[Dnsmasq-discuss] [EXTERNAL] Re: UEFI PXE Boot Issue: dhcp-option 60

[Wang Shanker]

Hi,

In theory, `dhcp-pxe-vendor` cannot prevent the special handling 
of dhcp-option 60 when replying to pxe clients. 

However, dnsmasq identifies a pxe client by matching "PXEClient"
string sent in the requests. By using this setting, you can specify
a dummy string for this like DUMMY6789, and normal pxe clients won't
be seen as pxe clients anymore by dnsmasq and thus the special 
handling of dhcp-option 60 is disabled.

As I wrote in my previous mail. I strongly suspect the `pxe-prompt`
option is the cause of the problem.

Cheers,

Miao Wang

> 2020年12月07日 22:04，Swanand Vaidya <Swanand.Vaidya at veritas.com> 写道：
> 
> Hi Geert,
> 
> Yes, the source I had taken included this commit. But as I understand it allow you to send specific value for vendor class in dhcp-option 60.
> I want to totally stop dhcp-option 60 from being sent as different clients may have different requirements.
> Does the new setting 'dhcp-pxe-vendor' allow you to stop dhcp-option 60 from being sent?
> 
> Thanks,
> -swanand
> 
> -----Original Message-----
> From: Geert Stappers <stappers at stappers.nl> 
> Sent: Monday, December 7, 2020 7:19 PM
> To: Swanand Vaidya <Swanand.Vaidya at veritas.com>; dnsmasq-discuss at lists.thekelleys.org.uk
> Subject: [EXTERNAL] Re: [Dnsmasq-discuss] UEFI PXE Boot Issue: dhcp-option 60
> 
> On Mon, Dec 07, 2020 at 01:11:18PM +0000, Swanand Vaidya wrote:
>> Hi,
>> 
>> I am trying to PXE boot a UEFI enabled Dell machine with dnsmasq 
>> acting as both the DHCP and TFTP server.
>> The client and server perform the DHCP steps: DHCP Discover, DHCP 
>> Offer, DHCP Request and DHCP Ack as expected.
>> 
>> But, thereafter, the client simply aborts the protocol (it does not do 
>> TFTP to download the NBP file syslinux.efi and others) and I can see 
>> error:
>> "PXE-E21: Remote boot canceled" on the client console.
>> 
>> The same dnsmasq configuration works for booting a BIOS based machine.
>> 
>> I found that dnsmasq is sending dhcp-option 60 with value as "PXEClient"
>> which is causing this issue.
>> 
>> I could not find any way to disable this from being sent to the client.
>> 
>> Finally, I modified the source code in rfc2131.c by adding "return"
>> statement at the top of the function pxe_misc(). The dnsmasq binary so 
>> built now works fine for booting the UEFI machine.
>> 
>> I would like to know:
>> 
>>  1.  If this is a known issue? I tried latest 2.82 version of dnsmasq
>>      as well as building from the latest source snapshot from HEAD.
> 
> Did that include http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=4ded96209e8346711f9d0b9e13a835d42835853d ?
> Yes, that is a very very fresh commit.  And it is 'PXEClient' related ...
> 
> 
>>  2.  Is there any way to disable dhcp-option 60 from being sent over
>>      to the client by setting some configuration param in
>>      dnsmasq.conf? We can force certain option to be sent using
>>      dhcp-option-force directive, but there is nothing for the opposite
>>      direction to "force disable" a specific DHCP option. (Setting
>>      dhcp-option = <option_number> without a value only works for
>>      certain dhcp options).
>> 
> 
> 
> 
>> Thanks,
> 
> You are welcome.
> 
> 
> 
>> -swanand
> 
> Regards
> Geert Stappers
> 
> P.S.
> I usually don't do "Reply to All", but I do take insults.
> --
> Silence is hard to parse
> 
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