Revert vendor directory to support old golang (GOPATH mode)

gomodule is still in progress to migrate for now, hence multus
team decide to keep vendor directory to support build without
gomodule.

vendor/github.com/vishvananda/netlink/route_linux.go

@@ -0,0 +1,743 @@
+package netlink
+
+import (
+	"fmt"
+	"net"
+	"strings"
+	"syscall"
+
+	"github.com/vishvananda/netlink/nl"
+	"github.com/vishvananda/netns"
+)
+
+// RtAttr is shared so it is in netlink_linux.go
+
+const (
+	SCOPE_UNIVERSE Scope = syscall.RT_SCOPE_UNIVERSE
+	SCOPE_SITE     Scope = syscall.RT_SCOPE_SITE
+	SCOPE_LINK     Scope = syscall.RT_SCOPE_LINK
+	SCOPE_HOST     Scope = syscall.RT_SCOPE_HOST
+	SCOPE_NOWHERE  Scope = syscall.RT_SCOPE_NOWHERE
+)
+
+const (
+	RT_FILTER_PROTOCOL uint64 = 1 << (1 + iota)
+	RT_FILTER_SCOPE
+	RT_FILTER_TYPE
+	RT_FILTER_TOS
+	RT_FILTER_IIF
+	RT_FILTER_OIF
+	RT_FILTER_DST
+	RT_FILTER_SRC
+	RT_FILTER_GW
+	RT_FILTER_TABLE
+)
+
+const (
+	FLAG_ONLINK    NextHopFlag = syscall.RTNH_F_ONLINK
+	FLAG_PERVASIVE NextHopFlag = syscall.RTNH_F_PERVASIVE
+)
+
+var testFlags = []flagString{
+	{f: FLAG_ONLINK, s: "onlink"},
+	{f: FLAG_PERVASIVE, s: "pervasive"},
+}
+
+func listFlags(flag int) []string {
+	var flags []string
+	for _, tf := range testFlags {
+		if flag&int(tf.f) != 0 {
+			flags = append(flags, tf.s)
+		}
+	}
+	return flags
+}
+
+func (r *Route) ListFlags() []string {
+	return listFlags(r.Flags)
+}
+
+func (n *NexthopInfo) ListFlags() []string {
+	return listFlags(n.Flags)
+}
+
+type MPLSDestination struct {
+	Labels []int
+}
+
+func (d *MPLSDestination) Family() int {
+	return nl.FAMILY_MPLS
+}
+
+func (d *MPLSDestination) Decode(buf []byte) error {
+	d.Labels = nl.DecodeMPLSStack(buf)
+	return nil
+}
+
+func (d *MPLSDestination) Encode() ([]byte, error) {
+	return nl.EncodeMPLSStack(d.Labels...), nil
+}
+
+func (d *MPLSDestination) String() string {
+	s := make([]string, 0, len(d.Labels))
+	for _, l := range d.Labels {
+		s = append(s, fmt.Sprintf("%d", l))
+	}
+	return strings.Join(s, "/")
+}
+
+func (d *MPLSDestination) Equal(x Destination) bool {
+	o, ok := x.(*MPLSDestination)
+	if !ok {
+		return false
+	}
+	if d == nil && o == nil {
+		return true
+	}
+	if d == nil || o == nil {
+		return false
+	}
+	if d.Labels == nil && o.Labels == nil {
+		return true
+	}
+	if d.Labels == nil || o.Labels == nil {
+		return false
+	}
+	if len(d.Labels) != len(o.Labels) {
+		return false
+	}
+	for i := range d.Labels {
+		if d.Labels[i] != o.Labels[i] {
+			return false
+		}
+	}
+	return true
+}
+
+type MPLSEncap struct {
+	Labels []int
+}
+
+func (e *MPLSEncap) Type() int {
+	return nl.LWTUNNEL_ENCAP_MPLS
+}
+
+func (e *MPLSEncap) Decode(buf []byte) error {
+	if len(buf) < 4 {
+		return fmt.Errorf("Lack of bytes")
+	}
+	native := nl.NativeEndian()
+	l := native.Uint16(buf)
+	if len(buf) < int(l) {
+		return fmt.Errorf("Lack of bytes")
+	}
+	buf = buf[:l]
+	typ := native.Uint16(buf[2:])
+	if typ != nl.MPLS_IPTUNNEL_DST {
+		return fmt.Errorf("Unknown MPLS Encap Type: %d", typ)
+	}
+	e.Labels = nl.DecodeMPLSStack(buf[4:])
+	return nil
+}
+
+func (e *MPLSEncap) Encode() ([]byte, error) {
+	s := nl.EncodeMPLSStack(e.Labels...)
