diff --git a/ipv4/control_bsd.go b/ipv4/control_bsd.go
index 63cd6c6..cd9dc87 100644
--- a/ipv4/control_bsd.go
+++ b/ipv4/control_bsd.go
@@ -55,7 +55,7 @@
 	if opt.isset(FlagTTL) {
 		b := make([]byte, syscall.CmsgSpace(1))
 		cmsg := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
-		cmsg.Level = syscall.IPPROTO_IP
+		cmsg.Level = ianaProtocolIP
 		cmsg.Type = syscall.IP_RECVTTL
 		cmsg.SetLen(syscall.CmsgLen(1))
 		oob = append(oob, b...)
@@ -63,7 +63,7 @@
 	if opt.isset(FlagDst) {
 		b := make([]byte, syscall.CmsgSpace(net.IPv4len))
 		cmsg := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
-		cmsg.Level = syscall.IPPROTO_IP
+		cmsg.Level = ianaProtocolIP
 		cmsg.Type = syscall.IP_RECVDSTADDR
 		cmsg.SetLen(syscall.CmsgLen(net.IPv4len))
 		oob = append(oob, b...)
@@ -71,7 +71,7 @@
 	if opt.isset(FlagInterface) {
 		b := make([]byte, syscall.CmsgSpace(syscall.SizeofSockaddrDatalink))
 		cmsg := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
-		cmsg.Level = syscall.IPPROTO_IP
+		cmsg.Level = ianaProtocolIP
 		cmsg.Type = syscall.IP_RECVIF
 		cmsg.SetLen(syscall.CmsgLen(syscall.SizeofSockaddrDatalink))
 		oob = append(oob, b...)
@@ -89,7 +89,7 @@
 	}
 	cm := &ControlMessage{}
 	for _, m := range cmsgs {
-		if m.Header.Level != syscall.IPPROTO_IP {
+		if m.Header.Level != ianaProtocolIP {
 			continue
 		}
 		switch m.Header.Type {
diff --git a/ipv4/control_linux.go b/ipv4/control_linux.go
index 51b9a14..cf2dcf0 100644
--- a/ipv4/control_linux.go
+++ b/ipv4/control_linux.go
@@ -47,7 +47,7 @@
 	if opt.isset(FlagTTL) {
 		b := make([]byte, syscall.CmsgSpace(1))
 		cmsg := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
-		cmsg.Level = syscall.IPPROTO_IP
+		cmsg.Level = ianaProtocolIP
 		cmsg.Type = syscall.IP_RECVTTL
 		cmsg.SetLen(syscall.CmsgLen(1))
 		oob = append(oob, b...)
@@ -55,7 +55,7 @@
 	if opt.isset(pktinfo) {
 		b := make([]byte, syscall.CmsgSpace(syscall.SizeofInet4Pktinfo))
 		cmsg := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
-		cmsg.Level = syscall.IPPROTO_IP
+		cmsg.Level = ianaProtocolIP
 		cmsg.Type = syscall.IP_PKTINFO
 		cmsg.SetLen(syscall.CmsgLen(syscall.SizeofInet4Pktinfo))
 		oob = append(oob, b...)
@@ -73,7 +73,7 @@
 	}
 	cm := &ControlMessage{}
 	for _, m := range cmsgs {
-		if m.Header.Level != syscall.IPPROTO_IP {
+		if m.Header.Level != ianaProtocolIP {
 			continue
 		}
 		switch m.Header.Type {
@@ -105,7 +105,7 @@
 	if pion {
 		b := make([]byte, syscall.CmsgSpace(syscall.SizeofInet4Pktinfo))
 		cmsg := (*syscall.Cmsghdr)(unsafe.Pointer(&b[0]))
-		cmsg.Level = syscall.IPPROTO_IP
+		cmsg.Level = ianaProtocolIP
 		cmsg.Type = syscall.IP_PKTINFO
 		cmsg.SetLen(syscall.CmsgLen(syscall.SizeofInet4Pktinfo))
 		data := b[syscall.CmsgLen(0):]
diff --git a/ipv4/doc.go b/ipv4/doc.go
index 05be70d..ffdb9ff 100644
--- a/ipv4/doc.go
+++ b/ipv4/doc.go
@@ -8,9 +8,7 @@
 // The package provides IP-level socket options that allow
 // manipulation of IPv4 facilities.  The IPv4 and basic host
 // requirements for IPv4 are defined in RFC 791, RFC 1112 and RFC
-// 1122.  A series of RFC 2474, RFC 2475, RFC 2597, RFC 2598 and RFC
-// 3168 describe how to use the type-of-service field in a DiffServ,
-// differentiated services environment.
+// 1122.
 //
 //
 // Unicasting
@@ -38,7 +36,7 @@
 // The outgoing packets will be labeled DiffServ assured forwarding
 // class 1 low drop precedence, as known as AF11 packets.
 //
-//			err := ipv4.NewConn(c).SetTOS(ipv4.DSCP_AF11)
+//			err := ipv4.NewConn(c).SetTOS(DiffServAF11)
 //			if err != nil {
 //				// error handling
 //			}
@@ -125,7 +123,7 @@
 //
 // The application can also send both unicast and multicast packets.
 //
-//		p.SetTOS(ipv4.DSCP_CS0)
+//		p.SetTOS(DiffServCS0)
 //		p.SetTTL(16)
 //		_, err = p.WriteTo(data, nil, src)
 //		if err != nil {
diff --git a/ipv4/example_test.go b/ipv4/example_test.go
index ac202d3..bd4dc67 100644
--- a/ipv4/example_test.go
+++ b/ipv4/example_test.go
@@ -23,7 +23,7 @@
 		}
 		go func(c net.Conn) {
 			defer c.Close()
-			err := ipv4.NewConn(c).SetTOS(ipv4.DSCP_AF11)
+			err := ipv4.NewConn(c).SetTOS(DiffServAF11)
 			if err != nil {
 				log.Fatal(err)
 			}
@@ -81,7 +81,7 @@
 				continue
 			}
 		}
-		p.SetTOS(ipv4.DSCP_CS7)
+		p.SetTOS(DiffServCS7)
 		p.SetTTL(16)
 		_, err = p.WriteTo(b[:n], nil, src)
 		if err != nil {
@@ -150,7 +150,7 @@
 	}
 	ifs = append(ifs, en1)
 
-	c, err := net.ListenPacket("ip4:89", "0.0.0.0")
+	c, err := net.ListenPacket("ip4:89", "0.0.0.0") // OSFP for IPv4
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -175,7 +175,7 @@
 	if err != nil {
 		log.Fatal(err)
 	}
-	r.SetTOS(ipv4.DSCP_CS6)
+	r.SetTOS(DiffServCS6)
 
 	parseOSPFHeader := func(b []byte) *OSPFHeader {
 		if len(b) < OSPFHeaderLen {
@@ -235,7 +235,7 @@
 	}
 	ifs = append(ifs, en1)
 
