RPCBIND: skip ipv6 link local when request is not from link local address

RPCINFO on macOS behaves different compared to other linux clients and
doesn't provide request address in rpcb structure of the
RPCBPROC_GETADDRLIST call which doesn't seem to be forbidden.

In this case RPCBIND uses RPC call's source address and picks a
closest corresponding local address. If there are no addresses in the
same subnet as the source address, return of RPCBIND may vary
depending on the order of addresses returned in getifaddrs. If a link
local precedes global address it may be returned even if the request
comes from neither a link local nor from link local in a different
scope, which will prevent services like nfs from working in tpc6
scenario on macOS clients. Issue can be seen only on FreeBSD rpcbind
port due to changes in workflow of addrmerge call.

Submitted by:	Dmitry Ovsyannikov (Dmitry.Ovsyannikov@dell.com)
Sponsored by:	Dell EMC

(cherry picked from commit d18c9a91979543adc182c7b28819691b64fda388)

2 files changed, 41 insertions, 5 deletions

diff --git a/usr.sbin/rpcbind/tests/addrmerge_test.c b/usr.sbin/rpcbind/tests/addrmerge_test.c
index e1600f1a4837..a29dc30fdde8 100644
--- a/usr.sbin/rpcbind/tests/addrmerge_test.c
+++ b/usr.sbin/rpcbind/tests/addrmerge_test.c
@@ -257,6 +257,22 @@ mock_tun0(void)
 	    IFF_UP | IFF_RUNNING | IFF_POINTOPOINT | IFF_MULTICAST, 0, false);
 }
 
+static void
+mock_mlxen0(void)
+{
+	mock_ifaddr4("mlxen0", "192.0.3.1", "255.255.255.128", "192.0.3.127",
+	    IFF_UP | IFF_BROADCAST | IFF_RUNNING | IFF_SIMPLEX | IFF_MULTICAST,
+	    false);
+	/* Setting link local address before ipv6 address*/
+	mock_ifaddr6("mlxen0", "fe80::4", "ffff:ffff:ffff:ffff::",
+	    "fe80::ffff:ffff:ffff:ffff",
+	    IFF_UP | IFF_BROADCAST | IFF_RUNNING | IFF_SIMPLEX | IFF_MULTICAST,
+	    3, false);
+	mock_ifaddr6("mlxen0", "2001:db8::7", "ffff:ffff:ffff:ffff::",
+	    "2001:db8::ffff:ffff:ffff:ffff",
+	    IFF_UP | IFF_BROADCAST | IFF_RUNNING | IFF_SIMPLEX | IFF_MULTICAST,
+	    0, false);
+}
 
 /* Stub rpcbind functions */
 int
@@ -835,6 +851,23 @@ ATF_TC_BODY(addrmerge_recvdstaddr6_rev, tc)
 	ATF_CHECK_STREQ("2001:db8::2.3.46", maddr);
 	free(maddr);
 }
+
+ATF_TC_WITHOUT_HEAD(addrmerge_ipv6_other_subnet);
+ATF_TC_BODY(addrmerge_ipv6_other_subnet, tc)
+{
+	char *maddr;
+
+	/* getifaddrs will return link local before normal ipv6 */
+	mock_lo0();
+	mock_mlxen0();
+	
+	maddr = do_addrmerge6("2001:db8:1::1.3.46");
+
+	/* We must return the closest ipv6 address*/
+	ATF_REQUIRE(maddr != NULL);
+	ATF_CHECK_STREQ("2001:db8::7.3.46", maddr);
+	free(maddr);
+}
 #endif /* INET6 */
 
 
@@ -864,6 +897,7 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, addrmerge_ipv6_linklocal_rev);
 	ATF_TP_ADD_TC(tp, addrmerge_recvdstaddr6);
 	ATF_TP_ADD_TC(tp, addrmerge_recvdstaddr6_rev);
+	ATF_TP_ADD_TC(tp, addrmerge_ipv6_other_subnet);
 #endif
 
 	return (atf_no_error());
diff --git a/usr.sbin/rpcbind/util.c b/usr.sbin/rpcbind/util.c
index 455578b657fb..e497e9227690 100644
--- a/usr.sbin/rpcbind/util.c
+++ b/usr.sbin/rpcbind/util.c
@@ -229,17 +229,19 @@ addrmerge(struct netbuf *caller, const char *serv_uaddr, const char *clnt_uaddr,
 			 * a link-local address then use the scope id to see
 			 * which one.
 			 */
-			if (IN6_IS_ADDR_LINKLOCAL(&SA2SIN6ADDR(ifsa)) &&
-			    IN6_IS_ADDR_LINKLOCAL(&SA2SIN6ADDR(caller_sa)) &&
-			    IN6_IS_ADDR_LINKLOCAL(&SA2SIN6ADDR(hint_sa))) {
-				if (SA2SIN6(ifsa)->sin6_scope_id ==
-				    SA2SIN6(caller_sa)->sin6_scope_id) {
+			if (IN6_IS_ADDR_LINKLOCAL(&SA2SIN6ADDR(ifsa))) {
+				if (IN6_IS_ADDR_LINKLOCAL(&SA2SIN6ADDR(caller_sa)) &&
+				    IN6_IS_ADDR_LINKLOCAL(&SA2SIN6ADDR(hint_sa)) &&
+				    (SA2SIN6(ifsa)->sin6_scope_id ==
+				     SA2SIN6(caller_sa)->sin6_scope_id)) {
 					const int goodness = 3;
 
 					if (bestif_goodness < goodness) {
 						bestif = ifap;
 						bestif_goodness = goodness;
 					}
+				} else {
+					continue;
 				}
 			}
 		}