net: attempt to use the same port for IPv4 and IPv6 if 0

src/network_utils.cpp

@@ -197,12 +197,26 @@ UdpSocket::openSockets(const SockAddr& bind4, const SockAddr& bind6)
 #if 1
     bound6 = {};
     if (bind6) {
+        if (bind6.getPort() == 0) {
+            // Attempt to use the same port as IPv4 with IPv6
+            if (auto p4 = bound4.getPort()) {
+                auto b6 = bind6;
+                b6.setPort(p4);
+                try {
+                    s6 = bindSocket(b6, bound6);
+                } catch (const DhtException& e) {
+                    logger.e("Can't bind inet6 socket: %s", e.what());
+                }
+            }
+        }
+        if (s6 == -1) {
             try {
                 s6 = bindSocket(bind6, bound6);
             } catch (const DhtException& e) {
                 logger.e("Can't bind inet6 socket: %s", e.what());
             }
         }
+    }
 #endif
 
     if (s4 == -1 && s6 == -1) {

src/utils.cpp

@@ -216,11 +216,11 @@ SockAddr::getMappedIPv4()
 }
 
 SockAddr
-SockAddr::getMappedIPv6() const
+SockAddr::getMappedIPv6()
 {
     auto family = getFamily();
     if (family != AF_INET)
-        return *this;
+        return std::move(*this);
     SockAddr ret;
     ret.setFamily(AF_INET6);
     ret.setPort(getPort());