Quiet compiler warning about uninitialized variable. Also rearrange QuicUdpSocketApi::SetupSocket to use the ipv6_only argument that is sent to the function.

The variable is passed to getsockopt to set the value, but the compiler is not smart enough to see that.

Protected by quic_restart_flag_quic_dual_stack_ecn.

PiperOrigin-RevId: 572623856

quiche/quic/core/quic_udp_socket_posix.inc

diff --git a/quiche/quic/core/quic_udp_socket_posix.inc b/quiche/quic/core/quic_udp_socket_posix.inc
index 26aed73..114b359 100644
--- a/quiche/quic/core/quic_udp_socket_posix.inc
+++ b/quiche/quic/core/quic_udp_socket_posix.inc
@@ -200,6 +200,13 @@
     return false;
   }
 
+  if (!(address_family == AF_INET6 && ipv6_only)) {
+    if (!EnableReceiveSelfIpAddressForV4(fd)) {
+      QUIC_LOG_FIRST_N(ERROR, 100)
+          << "Failed to enable receiving of self v4 ip";
+      return false;
+    }
+  }
   unsigned int set = 1;
   if (address_family == AF_INET &&
       setsockopt(fd, IPPROTO_IP, IP_RECVTOS, &set, sizeof(set)) != 0) {
@@ -213,26 +220,12 @@
                                    << "IPv6 socket";
       return false;
     }
-    int ipv6_only;
-    socklen_t len;
-    if (getsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &ipv6_only, &len) != 0) {
-      QUIC_LOG_FIRST_N(ERROR, 100) << "Could not query IPV6_V6ONLY";
-    } else if (ipv6_only != 1 &&
-               setsockopt(fd, IPPROTO_IP, IP_RECVTOS, &set, sizeof(set)) != 0) {
+    if (!ipv6_only &&
+        setsockopt(fd, IPPROTO_IP, IP_RECVTOS, &set, sizeof(set)) != 0) {
       QUIC_LOG_FIRST_N(ERROR, 100) << "Could not receive IPv4 ECN on "
                                    << "dual-stack socket";
       return false;
     }
-  }
-  if (!(address_family == AF_INET6 && ipv6_only)) {
-    if (!EnableReceiveSelfIpAddressForV4(fd)) {
-      QUIC_LOG_FIRST_N(ERROR, 100)
-          << "Failed to enable receiving of self v4 ip";
-      return false;
-    }
-  }
-
-  if (address_family == AF_INET6) {
     if (!EnableReceiveSelfIpAddressForV6(fd)) {
       QUIC_LOG_FIRST_N(ERROR, 100)
           << "Failed to enable receiving of self v6 ip";