-	c, err := net.ListenPacket("ip4:89", "0.0.0.0")
+	c, err := net.ListenPacket("ip4:89", "0.0.0.0") // OSPF for IPv4
 	if err != nil {
 		log.Fatal(err)
 	}
@@ -264,7 +264,7 @@
 	iph := &ipv4.Header{}
 	iph.Version = ipv4.Version
 	iph.Len = ipv4.HeaderLen
-	iph.TOS = ipv4.DSCP_CS6
+	iph.TOS = DiffServCS6
 	iph.TotalLen = ipv4.HeaderLen + len(ospf)
 	iph.TTL = 1
 	iph.Protocol = 89
diff --git a/ipv4/gen.go b/ipv4/gen.go
new file mode 100644
index 0000000..673065f
--- /dev/null
+++ b/ipv4/gen.go
@@ -0,0 +1,242 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+// This program generates internet protocol constatns and tables by
+// reading IANA protocol registries.
+//
+// Usage of this program:
+//	go run gen.go > iana.go
+package main
+
+import (
+	"bytes"
+	"encoding/xml"
+	"fmt"
+	"go/format"
+	"io"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+)
+
+var registries = []struct {
+	url   string
+	parse func(io.Writer, io.Reader) error
+}{
+	{
+		"http://www.iana.org/assignments/icmp-parameters",
+		parseICMPv4Parameters,
+	},
+	{
+		"http://www.iana.org/assignments/protocol-numbers/protocol-numbers.xml",
+		parseProtocolNumbers,
+	},
+}
+
+func main() {
+	var bb bytes.Buffer
+	fmt.Fprintf(&bb, "// go run gen.go\n")
+	fmt.Fprintf(&bb, "// GENERATED BY THE COMMAND ABOVE; DO NOT EDIT\n\n")
+	fmt.Fprintf(&bb, "package ipv4\n\n")
+	for _, r := range registries {
+		resp, err := http.Get(r.url)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		defer resp.Body.Close()
+		if resp.StatusCode != http.StatusOK {
+			fmt.Fprintf(os.Stderr, "got HTTP status code %v for %v\n", resp.StatusCode, r.url)
+			os.Exit(1)
+		}
+		if err := r.parse(&bb, resp.Body); err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		fmt.Fprintf(&bb, "\n")
+	}
+	b, err := format.Source(bb.Bytes())
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+	os.Stdout.Write(b)
+}
+
+func parseICMPv4Parameters(w io.Writer, r io.Reader) error {
+	dec := xml.NewDecoder(r)
+	var icp icmpv4Parameters
+	if err := dec.Decode(&icp); err != nil {
+		return err
+	}
+	prs := icp.escape(0)
+	fmt.Fprintf(w, "// %s, Updated: %s\n", icp.Title, icp.Updated)
+	fmt.Fprintf(w, "const (\n")
+	for _, pr := range prs {
+		if pr.Descr == "" {
+			continue
+		}
+		fmt.Fprintf(w, "ICMPType%s ICMPType = %d", pr.Descr, pr.Value)
+		fmt.Fprintf(w, "// %s\n", pr.OrigDescr)
+	}
+	fmt.Fprintf(w, ")\n\n")
+	fmt.Fprintf(w, "// %s, Updated: %s\n", icp.Title, icp.Updated)
+	fmt.Fprintf(w, "var icmpTypes = map[ICMPType]string{\n")
+	for _, pr := range prs {
+		if pr.Descr == "" {
+			continue
+		}
+		fmt.Fprintf(w, "%d: %q,\n", pr.Value, strings.ToLower(pr.OrigDescr))
+	}
+	fmt.Fprintf(w, "}\n")
+	return nil
+}
+
+type icmpv4Parameters struct {
+	XMLName    xml.Name              `xml:"registry"`
+	Title      string                `xml:"title"`
+	Updated    string                `xml:"updated"`
+	Registries []icmpv4ParamRegistry `xml:"registry"`
+}
+
+type icmpv4ParamRegistry struct {
+	Title   string              `xml:"title"`
+	Records []icmpv4ParamRecord `xml:"record"`
+}
+
+type icmpv4ParamRecord struct {
+	Value string `xml:"value"`
+	Descr string `xml:"description"`
+}
+
+type canonICMPv4ParamRecord struct {
+	OrigDescr string
+	Descr     string
+	Value     int
+}
+
+func (icp *icmpv4Parameters) escape(id int) []canonICMPv4ParamRecord {
+	prs := make([]canonICMPv4ParamRecord, len(icp.Registries[id].Records))
+	sr := strings.NewReplacer(
+		"Messages", "",
+		"Message", "",
+		"ICMP", "",
+		"+", "P",
+		"-", "",
+		"/", "",
+		".", "",
+		" ", "",
+	)
+	for i, pr := range icp.Registries[id].Records {
+		if strings.Contains(pr.Descr, "Reserved") ||
+			strings.Contains(pr.Descr, "Unassigned") ||
+			strings.Contains(pr.Descr, "Deprecated") ||
+			strings.Contains(pr.Descr, "Experiment") ||
+			strings.Contains(pr.Descr, "experiment") {
+			continue
+		}
+		ss := strings.Split(pr.Descr, "\n")
+		if len(ss) > 1 {
+			prs[i].Descr = strings.Join(ss, " ")
+		} else {
+			prs[i].Descr = ss[0]
+		}
+		s := strings.TrimSpace(prs[i].Descr)
+		prs[i].OrigDescr = s
+		prs[i].Descr = sr.Replace(s)
+		prs[i].Value, _ = strconv.Atoi(pr.Value)
+	}
+	return prs
+}
+
+func parseProtocolNumbers(w io.Writer, r io.Reader) error {
+	dec := xml.NewDecoder(r)
+	var pn protocolNumbers
+	if err := dec.Decode(&pn); err != nil {
+		return err
+	}
+	prs := pn.escape()
+	prs = append([]canonProtocolRecord{{
+		Name:  "IP",
+		Descr: "IPv4 encapsulation, pseudo protocol number",
+		Value: 0,
+	}}, prs...)
+	fmt.Fprintf(w, "// %s, Updated: %s\n", pn.Title, pn.Updated)
+	fmt.Fprintf(w, "const (\n")
+	for _, pr := range prs {
+		if pr.Name == "" {
+			continue
+		}
+		fmt.Fprintf(w, "ianaProtocol%s = %d", pr.Name, pr.Value)
+		s := pr.Descr
+		if s == "" {
+			s = pr.OrigName
+		}
+		fmt.Fprintf(w, "// %s\n", s)
+	}
+	fmt.Fprintf(w, ")\n")
+	return nil
+}
+
+type protocolNumbers struct {
+	XMLName  xml.Name         `xml:"registry"`
+	Title    string           `xml:"title"`
+	Updated  string           `xml:"updated"`
+	RegTitle string           `xml:"registry>title"`
+	Note     string           `xml:"registry>note"`
+	Records  []protocolRecord `xml:"registry>record"`
+}
+
+type protocolRecord struct {
+	Value string `xml:"value"`
+	Name  string `xml:"name"`
+	Descr string `xml:"description"`
+}
+
+type canonProtocolRecord struct {
+	OrigName string
+	Name     string
+	Descr    string
+	Value    int
+}
+
+func (pn *protocolNumbers) escape() []canonProtocolRecord {
+	prs := make([]canonProtocolRecord, len(pn.Records))
+	sr := strings.NewReplacer(
+		"-in-", "in",
+		"-within-", "within",
+		"-over-", "over",
+		"+", "P",
+		"-", "",
+		"/", "",
+		".", "",
+		" ", "",
+	)
+	for i, pr := range pn.Records {
+		prs[i].OrigName = pr.Name
+		s := strings.TrimSpace(pr.Name)
+		switch pr.Name {
+		case "ISIS over IPv4":
