On 10.06.2026 20:56, Luiz Angelo Daros de Luca wrote:

Implement the OT_DHCP6_VENDOR option type to properly handle the
DHCPv6 Vendor Class option (code 16) according to RFC 3315.

Previously, this option was marked as OT_INTERNAL, causing dnsmasq
to fail immediately if configured by name. Bypassing this block by
using the numerical option format (option6:16) caused the payload
to be formatted with an unintended string-length prefix. This broke
compliance because the RFC requires a fixed 4-byte Enterprise ID
at the beginning of the option, followed by data blocks.

This byte misalignment broke features like UEFI HTTP IPv6 Boot

With this patch, we complete the support for all UEFI boot methods:

# Vendor matching IPv4
dhcp-vendorclass=set:pxebios,PXEClient:Arch:00000
dhcp-vendorclass=set:pxeefi,PXEClient:Arch:00006
dhcp-vendorclass=set:pxeefi,PXEClient:Arch:00007
dhcp-vendorclass=set:pxeefi,PXEClient:Arch:00009
dhcp-vendorclass=set:httpefi,HTTPClient:Arch:00016

# Vendor matching IPv6
dhcp-match=set:pxeefi,option6:61,00:07
dhcp-match=set:pxeefi,option6:61,00:09
dhcp-match=set:httpefi,option6:61,00:10

# Set vendor class for HTTP IPv4 answers
dhcp-option=httpefi,60,HTTPClient

# Set vendor class for IPv6 answers (requires the patch in this thread)
dhcp-option=httpefi,option6:vendor-class,343,HTTPClient

# Set the IPv4 boot file for PXE and HTTP (I'm using iPXE)
dhcp-boot=tag:pxebios,ipxe/ipxe.pxe,tftpsrv.example.com,192.0.2.2
dhcp-boot=tag:pxeefi,ipxe/ipxe.efi,tftpsrv.example.com,192.0.2.2
dhcp-boot=tag:httpefi,http://192.0.2.2/ipxe/ipxe.efi,httpsrv.example.com

# Set the IPv6 boot file for PXE and HTTP (I'm using iPXE)
dhcp-option=pxeefi,option6:59,tftp://tftpsrv.example.com/ipxe/ipxe.efi
dhcp-option=httpefi,option6:59,http://[2001:db8::2]/ipxe/ipxe.efi

# This is specific for iPXE (after it has already booted,
independently from protocol IPv4/IPv6 or TFTP/HTTP)
dhcp-userclass=set:ipxe,iPXE
# When iPXE uses DHCPv4 first
dhcp-boot=tag:ipxe,/ipxe/ipxe.cfg/init.ipxe
# When iPXE uses DHCPv6 first
dhcp-option=ipxe,option6:59,http://[2001:db8::2]/ipxe/ipxe.cfg/init.ipxe

I didn't double check the Legacy BIOS boot, but I guess it should
work. It would be nice if something like this would be available for
the general public, like in docs, example config files or even man.

This is good. Patch applied, and I added a sentence in the man-page to cover the required enterprise number.

Could you expand the above into a short PXE-boot HOWTO. That would be very useful for many, I think.

Simon.

Regards,

Luiz

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