A friend in the community was trying to connect an SMF made by another
manufacturer with an SBI interface and found a big problem with Open5GS.
All of the code in the part that generates the Resource URI
from HTTP.location is invalid.
For example, suppose we create a Resource URI with SMContext as below.
{apiRoot}/nsmf-pdusession/<apiVersion>/sm-contexts/{smContextRef}
In this case, Open5GS extracted the {smContextRef} part of the HTTP.location
and appended it to the beginning
{apiRoot}/nsmf-pdusession/<apiVersion>/sm-contexts/.
This implementation may not work properly if the apiRoot changes.
Consider a different port number as shown below.
<HTTP.location>
127.0.0.4:9999/nsmf-pdusession/v1/sm-contexts/1
The SMF may send an apiRoot to the AMF with a changed port number,
in which case the AMF must honor it.
Therefore, instead of extracting only the smContextRef from HTTP.location,
we modified it to use the whole thing to create a Resource URI.
We modified all NFs that use HTTP.location in the same way, not just SMFs.
Cause is set according to particular NF standard.
Additionally:
- OGS_SBI_HTTP_STATUS_MEHTOD_NOT_ALLOWED typo fixed.
- [PCF] Fixed SM Policy establishment error handling
For bi-directions, the rules are created in the same form as for downlink
as shown below, so to apply them for uplink, we need to swap the rules
according to the interface.
RX : permit out from <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT> to <UE_IP> <UE_PORT>
GX : permit out from <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT> to <UE_IP> <UE_PORT>
PFCP : permit out from <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT> to <UE_IP> <UE_PORT>
RULE : Source <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT> Destination <UE_IP> <UE_PORT>
TFT : Local <UE_IP> <UE_PORT> REMOTE <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT>
RX : permit in from <UE_IP> <UE_PORT> to <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT>
GX : permit out from <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT> to <UE_IP> <UE_PORT>
PFCP : permit out from <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT> to <UE_IP> <UE_PORT>
RULE : Source <UE_IP> <UE_PORT> Destination <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT>
TFT : Local <UE_IP> <UE_PORT> REMOTE <P-CSCF_RTP_IP> <P-CSCF_RTP_PORT>
As mentioned in the sgwu.yaml configuration file, it is possible to configure multiple addresses with different source_interface values for the gtpu interface.
Following the this section, I defined two addresses, one with source_interface set to 0 and another with source_interface set to 1. My expectation was to see different addresses for the two PDRs in the Session Establishment Response message during session establishment. However, both addresses were the same, and it was the address I had set for source_interface = 0.
When I looked into the code, I found the reason for the issue. In the lib/pfcp/context.c file, on line 1185, the function that determines the address is called as follows:
...
} else {
ogs_gtpu_resource_t *resource = NULL;
resource = ogs_pfcp_find_gtpu_resource(
&ogs_gtp_self()->gtpu_resource_list,
pdr->dnn, OGS_PFCP_INTERFACE_ACCESS);
if (resource) {
...
In the last parameter of this function, a constant value, OGS_PFCP_INTERFACE_ACCESS, is used. This causes every PDR with any source_interface to be considered as "access," and the value 0 is used for its interface.
I replaced the value with pdr->src_if, and the bug was resolved.
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.