network,udev/net: add Kind= settings in [Match] section

This may be useful for writing .network or .link files matching with
virtual interfaces.

Closes #22541.

src/shared/net-condition.c

@@ -22,6 +22,7 @@ void net_match_clear(NetMatch *match) {
         match->path = strv_free(match->path);
         match->driver = strv_free(match->driver);
         match->iftype = strv_free(match->iftype);
+        match->kind = strv_free(match->kind);
         match->ifname = strv_free(match->ifname);
         match->property = strv_free(match->property);
         match->wlan_iftype = strv_free(match->wlan_iftype);
@@ -38,6 +39,7 @@ bool net_match_is_empty(const NetMatch *match) {
                 strv_isempty(match->path) &&
                 strv_isempty(match->driver) &&
                 strv_isempty(match->iftype) &&
+                strv_isempty(match->kind) &&
                 strv_isempty(match->ifname) &&
                 strv_isempty(match->property) &&
                 strv_isempty(match->wlan_iftype) &&
@@ -126,6 +128,7 @@ int net_match_config(
                 const struct hw_addr_data *permanent_hw_addr,
                 const char *driver,
                 unsigned short iftype,
+                const char *kind,
                 const char *ifname,
                 char * const *alternative_names,
                 enum nl80211_iftype wlan_iftype,
@@ -160,6 +163,9 @@ int net_match_config(
         if (!net_condition_test_strv(match->iftype, iftype_str))
                 return false;
 
+        if (!net_condition_test_strv(match->kind, kind))
+                return false;
+
         if (!net_condition_test_ifname(match->ifname, ifname, alternative_names))
                 return false;
 

src/shared/net-condition.h

@@ -15,7 +15,8 @@ typedef struct NetMatch {
         Set *permanent_hw_addr;
         char **path;
         char **driver;
-        char **iftype;
+        char **iftype; /* udev's DEVTYPE field or ARPHRD_XXX, e.g. ether, wlan. */
+        char **kind;   /* IFLA_INFO_KIND attribute, e.g. gre, gretap, erspan. */
         char **ifname;
         char **property;
         char **wlan_iftype;
@@ -33,6 +34,7 @@ int net_match_config(
                 const struct hw_addr_data *permanent_hw_addr,
                 const char *driver,
                 unsigned short iftype,
+                const char *kind,
                 const char *ifname,
                 char * const *alternative_names,
                 enum nl80211_iftype wlan_iftype,