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Bug #4745

open

osmo-mgw: Wrong IP address returned in SDP "o=" section

Added by pespin over 3 years ago. Updated over 1 year ago.

Status:
New
Priority:
Low
Assignee:
-
Category:
-
Target version:
-
Start date:
09/02/2020
Due date:
% Done:

0%

Spec Reference:
Tags:

Description

We are returning our local IP address in there when submitting an ACK, but in my opinion we show be returning the address of the client, basically re-generate whatever the client sent us in the request.

That's my understanding, but the spec is not really clear about that:
https://tools.ietf.org/html/rfc3435
https://tools.ietf.org/html/rfc4566

Actions #1

Updated by pespin over 3 years ago

Related function where the address is added to o=: mgcp_write_response_sdp()

Actions #2

Updated by laforge over 1 year ago

  • Tags set to simple

I think we need to clarify what is correct before jumping to any implementation

dexter, neels - what is your take on this?

Actions #3

Updated by dexter over 1 year ago

I think you are right. The o= field should indeed contain the IP address of the party that started the session. The osmo-mgcp-client seems to be correct already. The MGW is the only party that would need fixing. It should be simple to fix since its just meta data. We are not using the contents of the o= field to get the RTP ip address, that info is in the c= field.

Actions #4

Updated by dexter over 1 year ago

No the question is: Who begins the session. Is it the party that sends the CRCX without SDP or is it the MGW that assigns the session ID?

Actions #5

Updated by dexter over 1 year ago

RFC 4566, capter 5.2 says: "For privacy reasons, it is sometimes desirable to obfuscate the username and IP address of the session originator. If this is a concern, an arbitrary <username> and private <unicast-address> MAY be chosen to populate the "o=" field, provided that these are selected in a manner that does not affect the global uniqueness of the field." This would mean that if we return something like 255.255.255.255 in the field we are still spec compliant since the session id still ensures uniqueness.

Actions #6

Updated by pespin over 1 year ago

RFC 3435 "3.4 Encoding of the Session Description (SDP)":

   * The address SHOULD be the same address as provided in the
     connection information ("c=") field.
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