llmnrd: merge rtnl interface event loop into main select() loops

Instead of spawming a thread for the sole purpose of watching the rtnl
for (presumably) seldom events, just merge the select() for all sockets
together in one single main loop.

This reduces unnecessary complexity and makes llmnrd no longer require
any locking.

It also allows us to handle signals in a thread-safe manner (as there
aren't any ;) and thus the race condition on exit reported in #20

Closes #20
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

1 files changed, 84 insertions, 9 deletions

diff --git a/llmnrd.c b/llmnrd.c
index 2bc4a20..66a9f04 100644
--- a/llmnrd.c
+++ b/llmnrd.c
@@ -1,7 +1,7 @@
 /*
  * llmnrd -- LLMNR (RFC 4705) responder daemon.
  *
- * Copyright (C) 2014-2016 Tobias Klauser <tklauser@distanz.ch>
+ * Copyright (C) 2014-2017 Tobias Klauser <tklauser@distanz.ch>
  *
  * This file is part of llmnrd.
  *
@@ -38,6 +38,11 @@
 #include "iface.h"
 #include "llmnr.h"
 #include "llmnr-packet.h"
+#include "socket.h"
+
+static bool llmnrd_running = true;
+static int llmnrd_sock_ipv4 = -1;
+static int llmnrd_sock_ipv6 = -1;
 
 static const char *short_opts = "H:i:p:6dhV";
 static const struct option long_opts[] = {
@@ -82,8 +87,7 @@ static void signal_handler(int sig)
 	case SIGQUIT:
 	case SIGTERM:
 		log_info("Interrupt received. Stopping llmnrd.\n");
-		iface_stop();
-		llmnr_stop();
+		llmnrd_running = false;
 		break;
 	case SIGHUP:
 	default:
@@ -109,14 +113,32 @@ static void register_signal(int sig, void (*handler)(int))
 	}
 }
 
+static void iface_event_handle(enum iface_event_type type, unsigned char af,
+			       unsigned int ifindex)
+{
+	switch (af) {
+	case AF_INET:
+		socket_mcast_group_ipv4(llmnrd_sock_ipv4, ifindex, type == IFACE_ADD);
+		break;
+	case AF_INET6:
+		socket_mcast_group_ipv6(llmnrd_sock_ipv6, ifindex, type == IFACE_ADD);
+		break;
+	default:
+		/* ignore */
+		break;
+	}
+}
+
 int main(int argc, char **argv)
 {
-	int c, ret = EXIT_FAILURE;
+	int c, ret = -1;
 	long num_arg;
 	bool daemonize = false, ipv6 = false;
 	char *hostname = NULL;
 	char *iface = NULL;
 	uint16_t port = LLMNR_UDP_PORT;
+	int llmnrd_sock_rtnl = -1;
+	int nfds;
 
 	while ((c = getopt_long(argc, argv, short_opts, long_opts, NULL)) != -1) {
 		switch (c) {
@@ -166,18 +188,71 @@ int main(int argc, char **argv)
 	if (daemonize) {
 		if (daemon(0, 0) != 0) {
 			log_err("Failed to daemonize process: %s\n", strerror(errno));
-			return EXIT_FAILURE;
+			goto out;
 		}
 	}
 
-	if (llmnr_init(hostname, port, ipv6, iface) < 0)
+	log_info("Starting llmnrd on port %u, hostname %s\n", port, hostname);
+	if (iface)
+		log_info("Binding to interface %s\n", iface);
+
+	llmnrd_sock_ipv4 = socket_open_ipv4(port, iface);
+	if (llmnrd_sock_ipv4 < 0)
 		goto out;
 
-	if (iface_start_thread(ipv6, iface) < 0)
+	if (ipv6) {
+		llmnrd_sock_ipv6 = socket_open_ipv6(port, iface);
+		if (llmnrd_sock_ipv6 < 0)
+			goto out;
+	}
+
+	llmnrd_sock_rtnl = socket_open_rtnl(ipv6);
+	if (llmnrd_sock_rtnl < 0)
 		goto out;
 
-	ret = llmnr_run();
+	llmnr_init(hostname, ipv6);
+	iface_init(llmnrd_sock_rtnl, iface, ipv6, &iface_event_handle);
+
+	nfds = max(llmnrd_sock_ipv4, llmnrd_sock_rtnl);
+	if (llmnrd_sock_ipv6 >= 0)
+		nfds = max(nfds, llmnrd_sock_ipv6);
+	nfds += 1;
+
+	while (llmnrd_running) {
+		fd_set rfds;
+
+		FD_ZERO(&rfds);
+		FD_SET(llmnrd_sock_ipv4, &rfds);
+		FD_SET(llmnrd_sock_rtnl, &rfds);
+		if (llmnrd_sock_ipv6 >= 0)
+			FD_SET(llmnrd_sock_ipv6, &rfds);
+
+		ret = select(nfds, &rfds, NULL, NULL, NULL);
+		if (ret < 0) {
+			if (errno != EINTR)
+				log_err("Failed to select() on socket: %s\n", strerror(errno));
+			goto out;
+		} else if (ret) {
+			/* handle RTNL messages first so we can respond with
+			 * up-to-date information.
+			 */
+			if (FD_ISSET(llmnrd_sock_rtnl, &rfds))
+				iface_recv(llmnrd_sock_rtnl);
+			if (FD_ISSET(llmnrd_sock_ipv4, &rfds))
+				llmnr_recv(llmnrd_sock_ipv4);
+			if (llmnrd_sock_ipv6 >= 0 && FD_ISSET(llmnrd_sock_ipv6, &rfds))
+				llmnr_recv(llmnrd_sock_ipv6);
+		}
+	}
+
+	ret = 0;
 out:
+	if (llmnrd_sock_rtnl >= 0)
+		close(llmnrd_sock_rtnl);
+	if (llmnrd_sock_ipv6 >= 0)
+		close(llmnrd_sock_ipv6);
+	if (llmnrd_sock_ipv4 >= 0)
+		close(llmnrd_sock_ipv4);
 	free(hostname);
-	return ret;
+	return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }