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

[meshlink] / src / meshlink.c

diff --git a/src/meshlink.c b/src/meshlink.c
index a26c4181af4325193d2d59ba0268c52335f29c64..6df7c419261fc30f175ef016d00538c295d77f29 100644 (file)
--- 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);