You need to compile rp-l2tpd with debugging symbols and run it under gdb. When it segfaults, type "where" in gdb and e-mail me the output.
OK. I never do it before, so please correct me if I do something wrong.
./configure --enable-debug=yes make gdb
(gdb) file /home/install/l2tpd/rp-l2tp-0.3/l2tpd
Reading symbols from /home/install/l2tpd/rp-l2tp-0.3/l2tpd...done.
(gdb) set args -f -d 255
(gdb) show args
Argument list to give program being debugged when it is started is "-f -d 255".
(gdb) run
Starting program: /home/install/l2tpd/rp-l2tp-0.3/l2tpd -f -d 255
0.000 dgram_take_from_wire() -> type=SCCRQ, tid=0, sid=0, Nr=0, Ns=0
0.000 tunnel_new() -> 6191/0
Error: Peer 192.168.99.2 is not authorized to create a tunnel
0.000 tunnel_send_StopCCN(6191/26, 4, 0, Peer 192.168.99.2 is not authorized to create a tunnel)
Program received signal SIGSEGV, Segmentation fault. 0x0804bca3 in l2tp_dgram_add_avp (dgram=0x8059a08, tunnel=0x80597d0, mandatory=1, len=2, vendor=0, type=9, val=0xbffff80a) at dgram.c:603 603 if (tunnel &&
(gdb) where #0 0x0804bca3 in l2tp_dgram_add_avp (dgram=0x8059a08, tunnel=0x80597d0, mandatory=1, len=2, vendor=0, type=9, val=0xbffff80a) at dgram.c:603 #1 0x08050eb1 in tunnel_send_StopCCN (tunnel=0x80597d0, result_code=4, error_code=0, fmt=0x805572d "%s") at tunnel.c:1023 #2 0x08051598 in tunnel_set_params (tunnel=0x80597d0, dgram=0x80587a8) at tunnel.c:1359 #3 0x080507cb in tunnel_handle_SCCRQ (dgram=0x80587a8, es=0x8057b10, from=0xbffffa00) at tunnel.c:751 #4 0x0805044c in l2tp_tunnel_handle_received_control_datagram ( dgram=0x80587a8, es=0x8057b10, from=0xbffffa00) at tunnel.c:619 #5 0x0804dc3a in network_readable (es=0x8057b10, fd=9, flags=1, data=0x0) at network.c:134 #6 0x0805250e in Event_HandleEvent (es=0x8057b10) at event.c:208 #7 0x0804cce9 in main (argc=4, argv=0xbffffc24) at main.c:116 #8 0x420158d4 in __libc_start_main () from /lib/i686/libc.so.6
Hope it's that you looking for.
Regards.