+	native := nl.NativeEndian()
+	hdr := make([]byte, 4)
+	native.PutUint16(hdr, uint16(len(s)+4))
+	native.PutUint16(hdr[2:], nl.MPLS_IPTUNNEL_DST)
+	return append(hdr, s...), nil
+}
+
+func (e *MPLSEncap) String() string {
+	s := make([]string, 0, len(e.Labels))
+	for _, l := range e.Labels {
+		s = append(s, fmt.Sprintf("%d", l))
+	}
+	return strings.Join(s, "/")
+}
+
+func (e *MPLSEncap) Equal(x Encap) bool {
+	o, ok := x.(*MPLSEncap)
+	if !ok {
+		return false
+	}
+	if e == nil && o == nil {
+		return true
+	}
+	if e == nil || o == nil {
+		return false
+	}
+	if e.Labels == nil && o.Labels == nil {
+		return true
+	}
+	if e.Labels == nil || o.Labels == nil {
+		return false
+	}
+	if len(e.Labels) != len(o.Labels) {
+		return false
+	}
+	for i := range e.Labels {
+		if e.Labels[i] != o.Labels[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// RouteAdd will add a route to the system.
+// Equivalent to: `ip route add $route`
+func RouteAdd(route *Route) error {
+	return pkgHandle.RouteAdd(route)
+}
+
+// RouteAdd will add a route to the system.
+// Equivalent to: `ip route add $route`
+func (h *Handle) RouteAdd(route *Route) error {
+	flags := syscall.NLM_F_CREATE | syscall.NLM_F_EXCL | syscall.NLM_F_ACK
+	req := h.newNetlinkRequest(syscall.RTM_NEWROUTE, flags)
+	return h.routeHandle(route, req, nl.NewRtMsg())
+}
+
+// RouteReplace will add a route to the system.
+// Equivalent to: `ip route replace $route`
+func RouteReplace(route *Route) error {
+	return pkgHandle.RouteReplace(route)
+}
+
+// RouteReplace will add a route to the system.
+// Equivalent to: `ip route replace $route`
+func (h *Handle) RouteReplace(route *Route) error {
+	flags := syscall.NLM_F_CREATE | syscall.NLM_F_REPLACE | syscall.NLM_F_ACK
+	req := h.newNetlinkRequest(syscall.RTM_NEWROUTE, flags)
+	return h.routeHandle(route, req, nl.NewRtMsg())
+}
+
+// RouteDel will delete a route from the system.
+// Equivalent to: `ip route del $route`
+func RouteDel(route *Route) error {
+	return pkgHandle.RouteDel(route)
+}
+
+// RouteDel will delete a route from the system.
+// Equivalent to: `ip route del $route`
+func (h *Handle) RouteDel(route *Route) error {
+	req := h.newNetlinkRequest(syscall.RTM_DELROUTE, syscall.NLM_F_ACK)
+	return h.routeHandle(route, req, nl.NewRtDelMsg())
+}
+
+func (h *Handle) routeHandle(route *Route, req *nl.NetlinkRequest, msg *nl.RtMsg) error {
+	if (route.Dst == nil || route.Dst.IP == nil) && route.Src == nil && route.Gw == nil && route.MPLSDst == nil {
+		return fmt.Errorf("one of Dst.IP, Src, or Gw must not be nil")
+	}
+
+	family := -1
+	var rtAttrs []*nl.RtAttr
+
+	if route.Dst != nil && route.Dst.IP != nil {
+		dstLen, _ := route.Dst.Mask.Size()
+		msg.Dst_len = uint8(dstLen)
+		dstFamily := nl.GetIPFamily(route.Dst.IP)
+		family = dstFamily
+		var dstData []byte
+		if dstFamily == FAMILY_V4 {
+			dstData = route.Dst.IP.To4()
+		} else {
+			dstData = route.Dst.IP.To16()
+		}
+		rtAttrs = append(rtAttrs, nl.NewRtAttr(syscall.RTA_DST, dstData))
+	} else if route.MPLSDst != nil {
+		family = nl.FAMILY_MPLS
+		msg.Dst_len = uint8(20)
+		msg.Type = syscall.RTN_UNICAST
