[lwip-devel] Problems with DHCP hostname len

[Juan Jose Schiavoni]

Hi, my application hang when I enable the hostname for dhcp, that use lwip by default.
I found two problems: 1) the macro LWIP_MAX always set len in 255.
2) the loop while(len--) do not count of options bytes available.     

#if LWIP_NETIF_HOSTNAME
static void
dhcp_option_hostname(struct dhcp *dhcp, struct netif *netif)
{
  if (netif->hostname != NULL) {
    size_t namelen = strlen(netif->hostname);
    if (namelen > 0) {
      u8_t len;
      const char *p = netif->hostname;

      LWIP_ASSERT("DHCP: hostname is too long!", namelen <= 255);
      //len = LWIP_MAX(namelen, 255);
      len = LWIP_MIN(namelen, 255);

      // Shrink len to available bytes.
      if(((dhcp->options_out_len + 2) + len) > DHCP_OPTIONS_LEN){
          len = DHCP_OPTIONS_LEN - (dhcp->options_out_len + 2);
      }

      dhcp_option(dhcp, DHCP_OPTION_HOSTNAME, len);

      while (len--) {
        dhcp_option_byte(dhcp, *p++);
      }
    }
  }
}
#endif /* LWIP_NETIF_HOSTNAME */