lxccontainer: do_lxcapi_detach_interface to support detaching wlan devices

src/lxc/attach.c

@@ -213,7 +213,7 @@ static int lxc_attach_to_ns(pid_t pid, struct lxc_proc_context_info *ctx)
 	return 0;
 }
 
-static int lxc_attach_remount_sys_proc(void)
+int lxc_attach_remount_sys_proc(void)
 {
 	int ret;
 

src/lxc/attach.h

@@ -45,4 +45,6 @@ extern int lxc_attach(struct lxc_container *container,
 		      lxc_attach_exec_t exec_function, void *exec_payload,
 		      lxc_attach_options_t *options, pid_t *attached_process);
 
+extern int lxc_attach_remount_sys_proc(void);
+
 #endif /* __LXC_ATTACH_H */

src/lxc/lxccontainer.c

@@ -4752,6 +4752,7 @@ static bool do_lxcapi_detach_interface(struct lxc_container *c,
 {
 	int ret;
 	pid_t pid, pid_outside;
+	__do_free char *physname = NULL;
 
 	/*
 	 * TODO - if this is a physical device, then we need am_host_unpriv.
@@ -4787,6 +4788,19 @@ static bool do_lxcapi_detach_interface(struct lxc_container *c,
 			_exit(EXIT_FAILURE);
 		}
 
+		/* create new mount namespace for use with remounting /sys and is_wlan() below. */
+		ret = unshare(CLONE_NEWNS);
+		if (ret < 0) {
+			ERROR("Failed to unshare mount namespace");
+			_exit(EXIT_FAILURE);
+		}
+
+		/* set / recursively as private so that mount propagation doesn't affect us.  */
+		if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0) < 0) {
+			ERROR("Failed to recursively set / as private in mount namespace");
+			_exit(EXIT_FAILURE);
+		}
+
 		ret = lxc_netdev_isup(ifname);
 		if (ret < 0) {
 			ERROR("Failed to determine whether network device \"%s\" is up", ifname);
@@ -4802,7 +4816,14 @@ static bool do_lxcapi_detach_interface(struct lxc_container *c,
 			}
 		}
 
-		ret = lxc_netdev_move_by_name(ifname, pid_outside, dst_ifname);
+		/* remount /sys so is_wlan() can check if this device is a wlan device. */
+		lxc_attach_remount_sys_proc();
+		physname = is_wlan(ifname);
+		if (physname)
+			ret = lxc_netdev_move_wlan(physname, ifname, pid_outside, dst_ifname);
+		else
+			ret = lxc_netdev_move_by_name(ifname, pid_outside, dst_ifname);
+
 		/* -EINVAL means there is no netdev named as ifname. */
 		if (ret < 0) {
 			if (ret == -EINVAL)

src/lxc/network.c

@@ -666,7 +666,7 @@ out:
  * will be passed to lxc_netdev_move_wlan() which will free it when done.
  */
 #define PHYSNAME "/sys/class/net/%s/phy80211/name"
-static char *is_wlan(const char *ifname)
+char *is_wlan(const char *ifname)
 {
 	__do_free char *path = NULL;
 	int i, ret;
@@ -739,7 +739,7 @@ static int lxc_netdev_rename_by_name_in_netns(pid_t pid, const char *old,
 	_exit(lxc_netdev_rename_by_name(old, new));
 }
 
-static int lxc_netdev_move_wlan(char *physname, const char *ifname, pid_t pid,
+int lxc_netdev_move_wlan(char *physname, const char *ifname, pid_t pid,
 				const char *newname)
 {
 	char *cmd;

src/lxc/network.h

@@ -277,4 +277,8 @@ extern int lxc_network_recv_name_and_ifindex_from_child(struct lxc_handler *hand
 extern int lxc_netns_set_nsid(int netns_fd);
 extern int lxc_netns_get_nsid(__s32 fd);
 
+extern char *is_wlan(const char *ifname);
+extern int lxc_netdev_move_wlan(char *physname, const char *ifname, pid_t pid,
+				const char *newname);
+
 #endif /* __LXC_NETWORK_H */