icmp: add extensions for interface and next-hop identification
This change implements ICMP extensions for interface and next-hop
identification which are used for route trace applications as described
in RFC 5837.
Change-Id: I2435109b5e766e743b894b0280a537324975489d
Reviewed-on: https://go-review.googlesource.com/3112
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/icmp/interface.go b/icmp/interface.go
new file mode 100644
index 0000000..806b26b
--- /dev/null
+++ b/icmp/interface.go
@@ -0,0 +1,232 @@
+// Copyright 2015 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 icmp
+
+import (
+ "net"
+ "strings"
+
+ "golang.org/x/net/internal/iana"
+)
+
+const (
+ classInterfaceInfo = 2
+
+ afiIPv4 = 1
+ afiIPv6 = 2
+)
+
+const (
+ attrMTU = 1 << iota
+ attrName
+ attrIPAddr
+ attrIfIndex
+)
+
+// An InterfaceInfo represents interface and next-hop identification.
+type InterfaceInfo struct {
+ Class int // extension object class number
+ Type int // extension object sub-type
+ Interface *net.Interface
+ Addr *net.IPAddr
+}
+
+func (ifi *InterfaceInfo) nameLen() int {
+ if len(ifi.Interface.Name) > 63 {
+ return 64
+ }
+ l := 1 + len(ifi.Interface.Name)
+ return (l + 3) &^ 3
+}
+
+func (ifi *InterfaceInfo) attrsAndLen(proto int) (attrs, l int) {
+ l = 4
+ if ifi.Interface != nil && ifi.Interface.Index > 0 {
+ attrs |= attrIfIndex
+ l += 4
+ if len(ifi.Interface.Name) > 0 {
+ attrs |= attrName
+ l += ifi.nameLen()
+ }
+ if ifi.Interface.MTU > 0 {
+ attrs |= attrMTU
+ l += 4
+ }
+ }
+ if ifi.Addr != nil {
+ switch proto {
+ case iana.ProtocolICMP:
+ if ifi.Addr.IP.To4() != nil {
+ attrs |= attrIPAddr
+ l += 4 + net.IPv4len
+ }
+ case iana.ProtocolIPv6ICMP:
+ if ifi.Addr.IP.To16() != nil && ifi.Addr.IP.To4() == nil {
+ attrs |= attrIPAddr
+ l += 4 + net.IPv6len
+ }
+ }
+ }
+ return
+}
+
+// Len implements the Len method of Extension interface.
+func (ifi *InterfaceInfo) Len(proto int) int {
+ _, l := ifi.attrsAndLen(proto)
+ return l
+}
+
+// Marshal implements the Marshal method of Extension interface.
+func (ifi *InterfaceInfo) Marshal(proto int) ([]byte, error) {
+ attrs, l := ifi.attrsAndLen(proto)
+ b := make([]byte, l)
+ if err := ifi.marshal(proto, b, attrs, l); err != nil {
+ return nil, err
+ }
+ return b, nil
+}
+
+func (ifi *InterfaceInfo) marshal(proto int, b []byte, attrs, l int) error {
+ b[0], b[1] = byte(l>>8), byte(l)
+ b[2], b[3] = classInterfaceInfo, byte(ifi.Type)
+ for b = b[4:]; len(b) > 0 && attrs != 0; {
+ switch {
+ case attrs&attrIfIndex != 0:
+ b = ifi.marshalIfIndex(proto, b)
+ attrs &^= attrIfIndex
+ case attrs&attrIPAddr != 0:
+ b = ifi.marshalIPAddr(proto, b)
+ attrs &^= attrIPAddr
+ case attrs&attrName != 0:
+ b = ifi.marshalName(proto, b)
+ attrs &^= attrName
+ case attrs&attrMTU != 0:
+ b = ifi.marshalMTU(proto, b)
+ attrs &^= attrMTU
+ }
+ }
+ return nil
+}
+
+func (ifi *InterfaceInfo) marshalIfIndex(proto int, b []byte) []byte {
+ b[0], b[1], b[2], b[3] = byte(ifi.Interface.Index>>24), byte(ifi.Interface.Index>>16), byte(ifi.Interface.Index>>8), byte(ifi.Interface.Index)
+ return b[4:]
+}
+
