following the feedback I just pushed a branch (https://github.com/kamailio/kamailio/tree/grumvalski/siptrace_flag_fixes), which tries to address the issues discussed.

I've tried to split the commits so that each issue is handled separately.

With the first commit (https://github.com/kamailio/kamailio/commit/b64b3f03a9c6b69587ca360465f091f873f7274b) I fixed the incoming ACK for negative replies tracing: as discussed it makes no sense to check in the callback if tracing is enabled or not.

The second commit (https://github.com/kamailio/kamailio/commit/e28f464457eea47cc606c73cbfe4b30fcc8b542a) refactors the e2e CANCEL handling. With the previous implementation the incoming CANCEL captured would have the ANYADDR set as destination address. This commit also allows to have exactly the same behavior between transaction tracing (sip_trace_mode("t")) and legacy tracing (setflag + sip_trace()) when tracing a specific INVITE.

With the third (https://github.com/kamailio/kamailio/commit/080c6e07708f1964498a43e70c9b6240b5bdebcd) I've tried as much as possible to restore the legacy behavior when tracing all the requests without having duplicated captures for CANCEL and ACK for negative replies. I could achieve this for the CANCEL checking if the INVITE it refers to is already being traced (meaning that the CANCEL will be captured by the callback) but I couldn't for the ACK. I couldn't find a way to check if the ACK is for a negative reply (and thus it belongs to a transaction), without having the tm callbacks for ACK run, since both t_check and t_check_trans tm calls run the E2ECANCEL_IN callbacks.

I've tried different scenarios in both capturing modes (transaction and flag+trace):

1) Successful call (INVITE-200-ACK)

2) Error replied

3) Canceled call

4) locally generated CANCEL (timeout)

All looks good (except for the ACK issue) in both modes.

I would like to have the developers' feedback before opening a PR, there could be other scenarios/use cases I'm not considering here.

Thank you all.

Cheers,

Federico