[SOLVED] How to utilize ArpDxe driver in UEFI application

How to utilize ArpDxe driver in UEFI application

I'm trying to get ARP table with ArpDxe driver in UEFI application. Here is my code:

EFI_ARP_PROTOCOL* Arp;
EFI_STATUS Status;
UINT32 Count;
UINT32 Length;
EFI_ARP_FIND_DATA* Entries;
    
Status = gBS->LocateProtocol (
             &gEfiArpProtocolGuid,
             NULL,
             (VOID**)&Arp
             );

if (Status == EFI_SUCCESS) {
    Status = Arp->Find(Arp, true, NULL, &Length, &Count, &Entries, false);
    if (Status == EFI_SUCCESS) {
        //......
    }
}

The problem is, the ARP find function always returns EFI_NOT_FOUND. I try to ping a valid IP before running my application, try to call ARP request function before calling find function, and even try to call ARP add function to add a dummy data, but none of them causing something can be found. Can someone points me out what am I doing wrong?

Solution

Like most of the network protocols, ARP uses the service binding protocol to create new instances.

You have to:

Locate the service binding protocol

EFI_HANDLE ChildHandle = NULL;
EFI_SERVICE_BINDING_PROTOCOL* ArpSb;
gBS->LocateProtocol(&gEfiArpServiceBindingProtocolGuid,NULL,(VOID**)&ArpSb)

Create a new ARP instance

ArpSb->CreateChild(ArpSb, &ChildHandle)

Handle the EFI_ARP_PROTOCOL

gBS->HandleProtocol(ChildHandle, &gEfiArpProtocolGuid, (VOID**)&Arp)

Configure the new instances
```
Arp->Configure(Arp,...)
```

Destroy the instance when you are done

ArpSb->DestroyChild(ArpSb, ChildHandle)

When you search for the proctocol directly (without creating a new instance) you get an instance that belongs to some driver or app with unknown configuration.