[sr-dev] git:master: siputils: added new function is_first_hop()

[Juha Heinanen]

daniel,

is_first_hop() readme has this on replies:

  For incoming SIP replies, it means that top Record-Route URI is
  'myself' and source address is not matching it (to avoid detecting in
  case of local loops). Note that it does not detect spirals, which can
  have the condition for replies true also in the case of additional SIP
  reply receival.

in contact alias tutorial

https://sip-router.org/wiki/tutorials/alias-example?&#in-dialog_requests

i have implemented "is first hop" check by checking that reply does not
have any other r-r headers except the ones added by the proxy itself
when it relayed the request:

in request route i set

$avp("rr_count") = $rr_count;

and in reply route, i test

if ($rr_count == $avp(rr_count) + $rr_top_count) ...

i think that this method also works in case of spirals if i understand
correctly what spirals are.

do you have any comment about possible equivalence or non-equivalence of
the two methods?  could i safely use is_first_hop test also for replies
in contact alias tutorial?

-- juha