gen_protochain
static struct block *gen_protochain(int, int, int);
b0 = gen_protochain(v, Q_IP, dir);
b = gen_protochain(v, Q_IPV6, dir);
b1 = gen_protochain(v, Q_IP);
b1 = gen_protochain(v, Q_IPV6);
return gen_protochain(real_proto, proto, dir);
return gen_protochain((int)v, proto, dir);