diff --git a/unum/vendor/golang.org/x/net/icmp/message.go b/unum/vendor/golang.org/x/net/icmp/message.go
new file mode 100644
index 0000000..81140b0
--- /dev/null
+++ b/unum/vendor/golang.org/x/net/icmp/message.go
@@ -0,0 +1,152 @@
+// 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 provides basic functions for the manipulation of
+// messages used in the Internet Control Message Protocols,
+// ICMPv4 and ICMPv6.
+//
+// ICMPv4 and ICMPv6 are defined in RFC 792 and RFC 4443.
+// Multi-part message support for ICMP is defined in RFC 4884.
+// ICMP extensions for MPLS are defined in RFC 4950.
+// ICMP extensions for interface and next-hop identification are
+// defined in RFC 5837.
+package icmp // import "golang.org/x/net/icmp"
+
+import (
+	"encoding/binary"
+	"errors"
+	"net"
+	"syscall"
+
+	"golang.org/x/net/internal/iana"
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
+)
+
+// BUG(mikio): This package is not implemented on NaCl and Plan 9.
+
+var (
+	errMessageTooShort  = errors.New("message too short")
+	errHeaderTooShort   = errors.New("header too short")
+	errBufferTooShort   = errors.New("buffer too short")
+	errOpNoSupport      = errors.New("operation not supported")
+	errNoExtension      = errors.New("no extension")
+	errInvalidExtension = errors.New("invalid extension")
+)
+
+func checksum(b []byte) uint16 {
+	csumcv := len(b) - 1 // checksum coverage
+	s := uint32(0)
+	for i := 0; i < csumcv; i += 2 {
+		s += uint32(b[i+1])<<8 | uint32(b[i])
+	}
+	if csumcv&1 == 0 {
+		s += uint32(b[csumcv])
+	}
+	s = s>>16 + s&0xffff
+	s = s + s>>16
+	return ^uint16(s)
+}
+
+// A Type represents an ICMP message type.
+type Type interface {
+	Protocol() int
+}
+
+// A Message represents an ICMP message.
+type Message struct {
+	Type     Type        // type, either ipv4.ICMPType or ipv6.ICMPType
+	Code     int         // code
+	Checksum int         // checksum
+	Body     MessageBody // body
+}
+
+// Marshal returns the binary encoding of the ICMP message m.
+//
+// For an ICMPv4 message, the returned message always contains the
+// calculated checksum field.
+//
+// For an ICMPv6 message, the returned message contains the calculated
+// checksum field when psh is not nil, otherwise the kernel will
+// compute the checksum field during the message transmission.
+// When psh is not nil, it must be the pseudo header for IPv6.
+func (m *Message) Marshal(psh []byte) ([]byte, error) {
+	var mtype int
+	switch typ := m.Type.(type) {
+	case ipv4.ICMPType:
+		mtype = int(typ)
+	case ipv6.ICMPType:
+		mtype = int(typ)
+	default:
+		return nil, syscall.EINVAL
+	}
+	b := []byte{byte(mtype), byte(m.Code), 0, 0}
+	if m.Type.Protocol() == iana.ProtocolIPv6ICMP && psh != nil {
+		b = append(psh, b...)
+	}
+	if m.Body != nil && m.Body.Len(m.Type.Protocol()) != 0 {
+		mb, err := m.Body.Marshal(m.Type.Protocol())
+		if err != nil {
+			return nil, err
+		}
+		b = append(b, mb...)
+	}
+	if m.Type.Protocol() == iana.ProtocolIPv6ICMP {
+		if psh == nil { // cannot calculate checksum here
+			return b, nil
+		}
+		off, l := 2*net.IPv6len, len(b)-len(psh)
+		binary.BigEndian.PutUint32(b[off:off+4], uint32(l))
+	}
+	s := checksum(b)
+	// Place checksum back in header; using ^= avoids the
+	// assumption the checksum bytes are zero.
+	b[len(psh)+2] ^= byte(s)
+	b[len(psh)+3] ^= byte(s >> 8)
+	return b[len(psh):], nil
+}
+
+var parseFns = map[Type]func(int, []byte) (MessageBody, error){
+	ipv4.ICMPTypeDestinationUnreachable: parseDstUnreach,
+	ipv4.ICMPTypeTimeExceeded:           parseTimeExceeded,
+	ipv4.ICMPTypeParameterProblem:       parseParamProb,
+
+	ipv4.ICMPTypeEcho:      parseEcho,
+	ipv4.ICMPTypeEchoReply: parseEcho,
+
+	ipv6.ICMPTypeDestinationUnreachable: parseDstUnreach,
+	ipv6.ICMPTypePacketTooBig:           parsePacketTooBig,
+	ipv6.ICMPTypeTimeExceeded:           parseTimeExceeded,
+	ipv6.ICMPTypeParameterProblem:       parseParamProb,
+
+	ipv6.ICMPTypeEchoRequest: parseEcho,
+	ipv6.ICMPTypeEchoReply:   parseEcho,
+}
+
+// ParseMessage parses b as an ICMP message.
+// Proto must be either the ICMPv4 or ICMPv6 protocol number.
+func ParseMessage(proto int, b []byte) (*Message, error) {
+	if len(b) < 4 {
+		return nil, errMessageTooShort
+	}
+	var err error
+	m := &Message{Code: int(b[1]), Checksum: int(binary.BigEndian.Uint16(b[2:4]))}
+	switch proto {
+	case iana.ProtocolICMP:
+		m.Type = ipv4.ICMPType(b[0])
+	case iana.ProtocolIPv6ICMP:
+		m.Type = ipv6.ICMPType(b[0])
+	default:
+		return nil, syscall.EINVAL
+	}
+	if fn, ok := parseFns[m.Type]; !ok {
+		m.Body, err = parseDefaultMessageBody(proto, b[4:])
+	} else {
+		m.Body, err = fn(proto, b[4:])
+	}
+	if err != nil {
+		return nil, err
+	}
+	return m, nil
+}