#define _GNU_SOURCE

#include "getifaddrs.h"

static int netlink_msg_to_ifaddr(void* pctx, struct nlmsghdr* h) {
  struct ifaddrs_ctx* ctx = pctx;
  struct ifaddrs_storage *ifs, *ifs0 = NULL;
  struct ifinfomsg* ifi = NLMSG_DATA(h);
  struct ifaddrmsg* ifa = NLMSG_DATA(h);
  struct rtattr* rta;
  int stats_len = 0;

  if (h->nlmsg_type == RTM_NEWLINK) {
    for (rta = NLMSG_RTA(h, sizeof(*ifi)); NLMSG_RTAOK(rta, h); rta = RTA_NEXT(rta)) {
      if (rta->rta_type != IFLA_STATS)
        continue;
      stats_len = RTA_DATALEN(rta);
      break;
    }
  } else {
    for (ifs0 = ctx->hash[ifa->ifa_index % IFADDRS_HASH_SIZE]; ifs0; ifs0 = ifs0->hash_next)
      if (ifs0->index == ifa->ifa_index)
        break;
    if (!ifs0)
      return 0;
  }

  ifs = calloc(1, sizeof(struct ifaddrs_storage) + stats_len);
  if (ifs == 0)
    return -1;

  if (h->nlmsg_type == RTM_NEWLINK) {
    ifs->index = ifi->ifi_index;
    ifs->ifa.ifa_flags = ifi->ifi_flags;

    for (rta = NLMSG_RTA(h, sizeof(*ifi)); NLMSG_RTAOK(rta, h); rta = RTA_NEXT(rta)) {
      switch (rta->rta_type) {
        case IFLA_IFNAME:
          if (RTA_DATALEN(rta) < sizeof(ifs->name)) {
            memcpy(ifs->name, RTA_DATA(rta), RTA_DATALEN(rta));
            ifs->ifa.ifa_name = ifs->name;
          }
          break;
        case IFLA_ADDRESS:
          copy_lladdr(&ifs->ifa.ifa_addr, &ifs->addr, RTA_DATA(rta), RTA_DATALEN(rta),
                      ifi->ifi_index, ifi->ifi_type);
          break;
        case IFLA_BROADCAST:
          copy_lladdr(&ifs->ifa.ifa_broadaddr, &ifs->ifu, RTA_DATA(rta), RTA_DATALEN(rta),
                      ifi->ifi_index, ifi->ifi_type);
          break;
        case IFLA_STATS:
          ifs->ifa.ifa_data = (void*)(ifs + 1);
          memcpy(ifs->ifa.ifa_data, RTA_DATA(rta), RTA_DATALEN(rta));
          break;
      }
    }
    if (ifs->ifa.ifa_name) {
      unsigned int bucket = ifs->index % IFADDRS_HASH_SIZE;
      ifs->hash_next = ctx->hash[bucket];
      ctx->hash[bucket] = ifs;
    }
  } else {
    ifs->ifa.ifa_name = ifs0->ifa.ifa_name;
    ifs->ifa.ifa_flags = ifs0->ifa.ifa_flags;
    for (rta = NLMSG_RTA(h, sizeof(*ifa)); NLMSG_RTAOK(rta, h); rta = RTA_NEXT(rta)) {
      switch (rta->rta_type) {
        case IFA_ADDRESS:
          /* If ifa_addr is already set we, received an IFA_LOCAL before
           * so treat this as destination address */
          if (ifs->ifa.ifa_addr)
            copy_addr(&ifs->ifa.ifa_dstaddr, ifa->ifa_family, &ifs->ifu, RTA_DATA(rta),
                      RTA_DATALEN(rta), ifa->ifa_index);
          else
            copy_addr(&ifs->ifa.ifa_addr, ifa->ifa_family, &ifs->addr, RTA_DATA(rta),
                      RTA_DATALEN(rta), ifa->ifa_index);
          break;
        case IFA_BROADCAST:
          copy_addr(&ifs->ifa.ifa_broadaddr, ifa->ifa_family, &ifs->ifu, RTA_DATA(rta),
                    RTA_DATALEN(rta), ifa->ifa_index);
          break;
        case IFA_LOCAL:
          /* If ifa_addr is set and we get IFA_LOCAL, assume we have
           * a point-to-point network. Move address to correct field. */
          if (ifs->ifa.ifa_addr) {
            ifs->ifu = ifs->addr;
            ifs->ifa.ifa_dstaddr = &ifs->ifu.sa;
            memset(&ifs->addr, 0, sizeof(ifs->addr));
          }
          copy_addr(&ifs->ifa.ifa_addr, ifa->ifa_family, &ifs->addr, RTA_DATA(rta),
                    RTA_DATALEN(rta), ifa->ifa_index);
          break;
        case IFA_LABEL:
          if (RTA_DATALEN(rta) < sizeof(ifs->name)) {
            memcpy(ifs->name, RTA_DATA(rta), RTA_DATALEN(rta));
            ifs->ifa.ifa_name = ifs->name;
          }
          break;
      }
    }
    if (ifs->ifa.ifa_addr)
      gen_netmask(&ifs->ifa.ifa_netmask, ifa->ifa_family, &ifs->netmask, ifa->ifa_prefixlen);
  }

  if (ifs->ifa.ifa_name) {
    if (!ctx->first)
      ctx->first = ifs;
    if (ctx->last)
      ctx->last->ifa.ifa_next = &ifs->ifa;
    ctx->last = ifs;
  } else {
    free(ifs);
  }
  return 0;
}