### Description Kamailio has two IP interfaces: one (192.168.0.206) towards the Internet-based endpoints and the second (10.197.184.1) - toward my internal SIP servers. I am trying to disable the topology hiding when the messages are sent to my internal SIP servers. In order to achieve this, I added the special event_route block: ``` event_route[topoh:msg-outgoing] {      if ($sndfrom(ip) == "10.197.184.1" ) {         drop;      } } ``` The problem is that the topoh module generates ERROR when trying to parse the response for the "dropped" request: ``` Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [th_msg.c:401]: th_unmask_via(): =======via[1] Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [th_msg.c:402]: th_unmask_via(): hdr: [Via] Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [th_msg.c:404]: th_unmask_via(): body: 100: [SIP/2.0/UDP 10.197.184.1;branch=z9hG4bK3fe4.fc634d55237786cb052f1c0d4fd7d949.0;received=10.197.184.1] Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [th_msg.c:401]: th_unmask_via(): =======via[2] Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [th_msg.c:402]: th_unmask_via(): hdr: [Via] Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [th_msg.c:404]: th_unmask_via(): body: 96: [SIP/2.0/UDP 192.168.6.108:5260;received=192.168.6.108;TH=div;rport=5260;branch=z9hG4bK2821386093] Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [th_msg.c:438]: th_unmask_via(): +body: 5: [DÏã#Ã] Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) ERROR: <core> [core/parser/parse_via.c:1808]: parse_via(): bad char <D> on state 100 Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) ERROR: <core> [core/parser/parse_via.c:2704]: parse_via(): parsing via on: <DÏã#Ã Aug 11 09:32:57 weyl kamailio[31439]: X> Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) ERROR: <core> [core/parser/parse_via.c:2710]: parse_via(): via parse error Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) ERROR: topoh [th_msg.c:464]: th_unmask_via(): cannot find cookie in via2 Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [th_msg.c:597]: th_flip_record_route(): no record route header Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [topoh_mod.c:389]: th_msg_received(): adding cookie: uc Aug 11 09:32:57 weyl kamailio[31439]: 19(31536) DEBUG: topoh [th_msg.c:1034]: th_add_hdr_cookie(): added cookie header [TH: uch Aug 11 09:32:57 weyl kamailio[31439]: ] ``` This problem was also [topoh-error-logs.tar.gz](https://github.com/kamailio/kamailio/files/5056198/topoh-error-logs.tar.gz) discussed here: https://lists.kamailio.org/pipermail/sr-users/2019-February/104730.html. ### Troubleshooting

