Test whether created sockets are select()able

Conflicts:
	src/net.cpp

Github-Pull: #6412
Rebased-From: d422f9b1fd

src/compat.h

@@ -90,4 +90,12 @@ typedef u_int SOCKET;
 
 size_t strnlen_int( const char *start, size_t max_len);
 
+bool static inline IsSelectableSocket(SOCKET s) {
+#ifdef WIN32
+    return true;
+#else
+    return (s >= 0 && s < FD_SETSIZE);
+#endif
+}
+
 #endif // BITCOIN_COMPAT_H

src/net.cpp

@@ -403,6 +403,12 @@ CNode* ConnectNode(CAddress addrConnect, const char *pszDest)
     if (pszDest ? ConnectSocketByName(addrConnect, hSocket, pszDest, Params().GetDefaultPort(), nConnectTimeout, &proxyConnectionFailed) :
                   ConnectSocket(addrConnect, hSocket, nConnectTimeout, &proxyConnectionFailed))
     {
+        if (!IsSelectableSocket(hSocket)) {
+            LogPrintf("Cannot create connection: non-selectable socket created (fd >= FD_SETSIZE ?)\n");
+            CloseSocket(hSocket);
+            return NULL;
+        }
+
         addrman.Attempt(addrConnect);
 
         // Add node
@@ -871,8 +877,14 @@ void ThreadSocketHandler()
                     if (nErr != WSAEWOULDBLOCK)
                         LogPrintf("socket error accept failed: %s\n", NetworkErrorString(nErr));
                 }
+                else if (!IsSelectableSocket(hSocket))
+                {
+                    LogPrintf("connection from %s dropped: non-selectable socket\n", addr.ToString());
+                    CloseSocket(hSocket);
+                }
                 else if (nInbound >= nMaxConnections - MAX_OUTBOUND_CONNECTIONS)
                 {
+                    LogPrint("net", "connection from %s dropped (full)\n", addr.ToString());
                     CloseSocket(hSocket);
                 }
                 else if (CNode::IsBanned(addr) && !whitelisted)
@@ -1498,6 +1510,13 @@ bool BindListenPort(const CService &addrBind, string& strError, bool fWhiteliste
         LogPrintf("%s\n", strError);
         return false;
     }
+    if (!IsSelectableSocket(hListenSocket))
+    {
+        strError = "Error: Couldn't create a listenable socket for incoming connections";
+        LogPrintf("%s\n", strError);
+        return false;
+    }
+
 
 #ifndef WIN32
 #ifdef SO_NOSIGPIPE

src/netbase.cpp

@@ -267,6 +267,9 @@ bool static InterruptibleRecv(char* data, size_t len, int timeout, SOCKET& hSock
         } else { // Other error or blocking
             int nErr = WSAGetLastError();
             if (nErr == WSAEINPROGRESS || nErr == WSAEWOULDBLOCK || nErr == WSAEINVAL) {
+                if (!IsSelectableSocket(hSocket)) {
+                    return false;
+                }
                 struct timeval tval = MillisToTimeval(std::min(endTime - curTime, maxWait));
                 fd_set fdset;
                 FD_ZERO(&fdset);