[syslinux] EFI: PXE: "My IP is 0.0.0.0"

[Patrick Masotta]

OK there are problems.

From
https://sourceforge.net/p/edk2/mailman/message/31604654/
""In current EDKII implementation, all the network servicebinding protocols for a 
NIC device are installed together on the NIC's device handle, so you can get all 
of them when you have chosen a special NIC handle.""

Unfortunately there are PCs with UEFI implementations not following the former rule.

i.e. HP Elitebook 2570p (single NIC)

shell> dh
...
172: DevPath (..9,0x0)/MAC(FC15B4E81CAC,0x0))Net MNPSb ARPSb DHCPv4Sb TCPv4Sb IPv4Sb IPv4Config UDPv4Sb MTFTPv4Sb 
...
184: DevPath (..00:0000:0000:0000:0000:0000))Load Net Pxebc 
...
19D: DevPath (..v4(0.0.0.0,UDP,DHCP,0.0.0.0))Load Net Pxebc
...

shell> dh 172
Handle 172 (730D8A98)
   Dpath (730D8E98) 
      ACPI Device Path for Acpi
       HID PNP0A03, UID 0
      Hardware Device Path for PCI
       Function (0) Device (19)
      Messaging Device Path for MAC
       MAC (FC15B4E81CAC)
      AsStr: 'PciRoot(0x0)/Pci(0x19,0x0)/MAC(FC15B4E81CAC,0x0)'
   Net (730C5020) 
   MNPSb (722D0F40) 
   ARPSb (722C13A0) 
   DHCPv4Sb (722C4220) 
   TCPv4Sb (722A7330) 
   IPv4Sb (72DF2A20) 
   IPv4Config (722AF638) 
   UDPv4Sb (722A3EA0) 
   MTFTPv4Sb (7229B4A0) 
   D79DF6B0-EF44-43BD-9797-43E93BCF5FA8 (722A6318)
...

shell> dh 184
Handle 184 (722AE898)
   Dpath (722ADA18) 
      ACPI Device Path for Acpi
       HID PNP0A03, UID 0
      Hardware Device Path for PCI
       Function (0) Device (19)
      Messaging Device Path for MAC
       MAC (FC15B4E81CAC)
      Messaging Device Path for IPv6
       IPv6 (Not Available)
      AsStr: 'PciRoot(0x0)/Pci(0x19,0x0)/MAC(FC15B4E81CAC,0x0)/IPv6(0000:0000:0000:0000:0000:0000:0000:0000,UDP,DHCP,0000:0000:0000:0000:0000:0000:0000:0000)'
   Load (722BB7A8) 
   Net (730C5020) 
   Pxebc (722B0110) 

shell> dh 19D
Handle 19D (72284598)
   Dpath (72284618) 
      ACPI Device Path for Acpi
       HID PNP0A03, UID 0
      Hardware Device Path for PCI
       Function (0) Device (19)
      Messaging Device Path for MAC
       MAC (FC15B4E81CAC)
      Messaging Device Path for IPv4
       IPv4 (Local IP: 0.0.0.0:0)
            (Remote IP: 0.0.0.0:0)
            (Protocol: 0)
            (Source IP: DHCP)
      AsStr: 'PciRoot(0x0)/Pci(0x19,0x0)/MAC(FC15B4E81CAC,0x0)/IPv4(0.0.0.0,UDP,DHCP,0.0.0.0)'
   Load (72284728) 
   Net (730C5020) 
   Pxebc (722B0110) 

The booting syslinux.efi receives DeviceHandle = 19D (IPv4); this handle has also attached to it the Pxebc Protocol 
but it does not have attached the Service Binding Protocol UDPv4Sb (in this case under the handle 172 instead).

The HP 2570p is not really an old PC (~2013) then I can think if we continue using the "same handle" method we will have 
problems PXE booting lot of UEFI PCs.
I think when we receive the image_DeviceHandle we must save it but also parse the associated DevicePath saving the MAC address too.
When looking for Pxebc Protocol we can use the image_DeviceHandle, next when ServiceBinding we need to detect 
all the available SB handles of the required type, parse their DevicePath and take the one with a matching MAC.

Let me know if you see any alternative to MAC parsing considering this new info.

Best,
Patrick