Make DNS configurable per DNN

DNS configurable per DNN

• Keep ue_dns config on SMF level, will be used as default DNS value
• If user provides another ue_dns on DNN level, the global value will be overwritten.
• BUT: If a user does not provide the whole configuration, I do not take parts from the global configuration, I think that may be confusing. @arora What do you think about this?

Implements Feature Request #28 (closed)

Log output (extract)

[2023-07-03 21:18:36.523] [config ] [info] DNNs:
[2023-07-03 21:18:36.523] [config ] [info] - DNN:
[2023-07-03 21:18:36.523] [config ] [info]     + DNN......................................: oai
[2023-07-03 21:18:36.523] [config ] [info]     + PDU session type.........................: IPV4
[2023-07-03 21:18:36.523] [config ] [info]     + IPv4 pool................................: 12.1.1.151 - 12.1.1.253
[2023-07-03 21:18:36.523] [config ] [info]     + DNS Settings:
[2023-07-03 21:18:36.523] [config ] [info]       - Primary DNS IPv4.......................: 1.1.1.1
[2023-07-03 21:18:36.523] [config ] [info]       - Secondary DNS IPv4.....................: 1.1.1.1
[2023-07-03 21:18:36.523] [config ] [info] - DNN:
[2023-07-03 21:18:36.523] [config ] [info]     + DNN......................................: oai.ipv4
[2023-07-03 21:18:36.523] [config ] [info]     + PDU session type.........................: IPV4
[2023-07-03 21:18:36.523] [config ] [info]     + IPv4 pool................................: 12.1.1.51 - 12.1.1.150
[2023-07-03 21:18:36.523] [config ] [info]     + DNS Settings:
[2023-07-03 21:18:36.523] [config ] [info]       - Primary DNS IPv4.......................: 172.21.3.100
[2023-07-03 21:18:36.523] [config ] [info]       - Secondary DNS IPv4.....................: 8.8.8.8
[2023-07-03 21:18:36.523] [config ] [info] - DNN:
[2023-07-03 21:18:36.523] [config ] [info]     + DNN......................................: default
[2023-07-03 21:18:36.524] [config ] [info]     + PDU session type.........................: IPV4
[2023-07-03 21:18:36.524] [config ] [info]     + IPv4 pool................................: 12.1.1.2 - 12.1.1.50
[2023-07-03 21:18:36.524] [config ] [info]     + DNS Settings:
[2023-07-03 21:18:36.524] [config ] [info]       - Primary DNS IPv4.......................: 8.8.8.8
[2023-07-03 21:18:36.524] [config ] [info]       - Secondary DNS IPv4.....................: 1.1.1.1
[2023-07-03 21:18:36.524] [config ] [info] - DNN:
[2023-07-03 21:18:36.524] [config ] [info]     + DNN......................................: ims
[2023-07-03 21:18:36.524] [config ] [info]     + PDU session type.........................: IPV4V6
[2023-07-03 21:18:36.524] [config ] [info]     + IPv6 prefix..............................: 
[2023-07-03 21:18:36.524] [config ] [info]     + IPv4 pool................................: 14.1.1.2 - 14.1.1.253
[2023-07-03 21:18:36.524] [config ] [info]     + DNS Settings:
[2023-07-03 21:18:36.524] [config ] [info]       - Primary DNS IPv4.......................: 172.21.3.100
[2023-07-03 21:18:36.524] [config ] [info]       - Secondary DNS IPv4.....................: 8.8.8.8

Trace

As you can see in the trace, I have configured three different gnbsims with different DNNs and each of them has a different DNS setting. different_dns_settings_per_dnn.pcapng

• gnbsim: "default" DNN, DNS 8.8.8.8
• gnbsim2: "oai" DNN, DNS 1.1.1.1
• gnbsim3: "oai.ipv4" DNN, does not configure distinct DNN, so we take the global configuration 172.21.3.100

Discussion

@tien-thinh.nguyen @arora @defosseu I was really surprised to see that there is no DNS configuration in 3GPP 29.503 DnnConfiguration?? I think it is quite a basic feature and I wanted to integrate it into the UDM information, but that is not possible unfortunately (we could make it non-compliant). So for now, we just read it from the configuration. If the user does not configure the DNNs her and uses the one from UDM, we use the default DNS settings.