V_tcp_udp_tunneling_overhead
min_protoh += V_tcp_udp_tunneling_overhead;
to.to_mss -= V_tcp_udp_tunneling_overhead;
to.to_mss -= V_tcp_udp_tunneling_overhead;
to.to_mss -= V_tcp_udp_tunneling_overhead;
new = V_tcp_udp_tunneling_overhead;
V_tcp_udp_tunneling_overhead = new;
mssopt -= V_tcp_udp_tunneling_overhead;