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iproute2: Make "ip netns delete" more likely to succeed 

Sometimes "ip netns delete" fails because it can not delete the file a
network namespace was mounted on.  If this only happened when a
network namespace was really in use this would be fine, but today it
is possible to pin all network namespaces by simply having a long
running process started with "ip netns exec".

Every mount is copied when a network namespace is created so it is
impossible to prevent the mounts from getting into other mount
namespaces.  Modify all mounts in the files and subdirectories of
/var/run/netns to be shared mount points so that unmount events can
propogate, making it unlikely that "ip netns delete" will fail because
a directory is mounted in another mount namespace.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2013-01-17 14:47:18 +00:00 committed by Stephen Hemminger
parent 4395d48c78
commit 58a3e8270f
1 changed files with 24 additions and 0 deletions
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24
ip/ipnetns.c
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@ -208,6 +208,7 @@ static int netns_add(int argc, char **argv)
char netns_path[MAXPATHLEN];
const char *name;
int fd;
int made_netns_run_dir_mount = 0;
if (argc < 1) {
fprintf(stderr, "No netns name specified\n");
@ -220,6 +221,29 @@ static int netns_add(int argc, char **argv)
/* Create the base netns directory if it doesn't exist */
mkdir(NETNS_RUN_DIR, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH);
/* Make it possible for network namespace mounts to propogate between
* mount namespaces. This makes it likely that a unmounting a network
* namespace file in one namespace will unmount the network namespace
* file in all namespaces allowing the network namespace to be freed
* sooner.
*/
while (mount("", NETNS_RUN_DIR, "none", MS_SHARED | MS_REC, NULL)) {
/* Fail unless we need to make the mount point */
if (errno != EINVAL || made_netns_run_dir_mount) {
fprintf(stderr, "mount --make-shared %s failed: %s\n",
NETNS_RUN_DIR, strerror(errno));
return EXIT_FAILURE;
}
/* Upgrade NETNS_RUN_DIR to a mount point */
if (mount(NETNS_RUN_DIR, NETNS_RUN_DIR, "none", MS_BIND, NULL)) {
fprintf(stderr, "mount --bind %s %s failed: %s\n",
NETNS_RUN_DIR, NETNS_RUN_DIR, strerror(errno));
return EXIT_FAILURE;
}
made_netns_run_dir_mount = 1;
}
/* Create the filesystem state */
fd = open(netns_path, O_RDONLY|O_CREAT|O_EXCL, 0);
if (fd < 0) {