netbsd-8: panic: sockaddr_copy: source too long, 28 < 128 bytes

[Paul Ripke <stix%stix.id.au@localhost>]

I'm running netbsd-8 synced as of ~2018-10-30, and am continuing to
get occasional panics, about once a week on the prior kernel, and
another just now. Is this familiar to anybody? Core on hand, pointers
on what to look at appreciated.

NetBSD slave 8.0_STABLE NetBSD 8.0_STABLE (SLAVE) #1: Tue Oct 30 07:40:01 AEDT 2018  stix@slave:/home/netbsd/netbsd-8/obj.amd64/home/netbsd/netbsd-8/src/sys/arch/amd64/compile/SLAVE amd64

Nov  5 12:09:59 slave /netbsd: panic: sockaddr_copy: source too long, 28 < 128 bytes
Nov  5 12:09:59 slave /netbsd: cpu0: Begin traceback...
Nov  5 12:09:59 slave /netbsd: vpanic() at netbsd:vpanic+0x15d
Nov  5 12:09:59 slave /netbsd: snprintf() at netbsd:snprintf
Nov  5 12:09:59 slave /netbsd: sockaddr_copy() at netbsd:sockaddr_copy+0x7f
Nov  5 12:09:59 slave /netbsd: rtcache_setdst() at netbsd:rtcache_setdst+0x5d
Nov  5 12:09:59 slave /netbsd: rtcache_lookup2() at netbsd:rtcache_lookup2+0x5e
Nov  5 12:09:59 slave /netbsd: in6_selectroute() at netbsd:in6_selectroute+0x15a
Nov  5 12:09:59 slave /netbsd: in6_selectsrc() at netbsd:in6_selectsrc+0x100
Nov  5 12:09:59 slave /netbsd: udp6_output() at netbsd:udp6_output+0x246
Nov  5 12:09:59 slave /netbsd: udp6_send_wrapper() at netbsd:udp6_send_wrapper+0x51
Nov  5 12:09:59 slave /netbsd: sosend() at netbsd:sosend+0x77f
Nov  5 12:09:59 slave /netbsd: do_sys_sendmsg_so() at netbsd:do_sys_sendmsg_so+0x26d
Nov  5 12:09:59 slave /netbsd: do_sys_sendmsg() at netbsd:do_sys_sendmsg+0x85
Nov  5 12:09:59 slave /netbsd: sys_sendto() at netbsd:sys_sendto+0x5c
Nov  5 12:09:59 slave /netbsd: syscall() at netbsd:syscall+0x1ec
Nov  5 12:09:59 slave /netbsd: --- syscall (number 133) ---
Nov  5 12:09:59 slave /netbsd: 7db02a8eea4a:
Nov  5 12:09:59 slave /netbsd: cpu0: End traceback...

(gdb) p *src                                                                                                               
$3 = {
  sa_len = 128 '\200', 
  sa_family = 24 '\030', 
  sa_data = "\254\005\000\000\000\000 \001A\320\000\n^\207"
}

-- 
Paul Ripke
"Great minds discuss ideas, average minds discuss events, small minds
 discuss people."
-- Disputed: Often attributed to Eleanor Roosevelt. 1948.