ip6_tnl_locate
t = ip6_tnl_locate(net, &p1, 0);
t = ip6_tnl_locate(net, &p1, cmd == SIOCADDTUNNEL);
t = ip6_tnl_locate(net, &p1, 0);
t = ip6_tnl_locate(net, &nt->parms, 0);
t = ip6_tnl_locate(net, &p, 0);