DHCP_IP_UDP_SIZE   64 src/libsystemd-network/dhcp-protocol.h #define DHCP_MIN_OPTIONS_SIZE   DHCP_DEFAULT_MIN_SIZE - DHCP_IP_UDP_SIZE - DHCP_MESSAGE_SIZE
DHCP_IP_UDP_SIZE 1493 src/libsystemd-network/sd-dhcp-client.c         len -= DHCP_IP_UDP_SIZE;