Properly stop timer before freeing link level entries for IPv4 and IPv6

[• hselasky]

Summary

By running the following commands link level entries will leak.
This in particular causes a panic when ejecting USB type of ethernet devices.

DEF_ROUTE=x.x.x.x # replace with IP of your default route
vmstat -m | grep llt
arp -d $DEF_ROUTE
ping $DEF_ROUTE
vmstat -m | grep llt
arp -d $DEF_ROUTE
ping $DEF_ROUTE

Fix problem by adding missing callout_stop() calls.
Technically a callout_drain() call is required, though this patch is better than nothing.

[• hselasky]

Need to check for LLE_LINKED at entry of callout function. Seems some code path is not stopping the callouts!

[• hselasky]

I'm currently investigating the call to arptimer when LLE_LINKED is not set, who is not clearing the timer.

[• hselasky]

Here goes:

lltable_delete_addr() will unlink the entry and try to delete it, but doesn't stop the callout.

For example reproduce using the default route x.x.x.x:

vmstat -m | grep llt
arp -d x.x.x.x
ping x.x.x.x
vmstat -m | grep llt
arp -d x.x.x.x
ping x.x.x.x

I observe that the number of llt allocations doesn't drop after the deletion, which means the timer for the unlinked entry still has one reference which appears to be causing this arptimer panic.

[• hselasky]

Need to stop timer when deleting arp table entries.

[• hselasky]

Ping - any reviewers active on this one?

[melifaro]

In D4605#102190, @hselasky wrote:

Ping - any reviewers active on this one?

sorry, will take a look today.

[• hselasky]

Update patch to match 12-current.

[• hselasky]

Ping - this is still an issue in 12-current when yanking USB network devices.

[• hselasky]

Update patch for 12-current

[loos]

We run a similar fix in pfSense for quite some time now.