Idea for synchonous logging/review of debug + GSMTAP

Harald Welte laforge at
Tue Jan 29 10:22:31 UTC 2013

Hi all,

one of the problems when debugging PCU issues is: How to take proper
logs on-site where a problem shows up and give them back to the
developer(s) for analysis.  If you capture the PCU stdout or configure
file-based logging, you will have a hard time corellating that with PCAP
traces taken on the RLC/MAC side and/or on the Gb side.

Therefore I propose a new idea here and would like to get your review:

What about implementing a "GSMTAP" log target for libosmocore?  This way
we could encapsulate the log messages into a special GSMTAP message,
which would be sent synchronously in the GSMTAP stream together with
RLC/MAC messages on the lower end.

The same could in fact be utilized in osmo-bts, too.  This way we could
capture BTS log/debug output in-order to L1 messages that we receive and

What do you think about it?  I would be willing to draft the GSMTAP
sub-header format and write + submit the wireshark dissector, if
somebody wants to write libosmocore log target.

Ideally we would log _all_ messages to that target, and include the
subsystem and log level in a header field, so the log verbosity could
still be adjusted at the point of review, instead only at the time of


- Harald Welte <laforge at> 
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

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