#### Reproduction

<!-- If the issue can be reproduced, describe how it can be done. -->

#### Debugging Data

[topoh-error-logs.tar.gz](https://github.com/kamailio/kamailio/files/5056184/topoh-error-logs.tar.gz)

``` (paste your debugging data here) ```

#### Log Messages

ref. the attached file ``` (paste your log messages here) ```

#### SIP Traffic Ref. the attached file. A relevant SIP messages trace excerpt is here: ``` ==================== tag: rcv pid: 31533 process: 16 time: 1597138377.884735 date: Tue Aug 11 09:32:57 2020 proto: udp ipv4 srcip: 192.168.6.108 srcport: 5260 dstip: 192.168.0.206 dstport: 5060 ~~~~~~~~~~~~~~~~~~~~ INVITE sip:9992003@leotst.weyl.in.xorcom.com:5060 SIP/2.0^M Via: SIP/2.0/UDP 192.168.6.108:5260;rport;branch=z9hG4bK2821386093^M From: "9000" sip:2001@leotst.weyl.in.xorcom.com;tag=399dbddb56237da^M To: sip:9992003@leotst.weyl.in.xorcom.com:5060^M Call-ID: 9d993e292700d20@192.168.6.108^M CSeq: 20 INVITE^M Contact: sip:2001@192.168.6.108:5260;transport=UDP^M Max-Forwards: 70^M User-Agent: Htek UC903 V2.0.4.6.15 001fc11cc555^M Supported: replaces^M Subject: SIP Call^M Expires: 120^M Allow: INVITE, ACK, UPDATE, INFO, CANCEL, BYE, OPTIONS, REFER, SUBSCRIBE, NOTIFY, MESSAGE, PRACK^M Content-Type: application/sdp^M Content-Length: 236^M ^M v=0^M o=- 887 886 IN IP4 192.168.6.108^M s=SIP Call^M c=IN IP4 192.168.6.108^M t=0 0^M m=audio 12100 RTP/AVP 0 8 101^M a=rtpmap:0 PCMU/8000^M a=ptime:20^M a=rtpmap:8 PCMA/8000^M a=rtpmap:101 telephone-event/8000^M a=fmtp:101 0-11,16^M a=sendrecv^M .......................... ==================== tag: snd pid: 31533 process: 16 time: 1597138377.929560 date: Tue Aug 11 09:32:57 2020 proto: udp ipv4 srcip: 10.197.184.1 srcport: 5060 dstip: 10.197.184.108 dstport: 5060 ~~~~~~~~~~~~~~~~~~~~ INVITE sip:9992003@leotst.weyl.in.xorcom.com:5060 SIP/2.0^M Record-Route: sip:10.197.184.1;r2=on;lr;did=67a.f1e1^M Record-Route: sip:192.168.0.206;r2=on;lr;did=67a.f1e1^M Via: SIP/2.0/UDP 10.197.184.1;branch=z9hG4bK3fe4.fc634d55237786cb052f1c0d4fd7d949.0^M Via: SIP/2.0/UDP 192.168.6.108:5260;received=192.168.6.108;TH=div;rport=5260;branch=z9hG4bK2821386093^M From: "9000" sip:2001@leotst.weyl.in.xorcom.com;tag=399dbddb56237da^M To: sip:9992003@leotst.weyl.in.xorcom.com:5060^M Call-ID: 9d993e292700d20@192.168.6.108^M CSeq: 20 INVITE^M Contact: sip:2001@192.168.6.108:5260;transport=UDP;alias=192.168.6.108~5260~1^M Max-Forwards: 69^M User-Agent: Htek UC903 V2.0.4.6.15 001fc11cc555^M Supported: replaces^M Subject: SIP Call^M Expires: 120^M Allow: INVITE, ACK, UPDATE, INFO, CANCEL, BYE, OPTIONS, REFER, SUBSCRIBE, NOTIFY, MESSAGE, PRACK^M Content-Type: application/sdp^M Content-Length: 252^M TH: dih^M X-cpbxmt-srcip: 192.168.6.108^M ^M v=0^M o=- 887 886 IN IP4 10.197.184.1^M s=SIP Call^M c=IN IP4 10.197.184.1^M t=0 0^M m=audio 11554 RTP/AVP 0 8 101^M a=rtpmap:0 PCMU/8000^M a=ptime:20^M a=rtpmap:8 PCMA/8000^M a=rtpmap:101 telephone-event/8000^M a=fmtp:101 0-11,16^M a=sendrecv^M a=nortpproxy:yes^M |||||||||||||||||||| ==================== |||||||||||||||||||| ==================== tag: rcv pid: 31536 process: 19 time: 1597138377.930085 date: Tue Aug 11 09:32:57 2020 proto: udp ipv4 srcip: 10.197.184.108 srcport: 5060 dstip: 10.197.184.1 dstport: 5060 ~~~~~~~~~~~~~~~~~~~~ SIP/2.0 401 Unauthorized^M Via: SIP/2.0/UDP 10.197.184.1;branch=z9hG4bK3fe4.fc634d55237786cb052f1c0d4fd7d949.0;received=10.197.184.1^M Via: SIP/2.0/UDP 192.168.6.108:5260;received=192.168.6.108;TH=div;rport=5260;branch=z9hG4bK2821386093^M From: "9000" sip:2001@leotst.weyl.in.xorcom.com;tag=399dbddb56237da^M To: sip:9992003@leotst.weyl.in.xorcom.com:5060;tag=as36995166^M Call-ID: 9d993e292700d20@192.168.6.108^M CSeq: 20 INVITE^M Server: GHJ-5.1.10^M Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO, PUBLISH, MESSAGE^M Supported: replaces, timer^M WWW-Authenticate: Digest algorithm=MD5, realm="asterisk", nonce="34e38346"^M Content-Length: 0^M

```

### Possible Solutions

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### Additional Information

* **Kamailio Version** - output of `kamailio -v`

``` # kamailio -v version: kamailio 5.4.0 (x86_64/linux) flags: USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES, TLS_PTHREAD_MUTEX_SHARED ADAPTIVE_WAIT_LOOPS 1024, MAX_RECV_BUFFER_SIZE 262144, MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: unknown compiled with gcc 7.5.0

```

* **Operating System**:

``` Ubuntu 18.04 ```