Cellular Network Infrastructure » OsmoMGW

sammachin wrote:

I'm running:
osmo-mgw 1.3.0
osmo-bsc & msc report Version UNKNOWN

This is extremely odd and indicates you might be experiencing build issues. Please confirm your findings - if possible - using the latest osmocom:nightly packages.

I noticed this also, and I am wondering if it was a bug in the legacy code that was then worked around in the osmo-sip-connector (and also presumably, in the LCR when the gsm MNCC socket support was added)

See http://git.osmocom.org/osmo-sip-connector/tree/src/sdp.c#n168 in sdp_create_file().

You can quickly work around this for further testing by removing the ntohl() in line 168:

-       struct in_addr net = { .s_addr = ntohl(other->ip) };
+       struct in_addr net = { .s_addr = other->ip };

I also had to force the payload type here with

other->payload_type = 3

if using Full Rate

I have yet to track down the change that is causing the reversed IP to be sent to the MNCC socket.

This problem was obviously noticed at 34C3 and there were some patches made to deal with it.
http://git.osmocom.org/osmo-sip-connector/log/src?h=lynxis%2F34c3

Question is, Should the byte order in osmo-sip-connector be left as it is and should we fix the byte order being sent from osmoMSC, (which is possibly coming some way from osmoMGW?)

If we change osmo-sip-connector, it will break with legacy openbsc and also LCR will be broken, as LCR obviously is expecting the same byte order as unpatched osmo-sip-connector (LCR works with openbsc)

If it's any use, I checked MGCP, and the IP addresses in the SDP appear to be correct.

I think fixing this in osmo-sip-connector is the wrong way since this is not a bug in osmo-sip-connector. The problem is in osmo-msc, which is populating the ip struct memeber of struct gsm_mncc_rtp in the wrong byte oder. In order to make sure that this assumption is correct I checked how the SDP in the sip messages looks like when osmo-nitb is used. The IP byteorder looks correct there. Correcting the byte order in osmo-sip-connector would break osmo-nitb so fixing it in osmo-msc seems to be the right place.

See also: https://gerrit.osmocom.org/#/c/osmo-msc/+/11139

The patch made it into master, so we can close this now. However, Its still not clear to me why it worked all the time on my local machine...

I also had the issue, and I can confirm that it's fixed with @dexter's changes. Thank you!