netbsd-7 panic in rn_walknext via sysctl and rtsock

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

With a kernel from 2018-11-01 netbsd-7 sources:

(gdb) bt
#0  0xffffffff8065d56f in cpu_reboot (howto=howto@entry=260,
    bootstr=bootstr@entry=0x0)
    at /usr/src/7.0/sys/arch/amd64/amd64/machdep.c:671
#1  0xffffffff80894242 in vpanic (fmt=fmt@entry=0xffffffff80d50632 "trap",
    ap=ap@entry=0xfffffe813a780a60) at /usr/src/7.0/sys/kern/subr_prf.c:340
#2  0xffffffff808942fd in panic (fmt=fmt@entry=0xffffffff80d50632 "trap")
    at /usr/src/7.0/sys/kern/subr_prf.c:256
#3  0xffffffff808d7676 in trap (frame=0xfffffe813a780b80)
    at /usr/src/7.0/sys/arch/amd64/amd64/trap.c:304
#4  0xffffffff80100f26 in alltraps ()
#5  0xffffffff807aece4 in rn_walknext (printer=0x0, arg=0x0,
    rn=0x3a77b79e61ff6d35) at /usr/src/7.0/sys/net/radix.c:959
#6  rn_walktree (h=<optimized out>,
    f=f@entry=0xffffffff807f7d70 <rt_walktree_visitor>,
    w=w@entry=0xfffffe813a780ca8) at /usr/src/7.0/sys/net/radix.c:992
#7  0xffffffff807f7ea2 in rt_walktree (family=family@entry=2 '\002',
    f=f@entry=0xffffffff807fe930 <sysctl_dumpentry>,
    v=v@entry=0xfffffe813a780d08) at /usr/src/7.0/sys/net/rtbl.c:204
#8  0xffffffff807fee7f in sysctl_rtable (name=0xfffffe813a780e5c,
    namelen=<optimized out>, oldp=0x1bcad2000, oldlenp=0xfffffe813a780e48,
    newp=<optimized out>, newlen=<optimized out>, oname=0xfffffe813a780e50,
    l=0xfffffe8831a25240, rnode=0xfffffe813a5bf008)
    at /usr/src/7.0/sys/net/rtsock.c:1417
#9  0xffffffff806035ac in sysctl_dispatch (name=name@entry=0xfffffe813a780e50,
    namelen=6, oldp=0x1bcad2000, oldlenp=oldlenp@entry=0xfffffe813a780e48,
    newp=0x0, newlen=0, oname=oname@entry=0xfffffe813a780e50,
    l=l@entry=0xfffffe8831a25240, rnode=0xfffffe813a5bf008, rnode@entry=0x0)
    at /usr/src/7.0/sys/kern/kern_sysctl.c:451
#10 0xffffffff80603724 in sys___sysctl (l=0xfffffe8831a25240,
    uap=0xfffffe813a780f00, retval=<optimized out>)
    at /usr/src/7.0/sys/kern/kern_sysctl.c:307
#11 0xffffffff808af2ca in sy_call (rval=0xfffffe813a780eb8,
    uap=0xfffffe813a780f00, l=0xfffffe8831a25240,
    sy=0xffffffff81043580 <sysent+3232>)
    at /usr/src/7.0/sys/sys/syscallvar.h:61
#12 sy_invoke (code=202, rval=0xfffffe813a780eb8, uap=0xfffffe813a780f00,
    l=0xfffffe8831a25240, sy=0xffffffff81043580 <sysent+3232>)
    at /usr/src/7.0/sys/sys/syscallvar.h:85
#13 syscall (frame=0xfffffe813a780f00)
    at /usr/src/7.0/sys/arch/x86/x86/syscall.c:156
#14 0xffffffff80100691 in Xsyscall ()


#5  0xffffffff807aece4 in rn_walknext (printer=0x0, arg=0x0,
    rn=0x3a77b79e61ff6d35) at /usr/src/7.0/sys/net/radix.c:959
959                     rn = rn->rn_l;


#10 0xffffffff80603724 in sys___sysctl (l=0xfffffe8831a25240,
    uap=0xfffffe813a780f00, retval=<optimized out>)
    at /usr/src/7.0/sys/kern/kern_sysctl.c:307
307             error = sysctl_dispatch(&name[0], SCARG(uap, namelen),
(gdb) print name[0]
$3 = 4

I have a core, any suggestions on what to get from gdb?

--
Stephen