NLM_F_REPLACE
nl_flags = NLM_F_REPLACE;
if ((hdr->nlmsg_flags & (NLM_F_CREATE | NLM_F_REPLACE)) == 0)
if (hdr->nlmsg_flags & NLM_F_REPLACE) {
nlm_flags = NLM_F_REPLACE;
hdr->nlmsg_flags &= ~(NLM_F_REPLACE | NLM_F_CREATE);
hdr->nlmsg_flags |= NLM_F_REPLACE;
op_flags |= (nlm_flags & NLM_F_REPLACE) ? RTM_F_REPLACE : 0;
hdr->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
hdr->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;