Hi Jaco,
The "raw" socket type is only applicable to kea-dhcp4. It is not
available
for kea-dhcp6.
"raw" socket support relies on Kea capturing Ethernet frames directly at
Layer 2
of the OSI model; tun0 is a layer three interface.
/Peter
On 19/06/2025 11.16, Jaco Kroon wrote:
Hi Peter,
Is there an explanation of why when binding to tun0/172.17.0.0 and
using raw sockets the frame isn't received? Two specific notes for
this which may be relevant.
1. tun0 isn't ethernet.
2. In this case there are external nodes connecting to the "local"
node using tinc (not my choice) and then does a dhcp relay already.
Is there a possibility of making it such that if the interface is
ethernet then to use "raw" otherwise use "udp", even perhaps as
special "dhcp-socket-type" of say "etherraw" or some other phrase that
makes sense?
Being the author of dhcpv6relay plugin in pppd, and having seen how
tricky it can be to receive multicast traffic I get that raw sockets
may be a "simple" solution, but is there honestly no way to set a udp
socket to receive broadcast traffic? Even for 0.0 to
255.255.255.255? Description for SO_BROADCAST seems to relate more to
sending rather than receiving, but frankly, it seems odd that raw
sockets are required for receiving broadcast packets.
Yes, DHCPv6 is multicast not broadcast, so I may well be missing the
mark completely ...
Kind regards,
Jaco
On 2025/06/19 10:47, Peter Davies wrote:
Hi Jaco,
I am afraid it is not possible to mix the "udp" and "raw" socket
types.
The "interfaces-config"."interfaces" contain a list of interfaces
with an optional
IP address for Kea to listen to.
The "interface-config"."dhcp-socket-type" option contains information
about the
socket type to use.
Kea will not load a configuration containing multiple occurrences of
"interfaces-config".
If you need to mix socket types, you will need to run multiple Kea
processes.
Alternately, you could investigate the possibility of relaying the
local broadcast
traffic and using the "udp" socket type.
/Peter
On 18/06/2025 15.26, Jaco Kroon wrote:
Hi All,
ISC dhcpd always refused to bind non-ethernet sockets. Which was
fine, but resulted in some issues.
I'm now in a situation where I've got a setup where I've got a
couple of local interfaces (ethernet), which needs to bind raw, and
then a tun0 interface which is not ethernet, and based on testing
have to use udp sockets else kea-dhcp4 will not receive the incoming
(relayed) DHCP frames.
Is there any way to mix and match socket types within a single
kea-dhcp4 instance?
"interfaces": [ "tun0/172.17.0.0", "eth0", "eth1" ]
Is the current setup, and eth* works when "dhcp-socket-type":"raw",
and "tun0/..." when "dhcp-socket-type":"udp".
Suggestions and ideas?
Kind regards,
Jaco
--
Peter Davies
Support Engineer
Internet Systems Corporation
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