add FieldClassOperation to pcap and associated formatting changes

internet/pcap/capture.go

@@ -670,6 +670,7 @@ const (
 	FieldClassAddress                     // address
 	// FieldClassBinaryText represents long stretches of binary data such as BOOTP DHCPv4 field.
 	FieldClassBinaryText // binary-text
+	FieldClassOperation  // op
 )
 
 const octet = 8
@@ -718,8 +719,7 @@ var baseARPFields = [...]FrameField{
 		BitLength:      1 * octet,
 	},
 	{
-		Name:           "Opcode",
-		Class:          FieldClassType,
+		Class:          FieldClassOperation,
 		FrameBitOffset: 6 * octet,
 		BitLength:      2 * octet,
 	},
@@ -924,8 +924,7 @@ var baseUDPFields = [...]FrameField{
 
 var baseDHCPv4Fields = [...]FrameField{
 	{
-		Name:           "Opcode",
-		Class:          FieldClassType,
+		Class:          FieldClassOperation,
 		FrameBitOffset: 0,
 		BitLength:      1 * octet,
 	},

internet/pcap/format.go

@@ -112,7 +112,7 @@ func (f *Formatter) formatField(dst []byte, pktStartOff int, field FrameField, p
 		dst = hex.AppendEncode(dst, f.buf)
 	case FieldClassText:
 		dst = strconv.AppendQuote(dst, string(f.buf))
-	case FieldClassDst, FieldClassSrc, FieldClassSize, FieldClassAddress:
+	case FieldClassDst, FieldClassSrc, FieldClassSize, FieldClassAddress, FieldClassOperation:
 		// IP, MAC addresses and ports.
 		if field.BitLength <= 16 {
 			v, err := fieldAsUint(pkt, fieldBitStart, field.BitLength, field.RightAligned)

internet/pcap/stringers.go

@@ -23,11 +23,12 @@ func _() {
 	_ = x[FieldClassText-12]
 	_ = x[FieldClassAddress-13]
 	_ = x[FieldClassBinaryText-14]
+	_ = x[FieldClassOperation-15]
 }
 
-const _FieldClass_name = "undefinedsourcedestinationprotocolversiontypesizeflagsidentificationchecksumoptionspayloadtextaddressbinary-text"
+const _FieldClass_name = "undefinedsourcedestinationprotocolversiontypesizeflagsidentificationchecksumoptionspayloadtextaddressbinary-textop"
 
-var _FieldClass_index = [...]uint8{0, 9, 15, 26, 34, 41, 45, 49, 54, 68, 76, 83, 90, 94, 101, 112}
+var _FieldClass_index = [...]uint8{0, 9, 15, 26, 34, 41, 45, 49, 54, 68, 76, 83, 90, 94, 101, 112, 114}
 
 func (i FieldClass) String() string {
 	if i >= FieldClass(len(_FieldClass_index)-1) {