tools: move lxc-monitor to API symbols only

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

src/lxc/tools/lxc_monitor.c

@@ -20,22 +20,31 @@
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
+
+#define _GNU_SOURCE
+#define __STDC_FORMAT_MACROS
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <libgen.h>
+#include <poll.h>
+#include <regex.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <libgen.h>
 #include <unistd.h>
-#include <regex.h>
+#include <sys/param.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
 #include <sys/types.h>
+#include <sys/un.h>
 #include <sys/wait.h>
-#include <errno.h>
-#include <poll.h>
 
-#include "lxc.h"
-#include "log.h"
-#include "monitor.h"
+#include <lxc/lxccontainer.h>
+
 #include "arguments.h"
-#include "lxccontainer.h"
+#include "tool_utils.h"
 
 static bool quit_monitord;
 
@@ -82,6 +91,408 @@ static void close_fds(struct pollfd *fds, nfds_t nfds)
 	}
 }
 
+typedef enum {
+	lxc_msg_state,
+	lxc_msg_priority,
+	lxc_msg_exit_code,
+} lxc_msg_type_t;
+
+struct lxc_msg {
+	lxc_msg_type_t type;
+	char name[NAME_MAX+1];
+	int value;
+};
+
+typedef enum {
+	STOPPED,
+	STARTING,
+	RUNNING,
+	STOPPING,
+	ABORTING,
+	FREEZING,
+	FROZEN,
+	THAWED,
+	MAX_STATE,
+} lxc_state_t;
+
+static const char *const strstate[] = {
+    "STOPPED",  "STARTING", "RUNNING", "STOPPING",
+    "ABORTING", "FREEZING", "FROZEN",  "THAWED",
+};
+
+const char *lxc_state2str(lxc_state_t state)
+{
+	if (state < STOPPED || state > MAX_STATE - 1)
+		return NULL;
+	return strstate[state];
+}
+
+/* Note we don't use SHA-1 here as we don't want to depend on HAVE_GNUTLS.
+ * FNV has good anti collision properties and we're not worried
+ * about pre-image resistance or one-way-ness, we're just trying to make
+ * the name unique in the 108 bytes of space we have.
+ */
+#define FNV1A_64_INIT ((uint64_t)0xcbf29ce484222325ULL)
+static uint64_t fnv_64a_buf(void *buf, size_t len, uint64_t hval)
+{
+	unsigned char *bp;
+
+	for(bp = buf; bp < (unsigned char *)buf + len; bp++)
+	{
+		/* xor the bottom with the current octet */
+		hval ^= (uint64_t)*bp;
+
+		/* gcc optimised:
+		 * multiply by the 64 bit FNV magic prime mod 2^64
+		 */
+		hval += (hval << 1) + (hval << 4) + (hval << 5) +
+			(hval << 7) + (hval << 8) + (hval << 40);
+	}
+
+	return hval;
+}
+
+static int open_devnull(void)
+{
+	int fd = open("/dev/null", O_RDWR);
+
+	if (fd < 0)
+		fprintf(stderr, "%s - Failed to open \"/dev/null\"\n",
+			strerror(errno));
+
+	return fd;
+}
+
+static int set_stdfds(int fd)
+{
+	int ret;
+
+	if (fd < 0)
+		return -1;
+
+	ret = dup2(fd, STDIN_FILENO);
+	if (ret < 0)
+		return -1;
+
+	ret = dup2(fd, STDOUT_FILENO);
+	if (ret < 0)
+		return -1;
+
+	ret = dup2(fd, STDERR_FILENO);
+	if (ret < 0)
+		return -1;
+
+	return 0;
+}
+
+static int null_stdfds(void)
+{
+	int ret = -1;
+	int fd = open_devnull();
+
+	if (fd >= 0) {
+		ret = set_stdfds(fd);
+		close(fd);
+	}
+
+	return ret;
+}
+
+static int lxc_check_inherited(bool closeall, int *fds_to_ignore, size_t len_fds)
+{
+	struct dirent *direntp;
+	int fd, fddir;
+	size_t i;
+	DIR *dir;
+
+restart:
+	dir = opendir("/proc/self/fd");
+	if (!dir) {
+		fprintf(stderr, "%s - Failed to open directory\n",
+			strerror(errno));
+		return -1;
+	}
+
+	fddir = dirfd(dir);
+
+	while ((direntp = readdir(dir))) {
+		if (!strcmp(direntp->d_name, "."))
+			continue;
+
+		if (!strcmp(direntp->d_name, ".."))
+			continue;
+
+		if (lxc_safe_int(direntp->d_name, &fd) < 0)
+			continue;
+
+		for (i = 0; i < len_fds; i++)
+			if (fds_to_ignore[i] == fd)
+				break;
+
