DHCP packets dropped when repeated on LAN

[kenworth]

Hi folks,
This may or may not be related to my Asus router config or the latest Merlin code I'm running on it, but thought I would give it a shot. I have been experiencing significant RX packet drops on my Linux server which I recently upgraded from Fedora 18 to 20. Am seeing tens of thousands of drops per day. I have been able to trace the source of at least some of these drops to DHCP request packets originating on the wireless network and then being repeated on the LAN. In every case the Linux kernel will drop these packets, but for the same packets originating on the wired LAN it just ignores them. The only DHCP server on my network is on the Asus router (RT-AC66U) running Merlin 3.0.0.4.374.39. The router is set up in a standard AP configuration and one subnet across both wireless and LAN.

Any suggestions would be greatly appreciated. Thanks

 

[kenworth]

SOLVED: DHCP packets dropped when repeated on LAN

Solved the problem with the DHCP request packets coming from the wireless network. They must have been tagged with a VLAN id, and I did not have the 8021q module loaded in the kernel. Recent changes to the kernel now increment the rx_dropped counter under the following conditions:

- softnet backlog full (accounted in /proc/net/softnet_stat)
- bad vlan tag (not accounted)
- unknown/unregistered protocol (not accounted)

Issuing a modprobe 8021q resolves the issue.