+			prs[i].Name = "ISIS"
+		case "manet":
+			prs[i].Name = "MANET"
+		default:
+			prs[i].Name = sr.Replace(s)
+		}
+		ss := strings.Split(pr.Descr, "\n")
+		for i := range ss {
+			ss[i] = strings.TrimSpace(ss[i])
+		}
+		if len(ss) > 1 {
+			prs[i].Descr = strings.Join(ss, " ")
+		} else {
+			prs[i].Descr = ss[0]
+		}
+		prs[i].Value, _ = strconv.Atoi(pr.Value)
+	}
+	return prs
+}
diff --git a/ipv4/gentest.go b/ipv4/gentest.go
new file mode 100644
index 0000000..cc35225
--- /dev/null
+++ b/ipv4/gentest.go
@@ -0,0 +1,196 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+// This program generates internet protocol constants by reading IANA
+// protocol registries.
+//
+// Usage:
+//	go run gentest.go > iana_test.go
+package main
+
+import (
+	"bytes"
+	"encoding/xml"
+	"fmt"
+	"go/format"
+	"io"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+)
+
+var registries = []struct {
+	url   string
+	parse func(io.Writer, io.Reader) error
+}{
+	{
+		"http://www.iana.org/assignments/dscp-registry/dscp-registry.xml",
+		parseDSCPRegistry,
+	},
+	{
+		"http://www.iana.org/assignments/ipv4-tos-byte/ipv4-tos-byte.xml",
+		parseTOSTCByte,
+	},
+}
+
+func main() {
+	var bb bytes.Buffer
+	fmt.Fprintf(&bb, "// go run gentv.go\n")
+	fmt.Fprintf(&bb, "// GENERATED BY THE COMMAND ABOVE; DO NOT EDIT\n\n")
+	fmt.Fprintf(&bb, "package ipv4_test\n\n")
+	for _, r := range registries {
+		resp, err := http.Get(r.url)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		defer resp.Body.Close()
+		if resp.StatusCode != http.StatusOK {
+			fmt.Fprintf(os.Stderr, "got HTTP status code %v for %v\n", resp.StatusCode, r.url)
+			os.Exit(1)
+		}
+		if err := r.parse(&bb, resp.Body); err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+		fmt.Fprintf(&bb, "\n")
+	}
+	b, err := format.Source(bb.Bytes())
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+	os.Stdout.Write(b)
+}
+
+func parseDSCPRegistry(w io.Writer, r io.Reader) error {
+	dec := xml.NewDecoder(r)
+	var dr dscpRegistry
+	if err := dec.Decode(&dr); err != nil {
+		return err
+	}
+	drs := dr.escape()
+	fmt.Fprintf(w, "// %s, Updated: %s\n", dr.Title, dr.Updated)
+	fmt.Fprintf(w, "const (\n")
+	for _, dr := range drs {
+		fmt.Fprintf(w, "DiffServ%s = %#x", dr.Name, dr.Value)
+		fmt.Fprintf(w, "// %s\n", dr.OrigName)
+	}
+	fmt.Fprintf(w, ")\n")
+	return nil
+}
+
+type dscpRegistry struct {
+	XMLName     xml.Name     `xml:"registry"`
+	Title       string       `xml:"title"`
+	Updated     string       `xml:"updated"`
+	Note        string       `xml:"note"`
+	RegTitle    string       `xml:"registry>title"`
+	PoolRecords []dscpRecord `xml:"registry>record"`
+	Records     []dscpRecord `xml:"registry>registry>record"`
+}
+
+type dscpRecord struct {
+	Name  string `xml:"name"`
+	Space string `xml:"space"`
+}
+
+type canonDSCPRecord struct {
+	OrigName string
+	Name     string
+	Value    int
+}
+
+func (drr *dscpRegistry) escape() []canonDSCPRecord {
+	drs := make([]canonDSCPRecord, len(drr.Records))
+	sr := strings.NewReplacer(
+		"+", "",
+		"-", "",
+		"/", "",
+		".", "",
+		" ", "",
+	)
+	for i, dr := range drr.Records {
+		s := strings.TrimSpace(dr.Name)
+		drs[i].OrigName = s
+		drs[i].Name = sr.Replace(s)
+		n, err := strconv.ParseUint(dr.Space, 2, 8)
+		if err != nil {
+			continue
+		}
+		drs[i].Value = int(n) << 2
+	}
+	return drs
+}
+
+func parseTOSTCByte(w io.Writer, r io.Reader) error {
+	dec := xml.NewDecoder(r)
+	var ttb tosTCByte
+	if err := dec.Decode(&ttb); err != nil {
+		return err
+	}
+	trs := ttb.escape()
+	fmt.Fprintf(w, "// %s, Updated: %s\n", ttb.Title, ttb.Updated)
+	fmt.Fprintf(w, "const (\n")
+	for _, tr := range trs {
+		fmt.Fprintf(w, "%s = %#x", tr.Keyword, tr.Value)
+		fmt.Fprintf(w, "// %s\n", tr.OrigKeyword)
+	}
+	fmt.Fprintf(w, ")\n")
+	return nil
+}
+
+type tosTCByte struct {
+	XMLName  xml.Name          `xml:"registry"`
+	Title    string            `xml:"title"`
+	Updated  string            `xml:"updated"`
+	Note     string            `xml:"note"`
+	RegTitle string            `xml:"registry>title"`
+	Records  []tosTCByteRecord `xml:"registry>record"`
+}
+
+type tosTCByteRecord struct {
+	Binary  string `xml:"binary"`
+	Keyword string `xml:"keyword"`
+}
+
+type canonTOSTCByteRecord struct {
+	OrigKeyword string
+	Keyword     string
+	Value       int
+}
+
+func (ttb *tosTCByte) escape() []canonTOSTCByteRecord {
+	trs := make([]canonTOSTCByteRecord, len(ttb.Records))
+	sr := strings.NewReplacer(
+		"Capable", "",
+		"(", "",
+		")", "",
+		"+", "",
+		"-", "",
+		"/", "",
+		".", "",
+		" ", "",
+	)
+	for i, tr := range ttb.Records {
+		s := strings.TrimSpace(tr.Keyword)
+		trs[i].OrigKeyword = s
+		ss := strings.Split(s, " ")
+		if len(ss) > 1 {
+			trs[i].Keyword = strings.Join(ss[1:], " ")
+		} else {
+			trs[i].Keyword = ss[0]
+		}
+		trs[i].Keyword = sr.Replace(trs[i].Keyword)
+		n, err := strconv.ParseUint(tr.Binary, 2, 8)
+		if err != nil {
+			continue
+		}
+		trs[i].Value = int(n)
+	}
+	return trs
+}
diff --git a/ipv4/header.go b/ipv4/header.go
index 2e953fd..45bd27a 100644
--- a/ipv4/header.go
+++ b/ipv4/header.go
@@ -29,18 +29,6 @@
 //	http://tools.ietf.org/html/rfc1112
 // RFC 1122  Requirements for Internet Hosts
 //	http://tools.ietf.org/html/rfc1122
-// RFC 2474  Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers
-//	http://tools.ietf.org/html/rfc2474
-// RFC 2475  An Architecture for Differentiated Services
-//	http://tools.ietf.org/html/rfc2475
-// RFC 2597  Assured Forwarding PHB Group
-//	http://tools.ietf.org/html/rfc2597
-// RFC 2598  An Expedited Forwarding PHB
-//	http://tools.ietf.org/html/rfc2598
-// RFC 3168  The Addition of Explicit Congestion Notification (ECN) to IP
-//	http://tools.ietf.org/html/rfc3168
-// RFC 3260  New Terminology and Clarifications for Diffserv
-//	http://tools.ietf.org/html/rfc3260
 