+		rtAttrs = append(rtAttrs, nl.NewRtAttr(syscall.RTA_DST, nl.EncodeMPLSStack(*route.MPLSDst)))
+	}
+
+	if route.NewDst != nil {
+		if family != -1 && family != route.NewDst.Family() {
+			return fmt.Errorf("new destination and destination are not the same address family")
+		}
+		buf, err := route.NewDst.Encode()
+		if err != nil {
+			return err
+		}
+		rtAttrs = append(rtAttrs, nl.NewRtAttr(nl.RTA_NEWDST, buf))
+	}
+
+	if route.Encap != nil {
+		buf := make([]byte, 2)
+		native.PutUint16(buf, uint16(route.Encap.Type()))
+		rtAttrs = append(rtAttrs, nl.NewRtAttr(nl.RTA_ENCAP_TYPE, buf))
+		buf, err := route.Encap.Encode()
+		if err != nil {
+			return err
+		}
+		rtAttrs = append(rtAttrs, nl.NewRtAttr(nl.RTA_ENCAP, buf))
+	}
+
+	if route.Src != nil {
+		srcFamily := nl.GetIPFamily(route.Src)
+		if family != -1 && family != srcFamily {
+			return fmt.Errorf("source and destination ip are not the same IP family")
+		}
+		family = srcFamily
+		var srcData []byte
+		if srcFamily == FAMILY_V4 {
+			srcData = route.Src.To4()
+		} else {
+			srcData = route.Src.To16()
+		}
+		// The commonly used src ip for routes is actually PREFSRC
+		rtAttrs = append(rtAttrs, nl.NewRtAttr(syscall.RTA_PREFSRC, srcData))
+	}
+
+	if route.Gw != nil {
+		gwFamily := nl.GetIPFamily(route.Gw)
+		if family != -1 && family != gwFamily {
+			return fmt.Errorf("gateway, source, and destination ip are not the same IP family")
+		}
+		family = gwFamily
+		var gwData []byte
+		if gwFamily == FAMILY_V4 {
+			gwData = route.Gw.To4()
+		} else {
+			gwData = route.Gw.To16()
+		}
+		rtAttrs = append(rtAttrs, nl.NewRtAttr(syscall.RTA_GATEWAY, gwData))
+	}
+
+	if len(route.MultiPath) > 0 {
+		buf := []byte{}
+		for _, nh := range route.MultiPath {
+			rtnh := &nl.RtNexthop{
+				RtNexthop: syscall.RtNexthop{
+					Hops:    uint8(nh.Hops),
+					Ifindex: int32(nh.LinkIndex),
+					Flags:   uint8(nh.Flags),
+				},
+			}
+			children := []nl.NetlinkRequestData{}
+			if nh.Gw != nil {
+				gwFamily := nl.GetIPFamily(nh.Gw)
+				if family != -1 && family != gwFamily {
+					return fmt.Errorf("gateway, source, and destination ip are not the same IP family")
+				}
+				if gwFamily == FAMILY_V4 {
+					children = append(children, nl.NewRtAttr(syscall.RTA_GATEWAY, []byte(nh.Gw.To4())))
+				} else {
+					children = append(children, nl.NewRtAttr(syscall.RTA_GATEWAY, []byte(nh.Gw.To16())))
+				}
+			}
+			if nh.NewDst != nil {
+				if family != -1 && family != nh.NewDst.Family() {
+					return fmt.Errorf("new destination and destination are not the same address family")
+				}
+				buf, err := nh.NewDst.Encode()
+				if err != nil {
+					return err
+				}
+				children = append(children, nl.NewRtAttr(nl.RTA_NEWDST, buf))
+			}
+			if nh.Encap != nil {
+				buf := make([]byte, 2)
+				native.PutUint16(buf, uint16(nh.Encap.Type()))
+				rtAttrs = append(rtAttrs, nl.NewRtAttr(nl.RTA_ENCAP_TYPE, buf))
+				buf, err := nh.Encap.Encode()
+				if err != nil {
+					return err
+				}
+				children = append(children, nl.NewRtAttr(nl.RTA_ENCAP, buf))
+			}
+			rtnh.Children = children
+			buf = append(buf, rtnh.Serialize()...)
