From 89f4574e0b1553c8e5dcbfc275e829a759b697f6 Mon Sep 17 00:00:00 2001
From: Guus Sliepen <guus@tinc-vpn.org>
Date: Mon, 26 Mar 2012 14:46:09 +0100
Subject: [PATCH] Add support for systemd style socket activation.

If the LISTEN_FDS environment variable is set and tinc is run in the
foreground, tinc will use filedescriptors 3 to 3 + LISTEN_FDS for its listening
TCP sockets. For now, tinc will create matching listening UDP sockets itself.

There is no dependency on systemd or on libsystemd-daemon.
---
 src/net_setup.c | 133 +++++++++++++++++++++++++++++++-----------------
 src/tincd.c     |   6 +++
 2 files changed, 93 insertions(+), 46 deletions(-)

diff --git a/src/net_setup.c b/src/net_setup.c
index 4b90737f..d3940e72 100644
--- a/src/net_setup.c
+++ b/src/net_setup.c
@@ -581,71 +581,112 @@ static bool setup_myself(void) {
 
 	/* Open sockets */
 
-	listen_sockets = 0;
-	cfg = lookup_config(config_tree, "BindToAddress");
+	if(!do_detach && getenv("LISTEN_FDS")) {
+		sockaddr_t sa;
+		socklen_t salen;
 
-	do {
-		get_config_string(cfg, &address);
-		if(cfg)
-			cfg = lookup_config_next(config_tree, cfg);
+		listen_sockets = atoi(getenv("LISTEN_FDS"));
+#ifdef HAVE_UNSETENV
+		unsetenv("LISTEN_FDS");
+#endif
 
-		char *port = myport;
+		if(listen_sockets > MAXSOCKETS) {
+			logger(LOG_ERR, "Too many listening sockets");
+			return false;
+		}
 
-		if(address) {
-			char *space = strchr(address, ' ');
-			if(space) {
-				*space++ = 0;
-				port = space;
+		for(i = 0; i < listen_sockets; i++) {
+			salen = sizeof sa;
+			if(getsockname(i + 3, &sa.sa, &salen) < 0) {
+				logger(LOG_ERR, "Could not get address of listen fd %d: %s", i + 3, sockstrerror(errno));
+				return false;
 			}
 
-			if(!strcmp(address, "*"))
-				*address = 0;
-		}
+			listen_socket[i].tcp = i + 3;
+
+#ifdef FD_CLOEXEC
+		        fcntl(i + 3, F_SETFD, FD_CLOEXEC);
+#endif
 
-		hint.ai_family = addressfamily;
-		hint.ai_socktype = SOCK_STREAM;
-		hint.ai_protocol = IPPROTO_TCP;
-		hint.ai_flags = AI_PASSIVE;
+			listen_socket[i].udp = setup_vpn_in_socket(&sa);
+			if(listen_socket[i].udp < 0)
+				return false;
 
-		err = getaddrinfo(address && *address ? address : NULL, port, &hint, &ai);
-		free(address);
+			ifdebug(CONNECTIONS) {
+				hostname = sockaddr2hostname(&sa);
+				logger(LOG_NOTICE, "Listening on %s", hostname);
+				free(hostname);
+			}
 
-		if(err || !ai) {
-			logger(LOG_ERR, "System call `%s' failed: %s", "getaddrinfo",
-				   gai_strerror(err));
-			return false;
+			memcpy(&listen_socket[i].sa, &sa, salen);
 		}
+	} else {
+		listen_sockets = 0;
+		cfg = lookup_config(config_tree, "BindToAddress");
+
+		do {
+			get_config_string(cfg, &address);
+			if(cfg)
+				cfg = lookup_config_next(config_tree, cfg);
+
+			char *port = myport;
+
+			if(address) {
+				char *space = strchr(address, ' ');
+				if(space) {
+					*space++ = 0;
+					port = space;
+				}
+
+				if(!strcmp(address, "*"))
+					*address = 0;
+			}
+
+			hint.ai_family = addressfamily;
+			hint.ai_socktype = SOCK_STREAM;
+			hint.ai_protocol = IPPROTO_TCP;
+			hint.ai_flags = AI_PASSIVE;
 
-		for(aip = ai; aip; aip = aip->ai_next) {
-			if(listen_sockets >= MAXSOCKETS) {
-				logger(LOG_ERR, "Too many listening sockets");
+			err = getaddrinfo(address && *address ? address : NULL, port, &hint, &ai);
+			free(address);
+
+			if(err || !ai) {
+				logger(LOG_ERR, "System call `%s' failed: %s", "getaddrinfo",
+					   gai_strerror(err));
 				return false;
 			}
 
-			listen_socket[listen_sockets].tcp =
-				setup_listen_socket((sockaddr_t *) aip->ai_addr);
+			for(aip = ai; aip; aip = aip->ai_next) {
+				if(listen_sockets >= MAXSOCKETS) {
+					logger(LOG_ERR, "Too many listening sockets");
+					return false;
+				}
 
-			if(listen_socket[listen_sockets].tcp < 0)
-				continue;
+				listen_socket[listen_sockets].tcp =
+					setup_listen_socket((sockaddr_t *) aip->ai_addr);
 
-			listen_socket[listen_sockets].udp =
-				setup_vpn_in_socket((sockaddr_t *) aip->ai_addr);
+				if(listen_socket[listen_sockets].tcp < 0)
+					continue;
 
-			if(listen_socket[listen_sockets].udp < 0)
-				continue;
+				listen_socket[listen_sockets].udp =
+					setup_vpn_in_socket((sockaddr_t *) aip->ai_addr);
 
-			ifdebug(CONNECTIONS) {
-				hostname = sockaddr2hostname((sockaddr_t *) aip->ai_addr);
-				logger(LOG_NOTICE, "Listening on %s", hostname);
-				free(hostname);
-			}
+				if(listen_socket[listen_sockets].udp < 0)
+					continue;
 
-			memcpy(&listen_socket[listen_sockets].sa, aip->ai_addr, aip->ai_addrlen);
-			listen_sockets++;
-		}
+				ifdebug(CONNECTIONS) {
+					hostname = sockaddr2hostname((sockaddr_t *) aip->ai_addr);
+					logger(LOG_NOTICE, "Listening on %s", hostname);
+					free(hostname);
+				}
 
-		freeaddrinfo(ai);
-	} while(cfg);
+				memcpy(&listen_socket[listen_sockets].sa, aip->ai_addr, aip->ai_addrlen);
+				listen_sockets++;
+			}
+
+			freeaddrinfo(ai);
+		} while(cfg);
+	}
 
 	if(listen_sockets)
 		logger(LOG_NOTICE, "Ready");
diff --git a/src/tincd.c b/src/tincd.c
index 443301e0..148e13e4 100644
--- a/src/tincd.c
+++ b/src/tincd.c
@@ -539,6 +539,12 @@ int main(int argc, char **argv) {
 
 	g_argv = argv;
 
+	if(getenv("LISTEN_PID") && atoi(getenv("LISTEN_PID")) == getpid())
+		do_detach = false;
+#ifdef HAVE_UNSETENV
+	unsetenv("LISTEN_PID");
+#endif
+
 	init_configuration(&config_tree);
 
 	/* Slllluuuuuuurrrrp! */
-- 
2.20.1