In some scenarios, it happens that a request is received with the
IP xxx.xxx.xxx.xxx:14000 -> server:5060
Normally, we just force_rport() on all incoming requests so that we
reply to the real source port of the request, since most endpoints on
this installation are NAT'd.
However, occasionally we run into a scenario where an ALG or
misconfigured client incorrectly inserts an rport attribute into its
topmost Via, and really expects to receive a response at the
address/port indicated in the Via (i.e. 5060).
Does Kamailio offer a means of dealing with these on a selective basis?
Would refraining from calling force_rport() be enough? Or would it be
necessary to set reply_to_via=1 as well, thus breaking symmetrical
behaviour for the vast majority of the NAT'd endpoints?
In other words, I'm not 100% clear on the following:
1) What impact does force_rport() have if an 'rport' attribute is sent
by the client?
In this case, there should be nothing to "force"; I assume that if the
'rport' attribute is placed by the client, then the proxy will return
replies to the source port of the request even if force_rport() is not
called, because that's the RFC 3581-compatible thing to do. Right?
2) Does reply_to_via=1 override the behaviour hypothesised in #1?
3) Does reply_to_via=1 override force_rport()?
Alex Balashov | Principal | Evariste Systems LLC
Tel: +1-706-510-6800 (direct) / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
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