[Bug 230498] Fatal trap 12: page fault while in kernel mode in sysctl_dumpentry from sysctl NET_RT_DUMP

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=230498

--- Comment #20 from Franck Rousseau <Franck.Rousseau at imag.fr> ---
(In reply to commit-hook from comment #19)

As mentioned in comment #9 above, this patch breaks ppp, I get this when trying
to re-open a second connection, this is the stage at which the crash occured
before:
    PPp ON localhost> Warning: iface add: ioctl(SIOCAIFADDR, 192.168.0.2 ->
192.168.0.1): File exists
    Error: ipcp_InterfaceUp: unable to set ip address

Also, the patch in attachment #199450 does not fix this specific problem, we
still crash the kernel with the procedure described earlier in comment #12. As
I said, I could narrow down the cause and find a fix for our use case, by using
two different IPv4 addresses for Ethernet and PPP tun interfaces the kernel
does not crash anymore.

About the fix, I suspect that internal structures are corrupted, so any kind of
fix at this point will fail, for example with this patch on 11.2-p4 it looks
like I keep getting these values after the crash:

(kgdb) print rt->rt_ifp->if_flags
$3 = 3
(kgdb) print rt->rt_ifp->if_index
$4 = 63488

I will try to setup on-line debugging to watch internal structures and see if I
can get an idea of what is breaking things up.

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