 const (
 	Version      = 4  // protocol version
@@ -48,39 +36,6 @@
 	maxHeaderLen = 60 // sensible default, revisit if later RFCs define new usage of version and header length fields
 )
 
-const (
-	// DiffServ class selector codepoints in RFC 2474.
-	DSCP_CS0 = 0x00 // best effort
-	DSCP_CS1 = 0x20 // class 1
-	DSCP_CS2 = 0x40 // class 2
-	DSCP_CS3 = 0x60 // class 3
-	DSCP_CS4 = 0x80 // class 4
-	DSCP_CS5 = 0xa0 // expedited forwarding
-	DSCP_CS6 = 0xc0 // subsume deprecated IP precedence, internet control (routing information update)
-	DSCP_CS7 = 0xe0 // subsume deprecated IP precedence, network control (link, neighbor liveliness check)
-
-	// DiffServ assured forwarding codepoints in RFC 2474, 2475, 2597 and 3260.
-	DSCP_AF11 = 0x28 // class 1 low drop precedence
-	DSCP_AF12 = 0x30 // class 1 medium drop precedence
-	DSCP_AF13 = 0x38 // class 1 high drop precedence
-	DSCP_AF21 = 0x48 // class 2 low drop precedence
-	DSCP_AF22 = 0x50 // class 2 medium drop precedence
-	DSCP_AF23 = 0x58 // class 2 high drop precedence
-	DSCP_AF31 = 0x68 // class 3 low drop precedence
-	DSCP_AF32 = 0x70 // class 3 medium drop precedence
-	DSCP_AF33 = 0x78 // class 3 high drop precedence
-	DSCP_AF41 = 0x88 // class 4 low drop precedence
-	DSCP_AF42 = 0x90 // class 4 medium drop precedence
-	DSCP_AF43 = 0x98 // class 4 high drop precedence
-	DSCP_EF   = 0xb8 // expedited forwarding
-
-	// ECN codepoints in RFC 3168.
-	ECN_NOTECT = 0x00 // not ECN-capable transport
-	ECN_ECT1   = 0x01 // ECN-capable transport, ECT(1)
-	ECN_ECT0   = 0x02 // ECN-capable transport, ECT(0)
-	ECN_CE     = 0x03 // congestion experienced
-)
-
 type headerField int
 
