diff --git a/unum/vendor/golang.org/x/net/ipv4/header.go b/unum/vendor/golang.org/x/net/ipv4/header.go
new file mode 100644
index 0000000..8bb0f0f
--- /dev/null
+++ b/unum/vendor/golang.org/x/net/ipv4/header.go
@@ -0,0 +1,159 @@
+// 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 ipv4
+
+import (
+	"encoding/binary"
+	"fmt"
+	"net"
+	"runtime"
+	"syscall"
+
+	"golang.org/x/net/internal/socket"
+)
+
+const (
+	Version      = 4  // protocol version
+	HeaderLen    = 20 // header length without extension headers
+	maxHeaderLen = 60 // sensible default, revisit if later RFCs define new usage of version and header length fields
+)
+
+type HeaderFlags int
+
+const (
+	MoreFragments HeaderFlags = 1 << iota // more fragments flag
+	DontFragment                          // don't fragment flag
+)
+
+// A Header represents an IPv4 header.
+type Header struct {
+	Version  int         // protocol version
+	Len      int         // header length
+	TOS      int         // type-of-service
+	TotalLen int         // packet total length
+	ID       int         // identification
+	Flags    HeaderFlags // flags
+	FragOff  int         // fragment offset
+	TTL      int         // time-to-live
+	Protocol int         // next protocol
+	Checksum int         // checksum
+	Src      net.IP      // source address
+	Dst      net.IP      // destination address
+	Options  []byte      // options, extension headers
+}
+
+func (h *Header) String() string {
+	if h == nil {
+		return "<nil>"
+	}
+	return fmt.Sprintf("ver=%d hdrlen=%d tos=%#x totallen=%d id=%#x flags=%#x fragoff=%#x ttl=%d proto=%d cksum=%#x src=%v dst=%v", h.Version, h.Len, h.TOS, h.TotalLen, h.ID, h.Flags, h.FragOff, h.TTL, h.Protocol, h.Checksum, h.Src, h.Dst)
+}
+
+// Marshal returns the binary encoding of h.
+func (h *Header) Marshal() ([]byte, error) {
+	if h == nil {
+		return nil, syscall.EINVAL
+	}
+	if h.Len < HeaderLen {
+		return nil, errHeaderTooShort
+	}
+	hdrlen := HeaderLen + len(h.Options)
+	b := make([]byte, hdrlen)
+	b[0] = byte(Version<<4 | (hdrlen >> 2 & 0x0f))
+	b[1] = byte(h.TOS)
+	flagsAndFragOff := (h.FragOff & 0x1fff) | int(h.Flags<<13)
+	switch runtime.GOOS {
+	case "darwin", "dragonfly", "netbsd":
+		socket.NativeEndian.PutUint16(b[2:4], uint16(h.TotalLen))
+		socket.NativeEndian.PutUint16(b[6:8], uint16(flagsAndFragOff))
+	case "freebsd":
+		if freebsdVersion < 1100000 {
+			socket.NativeEndian.PutUint16(b[2:4], uint16(h.TotalLen))
+			socket.NativeEndian.PutUint16(b[6:8], uint16(flagsAndFragOff))
+		} else {
+			binary.BigEndian.PutUint16(b[2:4], uint16(h.TotalLen))
+			binary.BigEndian.PutUint16(b[6:8], uint16(flagsAndFragOff))
+		}
+	default:
+		binary.BigEndian.PutUint16(b[2:4], uint16(h.TotalLen))
+		binary.BigEndian.PutUint16(b[6:8], uint16(flagsAndFragOff))
+	}
+	binary.BigEndian.PutUint16(b[4:6], uint16(h.ID))
+	b[8] = byte(h.TTL)
+	b[9] = byte(h.Protocol)
+	binary.BigEndian.PutUint16(b[10:12], uint16(h.Checksum))
+	if ip := h.Src.To4(); ip != nil {
+		copy(b[12:16], ip[:net.IPv4len])
+	}
+	if ip := h.Dst.To4(); ip != nil {
+		copy(b[16:20], ip[:net.IPv4len])
+	} else {
+		return nil, errMissingAddress
+	}
+	if len(h.Options) > 0 {
+		copy(b[HeaderLen:], h.Options)
+	}
+	return b, nil
+}
+
+// Parse parses b as an IPv4 header and sotres the result in h.
+func (h *Header) Parse(b []byte) error {
+	if h == nil || len(b) < HeaderLen {
+		return errHeaderTooShort
+	}
+	hdrlen := int(b[0]&0x0f) << 2
+	if hdrlen > len(b) {
+		return errBufferTooShort
+	}
+	h.Version = int(b[0] >> 4)
+	h.Len = hdrlen
+	h.TOS = int(b[1])
+	h.ID = int(binary.BigEndian.Uint16(b[4:6]))
+	h.TTL = int(b[8])
+	h.Protocol = int(b[9])
+	h.Checksum = int(binary.BigEndian.Uint16(b[10:12]))
+	h.Src = net.IPv4(b[12], b[13], b[14], b[15])
+	h.Dst = net.IPv4(b[16], b[17], b[18], b[19])
+	switch runtime.GOOS {
+	case "darwin", "dragonfly", "netbsd":
+		h.TotalLen = int(socket.NativeEndian.Uint16(b[2:4])) + hdrlen
+		h.FragOff = int(socket.NativeEndian.Uint16(b[6:8]))
+	case "freebsd":
+		if freebsdVersion < 1100000 {
+			h.TotalLen = int(socket.NativeEndian.Uint16(b[2:4]))
+			if freebsdVersion < 1000000 {
+				h.TotalLen += hdrlen
+			}
+			h.FragOff = int(socket.NativeEndian.Uint16(b[6:8]))
+		} else {
+			h.TotalLen = int(binary.BigEndian.Uint16(b[2:4]))
+			h.FragOff = int(binary.BigEndian.Uint16(b[6:8]))
+		}
+	default:
+		h.TotalLen = int(binary.BigEndian.Uint16(b[2:4]))
+		h.FragOff = int(binary.BigEndian.Uint16(b[6:8]))
+	}
+	h.Flags = HeaderFlags(h.FragOff&0xe000) >> 13
+	h.FragOff = h.FragOff & 0x1fff
+	optlen := hdrlen - HeaderLen
+	if optlen > 0 && len(b) >= hdrlen {
+		if cap(h.Options) < optlen {
+			h.Options = make([]byte, optlen)
+		} else {
+			h.Options = h.Options[:optlen]
+		}
+		copy(h.Options, b[HeaderLen:hdrlen])
+	}
+	return nil
+}
+
+// ParseHeader parses b as an IPv4 header.
+func ParseHeader(b []byte) (*Header, error) {
+	h := new(Header)
+	if err := h.Parse(b); err != nil {
+		return nil, err
+	}
+	return h, nil
+}