net: do not allow resolving to an internal address

In order to prevent mixups, our internal range is never allowed as a resolve
result. This means that no user-provided string will ever be confused with an
internal address.

src/netbase.cpp

@@ -108,17 +108,22 @@ bool static LookupIntern(const char *pszName, std::vector<CNetAddr>& vIP, unsign
     struct addrinfo *aiTrav = aiRes;
     while (aiTrav != NULL && (nMaxSolutions == 0 || vIP.size() < nMaxSolutions))
     {
+        CNetAddr resolved;
         if (aiTrav->ai_family == AF_INET)
         {
             assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in));
-            vIP.push_back(CNetAddr(((struct sockaddr_in*)(aiTrav->ai_addr))->sin_addr));
+            resolved = CNetAddr(((struct sockaddr_in*)(aiTrav->ai_addr))->sin_addr);
         }
 
         if (aiTrav->ai_family == AF_INET6)
         {
             assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in6));
             struct sockaddr_in6* s6 = (struct sockaddr_in6*) aiTrav->ai_addr;
-            vIP.push_back(CNetAddr(s6->sin6_addr, s6->sin6_scope_id));
+            resolved = CNetAddr(s6->sin6_addr, s6->sin6_scope_id);
+        }
+        /* Never allow resolving to an internal address. Consider any such result invalid */
+        if (!resolved.IsInternal()) {
+            vIP.push_back(resolved);
         }
 
         aiTrav = aiTrav->ai_next;

src/test/netbase_tests.cpp

@@ -113,6 +113,11 @@ BOOST_AUTO_TEST_CASE(netbase_lookupnumeric)
     BOOST_CHECK(TestParse("[::]:8333", "[::]:8333"));
     BOOST_CHECK(TestParse("[127.0.0.1]", "127.0.0.1:65535"));
     BOOST_CHECK(TestParse(":::", "[::]:0"));
+
+    // verify that an internal address fails to resolve
+    BOOST_CHECK(TestParse("[fd6b:88c0:8724:1:2:3:4:5]", "[::]:0"));
+    // and that a one-off resolves correctly
+    BOOST_CHECK(TestParse("[fd6c:88c0:8724:1:2:3:4:5]", "[fd6c:88c0:8724:1:2:3:4:5]:65535"));
 }
 
 BOOST_AUTO_TEST_CASE(onioncat_test)