* Initial metrics support based on Prometheus
This commit introduces initial support for metrics in open5gs.
The metrics code is added as libogsmetrics (lib/metrics/), with a well
defined opaque API to manage different types of metrics, allowing for
different implementations for different technologies to scrap the
metrics (placed as lib/metrics/<impl>/. The implementation is right now
selected at build time, in order to be able to opt-out the related dependencies
for users not interested in the features. 2 implementations are already
provided in this commit to start with:
* void: Default implementation. Empty stubs, acts as a NOOP.
* prometheus: open5gs processes become Prometheus servers, offering
states through an http server to the Prometheus scrappers. Relies on
libprom (prometheus-client-ci [1] project) to track the metrics and format
them during export, and libmicrohttpd to make the export possible through
HTTP.
[1] https://github.com/digitalocean/prometheus-client-c
The prometheus-client-c is not well maintained nowadays in upstream, and
furthermore it uses a quite peculiar mixture of build systems (autolib
on the main dir, cmake for libprom in a subdir). This makes it difficult
to have it widely available in distros, and difficult to find it if it
is installed in the system. Hence, the best is to include it as a
meson subproject like we already do for freeDiameter. An open5gs fork is
requried in order to have an extra patch adding a top-level
CMakeList.txt in order to be able to includ eit from open5gs's meson
build. Furthermore, this allows adding bugfixes to the subproject if any
are found in the future.
* [SMF] Initial metrics support
* [SMF] Add metrics at gtp_node level
* docs: Add tutorial documenting metrics with Prometheus
The use of the Gy interface (SMF acting as CTF towards an OCS node) is
mandated through configuration file. Default value "enable: auto" will
only make use of it in case a Diameter peer announcing support for the
Credit-Control Application is found.
Upon subscriber session creation, and after auth check over Gx, the SMF
will create a Gy session with the OCS and only after that step the SMF
will accept the session back to the subscriber.
The OCS may then grant some traffic volumes/time and ask to be notified
back with updated measurements.
In order to get the measurements, the SMF relies on PFCP URR configured
to the UPF through Session Repoort Request messages.
When closing the subscriber session, the SMF will also terminate the Gy
session at the OCS.
So far only some specifics parts of the Gy interface as well as the PFCP
side are implemented. Those should be enough to at least have
volume/time thresholds granted by the OCS, which then will be able to
track subsriber resource use.
This patch doesn't implement the OCS side of the Gy interface, that's
left as a future exercise. The interface was tested using an OCS
emulator implemented in TTCN-3 [1]
[1] https://cgit.osmocom.org/osmo-ttcn3-hacks/
TODO:
* Use an event for the report, like SMF_EVT_N4_TIMER?
* Properly set Service identifier in Gy CCR
* SMF: Properly set pkt/octet volumes in Gy CCR
** Update when receiving PFCP Modify Response.
* Figure out best way to require Gy through config file in open5gs-smfd.
* Create a new sess-sm.c which handles smf_sess_t state through
Gx+Gy+PFCP creation, modification and tear down. This way we can do
stuff in parallel, for instance Gx+Gy. It will alsoavoid duplicating
some code paths due to Gy being optional.
* [CORE] tlv: Store mode in ogs_tlv_t
This allows specifying the format of the IE for each individual IE,
hence allowing messages containing IEs formatted in different ways.
This is needed in order to support parsing GTPv1-C, since messages
contain IEs with different structure (TLV vs TV). Hence, this is a
preparation patch to add support for parsing TVs in ogs-tlv.c/.h.
* [CORE] tlv: Support parsing msg with both TLV and TV in it
IEs of type TV are sometimes used in GTPv1-C. Current tlv parser/builder
doesn't provide with ways to parse messages which contain TV formatted
IEs. This patch adds the relevant types and ways to encode/decode them.
Furthermore, the current parser/builder allows parsing/building messages
containing the exact same format in all its IEs. A new parser function
is added which allows parsing messages of different types (TV, TLV)
mixed in the same message. In order to be able to do so, it uses the
general msg_mode passed to it in order to know the general TLV format
(in essence, the length of the Tag field, and also the length of the
Length field if applicable each IE).
Looking up the instance in the TLV description is left undone and
hadcoded to 0, since the only user so far requiring this API is GTPv1-C,
which has no instances.
* [CORE] tlv: Support repeated tag+instance parsing TLV message
In GTPv2C, repeated IEs (same tag) are easily differentiated by the
Instance byte, which provides info to match different decoded
structures. In GTPv1C though, there's no Instance byte, and we still
encounter repeated IEs (like GSN Address in Create PDP Context Request).
Hence, the TLV decoder needs to be updated to track count of IEs found
(identified by tag+instance, where instance is always 0 in GTPv1C) and
get the proper description index + offset into the decoded structure.
* [GTP]: Move GTPv2-C specifics to its own libgtp subdir
This will allow adding GTPv1-C code by the side. Most GTPv2 code is left
in this patch as "gtp" instead of renaming it to "gtp2" in order to
avoid massive changes. It can be done at a later stage if wanted.
* [GTP] Support generating GTPv1-C messages
* [SMF] Add Gn interface support
This patch introduces GTPv1C support to open5gs-smfd. With it,
open5gs-becomes a GGSN too, where SGSN can connect to, hence supporting
GERAN and UTRAN networks.
* [SMF] Fix potential null pointer dereference
Pointer "sess" was first dereferenced and later on checked for nullness.
This is clearly wrong. Rearrange the code path to make sure the check is
done first, then dereferenced.
* gitignore: Add subprojects/libtins
* cosmetic: Fix whitespace
Pau Espin
Sukchan Lee