kike: handle accept() errors better

Might prevent some denial of service attacks.

kike.c

@@ -3379,20 +3379,25 @@ irc_try_fetch_client (struct server_context *ctx, int listen_fd)
 	int fd = accept (listen_fd, (struct sockaddr *) &peer, &peer_len);
 	if (fd == -1)
 	{
-		if (errno == EAGAIN)
+		if (errno == EAGAIN || errno == EWOULDBLOCK)
 			return false;
-		if (errno == EINTR
-		 || errno == ECONNABORTED)
+		if (errno == EINTR)
 			return true;
 
-		// TODO: handle resource exhaustion (EMFILE, ENFILE) specially
-		//   (stop accepting new connections and wait until we close some;
-		//   also set a timer in case of ENFILE).
+		if (errno == EBADF
+		 || errno == EINVAL
+		 || errno == ENOTSOCK
+		 || errno == EOPNOTSUPP)
 			print_fatal ("%s: %s", "accept", strerror (errno));
-		irc_initiate_quit (ctx);
-		return false;
+
+		// OS kernels may return a wide range of unforeseeable errors.
+		// Assuming that they're either transient or caused by
+		// a connection that we've just extracted from the queue.
+		print_warning ("%s: %s", "accept", strerror (errno));
+		return true;
 	}
 
+	hard_assert (peer_len <= sizeof peer);
 	set_blocking (fd, false);
 
 	// A little bit questionable once the traffic gets high enough (IMO),