net: Move IsSelectableSocket check into socket creation

We use select in ConnectSocketDirectly, so this check needs to happen before
that.

IsSelectableSocket will not be relevant after upcoming changes to remove select.

src/net.cpp

@@ -446,9 +446,7 @@ CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCo
         SplitHostPort(std::string(pszDest), port, host);
         connected = ConnectThroughProxy(proxy, host, port, hSocket, nConnectTimeout, nullptr);
     }
-    if (connected) {
-        if (!IsSelectableSocket(hSocket)) {
-            LogPrintf("Cannot create connection: non-selectable socket created (fd >= FD_SETSIZE ?)\n");
+    if (!connected) {
         CloseSocket(hSocket);
         return nullptr;
     }
@@ -463,9 +461,6 @@ CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCo
     return pnode;
 }
 
-    return nullptr;
-}
-
 void CConnman::DumpBanlist()
 {
     SweepBanned(); // clean unused entries (if bantime has expired)

src/netbase.cpp

@@ -465,6 +465,12 @@ SOCKET CreateSocket(const CService &addrConnect)
     if (hSocket == INVALID_SOCKET)
         return INVALID_SOCKET;
 
+    if (!IsSelectableSocket(hSocket)) {
+        CloseSocket(hSocket);
+        LogPrintf("Cannot create connection: non-selectable socket created (fd >= FD_SETSIZE ?)\n");
+        return INVALID_SOCKET;
+    }
+
 #ifdef SO_NOSIGPIPE
     int set = 1;
     // Different way of disabling SIGPIPE on BSD