- Shared network selection should be done from the innermost relay

valid link-address field, rather than the outermost.  [ISC-Bugs #17764]

RELNOTES

@@ -64,6 +64,9 @@ work on other platforms. Please report any problems and suggested fixes to
 - A bug was fixed where the length of a hostname was miscalculated, so that
   hosts were given odd-looking domain names ("foo.bar.ba.example.com").
 
+- Shared network selection should be done from the innermost relay
+  valid link-address field, rather than the outermost.
+
 			Changes since 4.0.0 (new features)
 
 - Added DHCPv6 rapid commit support.

server/dhcpv6.c

@@ -3954,6 +3954,7 @@ shared_network_from_packet6(struct shared_network **shared,
 		if (!IN6_IS_ADDR_UNSPECIFIED(link_addr) &&
 		    !IN6_IS_ADDR_LINKLOCAL(link_addr)) {
 			first_link_addr = link_addr;
+			break;
 		}
 		chk_packet = chk_packet->dhcpv6_container_packet;
 	}