 const (
diff --git a/ipv4/iana.go b/ipv4/iana.go
new file mode 100644
index 0000000..254d019
--- /dev/null
+++ b/ipv4/iana.go
@@ -0,0 +1,179 @@
+// go run gen.go
+// GENERATED BY THE COMMAND ABOVE; DO NOT EDIT
+
+package ipv4
+
+// Internet Control Message Protocol (ICMP) Parameters, Updated: 2013-04-19
+const (
+	ICMPTypeEchoReply              ICMPType = 0  // Echo Reply
+	ICMPTypeDestinationUnreachable ICMPType = 3  // Destination Unreachable
+	ICMPTypeRedirect               ICMPType = 5  // Redirect
+	ICMPTypeEcho                   ICMPType = 8  // Echo
+	ICMPTypeRouterAdvertisement    ICMPType = 9  // Router Advertisement
+	ICMPTypeRouterSolicitation     ICMPType = 10 // Router Solicitation
+	ICMPTypeTimeExceeded           ICMPType = 11 // Time Exceeded
+	ICMPTypeParameterProblem       ICMPType = 12 // Parameter Problem
+	ICMPTypeTimestamp              ICMPType = 13 // Timestamp
+	ICMPTypeTimestampReply         ICMPType = 14 // Timestamp Reply
+	ICMPTypePhoturis               ICMPType = 40 // Photuris
+)
+
+// Internet Control Message Protocol (ICMP) Parameters, Updated: 2013-04-19
+var icmpTypes = map[ICMPType]string{
+	0:  "echo reply",
+	3:  "destination unreachable",
+	5:  "redirect",
+	8:  "echo",
+	9:  "router advertisement",
+	10: "router solicitation",
+	11: "time exceeded",
+	12: "parameter problem",
+	13: "timestamp",
+	14: "timestamp reply",
+	40: "photuris",
+}
+
+// Protocol Numbers, Updated: 2013-02-17
+const (
+	ianaProtocolIP             = 0   // IPv4 encapsulation, pseudo protocol number
+	ianaProtocolHOPOPT         = 0   // IPv6 Hop-by-Hop Option
+	ianaProtocolICMP           = 1   // Internet Control Message
+	ianaProtocolIGMP           = 2   // Internet Group Management
+	ianaProtocolGGP            = 3   // Gateway-to-Gateway
+	ianaProtocolIPv4           = 4   // IPv4 encapsulation
+	ianaProtocolST             = 5   // Stream
+	ianaProtocolTCP            = 6   // Transmission Control
+	ianaProtocolCBT            = 7   // CBT
+	ianaProtocolEGP            = 8   // Exterior Gateway Protocol
+	ianaProtocolIGP            = 9   // any private interior gateway (used by Cisco for their IGRP)
+	ianaProtocolBBNRCCMON      = 10  // BBN RCC Monitoring
+	ianaProtocolNVPII          = 11  // Network Voice Protocol
+	ianaProtocolPUP            = 12  // PUP
+	ianaProtocolARGUS          = 13  // ARGUS
+	ianaProtocolEMCON          = 14  // EMCON
+	ianaProtocolXNET           = 15  // Cross Net Debugger
+	ianaProtocolCHAOS          = 16  // Chaos
+	ianaProtocolUDP            = 17  // User Datagram
+	ianaProtocolMUX            = 18  // Multiplexing
+	ianaProtocolDCNMEAS        = 19  // DCN Measurement Subsystems
+	ianaProtocolHMP            = 20  // Host Monitoring
+	ianaProtocolPRM            = 21  // Packet Radio Measurement
+	ianaProtocolXNSIDP         = 22  // XEROX NS IDP
+	ianaProtocolTRUNK1         = 23  // Trunk-1
+	ianaProtocolTRUNK2         = 24  // Trunk-2
+	ianaProtocolLEAF1          = 25  // Leaf-1
+	ianaProtocolLEAF2          = 26  // Leaf-2
+	ianaProtocolRDP            = 27  // Reliable Data Protocol
+	ianaProtocolIRTP           = 28  // Internet Reliable Transaction
+	ianaProtocolISOTP4         = 29  // ISO Transport Protocol Class 4
+	ianaProtocolNETBLT         = 30  // Bulk Data Transfer Protocol
+	ianaProtocolMFENSP         = 31  // MFE Network Services Protocol
+	ianaProtocolMERITINP       = 32  // MERIT Internodal Protocol
+	ianaProtocolDCCP           = 33  // Datagram Congestion Control Protocol
+	ianaProtocol3PC            = 34  // Third Party Connect Protocol
+	ianaProtocolIDPR           = 35  // Inter-Domain Policy Routing Protocol
+	ianaProtocolXTP            = 36  // XTP
+	ianaProtocolDDP            = 37  // Datagram Delivery Protocol
+	ianaProtocolIDPRCMTP       = 38  // IDPR Control Message Transport Proto
+	ianaProtocolTPPP           = 39  // TP++ Transport Protocol
+	ianaProtocolIL             = 40  // IL Transport Protocol
+	ianaProtocolIPv6           = 41  // IPv6 encapsulation
+	ianaProtocolSDRP           = 42  // Source Demand Routing Protocol
+	ianaProtocolIPv6Route      = 43  // Routing Header for IPv6
+	ianaProtocolIPv6Frag       = 44  // Fragment Header for IPv6
+	ianaProtocolIDRP           = 45  // Inter-Domain Routing Protocol
+	ianaProtocolRSVP           = 46  // Reservation Protocol
+	ianaProtocolGRE            = 47  // Generic Routing Encapsulation
+	ianaProtocolDSR            = 48  // Dynamic Source Routing Protocol
+	ianaProtocolBNA            = 49  // BNA
+	ianaProtocolESP            = 50  // Encap Security Payload
+	ianaProtocolAH             = 51  // Authentication Header
+	ianaProtocolINLSP          = 52  // Integrated Net Layer Security  TUBA
+	ianaProtocolSWIPE          = 53  // IP with Encryption
+	ianaProtocolNARP           = 54  // NBMA Address Resolution Protocol
+	ianaProtocolMOBILE         = 55  // IP Mobility
+	ianaProtocolTLSP           = 56  // Transport Layer Security Protocol using Kryptonet key management
+	ianaProtocolSKIP           = 57  // SKIP
+	ianaProtocolIPv6ICMP       = 58  // ICMP for IPv6
+	ianaProtocolIPv6NoNxt      = 59  // No Next Header for IPv6
+	ianaProtocolIPv6Opts       = 60  // Destination Options for IPv6
+	ianaProtocolCFTP           = 62  // CFTP
+	ianaProtocolSATEXPAK       = 64  // SATNET and Backroom EXPAK
+	ianaProtocolKRYPTOLAN      = 65  // Kryptolan
+	ianaProtocolRVD            = 66  // MIT Remote Virtual Disk Protocol
+	ianaProtocolIPPC           = 67  // Internet Pluribus Packet Core
+	ianaProtocolSATMON         = 69  // SATNET Monitoring
+	ianaProtocolVISA           = 70  // VISA Protocol
+	ianaProtocolIPCV           = 71  // Internet Packet Core Utility
+	ianaProtocolCPNX           = 72  // Computer Protocol Network Executive
+	ianaProtocolCPHB           = 73  // Computer Protocol Heart Beat
+	ianaProtocolWSN            = 74  // Wang Span Network
+	ianaProtocolPVP            = 75  // Packet Video Protocol
+	ianaProtocolBRSATMON       = 76  // Backroom SATNET Monitoring
+	ianaProtocolSUNND          = 77  // SUN ND PROTOCOL-Temporary
+	ianaProtocolWBMON          = 78  // WIDEBAND Monitoring
+	ianaProtocolWBEXPAK        = 79  // WIDEBAND EXPAK
+	ianaProtocolISOIP          = 80  // ISO Internet Protocol
+	ianaProtocolVMTP           = 81  // VMTP
+	ianaProtocolSECUREVMTP     = 82  // SECURE-VMTP
+	ianaProtocolVINES          = 83  // VINES
+	ianaProtocolTTP            = 84  // TTP
+	ianaProtocolIPTM           = 84  // Protocol Internet Protocol Traffic Manager
+	ianaProtocolNSFNETIGP      = 85  // NSFNET-IGP
+	ianaProtocolDGP            = 86  // Dissimilar Gateway Protocol
+	ianaProtocolTCF            = 87  // TCF
+	ianaProtocolEIGRP          = 88  // EIGRP
+	ianaProtocolOSPFIGP        = 89  // OSPFIGP
+	ianaProtocolSpriteRPC      = 90  // Sprite RPC Protocol
+	ianaProtocolLARP           = 91  // Locus Address Resolution Protocol
+	ianaProtocolMTP            = 92  // Multicast Transport Protocol
+	ianaProtocolAX25           = 93  // AX.25 Frames
+	ianaProtocolIPIP           = 94  // IP-within-IP Encapsulation Protocol
+	ianaProtocolMICP           = 95  // Mobile Internetworking Control Pro.
+	ianaProtocolSCCSP          = 96  // Semaphore Communications Sec. Pro.
+	ianaProtocolETHERIP        = 97  // Ethernet-within-IP Encapsulation
+	ianaProtocolENCAP          = 98  // Encapsulation Header
+	ianaProtocolGMTP           = 100 // GMTP
+	ianaProtocolIFMP           = 101 // Ipsilon Flow Management Protocol
+	ianaProtocolPNNI           = 102 // PNNI over IP
+	ianaProtocolPIM            = 103 // Protocol Independent Multicast
+	ianaProtocolARIS           = 104 // ARIS
+	ianaProtocolSCPS           = 105 // SCPS
+	ianaProtocolQNX            = 106 // QNX
+	ianaProtocolAN             = 107 // Active Networks
+	ianaProtocolIPComp         = 108 // IP Payload Compression Protocol
+	ianaProtocolSNP            = 109 // Sitara Networks Protocol
+	ianaProtocolCompaqPeer     = 110 // Compaq Peer Protocol
+	ianaProtocolIPXinIP        = 111 // IPX in IP
+	ianaProtocolVRRP           = 112 // Virtual Router Redundancy Protocol
+	ianaProtocolPGM            = 113 // PGM Reliable Transport Protocol
+	ianaProtocolL2TP           = 115 // Layer Two Tunneling Protocol
+	ianaProtocolDDX            = 116 // D-II Data Exchange (DDX)
+	ianaProtocolIATP           = 117 // Interactive Agent Transfer Protocol
+	ianaProtocolSTP            = 118 // Schedule Transfer Protocol
+	ianaProtocolSRP            = 119 // SpectraLink Radio Protocol
+	ianaProtocolUTI            = 120 // UTI
+	ianaProtocolSMP            = 121 // Simple Message Protocol
+	ianaProtocolSM             = 122 // SM
+	ianaProtocolPTP            = 123 // Performance Transparency Protocol
+	ianaProtocolISIS           = 124 // ISIS over IPv4
+	ianaProtocolFIRE           = 125 // FIRE
+	ianaProtocolCRTP           = 126 // Combat Radio Transport Protocol
+	ianaProtocolCRUDP          = 127 // Combat Radio User Datagram
+	ianaProtocolSSCOPMCE       = 128 // SSCOPMCE
+	ianaProtocolIPLT           = 129 // IPLT
+	ianaProtocolSPS            = 130 // Secure Packet Shield
+	ianaProtocolPIPE           = 131 // Private IP Encapsulation within IP
+	ianaProtocolSCTP           = 132 // Stream Control Transmission Protocol
+	ianaProtocolFC             = 133 // Fibre Channel
+	ianaProtocolRSVPE2EIGNORE  = 134 // RSVP-E2E-IGNORE
+	ianaProtocolMobilityHeader = 135 // Mobility Header
+	ianaProtocolUDPLite        = 136 // UDPLite
+	ianaProtocolMPLSinIP       = 137 // MPLS-in-IP
+	ianaProtocolMANET          = 138 // MANET Protocols
+	ianaProtocolHIP            = 139 // Host Identity Protocol
+	ianaProtocolShim6          = 140 // Shim6 Protocol
+	ianaProtocolWESP           = 141 // Wrapped Encapsulating Security Payload
+	ianaProtocolROHC           = 142 // Robust Header Compression
+	ianaProtocolReserved       = 255 // Reserved
+)
diff --git a/ipv4/iana_test.go b/ipv4/iana_test.go
new file mode 100644
index 0000000..276230d
--- /dev/null
+++ b/ipv4/iana_test.go
@@ -0,0 +1,38 @@
+// go run gentv.go
+// GENERATED BY THE COMMAND ABOVE; DO NOT EDIT
+
+package ipv4_test
+
+// Differentiated Services Field Codepoints, Updated: 2010-05-11
+const (
+	DiffServCS0        = 0x0  // CS0
+	DiffServCS1        = 0x20 // CS1
+	DiffServCS2        = 0x40 // CS2
+	DiffServCS3        = 0x60 // CS3
+	DiffServCS4        = 0x80 // CS4
+	DiffServCS5        = 0xa0 // CS5
+	DiffServCS6        = 0xc0 // CS6
+	DiffServCS7        = 0xe0 // CS7
+	DiffServAF11       = 0x28 // AF11
+	DiffServAF12       = 0x30 // AF12
+	DiffServAF13       = 0x38 // AF13
+	DiffServAF21       = 0x48 // AF21
+	DiffServAF22       = 0x50 // AF22
+	DiffServAF23       = 0x58 // AF23
+	DiffServAF31       = 0x68 // AF31
+	DiffServAF32       = 0x70 // AF32
+	DiffServAF33       = 0x78 // AF33
+	DiffServAF41       = 0x88 // AF41
+	DiffServAF42       = 0x90 // AF42
+	DiffServAF43       = 0x98 // AF43
+	DiffServEFPHB      = 0xb8 // EF PHB
+	DiffServVOICEADMIT = 0xb0 // VOICE-ADMIT
+)
+
+// IPv4 TOS Byte and IPv6 Traffic Class Octet, Updated: 2001-09-06
+const (
+	NotECNTransport       = 0x0 // Not-ECT (Not ECN-Capable Transport)
+	ECNTransport1         = 0x1 // ECT(1) (ECN-Capable Transport(1))
+	ECNTransport0         = 0x2 // ECT(0) (ECN-Capable Transport(0))
+	CongestionExperienced = 0x3 // CE (Congestion Experienced)
+)
diff --git a/ipv4/icmp.go b/ipv4/icmp.go
new file mode 100644
index 0000000..d595967
--- /dev/null
+++ b/ipv4/icmp.go
@@ -0,0 +1,16 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ipv4
+
+// An ICMPType represents a type of ICMP message.
+type ICMPType int
+
+func (typ ICMPType) String() string {
+	s, ok := icmpTypes[typ]
+	if !ok {
+		return "<nil>"
+	}
+	return s
+}
diff --git a/ipv4/mockicmp_test.go b/ipv4/mockicmp_test.go
index 7b9ee06..b799197 100644
--- a/ipv4/mockicmp_test.go
+++ b/ipv4/mockicmp_test.go
@@ -5,22 +5,16 @@
 package ipv4_test
 
