Be slightly smarter about git-daemon client shutdown

Shut down connections that haven't even identified themselves as git
clients first.  That should get rid of people who just connect to the
port and wait for something to happen.

daemon.c

@@ -26,6 +26,12 @@ static int upload(char *dir, int dirlen)
 	    access("HEAD", R_OK))
 		return -1;
 
+	/*
+	 * We'll ignore SIGTERM from now on, we have a
+	 * good client.
+	 */
+	signal(SIGTERM, SIG_IGN);
+
 	/* git-upload-pack only ever reads stuff, so this is safe */
 	execlp("git-upload-pack", "git-upload-pack", ".", NULL);
 	return -1;
@@ -128,33 +134,24 @@ static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
  *
  * Really, this is just a place-holder for a _real_ algorithm.
  */
-static void kill_some_children(int connections, unsigned start, unsigned stop)
+static void kill_some_children(int signo, unsigned start, unsigned stop)
 {
 	start %= MAX_CHILDREN;
 	stop %= MAX_CHILDREN;
 	while (start != stop) {
 		if (!(start & 3))
-			kill(live_child[start].pid, SIGTERM);
+			kill(live_child[start].pid, signo);
 		start = (start + 1) % MAX_CHILDREN;
 	}
 }
 
-static void handle(int incoming, struct sockaddr_in *addr, int addrlen)
+static void check_max_connections(void)
 {
-	pid_t pid = fork();
-
-	if (pid) {
+	for (;;) {
 		int active;
 		unsigned spawned, reaped, deleted;
 
-		close(incoming);
-		if (pid < 0)
-			return;
-
 		spawned = children_spawned;
-		add_child(spawned % MAX_CHILDREN, pid, addr, addrlen);
-		children_spawned = ++spawned;
-
 		reaped = children_reaped;
 		deleted = children_deleted;
 
@@ -166,15 +163,36 @@ static void handle(int incoming, struct sockaddr_in *addr, int addrlen)
 		children_deleted = deleted;
 
 		active = spawned - deleted;
-		if (active > max_connections) {
-			kill_some_children(active, deleted, spawned);
+		if (active <= max_connections)
+			break;
 
-			/* Wait to make sure they're gone */
-			while (spawned - children_reaped > max_connections)
+		/* Kill some unstarted connections with SIGTERM */
+		kill_some_children(SIGTERM, deleted, spawned);
+		if (active <= max_connections << 1)
+			break;
+
+		/* If the SIGTERM thing isn't helping use SIGKILL */
+		kill_some_children(SIGKILL, deleted, spawned);
 		sleep(1);
 	}
+}
 
+static void handle(int incoming, struct sockaddr_in *addr, int addrlen)
+{
+	pid_t pid = fork();
 
+	if (pid) {
+		unsigned idx;
+
+		close(incoming);
+		if (pid < 0)
+			return;
+
+		idx = children_spawned % MAX_CHILDREN;
+		children_spawned++;
+		add_child(idx, pid, addr, addrlen);
+
+		check_max_connections();
 		return;
 	}