Modified ruri-user and dispatcher failover

[mtryfoss]

Description

We've got a situation where we use t_send_reply() to generate early 100 Trying, before an operation that might have a small delay. The result of this operation might lead to a change which adds parameters to ruri-user. This works as expected for normal operations, but when calling ds_next_dst()/ds_next_domain() the change to $rU is lost.

Troubleshooting

I then noticed that this is because t_send_reply() indirectly does a t_newtran() before change to $rU. If it's done in the opposite order, everything works as expected.

A workaround is to use for example sl_send_reply() and t_set_auto_inv_100(0), which works for me.
However, I'm unsure if this revert of user is expected behaviour?

Reproduction

$rU = $rU + ";npdi";
..
ds_select_dst(..);
then trigger a condition which executes failure_route and then use ds_next_dst() to fork serially.
$rU is then reverted to the original value in outgoing INVITE.

Additional Information

Reproduced in master.

[henningw]

If I understand your scenario correctly, this is expected and documented behaviour:
"Note that whenever failure_route is entered, uri is reset to value which it had on relaying."
https://www.kamailio.org/docs/modules/devel/modules/tm.html#tm.f.t_on_failure

[mtryfoss]

Sorry, missed that info.