pf_state_key_attach
if (pf_state_key_attach(skw, s, PF_SK_WIRE))
if (pf_state_key_attach(skw, s, PF_SK_WIRE)) {
if (pf_state_key_attach(sks, s, PF_SK_STACK)) {
int pf_state_key_attach(struct pf_state_key *, struct pf_state *, int);