BPF_MW_L4OFF
BPF_STMT(BPF_LDX+BPF_MEM, BPF_MW_L4OFF),
M[BPF_MW_L4OFF] = npc->npc_hlen;
M[BPF_MW_L4OFF] = npc->npc_hlen;
((1U << BPF_MW_IPVER) | (1U << BPF_MW_L4OFF) | (1U << BPF_MW_L4PROTO))
BPF_STMT(BPF_LDX+BPF_MEM, BPF_MW_L4OFF),
CHECK_TRUE(npf_bpfcop_run(BPF_MW_L4OFF) == sizeof(struct ip));