sd-netlink: introduce rtnl_rename_link()

src/libsystemd/sd-netlink/netlink-util.c

@@ -20,6 +20,13 @@ static int set_link_name(sd_netlink **rtnl, int ifindex, const char *name) {
         assert(name);
 
         /* Assign the requested name. */
+
+        if (!*rtnl) {
+                r = sd_netlink_open(rtnl);
+                if (r < 0)
+                        return r;
+        }
+
         r = sd_rtnl_message_new_link(*rtnl, &message, RTM_SETLINK, ifindex);
         if (r < 0)
                 return r;
@@ -31,6 +38,37 @@ static int set_link_name(sd_netlink **rtnl, int ifindex, const char *name) {
         return sd_netlink_call(*rtnl, message, 0, NULL);
 }
 
+int rtnl_rename_link(sd_netlink **rtnl, const char *orig_name, const char *new_name) {
+        _cleanup_(sd_netlink_unrefp) sd_netlink *our_rtnl = NULL;
+        int r, ifindex;
+
+        assert(orig_name);
+        assert(new_name);
+
+        /* This does not check alternative names. Callers must check the requested name is not used as an
+         * alternative name. */
+
+        if (streq(orig_name, new_name))
+                return 0;
+
+        if (!ifname_valid(new_name))
+                return -EINVAL;
+
+        if (!rtnl)
+                rtnl = &our_rtnl;
+        if (!*rtnl) {
+                r = sd_netlink_open(rtnl);
+                if (r < 0)
+                        return r;
+        }
+
+        ifindex = rtnl_resolve_ifname(rtnl, orig_name);
+        if (ifindex < 0)
+                return ifindex;
+
+        return set_link_name(rtnl, ifindex, new_name);
+}
+
 int rtnl_set_link_name(sd_netlink **rtnl, int ifindex, const char *name, char* const *alternative_names) {
         _cleanup_strv_free_ char **original_altnames = NULL, **new_altnames = NULL;
         bool altname_deleted = false;

src/libsystemd/sd-netlink/netlink-util.h

@@ -31,6 +31,7 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(MultipathRoute*, multipath_route_free);
 
 int multipath_route_dup(const MultipathRoute *m, MultipathRoute **ret);
 
+int rtnl_rename_link(sd_netlink **rtnl, const char *orig_name, const char *new_name);
 int rtnl_set_link_name(sd_netlink **rtnl, int ifindex, const char *name, char* const* alternative_names);
 static inline int rtnl_append_link_alternative_names(sd_netlink **rtnl, int ifindex, char* const *alternative_names) {
         return rtnl_set_link_name(rtnl, ifindex, NULL, alternative_names);

src/libsystemd/sd-netlink/test-netlink.c

@@ -681,6 +681,19 @@ TEST(rtnl_set_link_name) {
         _cleanup_free_ char *resolved = NULL;
         assert_se(rtnl_resolve_link_alternative_name(&rtnl, "test-additional-name", &resolved) == ifindex);
         assert_se(streq_ptr(resolved, "test-shortname"));
+        resolved = mfree(resolved);
+
+        assert_se(rtnl_rename_link(&rtnl, "test-shortname", "test-shortname") >= 0);
+        assert_se(rtnl_rename_link(&rtnl, "test-shortname", "test-shortname2") >= 0);
+        assert_se(rtnl_rename_link(NULL, "test-shortname2", "test-shortname3") >= 0);
+
+        assert_se(rtnl_resolve_link_alternative_name(&rtnl, "test-additional-name", &resolved) == ifindex);
+        assert_se(streq_ptr(resolved, "test-shortname3"));
+        resolved = mfree(resolved);
+
+        assert_se(rtnl_resolve_link_alternative_name(&rtnl, "test-shortname3", &resolved) == ifindex);
+        assert_se(streq_ptr(resolved, "test-shortname3"));
+        resolved = mfree(resolved);
 }
 
 DEFINE_TEST_MAIN(LOG_DEBUG);