+		if (fd == fddir || (i < len_fds && fd == fds_to_ignore[i]))
+			continue;
+
+		if (fd == 0 || fd == 1 || fd == 2)
+			continue;
+
+		if (closeall) {
+			close(fd);
+			closedir(dir);
+			goto restart;
+		}
+	}
+
+	closedir(dir);
+	return 0;
+}
+
+/* Enforces \0-termination for the abstract unix socket. This is not required
+ * but allows us to print it out.
+ *
+ * Older version of liblxc only allowed for 105 bytes to be used for the
+ * abstract unix domain socket name because the code for our abstract unix
+ * socket handling performed invalid checks. Since we \0-terminate we could now
+ * have a maximum of 106 chars. But to not break backwards compatibility we keep
+ * the limit at 105.
+ */
+static int lxc_monitor_sock_name(const char *lxcpath, struct sockaddr_un *addr)
+{
+	size_t len;
+	int ret;
+	char *path;
+	uint64_t hash;
+
+	/* addr.sun_path is only 108 bytes, so we hash the full name and
+	 * then append as much of the name as we can fit.
+	 */
+	memset(addr, 0, sizeof(*addr));
+	addr->sun_family = AF_UNIX;
+
+	/* strlen("lxc/") + strlen("/monitor-sock") + 1 = 18 */
+	len = strlen(lxcpath) + 18;
+	path = alloca(len);
+	ret = snprintf(path, len, "lxc/%s/monitor-sock", lxcpath);
+	if (ret < 0 || (size_t)ret >= len) {
+		fprintf(stderr, "failed to create name for monitor socket\n");
+		return -1;
+	}
+
+	/* Note: snprintf() will \0-terminate addr->sun_path on the 106th byte
+	 * and so the abstract socket name has 105 "meaningful" characters. This
+	 * is absolutely intentional. For further info read the comment for this
+	 * function above!
+	 */
+	len = sizeof(addr->sun_path) - 1;
+	hash = fnv_64a_buf(path, ret, FNV1A_64_INIT);
+	ret = snprintf(addr->sun_path, len, "@lxc/%016" PRIx64 "/%s", hash, lxcpath);
+	if (ret < 0) {
+		fprintf(stderr, "failed to create hashed name for monitor socket\n");
+		return -1;
+	}
+
+	/* replace @ with \0 */
+	addr->sun_path[0] = '\0';
+
+	return 0;
+}
+
+static int lxc_abstract_unix_connect(const char *path)
+{
+	int fd, ret;
+	size_t len;
+	struct sockaddr_un addr;
+
+	fd = socket(PF_UNIX, SOCK_STREAM, 0);
+	if (fd < 0)
+		return -1;
+
+	memset(&addr, 0, sizeof(addr));
+
+	addr.sun_family = AF_UNIX;
+
+	len = strlen(&path[1]);
+	/* do not enforce \0-termination */
+	if (len >= sizeof(addr.sun_path)) {
+		close(fd);
+		errno = ENAMETOOLONG;
+		return -1;
+	}
+	/* addr.sun_path[0] has already been set to 0 by memset() */
+	strncpy(&addr.sun_path[1], &path[1], strlen(&path[1]));
+
+	ret = connect(fd, (struct sockaddr *)&addr,
+		      offsetof(struct sockaddr_un, sun_path) + len + 1);
+	if (ret < 0) {
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
+static int lxc_monitor_open(const char *lxcpath)
+{
+	struct sockaddr_un addr;
+	int fd;
+	size_t retry;
+	size_t len;
+	int ret = -1;
+	int backoff_ms[] = {10, 50, 100};
+
+	if (lxc_monitor_sock_name(lxcpath, &addr) < 0)
+		return -1;
+
+	fd = socket(PF_UNIX, SOCK_STREAM, 0);
+	if (fd < 0) {
+		fprintf(stderr, "Failed to create socket: %s\n", strerror(errno));
+		return -errno;
+	}
+
+	len = strlen(&addr.sun_path[1]);
+	if (len >= sizeof(addr.sun_path) - 1) {
+		errno = ENAMETOOLONG;
+		ret = -errno;
+		fprintf(stderr, "name of monitor socket too long (%zu bytes): %s\n", len, strerror(errno));
+		goto on_error;
+	}
+
+	for (retry = 0; retry < sizeof(backoff_ms) / sizeof(backoff_ms[0]); retry++) {
+		fd = lxc_abstract_unix_connect(addr.sun_path);
+		if (fd != -1 || errno != ECONNREFUSED)
+			break;
+		fprintf(stderr, "Failed to connect to monitor socket. Retrying in %d ms: %s\n", backoff_ms[retry], strerror(errno));
