diff options
| -rw-r--r-- | lib/command.c | 4 | ||||
| -rw-r--r-- | lib/libfrr.c | 155 | ||||
| -rw-r--r-- | lib/libfrr.h | 5 |
3 files changed, 164 insertions, 0 deletions
diff --git a/lib/command.c b/lib/command.c index becba8452b..244bf86e8e 100644 --- a/lib/command.c +++ b/lib/command.c @@ -1633,6 +1633,10 @@ static int vty_write_config(struct vty *vty) return CMD_SUCCESS; } +/* cross-reference frr_daemon_state_save in libfrr.c + * the code there is similar but not identical (state files always use the same + * name for the new write, and don't keep a backup of previous state.) + */ static int file_write_config(struct vty *vty) { int fd, dirfd; diff --git a/lib/libfrr.c b/lib/libfrr.c index 85a906a7bc..131453c4de 100644 --- a/lib/libfrr.c +++ b/lib/libfrr.c @@ -1272,6 +1272,161 @@ void frr_fini(void) } } +struct json_object *frr_daemon_state_load(void) +{ + struct json_object *state; + char **state_path; + + assertf(di->state_paths, + "CODE BUG: daemon trying to load state, but no state path in frr_daemon_info"); + + for (state_path = di->state_paths; *state_path; state_path++) { + state = json_object_from_file(*state_path); + if (state) + return state; + } + + return json_object_new_object(); +} + +/* cross-reference file_write_config() in command.c + * the code there is similar but not identical (configs use a unique temporary + * name for writing and keep a backup of the previous config.) + */ +void frr_daemon_state_save(struct json_object **statep) +{ + struct json_object *state = *statep; + char *state_path, *slash, *temp_name, **other; + size_t name_len, json_len; + const char *json_str; + int dirfd, fd; + + assertf(di->state_paths, + "CODE BUG: daemon trying to save state, but no state path in frr_daemon_info"); + + state_path = di->state_paths[0]; + json_str = json_object_to_json_string_ext(state, + JSON_C_TO_STRING_PRETTY); + json_len = strlen(json_str); + + /* To correctly fsync() and ensure we have either consistent old state + * or consistent new state but no fs-damage garbage inbetween, we need + * to work with a directory fd. If we need that anyway we might as + * well use the dirfd with openat() & co in fd-relative operations. + */ + + slash = strrchr(state_path, '/'); + if (slash) { + char *state_dir; + + state_dir = XSTRDUP(MTYPE_TMP, state_path); + state_dir[slash - state_path] = '\0'; + dirfd = open(state_dir, O_DIRECTORY | O_RDONLY); + XFREE(MTYPE_TMP, state_dir); + + if (dirfd < 0) { + zlog_err("failed to open directory %pSQq for saving daemon state: %m", + state_dir); + return; + } + + /* skip to file name */ + slash++; + } else { + dirfd = open(".", O_DIRECTORY | O_RDONLY); + if (dirfd < 0) { + zlog_err( + "failed to open current directory for saving daemon state: %m"); + return; + } + + /* file name = path */ + slash = state_path; + } + + /* unlike saving configs, a temporary unique filename is unhelpful + * here as it might litter files on limited write-heavy storage + * (think switch with small NOR flash for frequently written data.) + * + * => always use filename with .sav suffix, worst case it litters one + * file. + */ + name_len = strlen(slash); + temp_name = XMALLOC(MTYPE_TMP, name_len + 5); + memcpy(temp_name, slash, name_len); + memcpy(temp_name + name_len, ".sav", 5); + + /* state file is always 0600, it's by and for FRR itself only */ + fd = openat(dirfd, temp_name, O_WRONLY | O_CREAT | O_TRUNC, 0600); + if (fd < 0) { + zlog_err("failed to open temporary daemon state save file for %pSQq: %m", + state_path); + goto out_closedir_free; + } + + while (json_len) { + ssize_t nwr = write(fd, json_str, json_len); + + if (nwr <= 0) { + zlog_err("failed to write temporary daemon state to %pSQq: %m", + state_path); + + close(fd); + unlinkat(dirfd, temp_name, 0); + goto out_closedir_free; + } + + json_str += nwr; + json_len -= nwr; + } + + /* fsync is theoretically implicit in close(), but... */ + if (fsync(fd) < 0) + zlog_warn("fsync for daemon state %pSQq failed: %m", state_path); + close(fd); + + /* this is the *actual* fsync that ensures we're consistent. The + * file fsync only syncs the inode, but not the directory entry + * referring to it. + */ + if (fsync(dirfd) < 0) + zlog_warn("directory fsync for daemon state %pSQq failed: %m", + state_path); + + /* atomic, hopefully. */ + if (renameat(dirfd, temp_name, dirfd, slash) < 0) { + zlog_err("renaming daemon state %pSQq to %pSQq failed: %m", + temp_name, state_path); + /* no unlink here, give the user a chance to investigate */ + goto out_closedir_free; + } + + /* and the rename needs to be synced too */ + if (fsync(dirfd) < 0) + zlog_warn("directory fsync for daemon state %pSQq failed after rename: %m", + state_path); + + /* daemon may specify other deprecated paths to load from; since we + * just saved successfully we should delete those. + */ + for (other = di->state_paths + 1; *other; other++) { + if (unlink(*other) == 0) + continue; + if (errno == ENOENT || errno == ENOTDIR) + continue; + + zlog_warn("failed to remove deprecated daemon state file %pSQq: %m", + *other); + } + +out_closedir_free: + XFREE(MTYPE_TMP, temp_name); + close(dirfd); + + json_object_free(state); + *statep = NULL; +} + #ifdef INTERP static const char interp[] __attribute__((section(".interp"), used)) = INTERP; diff --git a/lib/libfrr.h b/lib/libfrr.h index 189abf0aec..27b877da18 100644 --- a/lib/libfrr.h +++ b/lib/libfrr.h @@ -87,6 +87,7 @@ struct frr_daemon_info { const char *vty_path; const char *module_path; const char *script_path; + char **state_paths; const char *pathspace; bool zpathspace; @@ -162,6 +163,10 @@ extern void frr_vty_serv_stop(void); extern bool frr_zclient_addr(struct sockaddr_storage *sa, socklen_t *sa_len, const char *path); +struct json_object; +extern struct json_object *frr_daemon_state_load(void); +extern void frr_daemon_state_save(struct json_object **statep); + /* these two are before the protocol daemon does its own shutdown * it's named this way being the counterpart to frr_late_init */ DECLARE_KOOH(frr_early_fini, (), ()); |