Write config files atomically.

diff --git a/src/conf.c b/src/conf.c
index e0d3595041c2807d7393e912ff935b8584f0751c..bafa87d49c5bd5a563e9d82d5969ca4a51f7ec72 100644 (file)
--- a/src/conf.c
+++ b/src/conf.c
@@ -616,23 +616,36 @@ bool config_write(meshlink_handle_t *mesh, const char *conf_subdir, const char *
        }
 
        char path[PATH_MAX];
+       char tmp_path[PATH_MAX + 4];
        make_host_path(mesh, conf_subdir, name, path, sizeof(path));
+       snprintf(tmp_path, sizeof(tmp_path), "%s.tmp", path);
 
-       FILE *f = fopen(path, "w");
+       FILE *f = fopen(tmp_path, "w");
 
        if(!f) {
-               logger(mesh, MESHLINK_ERROR, "Failed to open `%s': %s", path, strerror(errno));
+               logger(mesh, MESHLINK_ERROR, "Failed to open `%s': %s", tmp_path, strerror(errno));
                return false;
        }
 
        if(!config_write_file(mesh, f, config, key)) {
-               logger(mesh, MESHLINK_ERROR, "Failed to write `%s': %s", path, strerror(errno));
+               logger(mesh, MESHLINK_ERROR, "Failed to write `%s': %s", tmp_path, strerror(errno));
+               fclose(f);
+               return false;
+       }
+
+       if(fsync(fileno(f))) {
+               logger(mesh, MESHLINK_ERROR, "Failed to sync `%s': %s", tmp_path, strerror(errno));
                fclose(f);
                return false;
        }
 
        if(fclose(f)) {
-               logger(mesh, MESHLINK_ERROR, "Failed to close `%s': %s", path, strerror(errno));
+               logger(mesh, MESHLINK_ERROR, "Failed to close `%s': %s", tmp_path, strerror(errno));
+               return false;
+       }
+
+       if(rename(tmp_path, path)) {
+               logger(mesh, MESHLINK_ERROR, "Failed to rename `%s' to `%s': %s", tmp_path, path, strerror(errno));
                return false;
        }
 
@@ -673,23 +686,36 @@ bool main_config_write(meshlink_handle_t *mesh, const char *conf_subdir, const c
        }
 
        char path[PATH_MAX];
+       char tmp_path[PATH_MAX + 4];
        make_main_path(mesh, conf_subdir, path, sizeof(path));
+       snprintf(tmp_path, sizeof(tmp_path), "%s.tmp", path);
 
-       FILE *f = fopen(path, "w");
+       FILE *f = fopen(tmp_path, "w");
 
        if(!f) {
-               logger(mesh, MESHLINK_ERROR, "Failed to open `%s': %s", path, strerror(errno));
+               logger(mesh, MESHLINK_ERROR, "Failed to open `%s': %s", tmp_path, strerror(errno));
                return false;
        }
 
        if(!config_write_file(mesh, f, config, key)) {
-               logger(mesh, MESHLINK_ERROR, "Failed to write `%s': %s", path, strerror(errno));
+               logger(mesh, MESHLINK_ERROR, "Failed to write `%s': %s", tmp_path, strerror(errno));
                fclose(f);
                return false;
        }
 
+       if(fsync(fileno(f))) {
+               logger(mesh, MESHLINK_ERROR, "Failed to sync `%s': %s", tmp_path, strerror(errno));
+               fclose(f);
+               return false;
+       }
+
+       if(rename(tmp_path, path)) {
+               logger(mesh, MESHLINK_ERROR, "Failed to rename `%s' to `%s': %s", tmp_path, path, strerror(errno));
+               return false;
+       }
+
        if(fclose(f)) {
-               logger(mesh, MESHLINK_ERROR, "Failed to close `%s': %s", path, strerror(errno));
+               logger(mesh, MESHLINK_ERROR, "Failed to close `%s': %s", tmp_path, strerror(errno));
                return false;
        }
 
@@ -777,6 +803,11 @@ bool invitation_write(meshlink_handle_t *mesh, const char *conf_subdir, const ch
                return false;
        }
 
+       if(fsync(fileno(f))) {
+               logger(mesh, MESHLINK_ERROR, "Failed to sync `%s': %s", path, strerror(errno));
+               return false;
+       }
+
        if(fclose(f)) {
                logger(mesh, MESHLINK_ERROR, "Failed to close `%s': %s", path, strerror(errno));
                return false;