[lxc-devel] [PATCH] rename physical nics at shutdown

[Serge Hallyn]

When a physical nic is being set up, store its ifindex and original name
in struct lxc_conf.  At reboot, reset the original name.
We can't just go over the original network list in lxc_conf at shutdown
because that may be tweaked in the meantime through the C api.  The
saved_nics list is only setup during lxc_spawn(), and restored and
freed after lxc_start.

Without this patch, if you take a container with physical nic eth1
renamed to eth0, start it, shut it down, and restart it, the last
restart will fail.

Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/1086244

Reported-by: Avijit Ghosh <avijit.ghosh at aricent.com>
Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
---
 src/lxc/conf.c    |   28 ++++++++++++++++++++++++++++
 src/lxc/conf.h    |    9 +++++++++
 src/lxc/execute.c |    6 ++++--
 src/lxc/start.c   |   38 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 79d96d7..45e0b31 100644
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -1821,6 +1821,21 @@ static int setup_network(struct lxc_list *network)
 	return 0;
 }
 
+void lxc_rename_phys_nics_on_shutdown(struct lxc_conf *conf)
+{
+	int i;
+
+	INFO("running to reset %d nic names", conf->num_savednics);
+	for (i=0; i<conf->num_savednics; i++) {
+		struct saved_nic *s = &conf->saved_nics[i];
+		INFO("resetting nic %d to %s\n", s->ifindex, s->orig_name);
+		lxc_netdev_rename_by_index(s->ifindex, s->orig_name);
+		free(s->orig_name);
+	}
+	conf->num_savednics = 0;
+	free(conf->saved_nics);
+}
+
 static int setup_private_host_hw_addr(char *veth1)
 {
 	struct ifreq ifr;
@@ -2710,6 +2725,18 @@ int lxc_clear_hooks(struct lxc_conf *c, const char *key)
 	return 0;
 }
 
+void lxc_clear_saved_nics(struct lxc_conf *conf)
+{
+	int i;
+
+	if (!conf->num_savednics)
+		return;
+	for (i=0; i < conf->num_savednics; i++)
+		free(conf->saved_nics[i].orig_name);
+	conf->saved_nics = 0;
+	free(conf->saved_nics);
+}
+
 void lxc_conf_free(struct lxc_conf *conf)
 {
 	if (!conf)
@@ -2737,5 +2764,6 @@ void lxc_conf_free(struct lxc_conf *conf)
 	lxc_clear_cgroups(conf, "lxc.cgroup");
 	lxc_clear_hooks(conf, "lxc.hook");
 	lxc_clear_mount_entries(conf);
+	lxc_clear_saved_nics(conf);
 	free(conf);
 }
diff --git a/src/lxc/conf.h b/src/lxc/conf.h
index 694bce4..3f6181f 100644
--- a/src/lxc/conf.h
+++ b/src/lxc/conf.h
@@ -211,6 +211,11 @@ enum lxchooks {
 	LXCHOOK_POSTSTOP, NUM_LXC_HOOKS};
 extern char *lxchook_names[NUM_LXC_HOOKS];
 
+struct saved_nic {
+	int ifindex;
+	char *orig_name;
+};
+
 struct lxc_conf {
 	char *fstab;
 	int tty;
@@ -221,6 +226,8 @@ struct lxc_conf {
 	struct utsname *utsname;
 	struct lxc_list cgroup;
 	struct lxc_list network;
+	struct saved_nic *saved_nics;
+	int num_savednics;
 	struct lxc_list mount_list;
 	struct lxc_list caps;
 	struct lxc_tty_info tty_info;
@@ -273,4 +280,6 @@ extern int lxc_clear_hooks(struct lxc_conf *c, const char *key);
  */
 
 extern int lxc_setup(const char *name, struct lxc_conf *lxc_conf);
+
+extern void lxc_rename_phys_nics_on_shutdown(struct lxc_conf *conf);
 #endif
diff --git a/src/lxc/execute.c b/src/lxc/execute.c
index 487765f..730b793 100644
--- a/src/lxc/execute.c
+++ b/src/lxc/execute.c
@@ -27,7 +27,6 @@
 #include <unistd.h>
 #include <stdlib.h>
 
-
 #include "log.h"
 #include "start.h"
 
@@ -134,9 +133,12 @@ int lxc_execute(const char *name, char *const argv[], int quiet,
 		.argv = argv,
 		.quiet = quiet
 	};
+	int ret;
 
 	if (lxc_check_inherited(conf, -1))
 		return -1;
 
-	return __lxc_start(name, conf, &execute_start_ops, &args);
+	ret = __lxc_start(name, conf, &execute_start_ops, &args);
+
+	return ret;
 }
diff --git a/src/lxc/start.c b/src/lxc/start.c
index 3e26b27..7320d74 100644
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -579,6 +579,37 @@ out_warn_father:
 	return -1;
 }
 
+int save_phys_nics(struct lxc_conf *conf)
+{
+	struct lxc_list *iterator;
+
+	lxc_list_for_each(iterator, &conf->network) {
+		struct lxc_netdev *netdev = iterator->elem;
+
+		if (netdev->type != LXC_NET_PHYS)
+			continue;
+		conf->saved_nics = realloc(conf->saved_nics,
+				(conf->num_savednics+1)*sizeof(struct saved_nic));
+		if (!conf->saved_nics) {
+			SYSERROR("failed to allocate memory");
+			return -1;
+		}
+		conf->saved_nics[conf->num_savednics].ifindex = netdev->ifindex;
+		conf->saved_nics[conf->num_savednics].orig_name = strdup(netdev->link);
+		if (!conf->saved_nics[conf->num_savednics].orig_name) {
+			SYSERROR("failed to allocate memory");
+			return -1;
+		}
+		INFO("stored saved_nic #%d idx %d name %s\n", conf->num_savednics,
+			conf->saved_nics[conf->num_savednics].ifindex,
+			conf->saved_nics[conf->num_savednics].orig_name);
+		conf->num_savednics++;
+	}
+
+	return 0;
+}
+
+
 int lxc_spawn(struct lxc_handler *handler)
 {
 	int failed_before_rename = 0;
@@ -613,6 +644,11 @@ int lxc_spawn(struct lxc_handler *handler)
 		}
 	}
 
+	if (save_phys_nics(handler->conf)) {
+		ERROR("failed to save physical nic info");
+		goto out_abort;
+	}
+
 	/*
 	 * if the rootfs is not a blockdev, prevent the container from
 	 * marking it readonly.
@@ -739,6 +775,8 @@ int __lxc_start(const char *name, struct lxc_conf *conf,
 		}
         }
 
+	lxc_rename_phys_nics_on_shutdown(handler->conf);
+
 	err =  lxc_error_set_and_log(handler->pid, status);
 out_fini:
 	lxc_delete_network(handler);
-- 
1.7.10.4