user-cr: UTS support and test

user-cr: UTS support and test

[Dan Smith]

This patch set against Oren's user-cr tree makes the necessary changes
to mktree.c to support restarting a checkpoint that contains UTS
namespace information.  It also includes a test program to be used for
verification.

[PATCH] Add UTS support to mktree

[Dan Smith]

Read the namespace records from the restore stream and do the unshare()
necessary to create a new namespace.  For UTS, set hostname and domainname
to match what was stored in the checkpoint.

Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 mktree.c |   66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 66 insertions(+), 0 deletions(-)

diff --git a/mktree.c b/mktree.c
index 55149dd..e0898db 100644
--- a/mktree.c
+++ b/mktree.c
@@ -14,6 +14,7 @@
 #include <unistd.h>
 #include <errno.h>
 #include <signal.h>
+#include <sched.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <asm/unistd.h>
@@ -101,6 +102,7 @@ static int cr_read_obj_type(struct cr_ctx *ctx, void *buf, int n, int type);
 
 static int cr_read_head(struct cr_ctx *ctx);
 static int cr_read_head_arch(struct cr_ctx *ctx);
+static int cr_read_namespaces(struct cr_ctx *ctx);
 static int cr_read_tree(struct cr_ctx *ctx);
 
 struct pid_swap {
@@ -191,6 +193,12 @@ int main(int argc, char *argv[])
 		exit(1);
 	}
 
+	ret = cr_read_namespaces(&ctx);
+	if (ret < 0) {
+		perror("read c/r namespaces");
+		exit(1);
+	}
+
 	ret = cr_fork_feeder(&ctx);
 	if (ret < 0)
 		exit(1);
@@ -557,6 +565,64 @@ static int cr_read_head_arch(struct cr_ctx *ctx)
 	return 0;
 }
 
+static int cr_read_task_namespaces(struct cr_ctx *ctx)
+{
+
+	struct cr_hdr_nsproxy hhn;
+	struct cr_hdr_utsns hhu;
+	int parent;
+
+	parent = cr_read_obj_type(ctx, &hhn, sizeof(hhn), CR_HDR_NSP);
+	if (parent < 0)
+		return parent;
+	else if (parent != 0) {
+		errno = -EINVAL;
+		return -1;
+	}
+
+	if (hhn.types == 0)
+		return 0;
+
+	if (unshare(CLONE_NEWUTS) != 0) {
+		perror("unshare(CLONE_NEWUTS)");
+		return -1;
+	}
+
+	if (hhn.types & CR_NSP_UTS) {
+		parent = cr_read_obj_type(ctx, &hhu, sizeof(hhu),
+					  CR_HDR_UTSNS);
+		if (parent < 0)
+			return parent;
+		else if (parent != 0) {
+			errno = -EINVAL;
+			return -1;
+		}
+
+		cr_dbg("UTS namespace nn=%s dn=%s\n",
+		       hhu.nodename,
+		       hhu.domainname);
+
+		sethostname(hhu.nodename, strlen(hhu.nodename));
+		setdomainname(hhu.domainname, strlen(hhu.domainname));
+	}
+
+	return 0;
+}
+
+static int cr_read_namespaces(struct cr_ctx *ctx)
+{
+	int n;
+	int ret = 0;
+
+	for (n = 0; n < ctx->pids_nr; n++) {
+		ret = cr_read_task_namespaces(ctx);
+		if (ret < 0)
+			break;
+	}
+
+	return ret;
+}
+
 static int cr_read_tree(struct cr_ctx *ctx)
 {
 	struct cr_hdr *h = (struct cr_hdr *) ctx->buf;
-- 
1.5.6.3

Re: [PATCH] Add UTS support to mktree

[Serge E. Hallyn]

