dhclient -P -6 ppp0 does not receive dhcp-server responses

[Udo van den Heuvel]

Hello,

We run fedora 34 on our boxes.
Dhclient stopped receiving responses from dhcp-server.
Dhclient only logs XMT steps.
This happens even with the (ipv6) firewall disabled.
Tcpdump shows the responses arriving.
Because of this I created bug
https://bugzilla.redhat.com/show_bug.cgi?id=1956209.

How can I investigate this issue further and fix it?

Kind regards,
Udo
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[Rob Janssen-2]

I think there is an error in your firewall.
You have "removed all rules for testing", but the policy is set to DROP.

# ip6tables -L -v -n -x
Chain INPUT (policy DROP 211 packets, 57041 bytes)
    pkts      bytes target     prot opt in     out     source               destination         

This means that ALL traffic will be dropped.

You need to do "ip6tables -P INPUT ACCEPT" and test again.

Rob

On 5/19/21 4:00 PM, Udo van den Heuvel wrote:

Hello,

We run fedora 34 on our boxes.
Dhclient stopped receiving responses from dhcp-server.
Dhclient only logs XMT steps.
This happens even with the (ipv6) firewall disabled.
Tcpdump shows the responses arriving.
Because of this I created bug https://bugzilla.redhat.com/show_bug.cgi?id=1956209.

How can I investigate this issue further and fix it?

Kind regards,
Udo

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[Udo van den Heuvel]

Hello,

On 19-05-2021 16:19, Rob Janssen wrote:
> ip6tables -P INPUT ACCEPT


Did that but no change.

Kind regards,
Udo
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[Michael De Roover]

Fedora uses firewalld alongside iptables I believe, maybe that's
blocking it. It tripped me up for a few days on another service too.

On Wed, 2021-05-19 at 16:26 +0200, Udo van den Heuvel wrote:

> Hello,
>
> On 19-05-2021 16:19, Rob Janssen wrote:
> > ip6tables -P INPUT ACCEPT
>
> Did that but no change.
>
> Kind regards,
> Udo
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users

--
Michael De Roover <[hidden email]>

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[Udo van den Heuvel]

Hello,

On 19-05-2021 16:31, Michael De Roover wrote:
> Fedora uses firewalld alongside iptables I believe, maybe that's
> blocking it. It tripped me up for a few days on another service too.

No firewalld found.
We use a derivative of the old ADSL4Linux firewall.

Kind regards,
Udo
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[Udo van den Heuvel]

Hello,

I found something weird.
I was playing around with the IPv6 side of the ethernet interface that
is the connection to the vdsl modem, and thus carries the PPPoE
connection, etc.
I removed IPv6 from the ethernet interface and also from the vlan
interface over this ethernet.
After restarting pppd (?) I suddenly received responses to dhclient's
prefix requests. (as this sequence (re)starts dhclient and then radvd)

So yes, a bit hairy but I think i got a solution now.
I will close the bug with redhat.
Thank you for thinking about this issue.

Kind regards,
Udo


On 19-05-2021 16:00, Udo van den Heuvel wrote:

> Hello,
>
> We run fedora 34 on our boxes.
> Dhclient stopped receiving responses from dhcp-server.
> Dhclient only logs XMT steps.
> This happens even with the (ipv6) firewall disabled.
> Tcpdump shows the responses arriving.
> Because of this I created bug
> https://bugzilla.redhat.com/show_bug.cgi?id=1956209.
>
> How can I investigate this issue further and fix it?
>
> Kind regards,
> Udo
> _______________________________________________
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> dhcp-users mailing list
> [hidden email]
> https://lists.isc.org/mailman/listinfo/dhcp-users

_______________________________________________
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