Wrong return code used by sl_reply_error()

[Norbixin]

Description

I wanted to change 478 response to 503 in case of t_relay() failure, but leave default behavior in rest error cases. I used part of code from "Example 1.1." inside https://www.kamailio.org/docs/modules/devel/modules/outbound.html. When I get -478 from t_relay() it works fine, but when this code is different sl_reply_erorr() don't use it as it should be.

This is my part of kamailio.cfg:

route[RELAY] {
    if (!t_relay()) {
        switch($rc) {
            case -478:
                xlog("L_WARN","T_Relay returned 478, sending back 503.\n");
                sl_send_reply("503", "Service Unavailable");
                exit;
            default:
                sl_reply_error();
                exit;
        }
    }
    exit;
}

When I log $rc value before sl_reply_error() it is valid, but not used by sl_reply_error() as SIP error value, it sends 500 instead.

Troubleshooting

Reproduction

I've added incorrect hostnames with flag 16 to set where the message should be sent and t_relay() returns -478. To check the default case inside switch I changed case -478 to -479.

Log Messages

1(8) ERROR: <core> [core/resolve.c:1731]: sip_hostport2su(): could not resolve hostname: "va4brhino"
 1(8) ERROR: tm [ut.h:309]: uri2dst2(): failed to resolve "va4brhino"
 1(8) ERROR: tm [t_fwd.c:1759]: t_forward_nonack(): failure to add branches
 1(8) ERROR: sl [sl_funcs.c:414]: sl_reply_error(): stateless error reply used: I'm terribly sorry, server error occurred (1/SL)

Logs with different route relay

route[RELAY] {
    if (!t_relay()) {
        switch($rc) {
            case -479:
                xlog("L_WARN","T_Relay returned 479, sending back 503.\n");
                sl_send_reply("503", "Service Unavailable");
                exit;
            default:
                xlog("L_WARN","Return code: $rc\n");
                sl_reply_error();
                exit;
        }
    }
    exit;
}

 1(8) ERROR: <core> [core/resolve.c:1731]: sip_hostport2su(): could not resolve hostname: "va4brhino"
 1(8) ERROR: tm [ut.h:309]: uri2dst2(): failed to resolve "va4brhino"
 1(8) ERROR: tm [t_fwd.c:1759]: t_forward_nonack(): failure to add branches
 1(8) WARNING: <script>: Return code: -478
 1(8) ERROR: sl [sl_funcs.c:414]: sl_reply_error(): stateless error reply used: I'm terribly sorry, server error occurred (1/SL)

Additional Information

• Kamailio Version - output of kamailio -v

version: kamailio 5.5.0 (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_BLOCKLIST, HAVE_RESOLV_RES
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 4.8.4

• Operating System:

Linux v4bkamailio 5.10.25-linuxkit #1 SMP Tue Mar 23 09:27:39 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

[miconda]

sl_send_error() is for generic error reply. You can send any reply code using send_reply("code", "text"), use sl_send_error() only when you want the behaviour from the C code. For further discussions, email to sr-users@lists.kamailio.org .

[pgrabowski]

Hi @miconda . I think you misunderstood bug here. Issue is that if and switch statements change behaviour of sl_send_error(). Same examples as configuration from this bug report are in Kamailio documentation so it looks like a bug, if not maybe documentation needs an update.

[miconda]

Then I still do not understand properly after your last comment.

Note that $rc can be updated by any kamailio action, so you should save its value in a $var(...) if you want to use it later. If you do an xlog(), after it the $rc is updated to the return of xlog().

[pgrabowski]

Please have a look at https://www.kamailio.org/docs/modules/devel/modules/outbound.html "Example 1.1. Edge Proxy Configuration" it uses exact same syntax. If expected behaviour is that any statement can affect sl_reply_error() then this example needs updating.