+func (ifi *InterfaceInfo) parseIfIndex(b []byte) ([]byte, error) {
+ if len(b) < 4 {
+ return nil, errMessageTooShort
+ }
+ ifi.Interface.Index = int(b[0])<<24 | int(b[1])<<16 | int(b[2])<<8 | int(b[3])
+ return b[4:], nil
+}
+
+func (ifi *InterfaceInfo) marshalIPAddr(proto int, b []byte) []byte {
+ switch proto {
+ case iana.ProtocolICMP:
+ b[0], b[1] = byte(afiIPv4>>8), byte(afiIPv4)
+ copy(b[4:4+net.IPv4len], ifi.Addr.IP.To4())
+ b = b[4+net.IPv4len:]
+ case iana.ProtocolIPv6ICMP:
+ b[0], b[1] = byte(afiIPv6>>8), byte(afiIPv6)
+ copy(b[4:4+net.IPv6len], ifi.Addr.IP.To16())
+ b = b[4+net.IPv6len:]
+ }
+ return b
+}
+
+func (ifi *InterfaceInfo) parseIPAddr(b []byte) ([]byte, error) {
+ if len(b) < 4 {
+ return nil, errMessageTooShort
+ }
+ afi := int(b[0])<<8 | int(b[1])
+ b = b[4:]
+ switch afi {
+ case afiIPv4:
+ if len(b) < net.IPv4len {
+ return nil, errMessageTooShort
+ }
+ ifi.Addr.IP = make(net.IP, net.IPv4len)
+ copy(ifi.Addr.IP, b[:net.IPv4len])
+ b = b[net.IPv4len:]
+ case afiIPv6:
+ if len(b) < net.IPv6len {
+ return nil, errMessageTooShort
+ }
+ ifi.Addr.IP = make(net.IP, net.IPv6len)
+ copy(ifi.Addr.IP, b[:net.IPv6len])
+ b = b[net.IPv6len:]
+ }
+ return b, nil
+}
+
+func (ifi *InterfaceInfo) marshalName(proto int, b []byte) []byte {
+ l := byte(ifi.nameLen())
+ b[0] = l
+ copy(b[1:], []byte(ifi.Interface.Name))
+ return b[l:]
+}
+
+func (ifi *InterfaceInfo) parseName(b []byte) ([]byte, error) {
+ if 4 > len(b) || len(b) < int(b[0]) {
+ return nil, errMessageTooShort
+ }
+ l := int(b[0])
+ var name [63]byte
+ copy(name[:], b[1:l])
+ ifi.Interface.Name = strings.Trim(string(name[:]), "\000")
+ return b[l:], nil
+}
+
+func (ifi *InterfaceInfo) marshalMTU(proto int, b []byte) []byte {
+ b[0], b[1], b[2], b[3] = byte(ifi.Interface.MTU>>24), byte(ifi.Interface.MTU>>16), byte(ifi.Interface.MTU>>8), byte(ifi.Interface.MTU)
+ return b[4:]
+}
+
+func (ifi *InterfaceInfo) parseMTU(b []byte) ([]byte, error) {
+ if len(b) < 4 {
+ return nil, errMessageTooShort
+ }
+ ifi.Interface.MTU = int(b[0])<<24 | int(b[1])<<16 | int(b[2])<<8 | int(b[3])
+ return b[4:], nil
+}
+
+func parseInterfaceInfo(b []byte) (Extension, error) {
+ ifi := &InterfaceInfo{
+ Class: int(b[2]),
+ Type: int(b[3]),
+ }
+ if ifi.Type&(attrIfIndex|attrName|attrMTU) != 0 {
+ ifi.Interface = &net.Interface{}
+ }
+ if ifi.Type&attrIPAddr != 0 {
+ ifi.Addr = &net.IPAddr{}
+ }
+ attrs := ifi.Type & (attrIfIndex | attrIPAddr | attrName | attrMTU)
+ for b = b[4:]; len(b) > 0 && attrs != 0; {
+ var err error
+ switch {
+ case attrs&attrIfIndex != 0:
+ b, err = ifi.parseIfIndex(b)
+ attrs &^= attrIfIndex
+ case attrs&attrIPAddr != 0:
+ b, err = ifi.parseIPAddr(b)
+ attrs &^= attrIPAddr
+ case attrs&attrName != 0:
+ b, err = ifi.parseName(b)
+ attrs &^= attrName
+ case attrs&attrMTU != 0:
+ b, err = ifi.parseMTU(b)
+ attrs &^= attrMTU
+ }
+ if err != nil {
+ return nil, err
+ }
+ }
+ if ifi.Interface != nil && ifi.Interface.Name != "" && ifi.Addr != nil && ifi.Addr.IP.To16() != nil && ifi.Addr.IP.To4() == nil {
+ ifi.Addr.Zone = ifi.Interface.Name
+ }
+ return ifi, nil
+}
