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Date:      Wed, 07 Nov 2018 18:02:56 +0000
From:      bugzilla-noreply@freebsd.org
To:        net@FreeBSD.org
Subject:   [Bug 227720] Kernel panic in ppp server
Message-ID:  <bug-227720-7501-omh0Qlsegj@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-227720-7501@https.bugs.freebsd.org/bugzilla/>
References:  <bug-227720-7501@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D227720

Franck Rousseau <Franck.Rousseau@imag.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |Franck.Rousseau@imag.fr

--- Comment #35 from Franck Rousseau <Franck.Rousseau@imag.fr> ---
Hi everyone, same kind of crash here on a 11.2-RELEASE-p4, it also crashes =
on
11.2-RELEASE, but it seems to be a long standing bug, we had similar issues=
 on
previous versions. I only have the crash logs for this latest release.

# uname -a
FreeBSD testpc 11.2-RELEASE-p4 FreeBSD 11.2-RELEASE-p4 #0: Thu Sep 27 08:16=
:24
UTC 2018     root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERI=
C=20
amd64
# dmidecode -s system-product-name
OptiPlex 7010
# sysctl hw.model
hw.model: Intel(R) Core(TM) i5-3570 CPU @ 3.40GHz

The crash occurs when we play with forwarding, a PPP server and ARP proxy, =
but
unfortunately we do not have a very precise procedure to reproduce it, also=
 it
crashes very consistently. We use FreeBSD for educational purposes, doing
practical work in computer networking. This is a simple setup where we use 3
computers, configure PC1 as a PPP client, that connects to PC2 that is a PPP
server and ARP proxy for PC1, and we finally check the IP connectivity from=
 PC3
that is on the same Ethernet LAN as PC2 and observe ARP activity.=20

If we activate forwarding, start the PPP server, connect the client, add an=
 ARP
published entry, it works ok as long as there is no mistake done (although I
cannot guarantee that it would run for hours). But when students make sever=
al
wrong tries, stop ppp, play with arp, restart ppp, at some point it crashes=
 (we
had dozens of crashes). It is rather easy to provoke this crash as I did to=
 get
the crash log, although there are various symptoms: ppp server not accepting
connections anymore unless we reboot, arp failing with socket memory error,
etc. until it crashes at some point. Quite hard to track this one down...

This bug seems to be somewhat similar to bug #230498 with the same location=
 and
cause.

The ppp client and server configs are trivial, over a serial line, plus pro=
xy
arp (arp -s 192.168.0.1 <eth@> pub)

default:
 set log Phase Chat LCP IPCP CCP tun command
 set device /dev/cuau0
 set speed 9600
 set accmap 000a0000
 set ctsrts off
 set cd off
 set timeout 0
server:
 set ifaddr 192.168.0.2 192.168.0.1 255.255.255.255

Here is the backtrace, I can provide the crash image and kernel.debug if
needed.

(kgdb) bt
#0  doadump (textdump=3D<value optimized out>) at pcpu.h:229
#1  0xffffffff80af673b in kern_reboot (howto=3D260) at
/usr/src/sys/kern/kern_shutdown.c:383
#2  0xffffffff80af6b61 in vpanic (fmt=3D<value optimized out>, ap=3D<value
optimized out>) at /usr/src/sys/kern/kern_shutdown.c:776
#3  0xffffffff80af69a3 in panic (fmt=3D<value optimized out>) at
/usr/src/sys/kern/kern_shutdown.c:707
#4  0xffffffff80f77fdf in trap_fatal (frame=3D0xfffffe04688ae320, eva=3D0) =
at
/usr/src/sys/amd64/amd64/trap.c:875
#5  0xffffffff80f78039 in trap_pfault (frame=3D0xfffffe04688ae320, usermode=
=3D0) at
pcpu.h:229
#6  0xffffffff80f77807 in trap (frame=3D0xfffffe04688ae320) at
/usr/src/sys/amd64/amd64/trap.c:415
#7  0xffffffff80f57fbc in calltrap () at
/usr/src/sys/amd64/amd64/exception.S:231
#8  0xffffffff80c0ce96 in sysctl_dumpentry (rn=3D0xfffff8000bc48410,
vw=3D0xfffffe04688ae690) at /usr/src/sys/net/rtsock.c:1559
#9  0xffffffff80c07aa0 in rn_walktree (h=3D<value optimized out>, f=3D<value
optimized out>, w=3D<value optimized out>)
    at /usr/src/sys/net/radix.c:1094
#10 0xffffffff80c0c7ff in sysctl_rtsock (oidp=3D<value optimized out>,
arg1=3D<value optimized out>, arg2=3D<value optimized out>,=20
    req=3D<value optimized out>) at /usr/src/sys/net/rtsock.c:1916
#11 0xffffffff80b03ccb in sysctl_root_handler_locked (oid=3D0xffffffff81a33=
f38,
arg1=3D0xfffffe04688ae908, arg2=3D4, req=3D0xfffffe04688ae840,=20
    tracker=3D0xfffffe04688ae7b8) at /usr/src/sys/kern/kern_sysctl.c:165
#12 0xffffffff80b03521 in sysctl_root (arg1=3D0xfffffe04688ae908, arg2=3D4)=
 at
/usr/src/sys/kern/kern_sysctl.c:1915
#13 0xffffffff80b03a46 in userland_sysctl (td=3D<value optimized out>,
name=3D0xfffffe04688ae900, namelen=3D6, old=3D0x0,=20
    oldlenp=3D<value optimized out>, inkernel=3D<value optimized out>, new=
=3D0x0,
newlen=3D0, retval=3D0xfffffe04688ae968, flags=3D0)
    at /usr/src/sys/kern/kern_sysctl.c:2011
#14 0xffffffff80b038cf in sys___sysctl (td=3D0xfffff80098410000,
uap=3D0xfffff80098410538) at /usr/src/sys/kern/kern_sysctl.c:1945
#15 0xffffffff80f79068 in amd64_syscall (td=3D0xfffff80098410000, traced=3D=
0) at
subr_syscall.c:132
#16 0xffffffff80f5880d in fast_syscall_common () at
/usr/src/sys/amd64/amd64/exception.S:479
#17 0x0000000801de047a in ?? ()
(kgdb) f 8=20=20=20
#8  0xffffffff80c0ce96 in sysctl_dumpentry (rn=3D0xfffff8000bc48410,
vw=3D0xfffffe04688ae690) at /usr/src/sys/net/rtsock.c:1559
1559                    info.rti_info[RTAX_IFP] =3D
rt->rt_ifp->if_addr->ifa_addr;
(kgdb) p rt->rt_ifp->if_addr
$1 =3D (struct ifaddr *) 0x0

--=20
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