 import (
+	"code.google.com/p/go.net/ipv4"
 	"errors"
 	"flag"
 )
 
 var testExternal = flag.Bool("external", true, "allow use of external networks during long test")
 
-const (
-	icmpv4EchoRequest = 8
-	icmpv4EchoReply   = 0
-	icmpv6EchoRequest = 128
-	icmpv6EchoReply   = 129
-)
-
 // icmpMessage represents an ICMP message.
 type icmpMessage struct {
-	Type     int             // type
+	Type     ipv4.ICMPType   // type
 	Code     int             // code
 	Checksum int             // checksum
 	Body     icmpMessageBody // body
@@ -43,10 +37,6 @@
 		}
 		b = append(b, mb...)
 	}
-	switch m.Type {
-	case icmpv6EchoRequest, icmpv6EchoReply:
-		return b, nil
-	}
 	csumcv := len(b) - 1 // checksum coverage
 	s := uint32(0)
 	for i := 0; i < csumcv; i += 2 {
@@ -70,11 +60,11 @@
 	if msglen < 4 {
 		return nil, errors.New("message too short")
 	}
-	m := &icmpMessage{Type: int(b[0]), Code: int(b[1]), Checksum: int(b[2])<<8 | int(b[3])}
+	m := &icmpMessage{Type: ipv4.ICMPType(b[0]), Code: int(b[1]), Checksum: int(b[2])<<8 | int(b[3])}
 	if msglen > 4 {
 		var err error
 		switch m.Type {
-		case icmpv4EchoRequest, icmpv4EchoReply, icmpv6EchoRequest, icmpv6EchoReply:
+		case ipv4.ICMPTypeEcho, ipv4.ICMPTypeEchoReply:
 			m.Body, err = parseICMPEcho(b[4:])
 			if err != nil {
 				return nil, err
diff --git a/ipv4/multicast_test.go b/ipv4/multicast_test.go
index 307eea1..a12d242 100644
--- a/ipv4/multicast_test.go
+++ b/ipv4/multicast_test.go
@@ -85,7 +85,7 @@
 	cf := ipv4.FlagTTL | ipv4.FlagDst | ipv4.FlagInterface
 	for i, toggle := range []bool{true, false, true} {
 		wb, err := (&icmpMessage{
-			Type: icmpv4EchoRequest, Code: 0,
+			Type: ipv4.ICMPTypeEcho, Code: 0,
 			Body: &icmpEcho{
 				ID: os.Getpid() & 0xffff, Seq: i + 1,
 				Data: []byte("HELLO-R-U-THERE"),
@@ -102,8 +102,8 @@
 		if err != nil {
 			t.Fatalf("parseICMPMessage failed: %v", err)
 		}
-		if m.Type != icmpv4EchoReply || m.Code != 0 {
-			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, icmpv4EchoReply, 0)
+		if m.Type != ipv4.ICMPTypeEchoReply || m.Code != 0 {
+			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, ipv4.ICMPTypeEchoReply, 0)
 		}
 	}
 }
@@ -144,7 +144,7 @@
 	cf := ipv4.FlagTTL | ipv4.FlagDst | ipv4.FlagInterface
 	for i, toggle := range []bool{true, false, true} {
 		wb, err := (&icmpMessage{
-			Type: icmpv4EchoRequest, Code: 0,
+			Type: ipv4.ICMPTypeEcho, Code: 0,
 			Body: &icmpEcho{
 				ID: os.Getpid() & 0xffff, Seq: i + 1,
 				Data: []byte("HELLO-R-U-THERE"),
@@ -161,8 +161,8 @@
 		if err != nil {
 			t.Fatalf("parseICMPMessage failed: %v", err)
 		}
-		if m.Type != icmpv4EchoReply || m.Code != 0 {
-			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, icmpv4EchoReply, 0)
+		if m.Type != ipv4.ICMPTypeEchoReply || m.Code != 0 {
+			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, ipv4.ICMPTypeEchoReply, 0)
 		}
 	}
 }
diff --git a/ipv4/multicastsockopt_test.go b/ipv4/multicastsockopt_test.go
index e8a7691..009364d 100644
--- a/ipv4/multicastsockopt_test.go
+++ b/ipv4/multicastsockopt_test.go
@@ -33,8 +33,8 @@
 }
 
 var multicastSockoptTests = []multicastSockoptTest{
-	{ipv4.DSCP_CS0 | ipv4.ECN_NOTECT, 127, 128, false, net.IPv4(224, 0, 0, 249)}, // see RFC 4727
-	{ipv4.DSCP_AF11 | ipv4.ECN_NOTECT, 255, 254, true, net.IPv4(224, 0, 0, 250)}, // see RFC 4727
+	{DiffServCS0 | NotECNTransport, 127, 128, false, net.IPv4(224, 0, 0, 249)}, // see RFC 4727
+	{DiffServAF11 | NotECNTransport, 255, 254, true, net.IPv4(224, 0, 0, 250)}, // see RFC 4727
 }
 
 func TestUDPMulticastSockopt(t *testing.T) {
diff --git a/ipv4/sockopt_bsd.go b/ipv4/sockopt_bsd.go
index 46ab31c..040a196 100644
--- a/ipv4/sockopt_bsd.go
+++ b/ipv4/sockopt_bsd.go
@@ -13,7 +13,7 @@
 )
 
 func ipv4MulticastTTL(fd int) (int, error) {
-	v, err := syscall.GetsockoptByte(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_TTL)
+	v, err := syscall.GetsockoptByte(fd, ianaProtocolIP, syscall.IP_MULTICAST_TTL)
 	if err != nil {
 		return 0, os.NewSyscallError("getsockopt", err)
 	}
@@ -21,7 +21,7 @@
 }
 
 func setIPv4MulticastTTL(fd int, v int) error {
-	err := syscall.SetsockoptByte(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_TTL, byte(v))
+	err := syscall.SetsockoptByte(fd, ianaProtocolIP, syscall.IP_MULTICAST_TTL, byte(v))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -29,7 +29,7 @@
 }
 
 func ipv4ReceiveDestinationAddress(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_RECVDSTADDR)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_RECVDSTADDR)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -37,7 +37,7 @@
 }
 
 func setIPv4ReceiveDestinationAddress(fd int, v bool) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_RECVDSTADDR, boolint(v))
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_RECVDSTADDR, boolint(v))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -45,7 +45,7 @@
 }
 
 func ipv4ReceiveInterface(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_RECVIF)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_RECVIF)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -53,7 +53,7 @@
 }
 
 func setIPv4ReceiveInterface(fd int, v bool) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_RECVIF, boolint(v))
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_RECVIF, boolint(v))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -61,7 +61,7 @@
 }
 
 func ipv4MulticastInterface(fd int) (*net.Interface, error) {
-	a, err := syscall.GetsockoptInet4Addr(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF)
+	a, err := syscall.GetsockoptInet4Addr(fd, ianaProtocolIP, syscall.IP_MULTICAST_IF)
 	if err != nil {
 		return nil, os.NewSyscallError("getsockopt", err)
 	}
@@ -75,7 +75,7 @@
 	}
 	var a [4]byte
 	copy(a[:], ip.To4())
-	err = syscall.SetsockoptInet4Addr(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF, a)
+	err = syscall.SetsockoptInet4Addr(fd, ianaProtocolIP, syscall.IP_MULTICAST_IF, a)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -83,7 +83,7 @@
 }
 
 func ipv4MulticastLoopback(fd int) (bool, error) {
-	v, err := syscall.GetsockoptByte(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_LOOP)
+	v, err := syscall.GetsockoptByte(fd, ianaProtocolIP, syscall.IP_MULTICAST_LOOP)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -91,7 +91,7 @@
 }
 
