ns: Support UTS namespace

Only two fields are modifiable -- hostname and domainname. So
read them on dump and write on restore.

File format is simple --

u32 magic
u32 length of nodename
u8[] nodename string
u32 length of domainname
u8[] domainname string

For OpenVZ we can write the release at the end, but this is later.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

cr-restore.c

@@ -1435,7 +1435,7 @@ static int restore_root_task(int fd, struct cr_options *opts)
 	 */
 
 	if (opts->with_namespaces)
-		ns_clone_flags = 0;
+		ns_clone_flags = CLONE_NEWUTS;
 	else
 		ns_clone_flags = 0;
 

cr-show.c

@@ -474,6 +474,9 @@ static int cr_parse_file(struct cr_options *opts)
 	case ITIMERS_MAGIC:
 		show_itimers(fd);
 		break;
+	case UTSNS_MAGIC:
+		show_utsns(fd);
+		break;
 	default:
 		pr_err("Unknown magic %x on %s\n", magic, opts->show_dump_file);
 		goto err;

crtools.c

@@ -97,6 +97,12 @@ struct cr_fd_desc_tmpl fdset_template[CR_FD_MAX] = {
 		.fmt	= FMT_FNAME_ITIMERS,
 		.magic	= ITIMERS_MAGIC,
 	},
+
+	/* UTS namespace */
+	[CR_FD_UTSNS] = {
+		.fmt	= FMT_FNAME_UTSNS,
+		.magic	= UTSNS_MAGIC,
+	},
 };
 
 static struct cr_fdset *alloc_cr_fdset(void)

include/crtools.h

@@ -35,6 +35,7 @@ enum {
 	 */
 
 	CR_FD_PSTREE,
+	CR_FD_UTSNS,
 
 	CR_FD_MAX
 };
@@ -75,6 +76,7 @@ extern struct cr_fd_desc_tmpl fdset_template[CR_FD_MAX];
 #define FMT_FNAME_UNIXSK	"unixsk-%d.img"
 #define FMT_FNAME_INETSK	"inetsk-%d.img"
 #define FMT_FNAME_ITIMERS	"itimers-%d.img"
+#define FMT_FNAME_UTSNS		"utsns-%d.img"
 
 extern int get_image_path(char *path, int size, const char *fmt, int pid);
 
@@ -103,6 +105,8 @@ struct cr_fdset {
 	CR_FD_DESC_USE(CR_FD_UNIXSK)		|\
 	CR_FD_DESC_USE(CR_FD_INETSK)		|\
 	CR_FD_DESC_USE(CR_FD_ITIMERS)		)
+#define CR_FD_DESC_NS				(\
+	CR_FD_DESC_USE(CR_FD_UTSNS)		)
 #define CR_FD_DESC_NONE			(0)
 
 int cr_dump_tasks(pid_t pid, struct cr_options *opts);

include/image.h

@@ -15,6 +15,7 @@
 #define UNIXSK_MAGIC	0x07070707
 #define INETSK_MAGIC	0x08080808
 #define ITIMERS_MAGIC	0x99009900
+#define UTSNS_MAGIC	0xA00A0AA0
 
 #define FDINFO_FD	1
 #define FDINFO_MAP	2

include/namespaces.h

@@ -3,4 +3,5 @@
 int dump_namespaces(int pid);
 int prepare_namespace(int pid, unsigned long clone_flags);
 int try_show_namespaces(int pid);
+void show_utsns(int fd);
 #endif

include/syscall.h

@@ -313,6 +313,10 @@ static long always_inline sys_setns(int fd, int nstype)
 	return syscall2(__NR_setns, (long)fd, (long)nstype);
 }
 
+#ifndef CLONE_NEWUTS
+#define CLONE_NEWUTS	0x04000000
+#endif
+
 #define setns	sys_setns
 
 #else /* CONFIG_X86_64 */

namespaces.c

@@ -2,6 +2,7 @@
 #include <fcntl.h>
 #include <sys/wait.h>
 #include <sys/types.h>
+#include <sys/utsname.h>
 #include "util.h"
 #include "crtools.h"
 #include "syscall.h"
@@ -27,9 +28,57 @@ out:
 	return ret;
 }
 
