In an Inter-RAT setup a UE could perform a RAU coming from a 4G network.
In that case the UE/MS is unknown to the SGSN and it should request the
SGSN context (MM, PDP) from the MME. This is done through the following
GTPv1C message exchange on the Gn interface of SGSN and MME:
SGSN -> MME: SGSN Context Request
SGSN <- MME: SGSN Context Response
SGSN -> MME: SGSN Context Acknowledge
This commit doesn't aim to be a complete implementation of the mentioned
procedure, since it's quite a complex one, with lots of fields and logic
required. This so far only implements in general the minimally
successful case by filling as much as possible the required set of
fields.
This will allow for a base onto which do incremental improvements and
fixes while testing against UEs and SGSNs (such as osmo-sgsn, which
doesn't yet support this procedure but will potentially earn it soon).
This commit doesn't implement the reverse direction, aka UE issuing cell
reselection 2G->4G. Initial support for this scenario will hopefully be
added soon as a follow-up patch, similar to this one.
Related: https://osmocom.org/issues/6294
(cherry picked from commit 3d693da73e)
In the past only GTPv2C was supported, and had the "gtp" generic prefix.
Later on, GTPv1C support was added, and "gtp1" prefix was used.
Let's move GTPv2C specific bits to have "gtp2" prefix too, and leave
"gtp" prefix for generic stuff among different GTP versions.
All process will be forcely exited if it failed to encode the S1AP/NGAP/GTP/PFCP message. It is to make sure there was no problem with the encoding of open5gs.
If both Delete-Session-Request/Response and
UEContextReleaseCommand/UEContextReleaseComplete are failed at the same time,
UE cannot attach to the EPC infinitely.
So, I've add the protection code
if timer expires when MME does not receive Delete-Session-Response.
- Set the number of UEs in units of AMF/MME instead of gNB/eNB.
- See default value as shown below
Number of UEs per AMF/MME : 4,096
Number of gNB/eNB per AMF/MME : 32
* HACK: Don't retransmit InitialContextSetupReq
Related: #256
* HACK: Don't use buggy sa1p_copy() in eNBConfigTransfer
Related: #257
* mme: don't reject with 'IMSI is unknown in HLR' (permanent reject)
* MME: Implement S6a result -> EMM cause code mapping
Closes: #263
* Spencer: modification to Haralds fix because macros are now renamed
* MME: don't assert on MAC failures of uplink NAS frames
Closes: #267
* MME: Avoid ogs_assert() in many situations
We don't want to crash the entire program just because a message
received from an external entity didn't match some of our expectations.
* compiles fine, checked DIFFs and only difference is the ogs_assert -> ogs_expect