diff --git a/vendor/github.com/google/gopacket/layers/tcpip.go b/vendor/github.com/google/gopacket/layers/tcpip.go
new file mode 100644
index 0000000..64ba51c
--- /dev/null
+++ b/vendor/github.com/google/gopacket/layers/tcpip.go
@@ -0,0 +1,104 @@
+// Copyright 2012 Google, Inc. All rights reserved.
+// Copyright 2009-2011 Andreas Krennmair. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the LICENSE file in the root of the source
+// tree.
+
+package layers
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/google/gopacket"
+)
+
+// Checksum computation for TCP/UDP.
+type tcpipchecksum struct {
+	pseudoheader tcpipPseudoHeader
+}
+
+type tcpipPseudoHeader interface {
+	pseudoheaderChecksum() (uint32, error)
+}
+
+func (ip *IPv4) pseudoheaderChecksum() (csum uint32, err error) {
+	if err := ip.AddressTo4(); err != nil {
+		return 0, err
+	}
+	csum += (uint32(ip.SrcIP[0]) + uint32(ip.SrcIP[2])) << 8
+	csum += uint32(ip.SrcIP[1]) + uint32(ip.SrcIP[3])
+	csum += (uint32(ip.DstIP[0]) + uint32(ip.DstIP[2])) << 8
+	csum += uint32(ip.DstIP[1]) + uint32(ip.DstIP[3])
+	return csum, nil
+}
+
+func (ip *IPv6) pseudoheaderChecksum() (csum uint32, err error) {
+	if err := ip.AddressTo16(); err != nil {
+		return 0, err
+	}
+	for i := 0; i < 16; i += 2 {
+		csum += uint32(ip.SrcIP[i]) << 8
+		csum += uint32(ip.SrcIP[i+1])
+		csum += uint32(ip.DstIP[i]) << 8
+		csum += uint32(ip.DstIP[i+1])
+	}
+	return csum, nil
+}
+
+// Calculate the TCP/IP checksum defined in rfc1071.  The passed-in csum is any
+// initial checksum data that's already been computed.
+func tcpipChecksum(data []byte, csum uint32) uint16 {
+	// to handle odd lengths, we loop to length - 1, incrementing by 2, then
+	// handle the last byte specifically by checking against the original
+	// length.
+	length := len(data) - 1
+	for i := 0; i < length; i += 2 {
+		// For our test packet, doing this manually is about 25% faster
+		// (740 ns vs. 1000ns) than doing it by calling binary.BigEndian.Uint16.
+		csum += uint32(data[i]) << 8
+		csum += uint32(data[i+1])
+	}
+	if len(data)%2 == 1 {
+		csum += uint32(data[length]) << 8
+	}
+	for csum > 0xffff {
+		csum = (csum >> 16) + (csum & 0xffff)
+	}
+	return ^uint16(csum)
+}
+
+// computeChecksum computes a TCP or UDP checksum.  headerAndPayload is the
+// serialized TCP or UDP header plus its payload, with the checksum zero'd
+// out. headerProtocol is the IP protocol number of the upper-layer header.
+func (c *tcpipchecksum) computeChecksum(headerAndPayload []byte, headerProtocol IPProtocol) (uint16, error) {
+	if c.pseudoheader == nil {
+		return 0, errors.New("TCP/IP layer 4 checksum cannot be computed without network layer... call SetNetworkLayerForChecksum to set which layer to use")
+	}
+	length := uint32(len(headerAndPayload))
+	csum, err := c.pseudoheader.pseudoheaderChecksum()
+	if err != nil {
+		return 0, err
+	}
+	csum += uint32(headerProtocol)
+	csum += length & 0xffff
+	csum += length >> 16
+	return tcpipChecksum(headerAndPayload, csum), nil
+}
+
+// SetNetworkLayerForChecksum tells this layer which network layer is wrapping it.
+// This is needed for computing the checksum when serializing, since TCP/IP transport
+// layer checksums depends on fields in the IPv4 or IPv6 layer that contains it.
+// The passed in layer must be an *IPv4 or *IPv6.
+func (i *tcpipchecksum) SetNetworkLayerForChecksum(l gopacket.NetworkLayer) error {
+	switch v := l.(type) {
+	case *IPv4:
+		i.pseudoheader = v
+	case *IPv6:
+		i.pseudoheader = v
+	default:
+		return fmt.Errorf("cannot use layer type %v for tcp checksum network layer", l.LayerType())
+	}
+	return nil
+}