[bug #53754] RFC violation: grub2 uses bootp-gateway IP as router

[Alexandra Faust]

URL:
  <http://savannah.gnu.org/bugs/?53754>

                 Summary: RFC violation: grub2 uses bootp-gateway IP as router
                 Project: GNU GRUB
            Submitted by: medic123de
            Submitted on: Wed 25 Apr 2018 06:22:58 PM UTC
                Category: Network
                Severity: Major
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 
                 Release: Git master
         Reproducibility: Every Time
         Planned Release: None

    _______________________________________________________

Details:

Hi Guys,
sadly I ran into an issue today.
we have several networks and use Ciscos IOS DHCP-helper to reflect dhcp/bootp
requests to our DHCP/BootP server.

Cisco sets the giaddr field to itself, but does not forward regular traffic (
as currently in standby ).

now grub2 kicks in and sets a hostroute to the bootp-server via that router.
sadly, that server is supposed to serve bootfiles also via tftp - and now does
timeout.

RFC 1542 states:
A BOOTP client MUST NOT interpret the 'giaddr' field of a BOOTREPLY
   message to be the IP address of an IP router.  A BOOTP client SHOULD
   completely ignore the contents of the 'giaddr' field in BOOTREPLY
   messages.

      DISCUSSION:
         The semantics of the 'giaddr' field were poorly defined.
         Section 7.5 of [1] states:

           "If 'giaddr' (gateway address) is nonzero, then the packets
           should be forwarded there first, in order to get to the
           server."

   In that sentence, "get to" refers to communication from the client to
   the server subsequent to the BOOTP exchange, such as a TFTP session.
   Unfortunately, the 'giaddr' field may contain the address of a BOOTP
   relay agent that is not itself an IP router (according to [1],
   Section 8, fifth paragraph), in which case, it will be useless as a
   first-hop for TFTP packets sent to the server (since, by definition,
   non-routers don't forward datagrams at the IP layer).

https://tools.ietf.org/html/rfc1542#section-3.4

can you please repair it in any way ?
( i tried to overwrite with DHCP static routes - but that didn't work either
)

nests
Alex



    _______________________________________________________

File Attachments:


-------------------------------------------------------
Date: Wed 25 Apr 2018 06:22:58 PM UTC  Name: efi-route.jpg  Size: 25KiB   By:
medic123de

<http://savannah.gnu.org/bugs/download.php?file_id=44032>

    _______________________________________________________

Reply to this item at:

  <http://savannah.gnu.org/bugs/?53754>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.gnu.org/