Add field for permanent hardware address

Linux 5.6 and higher support IFLA_PERM_ADDRESS, which contains the
permanent hardware address of the interface if an interface has such an
address. This can be used to identify interfaces even when the normal
hardware address has been changed.

Signed-off-by: Lorenz Brun <lorenz@monogon.tech>

link.go

@@ -55,6 +55,7 @@ type LinkAttrs struct {
 	GROIPv4MaxSize uint32
 	Vfs            []VfInfo // virtual functions available on link
 	Group          uint32
+	PermHWAddr     net.HardwareAddr
 	Slave          LinkSlave
 }
 

link_linux.go

@@ -2246,6 +2246,13 @@ func LinkDeserialize(hdr *unix.NlMsghdr, m []byte) (Link, error) {
 			base.NumRxQueues = int(native.Uint32(attr.Value[0:4]))
 		case unix.IFLA_GROUP:
 			base.Group = native.Uint32(attr.Value[0:4])
+		case unix.IFLA_PERM_ADDRESS:
+			for _, b := range attr.Value {
+				if b != 0 {
+					base.PermHWAddr = attr.Value[:]
+					break
+				}
+			}
 		}
 	}