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]

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

Post by 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

[Udo van den Heuvel]

Hello,

Post by Rob Janssen
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.

Post by Udo van den Heuvel
Hello,

Post by Rob Janssen
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
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[Udo van den Heuvel]

Hello,

Post by 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.

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

Kind regards,
Udo
_______________________________________________
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dhcp-users mailing list
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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

Post by 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
_______________________________________________
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
https://lists.isc.org/mailman/listinfo/dhcp-users

_______________________________________________
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
dhcp-***@lists.isc.org
https://lists.isc.org/mailman/listinfo/dhcp-users