conf, confile: add parsing of a shmounts config parameter

src/lxc/conf.c

@@ -23,6 +23,7 @@
 
 #define _GNU_SOURCE
 #include "config.h"
+#include "confile.h"
 
 #include <arpa/inet.h>
 #include <dirent.h>
@@ -647,6 +648,30 @@ unsigned long add_required_remount_flags(const char *s, const char *d,
 #endif
 }
 
+static int add_shmount_to_list(struct lxc_conf *conf) {
+	char new_mount[MAXPATHLEN];
+	size_t len_mount;
+	/* Offset for the leading '/' since the path_cont
+	 * is absolute inside the container */
+	int ret = -1, offset = 1;
+
+	/* +1 for the separating whitespace */
+	len_mount = strlen(conf->lxc_shmount.path_host) + 1
+			+ strlen(conf->lxc_shmount.path_cont) - offset
+			+ sizeof(" none bind,create=dir 0 0") - 1;
+
+	ret = snprintf(new_mount, len_mount + 1, "%s %s none bind,create=dir 0 0",
+				   conf->lxc_shmount.path_host, conf->lxc_shmount.path_cont + offset);
+	if (ret < 0 || (size_t)ret >= len_mount + 1)
+		return -1;
+
+	ret = add_elem_to_mount_list(new_mount, conf);
+	if (ret < 0)
+		ERROR("Failed to add new mount \"%s\" to the config", new_mount);
+
+	return ret;
+}
+
 static int lxc_mount_auto_mounts(struct lxc_conf *conf, int flags, struct lxc_handler *handler)
 {
 	int i, r;
@@ -783,6 +808,14 @@ static int lxc_mount_auto_mounts(struct lxc_conf *conf, int flags, struct lxc_ha
 		}
 	}
 
+	if (flags & LXC_AUTO_SHMOUNTS_MASK) {
+		int ret = add_shmount_to_list(conf);
+		if (ret < 0) {
+			ERROR("Failed to add shmount entry to container config");
+			return ret;
+		}
+	}
+
 	return 0;
 }
 

src/lxc/confile.c

@@ -1677,6 +1677,8 @@ static int set_config_mount_auto(const char *key, const char *value,
 		return -1;
 
 	for (autoptr = autos;; autoptr = NULL) {
+		bool is_shmounts = false;
+
 		token = strtok_r(autoptr, " \t", &sptr);
 		if (!token) {
 			ret = 0;
@@ -1686,6 +1688,12 @@ static int set_config_mount_auto(const char *key, const char *value,
 		for (i = 0; allowed_auto_mounts[i].token; i++) {
 			if (!strcmp(allowed_auto_mounts[i].token, token))
 				break;
+
+			if (strcmp("shmounts:", allowed_auto_mounts[i].token) == 0
+					&& strncmp("shmounts:", token, sizeof("shmounts:") - 1) == 0) {
+				is_shmounts = true;
+				break;
+			}
 		}
 
 		if (!allowed_auto_mounts[i].token) {
@@ -1695,6 +1703,14 @@ static int set_config_mount_auto(const char *key, const char *value,
 
 		lxc_conf->auto_mounts &= ~allowed_auto_mounts[i].mask;
 		lxc_conf->auto_mounts |= allowed_auto_mounts[i].flag;
+		if (is_shmounts) {
+			lxc_conf->lxc_shmount.path_host = strdup(token + (sizeof("shmounts:") - 1));
+			if (strcmp(lxc_conf->lxc_shmount.path_host, "") == 0) {
+				ERROR("Invalid shmounts path: empty");
+				break;
+			}
+			lxc_conf->lxc_shmount.path_cont = strdup("/dev/.lxc-mounts");
+		}
 	}
 
 	free(autos);
@@ -1726,6 +1742,10 @@ static int set_config_mount(const char *key, const char *value,
 	return 0;
 }
 
+int add_elem_to_mount_list(const char *value, struct lxc_conf *lxc_conf) {
+	return set_config_mount(NULL, value, lxc_conf, NULL);
+}
+
 static int set_config_cap_keep(const char *key, const char *value,
 			       struct lxc_conf *lxc_conf, void *data)
 {

src/lxc/confile.h

@@ -121,4 +121,6 @@ bool clone_update_unexp_ovl_paths(struct lxc_conf *conf, const char *oldpath,
 
 extern bool network_new_hwaddrs(struct lxc_conf *conf);
 
+extern int add_elem_to_mount_list(const char *value, struct lxc_conf *lxc_conf);
+
 #endif /* __LXC_CONFILE_H */