lwtunnel_headroom
res = mtu - lwtunnel_headroom(dst->lwtstate, mtu);
return mtu - lwtunnel_headroom(dst->lwtstate, mtu);
mtu -= lwtunnel_headroom(dst->lwtstate, mtu);
return mtu - lwtunnel_headroom(dst->lwtstate, mtu);
return mtu - lwtunnel_headroom(nhc->nhc_lwtstate, mtu);
return mtu - lwtunnel_headroom(nh->fib_nh_lws, mtu);
return mtu - lwtunnel_headroom(nh->fib_nh_lws, mtu);