void * pkt_push_ip(vlib_main_t *vm, vlib_buffer_t *b, ip_address_t *src, ip_address_t *dst, u32 proto, u8 csum_offload)
void * pkt_push_udp_and_ip(vlib_main_t *vm, vlib_buffer_t *b, u16 sp, u16 dp, ip_address_t *sip, ip_address_t *dip, u8 cksum_offload)