add vendor

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

@@ -0,0 +1,43 @@
+// Copyright 2012 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 Echo represents an ICMP echo request or reply message body.
+type Echo struct {
+	ID   int    // identifier
+	Seq  int    // sequence number
+	Data []byte // data
+}
+
+// Len implements the Len method of MessageBody interface.
+func (p *Echo) Len(proto int) int {
+	if p == nil {
+		return 0
+	}
+	return 4 + len(p.Data)
+}
+
+// Marshal implements the Marshal method of MessageBody interface.
+func (p *Echo) Marshal(proto int) ([]byte, error) {
+	b := make([]byte, 4+len(p.Data))
+	b[0], b[1] = byte(p.ID>>8), byte(p.ID)
+	b[2], b[3] = byte(p.Seq>>8), byte(p.Seq)
+	copy(b[4:], p.Data)
+	return b, nil
+}
+
+// parseEcho parses b as an ICMP echo request or reply message body.
+func parseEcho(proto int, b []byte) (MessageBody, error) {
+	bodyLen := len(b)
+	if bodyLen < 4 {
+		return nil, errMessageTooShort
+	}
+	p := &Echo{ID: int(b[0])<<8 | int(b[1]), Seq: int(b[2])<<8 | int(b[3])}
+	if bodyLen > 4 {
+		p.Data = make([]byte, bodyLen-4)
+		copy(p.Data, b[4:])
+	}
+	return p, nil
+}