 #define	ND6_EXCLUSIVE		LLE_EXCLUSIVE

usr.sbin/ndp/ndp.8

@@ -29,7 +29,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 9, 2012
+.Dd Jan 10, 2013
 .Dt NDP 8
 .Os
 .\"
@@ -192,6 +192,15 @@ on
 This flag is set by
 .Va net.inet6.ip6.auto_linklocal
 sysctl variable.
+.It Ic no_prefer_iface
+The address on the outgoing interface is preferred by source addess
+selection rule.
+If this flag is set, stop treating the address on the
+.Ar interface
+as special even when the
+.Ar interface
+is outgoing interface.
+The default value of this flag is off.
 .It Ic disabled
 Disable IPv6 operation on the interface.
 When disabled, the interface discards any IPv6 packets

usr.sbin/ndp/ndp.c

@@ -981,6 +981,9 @@ ifinfo(ifname, argc, argv)
 #endif
 #ifdef ND6_IFF_AUTO_LINKLOCAL
 		SETFLAG("auto_linklocal", ND6_IFF_AUTO_LINKLOCAL);
+#endif
+#ifdef ND6_IFF_NO_PREFER_IFACE
+		SETFLAG("no_prefer_iface", ND6_IFF_NO_PREFER_IFACE);
 #endif
 		SETVALUE("basereachable", ND.basereachable);
 		SETVALUE("retrans", ND.retrans);
@@ -1054,6 +1057,10 @@ ifinfo(ifname, argc, argv)
 #ifdef ND6_IFF_AUTO_LINKLOCAL
 		if ((ND.flags & ND6_IFF_AUTO_LINKLOCAL))
 			printf("auto_linklocal ");
+#endif
+#ifdef ND6_IFF_NO_PREFER_IFACE
+		if ((ND.flags & ND6_IFF_NO_PREFER_IFACE))
+			printf("no_prefer_iface ");
 #endif
 	}
 	putc('\n', stdout);