initial commit

vendor/golang.org/x/net/icmp/extension.go

@@ -0,0 +1,87 @@
+// 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
+
+// An Extension represents an ICMP extension.
+type Extension interface {
+	// Len returns the length of ICMP extension.
+	// Proto must be either the ICMPv4 or ICMPv6 protocol number.
+	Len(proto int) int
+
+	// Marshal returns the binary enconding of ICMP extension.
+	// Proto must be either the ICMPv4 or ICMPv6 protocol number.
+	Marshal(proto int) ([]byte, error)
+}
+
+const extensionVersion = 2
+
+func validExtensionHeader(b []byte) bool {
+	v := int(b[0]&0xf0) >> 4
+	s := uint16(b[2])<<8 | uint16(b[3])
+	if s != 0 {
+		s = checksum(b)
+	}
+	if v != extensionVersion || s != 0 {
+		return false
+	}
+	return true
+}
+
+// parseExtensions parses b as a list of ICMP extensions.
+// The length attribute l must be the length attribute field in
+// received icmp messages.
+//
+// It will return a list of ICMP extensions and an adjusted length
+// attribute that represents the length of the padded original
+// datagram field. Otherwise, it returns an error.
+func parseExtensions(b []byte, l int) ([]Extension, int, error) {
+	// Still a lot of non-RFC 4884 compliant implementations are
+	// out there. Set the length attribute l to 128 when it looks
+	// inappropriate for backwards compatibility.
+	//
+	// A minimal extension at least requires 8 octets; 4 octets
+	// for an extension header, and 4 octets for a single object
+	// header.
+	//
+	// See RFC 4884 for further information.
+	if 128 > l || l+8 > len(b) {
+		l = 128
+	}
+	if l+8 > len(b) {
+		return nil, -1, errNoExtension
+	}
+	if !validExtensionHeader(b[l:]) {
+		if l == 128 {
+			return nil, -1, errNoExtension
+		}
+		l = 128
+		if !validExtensionHeader(b[l:]) {
+			return nil, -1, errNoExtension
+		}
+	}
+	var exts []Extension
+	for b = b[l+4:]; len(b) >= 4; {
+		ol := int(b[0])<<8 | int(b[1])
+		if 4 > ol || ol > len(b) {
+			break
+		}
+		switch b[2] {
+		case classMPLSLabelStack:
+			ext, err := parseMPLSLabelStack(b[:ol])
+			if err != nil {
+				return nil, -1, err
+			}
+			exts = append(exts, ext)
+		case classInterfaceInfo:
+			ext, err := parseInterfaceInfo(b[:ol])
+			if err != nil {
+				return nil, -1, err
+			}
+			exts = append(exts, ext)
+		}
+		b = b[ol:]
+	}
+	return exts, l, nil
+}