begin adding packet capture functionality

arp/definitions.go

@@ -14,6 +14,7 @@ var (
 	errARPBufferFull  = errors.New("ARP client need handling:too many ops pending")
 	errShortARP       = errors.New("packet too short to be ARP")
 	errARPUnsupported = errors.New("ARP not supprortedf")
+	errLargeSizes     = errors.New("size of ARP protocol+hardware is unusually large")
 )
 
 // Operation represents the type of ARP packet, either request or reply/response.

arp/frame.go

@@ -138,9 +138,11 @@ func (afrm Frame) SwapTargetSender() {
 func (afrm Frame) ValidateSize(v *lneto.Validator) {
 	_, hlen := afrm.Hardware()
 	_, ilen := afrm.Protocol()
-	minLen := 8 + 2*(hlen+ilen)
+	minLen := 8 + 2*(int(hlen)+int(ilen))
 	if len(afrm.buf) < int(minLen) {
 		v.AddError(errShortARP)
+	} else if minLen > 255 {
+		v.AddError(errLargeSizes) // We don't want a uint8 overflow somewhere. This is probably a maliciously crafted packet.
 	}
 }