[IPV6]: Fix source address selection for ORCHID addresses

Skip the prefix length matching in source address selection for
orchid -> non-orchid addresses.

Overlay Routable Cryptographic Hash IDentifiers (RFC 4843,
2001:10::/28) are currenty not globally reachable. Without this
check a host with an ORCHID address can end up preferring those over
regular addresses when talking to other regular hosts in the 2001::/16
range thus breaking non-orchid connections.

Signed-off-by: Juha-Matti Tapio <jmtapio@verkkotelakka.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 15 insertions, 0 deletions

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index c0c019f72ba9..8b05c65415cb 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -384,6 +384,16 @@ static inline int ipv6_addr_v4mapped(const struct in6_addr *a)
 }
 
 /*
+ * Check for a RFC 4843 ORCHID address
+ * (Overlay Routable Cryptographic Hash Identifiers)
+ */
+static inline int ipv6_addr_orchid(const struct in6_addr *a)
+{
+        return ((a->s6_addr32[0] & htonl(0xfffffff0))
+                == htonl(0x20010010));
+}
+
+/*
  * find the first different bit between two addresses
  * length of address must be a multiple of 32bits
  */
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 101e0e70ba27..18e3a9825d81 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1125,6 +1125,11 @@ int ipv6_dev_get_saddr(struct net_device *daddr_dev,
                         if (hiscore.rule < 7)
                                 hiscore.rule++;
 #endif
+
+                        /* Skip rule 8 for orchid -> non-orchid address pairs. */
+                        if (ipv6_addr_orchid(&ifa->addr) && !ipv6_addr_orchid(daddr))
+                                continue;
+
                         /* Rule 8: Use longest matching prefix */
                         if (hiscore.rule < 8) {
                                 hiscore.matchlen = ipv6_addr_diff(&ifa_result->addr, daddr);