From: Guus Sliepen <guus@meshlink.io>
Date: Tue, 9 Oct 2018 12:06:04 +0000 (+0200)
Subject: Lock meshlink.conf to ensure only one instance can run at a time.
X-Git-Url: https://git.meshlink.io/?a=commitdiff_plain;h=92283d7342fabd882126a892b2636d57ff0458de;p=meshlink

Lock meshlink.conf to ensure only one instance can run at a time.
---

diff --git a/src/conf.c b/src/conf.c
index 5d5c46c1..e3574ea5 100644
--- a/src/conf.c
+++ b/src/conf.c
@@ -40,13 +40,7 @@ static int config_compare(const config_t *a, const config_t *b) {
 		return result;
 	}
 
-	result = a->line - b->line;
-
-	if(result) {
-		return result;
-	} else {
-		return a->file ? strcmp(a->file, b->file) : 0;
-	}
+	return result = a->line - b->line;
 }
 
 void init_configuration(splay_tree_t **config_tree) {
@@ -66,18 +60,8 @@ config_t *new_config(void) {
 }
 
 void free_config(config_t *cfg) {
-	if(cfg->variable) {
-		free(cfg->variable);
-	}
-
-	if(cfg->value) {
-		free(cfg->value);
-	}
-
-	if(cfg->file) {
-		free(cfg->file);
-	}
-
+	free(cfg->variable);
+	free(cfg->value);
 	free(cfg);
 }
 
@@ -89,7 +73,6 @@ config_t *lookup_config(splay_tree_t *config_tree, char *variable) {
 	config_t cfg, *found;
 
 	cfg.variable = variable;
-	cfg.file = NULL;
 	cfg.line = 0;
 
 	found = splay_search_closest_greater(config_tree, &cfg);
@@ -137,8 +120,8 @@ bool get_config_bool(const config_t *cfg, bool *result) {
 		return true;
 	}
 
-	logger(NULL, MESHLINK_ERROR, "\"yes\" or \"no\" expected for configuration variable %s in %s line %d",
-	       cfg->variable, cfg->file, cfg->line);
+	logger(NULL, MESHLINK_ERROR, "\"yes\" or \"no\" expected for configuration variable %s in line %d",
+	       cfg->variable, cfg->line);
 
 	return false;
 }
@@ -152,8 +135,8 @@ bool get_config_int(const config_t *cfg, int *result) {
 		return true;
 	}
 
-	logger(NULL, MESHLINK_ERROR, "Integer expected for configuration variable %s in %s line %d",
-	       cfg->variable, cfg->file, cfg->line);
+	logger(NULL, MESHLINK_ERROR, "Integer expected for configuration variable %s in line %d",
+	       cfg->variable, cfg->line);
 
 	return false;
 }
@@ -213,8 +196,8 @@ bool get_config_address(const config_t *cfg, struct addrinfo **result) {
 		return true;
 	}
 
-	logger(NULL, MESHLINK_ERROR, "Hostname or IP address expected for configuration variable %s in %s line %d",
-	       cfg->variable, cfg->file, cfg->line);
+	logger(NULL, MESHLINK_ERROR, "Hostname or IP address expected for configuration variable %s in line %d",
+	       cfg->variable, cfg->line);
 
 	return false;
 }
@@ -285,7 +268,6 @@ config_t *parse_config_line(char *line, const char *fname, int lineno) {
 	cfg = new_config();
 	cfg->variable = xstrdup(variable);
 	cfg->value = xstrdup(value);
-	cfg->file = xstrdup(fname);
 	cfg->line = lineno;
 
 	return cfg;
diff --git a/src/conf.h b/src/conf.h
index fd48ea64..fb29f02c 100644
--- a/src/conf.h
+++ b/src/conf.h
@@ -27,7 +27,6 @@
 typedef struct config_t {
 	char *variable;
 	char *value;
-	char *file;
 	int line;
 } config_t;
 
@@ -45,10 +44,6 @@ extern bool get_config_string(const config_t *, char **);
 extern bool set_config_string(config_t *, const char *);
 extern bool get_config_address(const config_t *, struct addrinfo **);
 
-extern config_t *parse_config_line(char *, const char *, int);
-extern bool read_config_file(struct splay_tree_t *, const char *);
-extern bool write_config_file(const struct splay_tree_t *, const char *);
-
 extern bool read_server_config(struct meshlink_handle *mesh);
 extern bool read_host_config(struct meshlink_handle *mesh, struct splay_tree_t *, const char *);
 extern bool write_host_config(struct meshlink_handle *mesh, const struct splay_tree_t *, const char *);
diff --git a/src/meshlink.c b/src/meshlink.c
index a26c4181..6df7c419 100644
--- a/src/meshlink.c
+++ b/src/meshlink.c
@@ -869,6 +869,8 @@ static const char *errstr[] = {
 	[MESHLINK_ESTORAGE] = "Storage error",
 	[MESHLINK_ENETWORK] = "Network error",
 	[MESHLINK_EPEER] = "Error communicating with peer",
+	[MESHLINK_ENOTSUP] = "Operation not supported",
+	[MESHLINK_EBUSY] = "MeshLink instance already in use",
 };
 
 const char *meshlink_strerror(meshlink_errno_t err) {
@@ -1116,6 +1118,32 @@ meshlink_handle_t *meshlink_open(const char *confbase, const char *name, const c
 		}
 	}
 
