sd_dhcp6_client_set_callback 917 src/network/networkd-link.c r = sd_dhcp6_client_set_callback(link->dhcp6_client, dhcp6_handler, sd_dhcp6_client_set_callback 42 src/systemd/sd-dhcp6-client.h int sd_dhcp6_client_set_callback(sd_dhcp6_client *client,