sd-network: add support to get DHCP4 address

src/libsystemd/sd-network/sd-network.c

@@ -229,6 +229,10 @@ _public_ int sd_network_link_get_timezone(int ifindex, char **ret) {
         return network_link_get_string(ifindex, "TIMEZONE", ret);
 }
 
+_public_ int sd_network_link_get_dhcp4_address(int ifindex, char **ret) {
+        return network_link_get_string(ifindex, "DHCP4_ADDRESS", ret);
+}
+
 _public_ int sd_network_link_get_dns(int ifindex, char ***ret) {
         return network_link_get_strv(ifindex, "DNS", ret);
 }

src/systemd/sd-network.h

@@ -110,6 +110,10 @@ int sd_network_link_get_network_file(int ifindex, char **filename);
  * IP addresses */
 int sd_network_link_get_dns(int ifindex, char ***ret);
 
+/* Get DHCP4 address for a given link. This is string representations of
+ * IPv4 address */
+int sd_network_link_get_dhcp4_address(int ifindex, char **ret);
+
 /* Get NTP entries for a given link. These are domain names or string
  * representations of IP addresses */
 int sd_network_link_get_ntp(int ifindex, char ***ret);