Error "security check failed: NULL To Header" when running siproxd

Hi,

we're trying to run siproxd as proxy for an Asterisk server running
behind a NAT in a private IP range. Asterisk runs on a Linux
(Eisfair) machine, while the NAT router running siproxd is a
NetBSD Sparc64 machine. siproxd (0.5.13 as well as 0.6.0) and
libosip2-2.2.2 compiled without problems.

The NAT router connects the internal network (192.168.1.x,
interface hme0) to the Internet (DSL using pppoe with dynamic
addresses and dyndns service, interface pppoe0). Port 5060
(outgoing) is redirected on the router using the rule

rdr hme0 0/0 port 5060 -> 127.0.0.1 port 5060 tcp/udp

in /etc/ipnat.conf, incoming ports 5060 as well as
10000-20000 are redirected to the Asterisk server:

rdr pppoe0 0/0 port 5060-5065 -> 192.168.1.200 port 5060 tcp/udp
rdr pppoe0 0/0 port 10000-20000 -> 192.168.1.200 port 10000 tcp/udp

Now, whenever the Asterisk server tries to register with a
provider (in the example below it's T-Online, but sipgate and
gmx cause the same problem), I get an error message:

security check failed: NULL To Header

This happens with siproxd versions 0.5.13 and 0.6.0. As far
as I can see from the packet log, there is a valid "To" header
field, so I suspect s.th. else may fail here (64 bit perhaps?
Big endian byte order? gcc is version 3.3.3)... any ideas?

I've attached the log excerpt and the config file below, if you
require more information please let me know...

Btw., we're mainly setting this up because gmx VoIP doesn't
seem to work with the NATed configuration (T-Online and
sipgate actually work for incoming as well as outgoing calls
without using a proxy). Do you have any experience running
siproxd against gmx?

-- Michael

02:19:01 ERROR:security.c:268 security check failed: NULL To Header
02:19:01 ERROR:siproxd.c:348 security_check_sip() failed... this is  
not good
---BUFFER DUMP follows---
   52 45 47 49 53 54 45 52 20 73 69 70 3a 74 65 6c REGISTER sip:tel
   2e 74 2d 6f 6e 6c 69 6e 65 2e 64 65 20 53 49 50 .t-online.de SIP
   2f 32 2e 30 0d 0a 56 69 61 3a 20 53 49 50 2f 32 /2.0..Via: SIP/2
   2e 30 2f 55 44 50 20 38 34 2e 31 36 35 2e xx xx .0/UDP 84.165.xx
   2e xx xx xx 3a 35 30 36 30 3b 62 72 61 6e 63 68 .xxx:5060;branch
   3d 7a 39 68 47 34 62 4b 35 64 64 63 61 38 37 62 =z9hG4bK5ddca87b
   3b 72 70 6f 72 74 0d 0a 46 72 6f 6d 3a 20 3c 73 ;rport..From: <s
   69 70 3a 30 33 32 32 32 39 32 xx xx xx xx xx xx ip:032229xxxxxx@
   74 65 6c 2e 74 2d 6f 6e 6c 69 6e 65 2e 64 65 3e tel.t-online.de>
   3b 74 61 67 3d 61 73 31 39 62 62 63 38 33 36 0d ;tag=as19bbc836.
   0a 54 6f 3a 20 3c 73 69 70 3a 30 33 32 32 32 39 .To: <sip:032229
   xx xx xx xx xx xx 40 74 65 6c 2e 74 2d 6f 6e 6c xxxxxx-0d41nNEFMzlmR6Xm/[email protected]
   69 6e 65 2e 64 65 3e 0d 0a 43 61 6c 6c 2d 49 44 ine.de>..Call-ID
   3a 20 37 66 63 36 63 62 66 32 34 30 34 35 62 62 : 7fc6cbf24045bb
   33 37 30 31 36 66 63 66 30 38 33 65 64 39 33 66 37016fcf083ed93f
   62 32 40 31 39 32 2e 31 36 38 2e 31 2e 32 30 30 b2-Q0ErXNX1Rubdv/[email protected]
   0d 0a 43 53 65 71 3a 20 31 30 36 20 52 45 47 49 ..CSeq: 106 REGI
   53 54 45 52 0d 0a 55 73 65 72 2d 41 67 65 6e 74 STER..User-Agent
   3a 20 41 73 74 65 72 69 73 6b 20 50 42 58 0d 0a : Asterisk PBX..
   4d 61 78 2d 46 6f 72 77 61 72 64 73 3a 20 37 30 Max-Forwards: 70
   0d 0a 45 78 70 69 72 65 73 3a 20 33 36 30 30 0d ..Expires: 3600.
   0a 43 6f 6e 74 61 63 74 3a 20 3c 73 69 70 3a 30 .Contact: <sip:0
   33 32 32 32 39 32 39 33 39 31 33 40 38 34 2e 31 [email protected]
   36 35 2e xx xx 2e xx xx xx 3e 0d 0a 45 76 65 6e 65.xx.xxx>..Even
   74 3a 20 72 65 67 69 73 74 72 61 74 69 6f 6e 0d t: registration.
   0a 43 6f 6e 74 65 6e 74 2d 4c 65 6e 67 74 68 3a .Content-Length:
   20 30 0d 0a 0d 0a                                0....

---end of BUFFER DUMP---

config:

if_inbound  = hme0
if_outbound = pppoe0
hosts_allow_reg = 192.168.1.0/24
hosts_allow_sip = 192.168.1.0/24
sip_listen_port = 5060
daemonize = 0
silence_log = 0
log_calls = 1
user = nobody
registration_file = /var/run/siproxd/siproxd_registrations
pid_file = /var/run/siproxd/siproxd.pid
rtp_proxy_enable = 1
rtp_port_low  = 10000
rtp_port_high = 20000
rtp_timeout = 300
default_expires = 600
debug_level = 0xffffffff
debug_port = 0


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