Add support for setting PDU Session Container Type to UL

[linouxis9]

Add support for setting PDU Session Container Type to UL in the GTP-U Extension Header.

This is required for PacketRusher and I would like to avoid using a gtp5g fork inside PacketRusher, I think it's better if this kind of work can be upstreamed :-)

I stuffed the field in FAR as I think it was the better fit, but if you have any suggestions on a better place, please say so.
The location of the field is a breaking change as well, so we might need to move that.

The related go-gtp5nl PR: free5gc/go-gtp5gnl#23

Thanks a lot!
Valentin

[tim-ywliu]

@linouxis9

You can use pdr->pdi->srcIntf to determine the direction.
If pdr->pdi->srcIntf == SRC_INTF_ACCESS means UL; pdr->pdi->srcIntf == SRC_INTF_CORE means DL.
Plz remove the new attr and replace it with pdr->pdi->srcIntf.

[linouxis9]

Thanks a ton @tim-ywliu for the tip, I'll do the requested change!
Cheers,
Valentin

[linouxis9]

Thanks a ton @tim-ywliu :-)!

[tim-ywliu]

@linouxis9

You can refer to https://github.com/free5gc/go-upf/blob/main/internal/forwarder/gtp5g.go#L330 to pass PDI_SRC_INTF to gtp5g.

SRC_INTF_ACCESS (0) means uplink.
SRC_INTF_CORE (1) means downlink.