Quoting Dan Smith (danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org):
> Read the namespace records from the restore stream and do the unshare()
> necessary to create a new namespace.  For UTS, set hostname and domainname
> to match what was stored in the checkpoint.
> 
> Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> ---
>  mktree.c |   66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 66 insertions(+), 0 deletions(-)
> 
> diff --git a/mktree.c b/mktree.c
> index 55149dd..e0898db 100644
> --- a/mktree.c
> +++ b/mktree.c
> @@ -14,6 +14,7 @@
>  #include <unistd.h>
>  #include <errno.h>
>  #include <signal.h>
> +#include <sched.h>
>  #include <sys/types.h>
>  #include <sys/wait.h>
>  #include <asm/unistd.h>
> @@ -101,6 +102,7 @@ static int cr_read_obj_type(struct cr_ctx *ctx, void *buf, int n, int type);
> 
>  static int cr_read_head(struct cr_ctx *ctx);
>  static int cr_read_head_arch(struct cr_ctx *ctx);
> +static int cr_read_namespaces(struct cr_ctx *ctx);
>  static int cr_read_tree(struct cr_ctx *ctx);
> 
>  struct pid_swap {
> @@ -191,6 +193,12 @@ int main(int argc, char *argv[])
>  		exit(1);
>  	}
> 
> +	ret = cr_read_namespaces(&ctx);
> +	if (ret < 0) {
> +		perror("read c/r namespaces");
> +		exit(1);
> +	}
> +
>  	ret = cr_fork_feeder(&ctx);
>  	if (ret < 0)
>  		exit(1);
> @@ -557,6 +565,64 @@ static int cr_read_head_arch(struct cr_ctx *ctx)
>  	return 0;
>  }
> 
> +static int cr_read_task_namespaces(struct cr_ctx *ctx)
> +{
> +
> +	struct cr_hdr_nsproxy hhn;
> +	struct cr_hdr_utsns hhu;
> +	int parent;
> +
> +	parent = cr_read_obj_type(ctx, &hhn, sizeof(hhn), CR_HDR_NSP);
> +	if (parent < 0)
> +		return parent;
> +	else if (parent != 0) {
> +		errno = -EINVAL;
> +		return -1;
> +	}
> +
> +	if (hhn.types == 0)
> +		return 0;
> +
> +	if (unshare(CLONE_NEWUTS) != 0) {
> +		perror("unshare(CLONE_NEWUTS)");
> +		return -1;
> +	}
> +
> +	if (hhn.types & CR_NSP_UTS) {
> +		parent = cr_read_obj_type(ctx, &hhu, sizeof(hhu),
> +					  CR_HDR_UTSNS);
> +		if (parent < 0)
> +			return parent;

Man this reinforces the point someone (Oren?) was making about
not being able to error out gracefully from a restart.  If we
fail right here, we're suddenly in our own uts namespace.  Which
coudl be fine for awhile, but could really mess with an admin's
mind.

Sure we could move the unshare() to after we've read all of
the namespace data, but then the same thing could happen if
the first step in fork_feeder fails.

> +		else if (parent != 0) {
> +			errno = -EINVAL;
> +			return -1;
> +		}
> +
> +		cr_dbg("UTS namespace nn=%s dn=%s\n",
> +		       hhu.nodename,
> +		       hhu.domainname);
> +
> +		sethostname(hhu.nodename, strlen(hhu.nodename));
> +		setdomainname(hhu.domainname, strlen(hhu.domainname));

*these *shoudln't* fail (if unshare succeeded), but it's still worth
checking.

> +	}
> +
> +	return 0;
> +}
> +
> +static int cr_read_namespaces(struct cr_ctx *ctx)
> +{
> +	int n;
> +	int ret = 0;
> +
> +	for (n = 0; n < ctx->pids_nr; n++) {
> +		ret = cr_read_task_namespaces(ctx);
> +		if (ret < 0)
> +			break;
> +	}
> +
> +	return ret;
> +}
> +
>  static int cr_read_tree(struct cr_ctx *ctx)
>  {
>  	struct cr_hdr *h = (struct cr_hdr *) ctx->buf;
> -- 
> 1.5.6.3
> 
> _______________________________________________
> Containers mailing list
> Containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
> https://lists.linux-foundation.org/mailman/listinfo/containers

Re: [PATCH] Add UTS support to mktree

[Dan Smith]

SH> *these *shoudln't* fail (if unshare succeeded), but it's still
SH> worth checking.