+	// Open the configuration file and lock it
+
+	mesh->conffile = fopen(filename, "r");
+
+	if(!mesh->conffile) {
+		logger(NULL, MESHLINK_ERROR, "Cannot not open %s: %s\n", filename, strerror(errno));
+		meshlink_close(mesh);
+		meshlink_errno = MESHLINK_ESTORAGE;
+		return NULL;
+	}
+
+#ifdef FD_CLOEXEC
+	fcntl(fileno(mesh->conffile), F_SETFD, FD_CLOEXEC);
+#endif
+
+#ifdef HAVE_MINGW
+	// TODO: use _locking()?
+#else
+	if(flock(fileno(mesh->conffile), LOCK_EX | LOCK_NB) != 0) {
+		logger(NULL, MESHLINK_ERROR, "Cannot lock %s: %s\n", filename, strerror(errno));
+		meshlink_close(mesh);
+		meshlink_errno = MESHLINK_EBUSY;
+		return NULL;
+	}
+#endif
+
 	// Read the configuration
 
 	init_configuration(&mesh->config);
@@ -1325,6 +1353,10 @@ void meshlink_close(meshlink_handle_t *mesh) {
 	free(mesh->confbase);
 	pthread_mutex_destroy(&(mesh->mesh_mutex));
 
+	if(mesh->conffile) {
+		fclose(mesh->conffile);
+        }
+
 	memset(mesh, 0, sizeof(*mesh));
 
 	free(mesh);
diff --git a/src/meshlink.h b/src/meshlink.h
index 15fb6e69..2f2e7f84 100644
--- a/src/meshlink.h
+++ b/src/meshlink.h
@@ -53,17 +53,18 @@ typedef struct meshlink_channel meshlink_channel_t;
 
 /// Code of most recent error encountered.
 typedef enum {
-	MESHLINK_OK,     ///< Everything is fine
-	MESHLINK_EINVAL, ///< Invalid parameter(s) to function call
-	MESHLINK_ENOMEM, ///< Out of memory
-	MESHLINK_ENOENT, ///< Node is not known
-	MESHLINK_EEXIST, ///< Node already exists
+	MESHLINK_OK,        ///< Everything is fine
+	MESHLINK_EINVAL,    ///< Invalid parameter(s) to function call
+	MESHLINK_ENOMEM,    ///< Out of memory
+	MESHLINK_ENOENT,    ///< Node is not known
+	MESHLINK_EEXIST,    ///< Node already exists
 	MESHLINK_EINTERNAL, ///< MeshLink internal error
-	MESHLINK_ERESOLV, ///< MeshLink could not resolve a hostname
-	MESHLINK_ESTORAGE, ///< MeshLink coud not load or write data from/to disk
-	MESHLINK_ENETWORK, ///< MeshLink encountered a network error
-	MESHLINK_EPEER, ///< A peer caused an error
-	MESHLINK_ENOTSUP, ///< The operation is not supported in the current configuration of MeshLink
+	MESHLINK_ERESOLV,   ///< MeshLink could not resolve a hostname
+	MESHLINK_ESTORAGE,  ///< MeshLink coud not load or write data from/to disk
+	MESHLINK_ENETWORK,  ///< MeshLink encountered a network error
+	MESHLINK_EPEER,     ///< A peer caused an error
+	MESHLINK_ENOTSUP,   ///< The operation is not supported in the current configuration of MeshLink
+	MESHLINK_EBUSY,     ///< The MeshLink instance is already in use by another process
 } meshlink_errno_t;
 
 /// Device class
diff --git a/src/meshlink_internal.h b/src/meshlink_internal.h
index 545bd526..92774c49 100644
--- a/src/meshlink_internal.h
+++ b/src/meshlink_internal.h
@@ -66,6 +66,7 @@ struct meshlink_handle {
 	dev_class_t devclass;
 
 	char *confbase;
+	FILE *conffile;
 
 	meshlink_receive_cb_t receive_cb;
 	meshlink_node_status_cb_t node_status_cb;
diff --git a/src/net_socket.c b/src/net_socket.c
index 1e981af6..ea5fdaa0 100644
--- a/src/net_socket.c
+++ b/src/net_socket.c
@@ -782,8 +782,8 @@ void try_outgoing_connections(meshlink_handle_t *mesh) {
 
 		if(!check_id(name)) {
 			logger(mesh, MESHLINK_ERROR,
-			       "Invalid name for outgoing connection in %s line %d",
-			       cfg->file, cfg->line);
+			       "Invalid name for outgoing connection in line %d",
+			       cfg->line);
 			free(name);
 			continue;
 		}