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Bug #9466

DHCP (IPv4) relay mistakenly listening on upstream interface

Added by Foster Snowhill 3 months ago. Updated about 2 months ago.

Status:
Feedback
Priority:
Normal
Assignee:
Category:
DHCP Relay
Target version:
Start date:
04/10/2019
Due date:
% Done:

100%

Estimated time:
Affected Version:
All
Affected Architecture:

Description

Hello!

Not sure if this is dhcrelay's intended behaviour, but it is listening on the upstream interface when it's not asked to, and thus duplicates packets coming from inside the upstream network.

My interfaces:

  • LAN_TN = lan = vmx0 (192.168.2.1/24)
  • LAN_UN = opt3 = vmx0.10 (192.168.3.1/24)
  • LAN_Docker = opt7 = vmx0.20 (192.168.6.1/24)

DHCP relay is configured as shown in the attached relay_config.png. Config.xml looks like this:

<dhcrelay>
    <interface>opt7,opt3</interface>
    <server>192.168.2.8</server>
    <agentoption></agentoption>
    <enable></enable>
</dhcrelay>

However it starts up listening on the upstream as well:

/usr/local/sbin/dhcrelay -i vmx0.20 -i vmx0.10 -i vmx0 -a -m replace 192.168.2.8

which causes it to catch the broadcast packets on the upstream network and duplicate those requests, as seen on packets.png. pfSense 2.4.4-p2 running on amd64, ESXi VM.

Not critical im my setup, but might be problematic for those whose upstream DHCP server is located on the WAN, for example.

packets.png (15.7 KB) packets.png Duplicated packets as seen from the client Foster Snowhill, 04/10/2019 08:54 AM
relay_config.png (30.4 KB) relay_config.png DHCP relay configuration in web UI Foster Snowhill, 04/10/2019 08:54 AM

Associated revisions

Revision f427d68d (diff)
Added by Jim Pingle about 2 months ago

Teach dhcrelay about upstream and downstream interfaces. Fixes #9466

No config changes or UI changes, it is handled automatically.

Revision ef0045d8 (diff)
Added by Jim Pingle about 2 months ago

Teach dhcrelay about upstream and downstream interfaces. Fixes #9466

No config changes or UI changes, it is handled automatically.

(cherry picked from commit f427d68dbca5ed9941b3bc01be1c4d81417c134f)

History

#1 Updated by Jim Pingle 3 months ago

  • Assignee set to Jim Pingle
  • Target version set to 2.5.0
  • Affected Version changed from 2.4.4_2 to All

Once upon a time that was necessary to see the return traffic. The most recent version of dhcrelay now supports a concept of separate upstream (-iu) and downstream (-id) interfaces so the syntax should be updated to follow that convention. Hopefully that will take care of this.

#2 Updated by Jim Pingle about 2 months ago

  • Status changed from New to Feedback
  • % Done changed from 0 to 100

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