diff --git a/unum/vendor/golang.org/x/net/ipv4/sys_darwin.go b/unum/vendor/golang.org/x/net/ipv4/sys_darwin.go
new file mode 100644
index 0000000..e8fb191
--- /dev/null
+++ b/unum/vendor/golang.org/x/net/ipv4/sys_darwin.go
@@ -0,0 +1,93 @@
+// Copyright 2014 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 (
+	"net"
+	"strconv"
+	"strings"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/net/internal/iana"
+	"golang.org/x/net/internal/socket"
+)
+
+var (
+	ctlOpts = [ctlMax]ctlOpt{
+		ctlTTL:       {sysIP_RECVTTL, 1, marshalTTL, parseTTL},
+		ctlDst:       {sysIP_RECVDSTADDR, net.IPv4len, marshalDst, parseDst},
+		ctlInterface: {sysIP_RECVIF, syscall.SizeofSockaddrDatalink, marshalInterface, parseInterface},
+	}
+
+	sockOpts = map[int]*sockOpt{
+		ssoTOS:                {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_TOS, Len: 4}},
+		ssoTTL:                {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_TTL, Len: 4}},
+		ssoMulticastTTL:       {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_MULTICAST_TTL, Len: 1}},
+		ssoMulticastInterface: {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_MULTICAST_IF, Len: 4}},
+		ssoMulticastLoopback:  {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_MULTICAST_LOOP, Len: 4}},
+		ssoReceiveTTL:         {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_RECVTTL, Len: 4}},
+		ssoReceiveDst:         {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_RECVDSTADDR, Len: 4}},
+		ssoReceiveInterface:   {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_RECVIF, Len: 4}},
+		ssoHeaderPrepend:      {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_HDRINCL, Len: 4}},
+		ssoStripHeader:        {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_STRIPHDR, Len: 4}},
+		ssoJoinGroup:          {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_ADD_MEMBERSHIP, Len: sizeofIPMreq}, typ: ssoTypeIPMreq},
+		ssoLeaveGroup:         {Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_DROP_MEMBERSHIP, Len: sizeofIPMreq}, typ: ssoTypeIPMreq},
+	}
+)
+
+func init() {
+	// Seems like kern.osreldate is veiled on latest OS X. We use
+	// kern.osrelease instead.
+	s, err := syscall.Sysctl("kern.osrelease")
+	if err != nil {
+		return
+	}
+	ss := strings.Split(s, ".")
+	if len(ss) == 0 {
+		return
+	}
+	// The IP_PKTINFO and protocol-independent multicast API were
+	// introduced in OS X 10.7 (Darwin 11). But it looks like
+	// those features require OS X 10.8 (Darwin 12) or above.
+	// See http://support.apple.com/kb/HT1633.
+	if mjver, err := strconv.Atoi(ss[0]); err != nil || mjver < 12 {
+		return
+	}
+	ctlOpts[ctlPacketInfo].name = sysIP_PKTINFO
+	ctlOpts[ctlPacketInfo].length = sizeofInetPktinfo
+	ctlOpts[ctlPacketInfo].marshal = marshalPacketInfo
+	ctlOpts[ctlPacketInfo].parse = parsePacketInfo
+	sockOpts[ssoPacketInfo] = &sockOpt{Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_RECVPKTINFO, Len: 4}}
+	sockOpts[ssoMulticastInterface] = &sockOpt{Option: socket.Option{Level: iana.ProtocolIP, Name: sysIP_MULTICAST_IF, Len: sizeofIPMreqn}, typ: ssoTypeIPMreqn}
+	sockOpts[ssoJoinGroup] = &sockOpt{Option: socket.Option{Level: iana.ProtocolIP, Name: sysMCAST_JOIN_GROUP, Len: sizeofGroupReq}, typ: ssoTypeGroupReq}
+	sockOpts[ssoLeaveGroup] = &sockOpt{Option: socket.Option{Level: iana.ProtocolIP, Name: sysMCAST_LEAVE_GROUP, Len: sizeofGroupReq}, typ: ssoTypeGroupReq}
+	sockOpts[ssoJoinSourceGroup] = &sockOpt{Option: socket.Option{Level: iana.ProtocolIP, Name: sysMCAST_JOIN_SOURCE_GROUP, Len: sizeofGroupSourceReq}, typ: ssoTypeGroupSourceReq}
+	sockOpts[ssoLeaveSourceGroup] = &sockOpt{Option: socket.Option{Level: iana.ProtocolIP, Name: sysMCAST_LEAVE_SOURCE_GROUP, Len: sizeofGroupSourceReq}, typ: ssoTypeGroupSourceReq}
+	sockOpts[ssoBlockSourceGroup] = &sockOpt{Option: socket.Option{Level: iana.ProtocolIP, Name: sysMCAST_BLOCK_SOURCE, Len: sizeofGroupSourceReq}, typ: ssoTypeGroupSourceReq}
+	sockOpts[ssoUnblockSourceGroup] = &sockOpt{Option: socket.Option{Level: iana.ProtocolIP, Name: sysMCAST_UNBLOCK_SOURCE, Len: sizeofGroupSourceReq}, typ: ssoTypeGroupSourceReq}
+}
+
+func (pi *inetPktinfo) setIfindex(i int) {
+	pi.Ifindex = uint32(i)
+}
+
+func (gr *groupReq) setGroup(grp net.IP) {
+	sa := (*sockaddrInet)(unsafe.Pointer(uintptr(unsafe.Pointer(gr)) + 4))
+	sa.Len = sizeofSockaddrInet
+	sa.Family = syscall.AF_INET
+	copy(sa.Addr[:], grp)
+}
+
+func (gsr *groupSourceReq) setSourceGroup(grp, src net.IP) {
+	sa := (*sockaddrInet)(unsafe.Pointer(uintptr(unsafe.Pointer(gsr)) + 4))
+	sa.Len = sizeofSockaddrInet
+	sa.Family = syscall.AF_INET
+	copy(sa.Addr[:], grp)
+	sa = (*sockaddrInet)(unsafe.Pointer(uintptr(unsafe.Pointer(gsr)) + 132))
+	sa.Len = sizeofSockaddrInet
+	sa.Family = syscall.AF_INET
+	copy(sa.Addr[:], src)
+}