if_nametoindex_nl
uint32_t ifindex = if_nametoindex_nl(ss, ctx->ifname);
ifahdr->ifa_index = if_nametoindex_nl(ctx->io_ss, ctx->ifname);
ifahdr->ifa_index = if_nametoindex_nl(ctx->io_ss, ctx->ifname);
uint32_t if_nametoindex_nl(struct snl_state *ss, const char *ifname);