confile: add lxc.console.buffer.logfile

doc/lxc.container.conf.sgml.in

@@ -709,6 +709,26 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 
         <varlistentry>
           <term>
+            <option>lxc.console.buffer.logfile</option>
+          </term>
+          <listitem>
+            <para>
+            Setting this option instructs liblxc to write the in-memory
+            ringbuffer to disk. For performance reasons liblxc will only write
+            the in-memory ringbuffer to disk when requested. Note that the this
+            option is only used by liblxc when
+            <option>lxc.console.buffer.size</option> is set.
+
+            By default liblxc will dump the contents of the in-memory ringbuffer
+            to disk when the container terminates. This allows users to diagnose
+            boot failures when the container crashed before an API request to
+            retrieve the in-memory ringbuffer could be sent or handled.
+            </para>
+          </listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term>
             <option>lxc.console.logfile</option>
           </term>
           <listitem>

src/lxc/commands.c

@@ -1051,7 +1051,7 @@ static int lxc_cmd_console_log_callback(int fd, struct lxc_cmd_req *req,
 
 	if (log->write_logfile && rsp.datalen > 0) {
 		rsp.ret = -ENOENT;
-		if (!console->log_path)
+		if (!console->buffer_log_file)
 			goto out;
 
 		rsp.ret = lxc_console_write_ringbuffer(console);

src/lxc/conf.c

@@ -2430,9 +2430,11 @@ struct lxc_conf *lxc_conf_init(void)
 	new->loglevel = LXC_LOG_LEVEL_NOTSET;
 	new->personality = -1;
 	new->autodev = 1;
+	new->console.buffer_log_file = NULL;
+	new->console.buffer_log_file_fd = -1;
+	new->console.buffer_size = 0;
 	new->console.log_path = NULL;
 	new->console.log_fd = -1;
-	new->console.buffer_size = 0;
 	new->console.path = NULL;
 	new->console.peer = -1;
 	new->console.peerpty.busy = -1;
@@ -3461,6 +3463,7 @@ void lxc_conf_free(struct lxc_conf *conf)
 		return;
 	if (current_config == conf)
 		current_config = NULL;
+	free(conf->console.buffer_log_file);
 	free(conf->console.log_path);
 	free(conf->console.path);
 	if (conf->console.buffer_size > 0 && conf->console.ringbuf.addr)

src/lxc/conf.h

@@ -153,7 +153,17 @@ struct lxc_console {
 	char name[MAXPATHLEN];
 	struct termios *tios;
 	struct lxc_tty_state *tty_state;
+
+	/* size of the ringbuffer */
 	uint64_t buffer_size;
+
+	/* path to the log file for the ringbuffer */
+	char *buffer_log_file;
+
+	/* fd to the log file for the ringbuffer */
+	int buffer_log_file_fd;
+
+	/* the in-memory ringbuffer */
 	struct lxc_ringbuf ringbuf;
 };
 

src/lxc/confile.c

@@ -83,6 +83,7 @@ lxc_config_define(cap_keep);
 lxc_config_define(cgroup_controller);
 lxc_config_define(cgroup_dir);
 lxc_config_define(console_logfile);
+lxc_config_define(console_buffer_logfile);
 lxc_config_define(console_buffer_size);
 lxc_config_define(console_path);
 lxc_config_define(environment);
@@ -149,12 +150,13 @@ static struct lxc_config_t config[] = {
 	{ "lxc.cap.keep",                  false,                  set_config_cap_keep,                    get_config_cap_keep,                    clr_config_cap_keep,                  },
 	{ "lxc.cgroup.dir",                false,                  set_config_cgroup_dir,                  get_config_cgroup_dir,                  clr_config_cgroup_dir,                },
 	{ "lxc.cgroup",                    false,                  set_config_cgroup_controller,           get_config_cgroup_controller,           clr_config_cgroup_controller,         },
+	{ "lxc.console.buffer.logfile",    false,                  set_config_console_buffer_logfile,      get_config_console_buffer_logfile,      clr_config_console_buffer_logfile,    },
 	{ "lxc.console.buffer.size",       false,                  set_config_console_buffer_size,         get_config_console_buffer_size,         clr_config_console_buffer_size,       },
 	{ "lxc.console.logfile",           false,                  set_config_console_logfile,             get_config_console_logfile,             clr_config_console_logfile,           },
 	{ "lxc.console.path",              false,                  set_config_console_path,                get_config_console_path,                clr_config_console_path,              },
 	{ "lxc.environment",               false,                  set_config_environment,                 get_config_environment,                 clr_config_environment,               },
 	{ "lxc.ephemeral",                 false,                  set_config_ephemeral,                   get_config_ephemeral,                   clr_config_ephemeral,                 },
-	{ "lxc.execute.cmd",               false,                  set_config_execute_cmd,                 get_config_execute_cmd,                 clr_config_execute_cmd,                  },
+	{ "lxc.execute.cmd",               false,                  set_config_execute_cmd,                 get_config_execute_cmd,                 clr_config_execute_cmd,               },
 	{ "lxc.group",                     false,                  set_config_group,                       get_config_group,                       clr_config_group,                     },
 	{ "lxc.hook.autodev",              false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
 	{ "lxc.hook.clone",                false,                  set_config_hooks,                       get_config_hooks,                       clr_config_hooks,                     },
@@ -1841,6 +1843,13 @@ static int set_config_console_buffer_size(const char *key, const char *value,
 	return 0;
 }
 
