[syslinux] pxelinux 4.03 taking forever to find ..../pxelinux.cfg/default

[Gene Cumm]

On Tue, Nov 16, 2010 at 15:26, Geert Stappers <stappers at stappers.nl> wrote:
> Op 20101116 om 07:16 schreef Gene Cumm:
>> On Tue, Nov 16, 2010 at 06:08, Doug Scoular <dscoular at gmail.com> wrote:
>> > Hi,
>> > Is there anything that controls the speed with which pxelinux.0 (4.03)
>> > enumerates the files in .../pxelinux.cfg before it reaches the
>> > .../pxelinux.cfg/default file ?
>> >
>> >    pxelinux.cfg/01-00-50-56-ba-48-0e
>> >    pxelinux.cfg/AC12B2D9
>> >    pxelinux.cfg/AC12B2D
>> >    pxelinux.cfg/AC12B2
>> >    pxelinux.cfg/AC12B
>> >    pxelinux.cfg/AC12
>> >    pxelinux.cfg/AC1
>> >    pxelinux.cfg/AC
>> >    pxelinux.cfg/A
>> >    pxelinux.cfg/default
>> >
>> > It's taking several minutes before moving on to the next file... any
>> > thoughts on why this would be ?
>>
>> Probably timeouts.  If your TFTPD is not returning a file not found
>> (OpCode: Error Code (5); Error Code: File not found (1)), that could
>> cause PXELINUX to wait for the TFTP timeout before attempting the next
>> file.  I think the default TFTP timeout in PXELINUX is 60 seconds.
>> Try a packet capture and watch the interactions of your TFTPD and
>> PXELINUX client.  You should see a client read request followed by a
>> daemon file not found.
>
> The thing I would like to know is, if the TFTP server is able
> to do a succesfull reverse lookup of the IP adress of the client.
>
> I think that the delay is caused by a incomplete configured DNS,
> Domain Name Server.

It's an interesting idea but I didn't think PXE clients register with
DNS or present a hostname in the DHCP request.  I also don't know of
any TFTPD that would even think of trying to use a name service (DNS,
/etc/hosts, etc) to resolve an identity.  I think that if there was a
TFTPD that could do this (optionally or not), this feature should only
be reserved for PXE use on a more secured networks where you know the
identity of every host (ie complete /etc/hosts and /etc/ethers) and
not used on a more general purpose network.  (But why would you be
using PXE, an insecure protocol that trusts the network and could
compromise a machine, on a secured network?)

-- 
-Gene