ip_ecn_egress
if (ip_ecn_egress((ifp->if_flags & IFF_LINK1) ? ECN_ALLOWED:
ip_ecn_egress(ECN_ALLOWED, &otos, &itos);
ip_ecn_egress(ECN_NOCARE, &otos, &itos);
ret = ip_ecn_egress(mode, &outer8, &inner8);
extern int ip_ecn_egress(int, const uint8_t *, uint8_t *);