Kernel: Treat a backlog argument of 0 to listen() as if it was 1

As per POSIX, the behavior of listen() with a backlog value of 0 is
implementation defined: "A backlog argument of 0 may allow the socket
to accept connections, in which case the length of the listen queue may
be set to an implementation-defined minimum value."
Since creating a socket that can't accept any connections seems
relatively useless, and as other platforms (Linux, FreeBSD, etc) chose
to support accepting connections with this backlog value, support it as
well by normalizing it to 1.

Author: IdanHo

Kernel/Syscalls/socket.cpp

@@ -65,8 +65,14 @@ ErrorOr<FlatPtr> Process::sys$bind(int sockfd, Userspace<sockaddr const*> addres
 ErrorOr<FlatPtr> Process::sys$listen(int sockfd, int backlog)
 {
     VERIFY_NO_PROCESS_BIG_LOCK(this);
-    if (backlog < 0)
-        backlog = 0;
+    // As per POSIX, the behavior of listen() with a backlog value of 0 is implementation defined:
+    // "A backlog argument of 0 may allow the socket to accept connections, in which case the length of the listen queue may be set to an implementation-defined minimum value."
+    // Since creating a socket that can't accept any connections seems relatively useless, and as other platforms (Linux, FreeBSD, etc) chose to support accepting connections
+    // with this backlog value, support it as well by normalizing it to 1.
+    // Also, as per POSIX, the behaviour of a negative backlog value is equivalent to a backlog value of 0:
+    // "If listen() is called with a backlog argument value that is less than 0, the function behaves as if it had been called with a backlog argument value of 0."
+    if (backlog <= 0)
+        backlog = 1;
     auto description = TRY(open_file_description(sockfd));
     if (!description->is_socket())
         return ENOTSOCK;