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### Description

<!-- Explain what you did, what you expected to happen, and what actually happened. -->

### Troubleshooting

#### Reproduction

we have an issue with our Kamailio.

This configuration is multi-homed, we have two network interfaces, one on a private network and on the public Internet. Kamailio is configured to listen on port 5060 and 5066 on both interfaces. We register two users Alice and Bob on the public Internet using port 5066. Both users are behind a NAT and we capture the SIP exchange on the proxy server.

We have set the parameter mhomed=1


The ACK packet gets relayed with the wrong source port. Then the NAT rejects the packet and the call cannot be established.

Also, if we set mhomed=0 it works BUT we are not sure that multi homed is handled correctly.

the issue seems to be located in the RR module and the loose_route() function. In the after_loose() function in loose.c, the function set_force_socket() is called only if a DOUBLE route is mentioned in the route set of the ACK message

But when both users are using 5066 as proxy port, we get only ONE route for the proxy in the route set (and to us it is OK). In this case, we get a trace:

"No next URI found"

and the code exits. Later in the message processing, when t_relay() is called, the forward_request() selects the first socket defined in our configuration instead.

At this point, we can't presume what socket we be select. We believe that it is a software bug and that after_loose() should force the send_socket even though we have only one route in the route set

#### Debugging Data

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gdb /path/to/kamailio /path/to/corefile bt full info locals list

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

#### Log Messages

<!-- Check the syslog file and if there are relevant log messages printed by Kamailio, add them next, or attach to issue, or provide a link to download them (e.g., to a pastebin site). -->

``` (paste your log messages here) ```

#### SIP Traffic

<!-- If the issue is exposed by processing specific SIP messages, grab them with ngrep or save in a pcap file, then add them next, or attach to issue, or provide a link to download them (e.g., to a pastebin site). -->

``` (paste your sip traffic here) ```

### Possible Solutions Adding the process of set_force_socket in case we have one route and only.

L.808 if (res > 0) { /* No next route found */ LM_DBG("No next URI found\n");

if (!use_ob) { if ((si = grep_sock_info( &puri.host, puri.port_no?puri.port_no:proto_default_port(puri.proto), puri.proto)) != 0) { set_force_socket(_m, si); } else if ((si = grep_sock_info( &puri.host, puri.port_no, puri.proto)) != 0) { set_force_socket(_m, si); } else { if (enable_socket_mismatch_warning) { LM_WARN("no socket found to match second RR (%.*s)\n", rt->nameaddr.uri.len, ZSW(rt->nameaddr.uri.s)); if(!is_myself(&puri)) { LM_WARN("second RR uri is not myself (%.*s)\n", rt->nameaddr.uri.len, ZSW(rt->nameaddr.uri.s)); } } } }

status = (preloaded ? NOT_RR_DRIVEN : RR_DRIVEN); goto done; }

### Additional Information

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

``` (paste your output here) ```

* **Operating System**:

<!-- Details about the operating system, the type: Linux (e.g.,: Debian 8.4, Ubuntu 16.04, CentOS 7.1, ...), MacOS, xBSD, Solaris, ...; Kernel details (output of `uname -a`) -->

``` (paste your output here) ```