 func setIPv4MulticastLoopback(fd int, v bool) error {
-	err := syscall.SetsockoptByte(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_LOOP, byte(boolint(v)))
+	err := syscall.SetsockoptByte(fd, ianaProtocolIP, syscall.IP_MULTICAST_LOOP, byte(boolint(v)))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -103,7 +103,7 @@
 	if err := setSyscallIPMreq(mreq, ifi); err != nil {
 		return err
 	}
-	err := syscall.SetsockoptIPMreq(fd, syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreq)
+	err := syscall.SetsockoptIPMreq(fd, ianaProtocolIP, syscall.IP_ADD_MEMBERSHIP, mreq)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -115,7 +115,7 @@
 	if err := setSyscallIPMreq(mreq, ifi); err != nil {
 		return err
 	}
-	err := syscall.SetsockoptIPMreq(fd, syscall.IPPROTO_IP, syscall.IP_DROP_MEMBERSHIP, mreq)
+	err := syscall.SetsockoptIPMreq(fd, ianaProtocolIP, syscall.IP_DROP_MEMBERSHIP, mreq)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
diff --git a/ipv4/sockopt_freebsd.go b/ipv4/sockopt_freebsd.go
index 6bcd66f..8c4d2cb 100644
--- a/ipv4/sockopt_freebsd.go
+++ b/ipv4/sockopt_freebsd.go
@@ -10,7 +10,7 @@
 )
 
 func ipv4SendSourceAddress(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_SENDSRCADDR)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_SENDSRCADDR)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -18,7 +18,7 @@
 }
 
 func setIPv4SendSourceAddress(fd int, v bool) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_SENDSRCADDR, boolint(v))
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_SENDSRCADDR, boolint(v))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
diff --git a/ipv4/sockopt_linux.go b/ipv4/sockopt_linux.go
index 8c0ca06..22f78c9 100644
--- a/ipv4/sockopt_linux.go
+++ b/ipv4/sockopt_linux.go
@@ -11,7 +11,7 @@
 )
 
 func ipv4ReceiveTOS(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_RECVTOS)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_RECVTOS)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -19,7 +19,7 @@
 }
 
 func setIPv4ReceiveTOS(fd int, v bool) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_RECVTOS, boolint(v))
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_RECVTOS, boolint(v))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -27,7 +27,7 @@
 }
 
 func ipv4MulticastTTL(fd int) (int, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_TTL)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_MULTICAST_TTL)
 	if err != nil {
 		return 0, os.NewSyscallError("getsockopt", err)
 	}
@@ -35,7 +35,7 @@
 }
 
 func setIPv4MulticastTTL(fd int, v int) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_TTL, v)
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_MULTICAST_TTL, v)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -43,7 +43,7 @@
 }
 
 func ipv4PacketInfo(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_PKTINFO)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_PKTINFO)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -51,7 +51,7 @@
 }
 
 func setIPv4PacketInfo(fd int, v bool) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_PKTINFO, boolint(v))
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_PKTINFO, boolint(v))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -59,7 +59,7 @@
 }
 
 func ipv4MulticastInterface(fd int) (*net.Interface, error) {
-	mreqn, err := syscall.GetsockoptIPMreqn(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF)
+	mreqn, err := syscall.GetsockoptIPMreqn(fd, ianaProtocolIP, syscall.IP_MULTICAST_IF)
 	if err != nil {
 		return nil, os.NewSyscallError("getsockopt", err)
 	}
@@ -74,7 +74,7 @@
 	if ifi != nil {
 		mreqn.Ifindex = int32(ifi.Index)
 	}
-	err := syscall.SetsockoptIPMreqn(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF, mreqn)
+	err := syscall.SetsockoptIPMreqn(fd, ianaProtocolIP, syscall.IP_MULTICAST_IF, mreqn)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -82,7 +82,7 @@
 }
 
 func ipv4MulticastLoopback(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_LOOP)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_MULTICAST_LOOP)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -90,7 +90,7 @@
 }
 
 func setIPv4MulticastLoopback(fd int, v bool) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_LOOP, boolint(v))
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_MULTICAST_LOOP, boolint(v))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -102,7 +102,7 @@
 	if ifi != nil {
 		mreqn.Ifindex = int32(ifi.Index)
 	}
-	err := syscall.SetsockoptIPMreqn(fd, syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreqn)
+	err := syscall.SetsockoptIPMreqn(fd, ianaProtocolIP, syscall.IP_ADD_MEMBERSHIP, mreqn)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -114,7 +114,7 @@
 	if ifi != nil {
 		mreqn.Ifindex = int32(ifi.Index)
 	}
-	err := syscall.SetsockoptIPMreqn(fd, syscall.IPPROTO_IP, syscall.IP_DROP_MEMBERSHIP, mreqn)
+	err := syscall.SetsockoptIPMreqn(fd, ianaProtocolIP, syscall.IP_DROP_MEMBERSHIP, mreqn)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
diff --git a/ipv4/sockopt_unix.go b/ipv4/sockopt_unix.go
index ef000ec..f5c1092 100644
--- a/ipv4/sockopt_unix.go
+++ b/ipv4/sockopt_unix.go
@@ -12,7 +12,7 @@
 )
 
 func ipv4TOS(fd int) (int, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_TOS)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_TOS)
 	if err != nil {
 		return 0, os.NewSyscallError("getsockopt", err)
 	}
@@ -20,7 +20,7 @@
 }
 
 func setIPv4TOS(fd int, v int) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_TOS, v)
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_TOS, v)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -28,7 +28,7 @@
 }
 
 func ipv4TTL(fd int) (int, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_TTL)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_TTL)
 	if err != nil {
 		return 0, os.NewSyscallError("getsockopt", err)
 	}
@@ -36,7 +36,7 @@
 }
 
 func setIPv4TTL(fd int, v int) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_TTL, v)
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_TTL, v)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -44,7 +44,7 @@
 }
 
 func ipv4ReceiveTTL(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_RECVTTL)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_RECVTTL)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -52,7 +52,7 @@
 }
 
 func setIPv4ReceiveTTL(fd int, v bool) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_RECVTTL, boolint(v))
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_RECVTTL, boolint(v))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -60,7 +60,7 @@
 }
 
 func ipv4HeaderPrepend(fd int) (bool, error) {
-	v, err := syscall.GetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_HDRINCL)
+	v, err := syscall.GetsockoptInt(fd, ianaProtocolIP, syscall.IP_HDRINCL)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -68,7 +68,7 @@
 }
 
 func setIPv4HeaderPrepend(fd int, v bool) error {
-	err := syscall.SetsockoptInt(fd, syscall.IPPROTO_IP, syscall.IP_HDRINCL, boolint(v))
+	err := syscall.SetsockoptInt(fd, ianaProtocolIP, syscall.IP_HDRINCL, boolint(v))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
diff --git a/ipv4/sockopt_windows.go b/ipv4/sockopt_windows.go
index b1e4edf..e84be74 100644
--- a/ipv4/sockopt_windows.go
+++ b/ipv4/sockopt_windows.go
@@ -17,7 +17,7 @@
 func ipv4TOS(fd syscall.Handle) (int, error) {
 	var v int32
 	l := int32(4)
-	err := syscall.Getsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_TOS), (*byte)(unsafe.Pointer(&v)), &l)
+	err := syscall.Getsockopt(fd, ianaProtocolIP, syscall.IP_TOS, (*byte)(unsafe.Pointer(&v)), &l)
 	if err != nil {
 		return 0, os.NewSyscallError("getsockopt", err)
 	}
@@ -26,7 +26,7 @@
 