+		usleep(backoff_ms[retry] * 1000);
+	}
+
+	if (fd < 0) {
+		ret = -errno;
+		fprintf(stderr, "Failed to connect to monitor socket: %s\n", strerror(errno));
+		goto on_error;
+	}
+
+	return fd;
+
+on_error:
+	close(fd);
+	return ret;
+}
+
+static int lxc_monitor_read_fdset(struct pollfd *fds, nfds_t nfds,
+				  struct lxc_msg *msg, int timeout)
+{
+	nfds_t i;
+	int ret;
+
+	ret = poll(fds, nfds, timeout * 1000);
+	if (ret == -1)
+		return -1;
+	else if (ret == 0)
+		return -2;  /* timed out */
+
+	/* Only read from the first ready fd, the others will remain ready for
+	 * when this routine is called again.
+	 */
+	for (i = 0; i < nfds; i++) {
+		if (fds[i].revents != 0) {
+			fds[i].revents = 0;
+			ret = recv(fds[i].fd, msg, sizeof(*msg), 0);
+			if (ret <= 0) {
+				fprintf(stderr, "%s - Failed to receive message. Did monitord die?\n", strerror(errno));
+				return -1;
+			}
+			return ret;
+		}
+	}
+
+	return -1;
+}
+
+#define LXC_MONITORD_PATH LIBEXECDIR "/lxc/lxc-monitord"
+
+/* Used to spawn a monitord either on startup of a daemon container, or when
+ * lxc-monitor starts.
+ */
+static int lxc_monitord_spawn(const char *lxcpath)
+{
+	int ret;
+	int pipefd[2];
+	char pipefd_str[TOOL_NUMSTRLEN64];
+	pid_t pid1, pid2;
+
+	char *const args[] = {
+	    LXC_MONITORD_PATH,
+	    (char *)lxcpath,
+	    pipefd_str,
+	    NULL,
+	};
+
+	/* double fork to avoid zombies when monitord exits */
+	pid1 = fork();
+	if (pid1 < 0) {
+		fprintf(stderr, "Failed to fork()\n");
+		return -1;
+	}
+
+	if (pid1) {
+		if (waitpid(pid1, NULL, 0) != pid1)
+			return -1;
+		return 0;
+	}
+
+	if (pipe(pipefd) < 0) {
+		fprintf(stderr, "Failed to create pipe\n");
+		exit(EXIT_FAILURE);
+	}
+
+	pid2 = fork();
+	if (pid2 < 0) {
+		fprintf(stderr, "Failed to fork()\n");
+		exit(EXIT_FAILURE);
+	}
+
+	if (pid2) {
+		char c;
+		/* Wait for daemon to create socket. */
+		close(pipefd[1]);
+
+		/* Sync with child, we're ignoring the return from read
+		 * because regardless if it works or not, either way we've
+		 * synced with the child process. the if-empty-statement
+		 * construct is to quiet the warn-unused-result warning.
+		 */
+		if (read(pipefd[0], &c, 1))
+			;
+
+		close(pipefd[0]);
+
+		exit(EXIT_SUCCESS);
+	}
+
+	if (setsid() < 0) {
+		fprintf(stderr, "Failed to setsid()\n");
+		exit(EXIT_FAILURE);
+	}
+
+	lxc_check_inherited(true, &pipefd[1], 1);
+	if (null_stdfds() < 0) {
+		fprintf(stderr, "Failed to dup2() standard file descriptors to /dev/null\n");
+		exit(EXIT_FAILURE);
+	}
+
+	close(pipefd[0]);
+
+	ret = snprintf(pipefd_str, TOOL_NUMSTRLEN64, "%d", pipefd[1]);
+	if (ret < 0 || ret >= TOOL_NUMSTRLEN64) {
+		fprintf(stderr, "Failed to create pid argument to pass to monitord\n");
+		exit(EXIT_FAILURE);
+	}
+
+	execvp(args[0], args);
+	fprintf(stderr, "Failed to exec lxc-monitord\n");
+
+	exit(EXIT_FAILURE);
+}
+
 int main(int argc, char *argv[])
 {
 	char *regexp;
@@ -109,7 +520,6 @@ int main(int argc, char *argv[])
 
 	if (lxc_log_init(&log))
 		exit(rc_main);
-	lxc_log_options_no_override();
 
 	/* REMOVE IN LXC 3.0 */
 	setenv("LXC_UPDATE_CONFIG_FORMAT", "1", 0);
@@ -160,7 +570,7 @@ int main(int argc, char *argv[])
 	}
 
 	nfds = my_args.lxcpath_cnt;
-	for (i = 0; i < nfds; i++) {
+	for (i = 0; (unsigned long)i < nfds; i++) {
 		int fd;
 
 		lxc_monitord_spawn(my_args.lxcpath[i]);

src/lxc/tools/tool_utils.h

@@ -34,6 +34,7 @@
 #include "tool_list.h"
 
 #define TOOL_MAXPATHLEN 4096
+#define TOOL_NUMSTRLEN64 21
 
 #ifndef CLONE_PARENT_SETTID
 #define CLONE_PARENT_SETTID 0x00100000