sd_dhcp_client_set_callback  612 src/network/networkd-dhcp4.c         r = sd_dhcp_client_set_callback(link->dhcp_client, dhcp4_handler, link);
sd_dhcp_client_set_callback   43 src/systemd/sd-dhcp-client.h int sd_dhcp_client_set_callback(sd_dhcp_client *client, sd_dhcp_client_cb_t cb,