+static int dump_uts_string(int fd, char *str)
+{
+	int ret;
+	u32 len;
+
+	len = strlen(str);
+	ret = write_img(fd, &len);
+	if (ret == 0)
+		ret = write_img_buf(fd, str, len);
+
+	return ret;
+}
+
+static int dump_uts_ns(int ns_pid, struct cr_fdset *fdset)
+{
+	int fd, ret;
+	struct utsname ubuf;
+
+	ret = switch_ns(ns_pid, CLONE_NEWUTS, "uts");
+	if (ret < 0)
+		return ret;
+
+	ret = uname(&ubuf);
+	if (ret < 0) {
+		pr_perror("Error calling uname\n");
+		return ret;
+	}
+
+	fd = fdset->fds[CR_FD_UTSNS];
+
+	ret = dump_uts_string(fd, ubuf.nodename);
+	if (!ret)
+		ret = dump_uts_string(fd, ubuf.domainname);
+
+	return ret;
+}
+
 static int do_dump_namespaces(int ns_pid)
 {
-	return 0;
+	struct cr_fdset *fdset;
+	int ret;
+
+	fdset = cr_fdset_open(ns_pid, CR_FD_DESC_NS, NULL);
+	if (fdset == NULL)
+		return -1;
+
+	ret = dump_uts_ns(ns_pid, fdset);
+
+	close_cr_fdset(&fdset);
+	return ret;
+
 }
 
 int dump_namespaces(int ns_pid)
@@ -75,6 +124,67 @@ int dump_namespaces(int ns_pid)
 	return 0;
 }
 
+static int prepare_uts_str(int fd, char *n)
+{
+	int ret;
+	u32 len;
+	char str[65], path[128];
+
+	ret = read_img(fd, &len);
+	if (ret > 0) {
+		if (len >= 65) {
+			pr_err("Corrupted %s\n", n);
+			return -1;
+		}
+
+		ret = read_img_buf(fd, str, len);
+		if (ret < 0)
+			return -1;
+
+		str[len] = '\0';
+
+		snprintf(path, sizeof(path),
+				"/proc/sys/kernel/%s", n);
+		fd = open(path, O_WRONLY);
+		if (fd < 0) {
+			pr_perror("Can't open %s\n", path);
+			return -1;
+		}
+
+		pr_info("Restoging %s to [%s]\n", n, str);
+
+		ret = write(fd, str, len);
+		close(fd);
+		if (ret != len) {
+			pr_perror("Can't write %s to %s\n",
+					str, path);
+			return -1;
+		}
+
+		ret = 0;
+	}
+
+	return ret;
+}
+
+static int prepare_utsns(int pid)
+{
+	int fd, ret;
+	u32 len;
+	char str[65];
+
+	fd = open_image_ro(CR_FD_UTSNS, pid);
+	if (fd < 0)
+		return -1;
+
+	ret = prepare_uts_str(fd, "hostname");
+	if (!ret)
+		ret = prepare_uts_str(fd, "domainname");
+
+	close(fd);
+	return ret;
+}
+
 int prepare_namespace(int pid, unsigned long clone_flags)
 {
 	int ret = 0;
@@ -82,10 +192,52 @@ int prepare_namespace(int pid, unsigned long clone_flags)
 	pr_info("Restoring namespaces %d flags %lx\n",
 			pid, clone_flags);
 
+	if (clone_flags & CLONE_NEWUTS)
+		ret = prepare_utsns(pid);
+
 	return ret;
 }
 
+static void show_uts_string(int fd, char *n)
+{
+	int ret;
+	u32 len;
+	char str[65];
+
+	ret = read_img(fd, &len);
+	if (ret > 0) {
+		if (len >= 65) {
+			pr_err("Corrupted hostname\n");
+			return;
+		}
+
+		ret = read_img_buf(fd, str, len);
+		if (ret < 0)
+			return;
+
+		str[len] = '\0';
+		pr_info("%s: [%s]\n", n, str);
+	}
+}
+
+void show_utsns(int fd)
+{
+	pr_img_head(CR_FD_UTSNS);
+	show_uts_string(fd, "hostname");
+	show_uts_string(fd, "domainname");
+	pr_img_tail(CR_FD_UTSNS);
+}
+
 int try_show_namespaces(int ns_pid)
 {
+	struct cr_fdset *fdset;
+
+	fdset = prep_cr_fdset_for_restore(ns_pid, CR_FD_DESC_NS);
+	if (!fdset)
+		return -1;
+
+	show_utsns(fdset->fds[CR_FD_UTSNS]);
+
+	close_cr_fdset(&fdset);
 	return 0;
 }