It must be tc_u_common associated with that tp (i.e. tp->data).
Proof:
	* both ->ht_up and ->tp_c are assign-once
	* ->tp_c of anything inserted into tp_c->hlist is tp_c
	* hnodes never get reinserted into the lists or moved
between those, so anything found by u32_lookup_ht(tp->data, ...)
will have ->tp_c equal to tp->data.
	* tp->root->tp_c == tp->data.
	* ->ht_up of anything inserted into hnode->ht[...] is
equal to hnode.
	* knodes never get reinserted into hash chains or moved
between those, so anything returned by u32_lookup_key(ht, ...)
will have ->ht_up equal to ht.
	* any knode returned by u32_get(tp, ...) will have ->ht_up->tp_c
point to tp->data
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>