cgmanager: implement attach

src/lxc/attach.c

@@ -698,32 +698,8 @@ int lxc_attach(const char* name, const char* lxcpath, lxc_attach_exec_t exec_fun
 
 		/* attach to cgroup, if requested */
 		if (options->attach_flags & LXC_ATTACH_MOVE_TO_CGROUP) {
-			struct cgroup_meta_data *meta_data;
-			struct cgroup_process_info *container_info;
-
-			meta_data = lxc_cgroup_load_meta();
-			if (!meta_data) {
-				ERROR("could not move attached process %ld to cgroup of container", (long)pid);
+			if (!lxc_cgroup_attach(name, lxcpath, pid))
 				goto cleanup_error;
-			}
-
-			container_info = lxc_cgroup_get_container_info(name, lxcpath, meta_data);
-			lxc_cgroup_put_meta(meta_data);
-			if (!container_info) {
-				ERROR("could not move attached process %ld to cgroup of container", (long)pid);
-				goto cleanup_error;
-			}
-
-			/*
-			 * TODO - switch over to using a cgroup_operation.  We can't use
-			 * cgroup_enter() as that takes a handler.
-			 */
-			ret = lxc_cgroupfs_enter(container_info, pid, false);
-			lxc_cgroup_process_info_free(container_info);
-			if (ret < 0) {
-				ERROR("could not move attached process %ld to cgroup of container", (long)pid);
-				goto cleanup_error;
-			}
 		}
 
 		/* Let the child process know to go ahead */

src/lxc/cgroup.c

@@ -2303,6 +2303,34 @@ bool cgroupfs_setup_limits(struct lxc_handler *h, bool with_devices)
 	return do_setup_cgroup_limits(h, &h->conf->cgroup, with_devices) == 0;
 }
 
+bool lxc_cgroupfs_attach(const char *name, const char *lxcpath, pid_t pid)
+{
+	struct cgroup_meta_data *meta_data;
+	struct cgroup_process_info *container_info;
+	int ret;
+
+	meta_data = lxc_cgroup_load_meta();
+	if (!meta_data) {
+		ERROR("could not move attached process %d to cgroup of container", pid);
+		return false;
+	}
+
+	container_info = lxc_cgroup_get_container_info(name, lxcpath, meta_data);
+	lxc_cgroup_put_meta(meta_data);
+	if (!container_info) {
+		ERROR("could not move attached process %d to cgroup of container", pid);
+		return false;
+	}
+
+	ret = lxc_cgroupfs_enter(container_info, pid, false);
+	lxc_cgroup_process_info_free(container_info);
+	if (ret < 0) {
+		ERROR("could not move attached process %d to cgroup of container", pid);
+		return false;
+	}
+	return true;
+}
+
 static struct cgroup_ops cgfs_ops = {
 	.destroy = cgfs_destroy,
 	.init = cgfs_init,
@@ -2315,6 +2343,7 @@ static struct cgroup_ops cgfs_ops = {
 	.unfreeze_fromhandler = cgfs_unfreeze_fromhandler,
 	.setup_limits = cgroupfs_setup_limits,
 	.name = "cgroupfs",
+	.attach = lxc_cgroupfs_attach,
 	.chown = NULL,
 };
 static void init_cg_ops(void)
@@ -2421,3 +2450,9 @@ bool cgroup_chown(struct lxc_handler *handler)
 		return active_cg_ops->chown(handler);
 	return true;
 }
+
+bool lxc_cgroup_attach(const char *name, const char *lxcpath, pid_t pid)
+{
+	init_cg_ops();
+	return active_cg_ops->attach(name, lxcpath, pid);
+}

src/lxc/cgroup.h

@@ -182,6 +182,7 @@ struct cgroup_ops {
 	int (*unfreeze_fromhandler)(struct lxc_handler *handler);
 	bool (*setup_limits)(struct lxc_handler *handler, bool with_devices);
 	bool (*chown)(struct lxc_handler *handler);
+	bool (*attach)(const char *name, const char *lxcpath, pid_t pid);
 	const char *name;
 };
 
@@ -216,6 +217,7 @@ extern bool cgroup_enter(struct lxc_handler *handler);
 extern void cgroup_cleanup(struct lxc_handler *handler);
 extern bool cgroup_create_legacy(struct lxc_handler *handler);
 extern char *cgroup_get_cgroup(struct lxc_handler *handler, const char *subsystem);
+extern bool lxc_cgroup_attach(const char *name, const char *lxcpath, pid_t pid);
 extern int lxc_cgroup_set(const char *filename, const char *value, const char *name, const char *lxcpath);
 extern int lxc_cgroup_get(const char *filename, char *value, size_t len, const char *name, const char *lxcpath);
 extern int lxc_unfreeze_fromhandler(struct lxc_handler *handler);

src/lxc/utils.c

@@ -1111,3 +1111,28 @@ int randseed(bool srand_it)
 
 	return seed;
 }
+
+uid_t get_ns_uid(uid_t orig)
+{
+	char *line = NULL;
+	size_t sz = 0;
+	uid_t nsid, hostid, range;
+	FILE *f = fopen("/proc/self/uid_map", "r");
+	if (!f)
+		return 0;
+
+	while (getline(&line, &sz, f) != -1) {
+		if (sscanf(line, "%u %u %u", &nsid, &hostid, &range) != 3)
+			continue;
+		if (hostid <= orig && hostid + range > orig) {
+			nsid += orig - hostid;
+			goto found;
+		}
+	}
+
+	nsid = 0;
+found:
+	fclose(f);
+	free(line);
+	return nsid;
+}

src/lxc/utils.h

@@ -265,4 +265,9 @@ extern int randseed(bool);
 inline static bool am_unpriv(void) {
 	return geteuid() != 0;
 }
+
+/*
+ * parse /proc/self/uid_map to find what @orig maps to
+ */
+extern uid_t get_ns_uid(uid_t orig);
 #endif