"panic: ipintr no HDR" when attempting to connect OpenBSD running l2tp/IPsec
I ran into this issue last night when I was testing out a trivial VPN
config & assumed it may have been related to virtualbox but I've just
replicated it on a ThinkPad X60s.
panic: ipintr no HDR
Stopped at Debugger+0x7: leave
Tid PID UID PRFLAGS PFLAGS CPU COMMAND
21363 21363 82 0x10 0 1 npppd
Debugger ( ) at Debugger+0x7
panic( ) at panic+0x71
ipintr( ) at ipintr+0x34
netintr( ) at netintr+0x78
softintr_dispatch(1) at softintr_dispatch+0x5f
Xsoftnet() at Xsoftnet+0x12
Confirmed issue on 5.8-RELEASE amd64, the -current snapshot from
yesterday #1575 (2/12/2015) (SP kernel) on virtualbox 5 and the i386
snapshot from 14/11/2015 #1378 (SMP kernel) on a ThinkPad X60s.
In each case no changes were made to the default OpenBSD install other
than assigning a IP address to network interface, adding a user to
/etc/npppd/nppd-users & adding a ipsec.conf.
ike passive esp transport proto udp from 220.127.116.11 to any port 1701 \
main auth "hmac-sha1" enc "3des" group modp1024 psk "password".
(have to use these crypto settings because it's not possible to
connect from a manually configured VPN on OS X otherwise, it's just
for my testing purposes to "succeed", not what's used in production).
ipsecctl -f /etc/ipsec.conf
On OS X (tested with 10.11.1)
System Preferences > Network, add a L2TP over IPsec VPN, fill in the
username, password & psk. hit connect.
Upon establishing a connecting succesfully, OS X will start the timer
& display the I/O indicator at which point OpenBSD will have panicked.