Oops, yep :)

-- 
Dan Smith
IBM Linux Technology Center
email: danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org

[PATCH] Add a simple UTS test program

[Dan Smith]

This program creates a top-level UTS namespace and then forks a child.  The
parent sets the hostname to a different value every second and the child
prints the value.  If the child's value changes with the parent, even after
restart, then the pair are running in the same UTS namespace.  The test
self-checkpoints every iteration.

Signed-off-by: Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
---
 utstest.c |  114 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 114 insertions(+), 0 deletions(-)
 create mode 100644 utstest.c

diff --git a/utstest.c b/utstest.c
new file mode 100644
index 0000000..1afca49
--- /dev/null
+++ b/utstest.c
@@ -0,0 +1,114 @@
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sched.h>
+#include <string.h>
+#include <stdlib.h>
+#include <asm/unistd.h>
+
+#define OUTFILE "/tmp/cr-test.out"
+#define CKPTDIR "/tmp"
+
+int ckpt = 0;
+
+int do_checkpoint(void)
+{
+	char fn[256];
+	int fd;
+	int ret;
+
+	snprintf(fn, sizeof(fn)-1, CKPTDIR "/ckpt-%i", ckpt++);
+
+	fd = open(fn, O_WRONLY | O_CREAT | O_TRUNC, 0666);
+	if (fd < 0) {
+		perror(fn);
+		return -1;
+	}
+
+	ret = syscall(__NR_checkpoint, getpid(), fd, 0);
+	if (ret < 0)
+		printf("Checkpoint to %s returned %i (%m)\n", fn, ret);
+
+	close(fd);
+
+	return ret;
+}
+
+void child(int fd, int subunshare)
+{
+	char hostname[256] = "foo";
+	int ret;
+
+	if (subunshare) {
+		ret = unshare(CLONE_NEWUTS);
+		if (ret) {
+			printf("unshare: %m");
+			exit(1);
+		}
+	}
+
+	while (1) {
+		ret = gethostname(hostname, sizeof(hostname));
+		if (ret) {
+			perror("gethostname");
+			_exit(1);
+		}
+
+		printf("Hostname in child is:  %s\n", hostname);
+		sleep(1);
+	}
+}
+
+int main(int argc, char **argv)
+{
+	int ret;
+	int fd;
+	int i = 0;
+	int subunshare = 0;
+
+#ifndef NOUTS
+	ret = unshare(CLONE_NEWUTS);
+	if (ret) {
+		perror("unshare");
+		return 1;
+	}
+#endif
+
+	/* Pass '-u' to test nested namespace */
+	if ((argc == 2) && (strcmp(argv[1], "-u") == 0))
+		subunshare = 1;
+
+	fd = open(OUTFILE, O_RDWR | O_CREAT | O_TRUNC, 0666);
+	if (fd < 0) {
+		perror(OUTFILE);
+		return 1;
+	}
+
+	dup2(fd, 1);
+	dup2(fd, 2);
+	close(0);
+
+	setlinebuf(stdout);
+	setlinebuf(stderr);
+
+	if (fork() == 0)
+		child(fd, subunshare);
+
+	while (1) {
+#ifndef NOUTS
+		char hostname[256];
+
+		snprintf(hostname, sizeof(hostname)-1, "test%i", i++);
+		ret = sethostname(hostname, strlen(hostname));
+		if (ret) {
+			perror("sethostname");
+			return 1;
+		}
+
+		printf("Hostname in parent is: %s\n", hostname);
+#endif
+		do_checkpoint();
+		sleep(1);
+	}
+}
-- 
1.5.6.3