[IPV6]: Fix source address selection.

Two additional labels (RFC 3484, sec. 10.3) for IPv6 addreses
are defined to make a distinction between global unicast
addresses and Unique Local Addresses (fc00::/7, RFC 4193) and
Teredo (2001::/32, RFC 4380). It is necessary to avoid attempts
of connection that would either fail (eg. fec0:: to 2001:feed::)
or be sub-optimal (2001:0:: to 2001:feed::).
Signed-off-by: NŁukasz Stelmach <stlman@poczta.fm>
Signed-off-by: NYOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -862,6 +862,8 @@ static int inline ipv6_saddr_label(const struct in6_addr *addr, int type)
   * 	2002::/16		2
   * 	::/96			3
   * 	::ffff:0:0/96		4
+  *	fc00::/7		5
+  * 	2001::/32		6
   */
 	if (type & IPV6_ADDR_LOOPBACK)
 		return 0;
@@ -869,8 +871,12 @@ static int inline ipv6_saddr_label(const struct in6_addr *addr, int type)
 		return 3;
 	else if (type & IPV6_ADDR_MAPPED)
 		return 4;
+	else if (addr->s6_addr32[0] == htonl(0x20010000))
+		return 6;
 	else if (addr->s6_addr16[0] == htons(0x2002))
 		return 2;
+	else if ((addr->s6_addr[0] & 0xfe) == 0xfc)
+		return 5;
 	return 1;
 }