Monitor kernel variable with ddb(4)

[Andriy Voskoboinyk]

Sat, 12 Aug 2017 22:42:21 +0300 було написано Farhan Khan
<khanzf at gmail.com>:

> Hi all,
>
> I am trying to figure out where a net80211's vap flags are modified. I  
> see
> that memory is originally allocated here:
> http://src.illumos.org/source/xref/freebsd-head/sys/net/if.c#445.  
> However,
> I cannot figure out where the ifp->if_flags and if->if_drv_flags are ever
> modified in the kernel.
>
> Someone suggested using ddb(4), so I entered the live debugger using  
> sysctl
> debug.kdb.enter=1
>
> I then set a breakpoint at if_alloc.
>
> However, I cannot seem to figure out the next steps to monitor where the
> ifp->if_flags or if->if_drv_flags are updated.
>
> Full explanation - My kernel module is immediately unloading, but I am  
> not
> certain why. I traced it back in the ieee80211 code to those flags, but  
> not
> sure where they are updated.
>
> Any ideas? Thank you!

Hi,

You can use 'show all vaps/a' command to show all currently existing vaps
(see ieee80211_ddb(9) for other commands).