 func setIPv4TOS(fd syscall.Handle, v int) error {
 	vv := int32(v)
-	err := syscall.Setsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_TOS), (*byte)(unsafe.Pointer(&vv)), 4)
+	err := syscall.Setsockopt(fd, ianaProtocolIP, syscall.IP_TOS, (*byte)(unsafe.Pointer(&vv)), 4)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -36,7 +36,7 @@
 func ipv4TTL(fd syscall.Handle) (int, error) {
 	var v int32
 	l := int32(4)
-	err := syscall.Getsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_TTL), (*byte)(unsafe.Pointer(&v)), &l)
+	err := syscall.Getsockopt(fd, ianaProtocolIP, syscall.IP_TTL, (*byte)(unsafe.Pointer(&v)), &l)
 	if err != nil {
 		return 0, os.NewSyscallError("getsockopt", err)
 	}
@@ -45,7 +45,7 @@
 
 func setIPv4TTL(fd syscall.Handle, v int) error {
 	vv := int32(v)
-	err := syscall.Setsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_TTL), (*byte)(unsafe.Pointer(&vv)), 4)
+	err := syscall.Setsockopt(fd, ianaProtocolIP, syscall.IP_TTL, (*byte)(unsafe.Pointer(&vv)), 4)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -55,7 +55,7 @@
 func ipv4MulticastTTL(fd syscall.Handle) (int, error) {
 	var v int32
 	l := int32(4)
-	err := syscall.Getsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_MULTICAST_TTL), (*byte)(unsafe.Pointer(&v)), &l)
+	err := syscall.Getsockopt(fd, ianaProtocolIP, syscall.IP_MULTICAST_TTL, (*byte)(unsafe.Pointer(&v)), &l)
 	if err != nil {
 		return 0, os.NewSyscallError("getsockopt", err)
 	}
@@ -64,7 +64,7 @@
 
 func setIPv4MulticastTTL(fd syscall.Handle, v int) error {
 	vv := int32(v)
-	err := syscall.Setsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_MULTICAST_TTL), (*byte)(unsafe.Pointer(&vv)), 4)
+	err := syscall.Setsockopt(fd, ianaProtocolIP, syscall.IP_MULTICAST_TTL, (*byte)(unsafe.Pointer(&vv)), 4)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -114,7 +114,7 @@
 func ipv4MulticastInterface(fd syscall.Handle) (*net.Interface, error) {
 	var a [4]byte
 	l := int32(4)
-	err := syscall.Getsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_MULTICAST_IF), (*byte)(unsafe.Pointer(&a[0])), &l)
+	err := syscall.Getsockopt(fd, ianaProtocolIP, syscall.IP_MULTICAST_IF, (*byte)(unsafe.Pointer(&a[0])), &l)
 	if err != nil {
 		return nil, os.NewSyscallError("getsockopt", err)
 	}
@@ -128,7 +128,7 @@
 	}
 	var a [4]byte
 	copy(a[:], ip.To4())
-	err = syscall.Setsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_MULTICAST_IF), (*byte)(unsafe.Pointer(&a[0])), 4)
+	err = syscall.Setsockopt(fd, ianaProtocolIP, syscall.IP_MULTICAST_IF, (*byte)(unsafe.Pointer(&a[0])), 4)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -138,7 +138,7 @@
 func ipv4MulticastLoopback(fd syscall.Handle) (bool, error) {
 	var v int32
 	l := int32(4)
-	err := syscall.Getsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_MULTICAST_LOOP), (*byte)(unsafe.Pointer(&v)), &l)
+	err := syscall.Getsockopt(fd, ianaProtocolIP, syscall.IP_MULTICAST_LOOP, (*byte)(unsafe.Pointer(&v)), &l)
 	if err != nil {
 		return false, os.NewSyscallError("getsockopt", err)
 	}
@@ -147,7 +147,7 @@
 
 func setIPv4MulticastLoopback(fd syscall.Handle, v bool) error {
 	vv := int32(boolint(v))
-	err := syscall.Setsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_MULTICAST_LOOP), (*byte)(unsafe.Pointer(&vv)), 4)
+	err := syscall.Setsockopt(fd, ianaProtocolIP, syscall.IP_MULTICAST_LOOP, (*byte)(unsafe.Pointer(&vv)), 4)
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -159,7 +159,7 @@
 	if err := setSyscallIPMreq(mreq, ifi); err != nil {
 		return err
 	}
-	err := syscall.Setsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_ADD_MEMBERSHIP), (*byte)(unsafe.Pointer(mreq)), int32(unsafe.Sizeof(*mreq)))
+	err := syscall.Setsockopt(fd, ianaProtocolIP, syscall.IP_ADD_MEMBERSHIP, (*byte)(unsafe.Pointer(mreq)), int32(unsafe.Sizeof(*mreq)))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
@@ -171,7 +171,7 @@
 	if err := setSyscallIPMreq(mreq, ifi); err != nil {
 		return err
 	}
-	err := syscall.Setsockopt(fd, int32(syscall.IPPROTO_IP), int32(syscall.IP_DROP_MEMBERSHIP), (*byte)(unsafe.Pointer(mreq)), int32(unsafe.Sizeof(*mreq)))
+	err := syscall.Setsockopt(fd, ianaProtocolIP, syscall.IP_DROP_MEMBERSHIP, (*byte)(unsafe.Pointer(mreq)), int32(unsafe.Sizeof(*mreq)))
 	if err != nil {
 		return os.NewSyscallError("setsockopt", err)
 	}
diff --git a/ipv4/unicast_test.go b/ipv4/unicast_test.go
index c601ee1..5a0061e 100644
--- a/ipv4/unicast_test.go
+++ b/ipv4/unicast_test.go
@@ -53,7 +53,7 @@
 	cf := ipv4.FlagTTL | ipv4.FlagDst | ipv4.FlagInterface
 	for i, toggle := range []bool{true, false, true} {
 		wb, err := (&icmpMessage{
-			Type: icmpv4EchoRequest, Code: 0,
+			Type: ipv4.ICMPTypeEcho, Code: 0,
 			Body: &icmpEcho{
 				ID: os.Getpid() & 0xffff, Seq: i + 1,
 				Data: []byte("HELLO-R-U-THERE"),
@@ -70,8 +70,8 @@
 		if err != nil {
 			t.Fatalf("parseICMPMessage failed: %v", err)
 		}
-		if m.Type != icmpv4EchoReply || m.Code != 0 {
-			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, icmpv4EchoReply, 0)
+		if m.Type != ipv4.ICMPTypeEchoReply || m.Code != 0 {
+			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, ipv4.ICMPTypeEchoReply, 0)
 		}
 	}
 }
@@ -98,7 +98,7 @@
 	cf := ipv4.FlagTTL | ipv4.FlagDst | ipv4.FlagInterface
 	for i, toggle := range []bool{true, false, true} {
 		wb, err := (&icmpMessage{
-			Type: icmpv4EchoRequest, Code: 0,
+			Type: ipv4.ICMPTypeEcho, Code: 0,
 			Body: &icmpEcho{
 				ID: os.Getpid() & 0xffff, Seq: i + 1,
 				Data: []byte("HELLO-R-U-THERE"),
@@ -115,8 +115,8 @@
 		if err != nil {
 			t.Fatalf("parseICMPMessage failed: %v", err)
 		}
-		if m.Type != icmpv4EchoReply || m.Code != 0 {
-			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, icmpv4EchoReply, 0)
+		if m.Type != ipv4.ICMPTypeEchoReply || m.Code != 0 {
+			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, ipv4.ICMPTypeEchoReply, 0)
 		}
 	}
 }
diff --git a/ipv4/unicastsockopt_test.go b/ipv4/unicastsockopt_test.go
index ea9bb76..3816ab3 100644
--- a/ipv4/unicastsockopt_test.go
+++ b/ipv4/unicastsockopt_test.go
@@ -28,8 +28,8 @@
 }
 
 var unicastSockoptTests = []unicastSockoptTest{
-	{ipv4.DSCP_CS0 | ipv4.ECN_NOTECT, 127},
-	{ipv4.DSCP_AF11 | ipv4.ECN_NOTECT, 255},
+	{DiffServCS0 | NotECNTransport, 127},
+	{DiffServAF11 | NotECNTransport, 255},
 }
 
 func TestTCPUnicastSockopt(t *testing.T) {