+static int set_config_console_buffer_logfile(const char *key, const char *value,
+					     struct lxc_conf *lxc_conf,
+					     void *data)
+{
+	return set_config_path_item(&lxc_conf->console.buffer_log_file, value);
+}
+
 int append_unexp_config_line(const char *line, struct lxc_conf *conf)
 {
 	size_t len = conf->unexpanded_len, linelen = strlen(line);
@@ -3098,6 +3107,13 @@ static int get_config_console_buffer_size(const char *key, char *retv,
 	return lxc_get_conf_uint64(c, retv, inlen, c->autodev);
 }
 
+static int get_config_console_buffer_logfile(const char *key, char *retv,
+					     int inlen, struct lxc_conf *c,
+					     void *data)
+{
+	return lxc_get_conf_str(retv, inlen, c->console.buffer_log_file);
+}
+
 static int get_config_seccomp_profile(const char *key, char *retv, int inlen,
 				      struct lxc_conf *c, void *data)
 {
@@ -3509,6 +3525,15 @@ static inline int clr_config_console_buffer_size(const char *key,
 	return 0;
 }
 
+static inline int clr_config_console_buffer_logfile(const char *key,
+						    struct lxc_conf *c,
+						    void *data)
+{
+	free(c->console.buffer_log_file);
+	c->console.buffer_log_file = NULL;
+	return 0;
+}
+
 static inline int clr_config_seccomp_profile(const char *key,
 					     struct lxc_conf *c, void *data)
 {

src/lxc/console.c

@@ -558,19 +558,19 @@ int lxc_console_write_ringbuffer(struct lxc_console *console)
 	uint64_t used;
 	struct lxc_ringbuf *buf = &console->ringbuf;
 
-	if (!console->log_path)
+	if (!console->buffer_log_file)
 		return 0;
 
 	used = lxc_ringbuf_used(buf);
 	if (used == 0)
 		return 0;
 
-	fd = lxc_unpriv(open(console->log_path, O_CLOEXEC | O_RDWR | O_CREAT | O_TRUNC, 0600));
+	fd = lxc_unpriv(open(console->buffer_log_file, O_CLOEXEC | O_RDWR | O_CREAT | O_TRUNC, 0600));
 	if (fd < 0) {
-		SYSERROR("Failed to open console log file \"%s\"", console->log_path);
+		SYSERROR("Failed to open console log file \"%s\"", console->buffer_log_file);
 		return -EIO;
 	}
-	DEBUG("Using \"%s\" as console log file", console->log_path);
+	DEBUG("Using \"%s\" as console log file", console->buffer_log_file);
 
 	r_addr = lxc_ringbuf_get_read_addr(buf);
 	ret = lxc_write_nointr(fd, r_addr, used);
@@ -698,7 +698,7 @@ int lxc_console_create(struct lxc_conf *conf)
 		goto err;
 	}
 
-	if (console->log_path && console->buffer_size <= 0) {
+	if (console->log_path) {
 		console->log_fd = lxc_unpriv(open(console->log_path, O_CLOEXEC | O_RDWR | O_CREAT | O_APPEND, 0600));
 		if (console->log_fd < 0) {
 			SYSERROR("Failed to open console log file \"%s\"", console->log_path);