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pespin has posted comments on this change. ( 
https://gerrit.osmocom.org/c/osmo-mgw/+/35205?usp=email )

Change subject: IuUP: allow Initialization from any address if not yet set
......................................................................


Patch Set 2:

(3 comments)

Commit Message:

https://gerrit.osmocom.org/c/osmo-mgw/+/35205/comment/158c6533_50887307
PS1, Line 28: Decided for now that it's not worth the extra effort to make this 
more
            : restrictive
> ok, I understand. […]
"we do allow any source address to send MGCP to the MGW and actually". This is 
easily constraint by selecting a proper IP address like a localhost address 
when configuring osmo-mgw local MGCP address, or binding to an IP address only 
available on a given interface.
The problem with "security" from the RTP ports comes from the fact that the 
remote IP address is selected by a 3rd entity/node connected to us, and 
osmo-mgw uses ip probing to find out how to connect.


File src/libosmo-mgcp/mgcp_network.c:

https://gerrit.osmocom.org/c/osmo-mgw/+/35205/comment/d09ff72c_2e8481ca
PS1, Line 838:  if (mgcp_conn_rtp_is_iuup(conn) && !conn->iuup.configured) {
> (There are two places to indicate codecs, one in the MGCP header which we 
> basically ignore, and the  […]
With current master (at least from yesterday) yes, you are right. However,
as I mentioned I merged a patch in osmo-hnbgw to announce a "hnb IuUP address" 
to osmo-mgw right from the first RAN-side MGCP CRCX, by using the Iuh remote IP 
address at the hnbgw, so that osmo-mgw can guess correctly its binding IuUP 
address in the assumed general case where Iuh IP address = IuUP IP address in 
HNB. See
https://gitea.osmocom.org/cellular-infrastructure/osmo-hnbgw/commit/656d1d27788a000b93f00cf9cdf659e0dacadde7

Besides that, libosmo-mgcp-client needs to be adapted in order to allow 
submitting an IP address on the wire (CRCX) even if the port is yet not known 
(port=0). This is what this osmo-mgw.git patch is accomplishing:
https://gerrit.osmocom.org/c/osmo-mgw/+/35152

As you see, with this patch the generated CRCX now contains an SDP, and hence 
it doesn't go through the add_lco() path, but through the add_sdp() (because 
it's the only way to provide an IP address to osmo-mgw so it does the ip 
probing).

Now that you processed all the above, read again my previous comment to 
understand the modifications (going back more or less to version 1 of the patch 
to send the codec in the CRCX even if the port=0).


File src/libosmo-mgcp/mgcp_network.c:

https://gerrit.osmocom.org/c/osmo-mgw/+/35205/comment/6a20a4bb_df864304
PS2, Line 837: != 0)
> (i find this really hard to read. […]
It's not a bool, it's a tristate 1, 0, -1. It's a bool + error. So in here we 
are handling error as "consider it as not set".



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Gerrit-Project: osmo-mgw
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Gerrit-Change-Id: I6c365559a7bd197349f0ea99f7a13b56a4bb580b
Gerrit-Change-Number: 35205
Gerrit-PatchSet: 2
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