udev/net: assign alternative names only on add uevent

Previously, we first assign alternative names to a network interface,
then later change its main name if requested. So, we could not assign
the name that currently assigned as the main name of an interface as an
alternative name. So, we retry to assign the previous main name as an
alternative name on later move uevent.

However, that causes some confusing situation. E.g. if a .link file has
```
Name=foo
AlternativeNames=foo baz
```
then even if the interface is renamed by a user e.g. by invoking 'ip link'
command manually, the interface can be still referenced as 'foo', as the
name is now assigned as an alternative name.

This makes the order of name assignment inverse: the main name is first
changed, and then the requested alternative names are assigned. And
udevd do not assign alternative names on move uevent.

Replaces #27506.

src/udev/net/link-config.c

@@ -365,6 +365,7 @@ Link *link_free(Link *link) {
         sd_device_unref(link->device);
         free(link->kind);
         free(link->driver);
+        strv_free(link->altnames);
         return mfree(link);
 }
 
@@ -793,19 +794,22 @@ no_rename:
         return 0;
 }
 
-static int link_apply_alternative_names(Link *link, sd_netlink **rtnl) {
-        _cleanup_strv_free_ char **altnames = NULL, **current_altnames = NULL;
+static int link_generate_alternative_names(Link *link) {
+        _cleanup_strv_free_ char **altnames = NULL;
         LinkConfig *config;
         sd_device *device;
         int r;
 
         assert(link);
-        assert(link->config);
-        assert(link->device);
-        assert(rtnl);
+        config = ASSERT_PTR(link->config);
+        device = ASSERT_PTR(link->device);
+        assert(!link->altnames);
 
-        config = link->config;
-        device = link->device;
+        if (link->action != SD_DEVICE_ADD) {
+                log_link_debug(link, "Skipping to apply AlternativeNames= and AlternativeNamesPolicy= on '%s' uevent.",
+                               device_action_to_string(link->action));
+                return 0;
+        }
 
         if (config->alternative_names) {
                 altnames = strv_copy(config->alternative_names);
@@ -843,22 +847,7 @@ static int link_apply_alternative_names(Link *link, sd_netlink **rtnl) {
                         }
                 }
 
-        strv_remove(altnames, link->ifname);
-
-        r = rtnl_get_link_alternative_names(rtnl, link->ifindex, &current_altnames);
-        if (r < 0)
-                log_link_debug_errno(link, r, "Failed to get alternative names, ignoring: %m");
-
-        STRV_FOREACH(p, current_altnames)
-                strv_remove(altnames, *p);
-
-        strv_uniq(altnames);
-        strv_sort(altnames);
-        r = rtnl_set_link_alternative_names(rtnl, link->ifindex, altnames);
-        if (r < 0)
-                log_link_full_errno(link, r == -EOPNOTSUPP ? LOG_DEBUG : LOG_WARNING, r,
-                                    "Could not set AlternativeName= or apply AlternativeNamesPolicy=, ignoring: %m");
-
+        link->altnames = TAKE_PTR(altnames);
         return 0;
 }
 
@@ -960,7 +949,7 @@ int link_apply_config(LinkConfigContext *ctx, sd_netlink **rtnl, Link *link) {
         if (r < 0)
                 return r;
 
-        r = link_apply_alternative_names(link, rtnl);
+        r = link_generate_alternative_names(link);
         if (r < 0)
                 return r;
 

src/udev/net/link-config.h

@@ -27,6 +27,7 @@ typedef struct Link {
         int ifindex;
         const char *ifname;
         const char *new_name;
+        char **altnames;
 
         LinkConfig *config;
         sd_device *device;

src/udev/udev-builtin-net_setup_link.c

@@ -52,6 +52,8 @@ static int builtin_net_setup_link(UdevEvent *event, int argc, char **argv, bool
         if (link->new_name)
                 udev_builtin_add_property(dev, test, "ID_NET_NAME", link->new_name);
 
+        event->altnames = TAKE_PTR(link->altnames);
+
         STRV_FOREACH(d, link->config->dropins) {
                 _cleanup_free_ char *escaped = NULL;
 

src/udev/udev-event.c

@@ -87,6 +87,7 @@ UdevEvent *udev_event_free(UdevEvent *event) {
         ordered_hashmap_free_free_free(event->seclabel_list);
         free(event->program_result);
         free(event->name);
+        strv_free(event->altnames);
 
         return mfree(event);
 }
@@ -914,9 +915,6 @@ static int rename_netif(UdevEvent *event) {
 
         dev = ASSERT_PTR(event->dev);
 
-        if (!device_for_action(dev, SD_DEVICE_ADD))
-                return 0; /* Rename the interface only when it is added. */
-
         r = sd_device_get_ifindex(dev, &ifindex);
         if (r == -ENOENT)
                 return 0; /* Device is not a network interface. */
@@ -976,7 +974,7 @@ static int rename_netif(UdevEvent *event) {
                 goto revert;
         }
 
-        r = rtnl_set_link_name(&event->rtnl, ifindex, event->name, NULL);
+        r = rtnl_set_link_name(&event->rtnl, ifindex, event->name, event->altnames);
         if (r < 0) {
                 if (r == -EBUSY) {
                         log_device_info(dev, "Network interface '%s' is already up, cannot rename to '%s'.",
@@ -1007,6 +1005,35 @@ revert:
         return r;
 }
 
+static int assign_altnames(UdevEvent *event) {
+        sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
+        int ifindex, r;
+        const char *s;
+
+        if (strv_isempty(event->altnames))
+                return 0;
+
+        r = sd_device_get_ifindex(dev, &ifindex);
+        if (r == -ENOENT)
+                return 0; /* Device is not a network interface. */
+        if (r < 0)
+                return log_device_warning_errno(dev, r, "Failed to get ifindex: %m");
+
+        r = sd_device_get_sysname(dev, &s);
+        if (r < 0)
+                return log_device_warning_errno(dev, r, "Failed to get sysname: %m");
+
+        /* Filter out the current interface name. */
+        strv_remove(event->altnames, s);
+
+        r = rtnl_append_link_alternative_names(&event->rtnl, ifindex, event->altnames);
+        if (r < 0)
+                log_device_full_errno(dev, r == -EOPNOTSUPP ? LOG_DEBUG : LOG_WARNING, r,
+                                      "Could not set AlternativeName= or apply AlternativeNamesPolicy=, ignoring: %m");
+
+        return 0;
+}
+
 static int update_devnode(UdevEvent *event) {
         sd_device *dev = ASSERT_PTR(ASSERT_PTR(event)->dev);
         int r;
@@ -1148,9 +1175,13 @@ int udev_event_execute_rules(
 
         DEVICE_TRACE_POINT(rules_finished, dev);
 
-        r = rename_netif(event);
-        if (r < 0)
-                return r;
+        if (action == SD_DEVICE_ADD) {
+                r = rename_netif(event);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        (void) assign_altnames(event);
+        }
 
         r = update_devnode(event);
         if (r < 0)

src/udev/udev-event.h

@@ -22,6 +22,7 @@ typedef struct UdevEvent {
         sd_device *dev_parent;
         sd_device *dev_db_clone;
         char *name;
+        char **altnames;
         char *program_result;
         mode_t mode;
         uid_t uid;