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strange message from dnsmasq

Discussion in 'Tomato Firmware' started by Odin-60, Mar 14, 2007.

  1. Odin-60

    Odin-60 LI Guru Member

    Tomato 1.05 on WRT54GL.

    This morning I found the following in the log file:

    Mar 14 04:38:17 WRT54GL daemon.info dnsmasq[7641]: DHCPINFORM(br0) 0.0.0.0 <null>

    What does it mean? The dnsmasq documentation does not even
    mention this message. Besides, in my LAN the only computer that
    was up at 4:38 has a fixed, self-assigned IP address and does not
    use dhcp.

    <edit>
    Google finds two incidents of this kind mentioned:
    http://www.openlinksys.info/forum/viewthread.php?forum_id=32&thread_id=2286
    and
    http://extern.eisfair.org/fli4l_newsportal/article.php?id=186822&group=spline.fli4l
    The former is related with Tomato, too. The latter affects fli4l.
    Neither was explained so far.
     
  2. MelechRic

    MelechRic LI Guru Member

    I went and downloaded the latest dnsmasq source and did a search on "DHCPINFORM" within the src directory. The only file that references this string is called rfc2131.c. RFC 2131 is the DHCP specification and I assume that this is where it's implemented within dnsmasq.

    Looking on google for RFC 2131:

    http://www.faqs.org/rfcs/rfc2131.html

    These snippets might be of interest to you:

    Code:
       DHCPINFORM   -  Client to server, asking only for local configuration
                       parameters; client already has externally configured
                       network address.
    
    ...
    
    3.4 Obtaining parameters with externally configured network address
    
       If a client has obtained a network address through some other means
       (e.g., manual configuration), it may use a DHCPINFORM request message
    
       to obtain other local configuration parameters.  Servers receiving a
       DHCPINFORM message construct a DHCPACK message with any local
       configuration parameters appropriate for the client without:
       allocating a new address, checking for an existing binding, filling
       in 'yiaddr' or including lease time parameters.  The servers SHOULD
       unicast the DHCPACK reply to the address given in the 'ciaddr' field
       of the DHCPINFORM message.
    
       The server SHOULD check the network address in a DHCPINFORM message
       for consistency, but MUST NOT check for an existing lease.  The
       server forms a DHCPACK message containing the configuration
       parameters for the requesting client and sends the DHCPACK message
       directly to the client.
    
    Seems like your client (with a fixed ip address) is asking for local configuration parameters.

    At this point I'll stop quoting the RFC and let you look for yourself. :D


    EDIT:

    More (interesting?) reading:
    http://www.tcpipguide.com/free/t_DHCPParameterConfigurationProcessForClientsWithNon-2.htm
    http://www.tcpipguide.com/free/t_DHCPOptionsOptionFormatandOptionOverloading.htm

    http://support.microsoft.com/kb/232703
     
  3. digitalgeek

    digitalgeek Network Guru Member

    You might wabt to try using static dhcp for this device
     
  4. Odin-60

    Odin-60 LI Guru Member

    Thank you for the explanation. On the client in question the OS had just
    been updated (*); maybe sending of the DHCPINFORM request was a
    newly introduced feature,; this could explain why I had never noticed it
    before. In any case I'm happy that this is nothing I need to worry about.

    (*) Mac OSX 10.4.8 to 10.4.9
     
  5. MelechRic

    MelechRic LI Guru Member

    Well, I'm glad I could help. Now I find myself curious as to what these "local configuration parameters" are for. I guess I'll read a few more of the articles I originally posted . :)
     

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