+		}
+		rtAttrs = append(rtAttrs, nl.NewRtAttr(syscall.RTA_MULTIPATH, buf))
+	}
+
+	if route.Table > 0 {
+		if route.Table >= 256 {
+			msg.Table = syscall.RT_TABLE_UNSPEC
+			b := make([]byte, 4)
+			native.PutUint32(b, uint32(route.Table))
+			rtAttrs = append(rtAttrs, nl.NewRtAttr(syscall.RTA_TABLE, b))
+		} else {
+			msg.Table = uint8(route.Table)
+		}
+	}
+
+	if route.Priority > 0 {
+		b := make([]byte, 4)
+		native.PutUint32(b, uint32(route.Priority))
+		rtAttrs = append(rtAttrs, nl.NewRtAttr(syscall.RTA_PRIORITY, b))
+	}
+	if route.Tos > 0 {
+		msg.Tos = uint8(route.Tos)
+	}
+	if route.Protocol > 0 {
+		msg.Protocol = uint8(route.Protocol)
+	}
+	if route.Type > 0 {
+		msg.Type = uint8(route.Type)
+	}
+
+	msg.Flags = uint32(route.Flags)
+	msg.Scope = uint8(route.Scope)
+	msg.Family = uint8(family)
+	req.AddData(msg)
+	for _, attr := range rtAttrs {
+		req.AddData(attr)
+	}
+
+	var (
+		b      = make([]byte, 4)
+		native = nl.NativeEndian()
+	)
+	native.PutUint32(b, uint32(route.LinkIndex))
+
+	req.AddData(nl.NewRtAttr(syscall.RTA_OIF, b))
+
+	_, err := req.Execute(syscall.NETLINK_ROUTE, 0)
+	return err
+}
+
+// RouteList gets a list of routes in the system.
+// Equivalent to: `ip route show`.
+// The list can be filtered by link and ip family.
+func RouteList(link Link, family int) ([]Route, error) {
+	return pkgHandle.RouteList(link, family)
+}
+
+// RouteList gets a list of routes in the system.
+// Equivalent to: `ip route show`.
+// The list can be filtered by link and ip family.
+func (h *Handle) RouteList(link Link, family int) ([]Route, error) {
+	var routeFilter *Route
+	if link != nil {
+		routeFilter = &Route{
+			LinkIndex: link.Attrs().Index,
+		}
+	}
+	return h.RouteListFiltered(family, routeFilter, RT_FILTER_OIF)
+}
+
+// RouteListFiltered gets a list of routes in the system filtered with specified rules.
+// All rules must be defined in RouteFilter struct
+func RouteListFiltered(family int, filter *Route, filterMask uint64) ([]Route, error) {
+	return pkgHandle.RouteListFiltered(family, filter, filterMask)
+}
+
+// RouteListFiltered gets a list of routes in the system filtered with specified rules.
+// All rules must be defined in RouteFilter struct
+func (h *Handle) RouteListFiltered(family int, filter *Route, filterMask uint64) ([]Route, error) {
+	req := h.newNetlinkRequest(syscall.RTM_GETROUTE, syscall.NLM_F_DUMP)
+	infmsg := nl.NewIfInfomsg(family)
+	req.AddData(infmsg)
+
+	msgs, err := req.Execute(syscall.NETLINK_ROUTE, syscall.RTM_NEWROUTE)
+	if err != nil {
+		return nil, err
+	}
+
+	var res []Route
+	for _, m := range msgs {
+		msg := nl.DeserializeRtMsg(m)
+		if msg.Flags&syscall.RTM_F_CLONED != 0 {
+			// Ignore cloned routes
+			continue
+		}
+		if msg.Table != syscall.RT_TABLE_MAIN {
+			if filter == nil || filter != nil && filterMask&RT_FILTER_TABLE == 0 {
+				// Ignore non-main tables
+				continue
+			}
+		}
+		route, err := deserializeRoute(m)
+		if err != nil {
+			return nil, err
+		}
+		if filter != nil {
+			switch {
+			case filterMask&RT_FILTER_TABLE != 0 && filter.Table != syscall.RT_TABLE_UNSPEC && route.Table != filter.Table:
+				continue
+			case filterMask&RT_FILTER_PROTOCOL != 0 && route.Protocol != filter.Protocol:
+				continue
+			case filterMask&RT_FILTER_SCOPE != 0 && route.Scope != filter.Scope:
+				continue
+			case filterMask&RT_FILTER_TYPE != 0 && route.Type != filter.Type:
+				continue
+			case filterMask&RT_FILTER_TOS != 0 && route.Tos != filter.Tos:
+				continue
+			case filterMask&RT_FILTER_OIF != 0 && route.LinkIndex != filter.LinkIndex:
+				continue
+			case filterMask&RT_FILTER_IIF != 0 && route.ILinkIndex != filter.ILinkIndex:
+				continue
+			case filterMask&RT_FILTER_GW != 0 && !route.Gw.Equal(filter.Gw):
+				continue
+			case filterMask&RT_FILTER_SRC != 0 && !route.Src.Equal(filter.Src):
+				continue
+			case filterMask&RT_FILTER_DST != 0:
+				if filter.MPLSDst == nil || route.MPLSDst == nil || (*filter.MPLSDst) != (*route.MPLSDst) {
+					if !ipNetEqual(route.Dst, filter.Dst) {
+						continue
+					}
+				}
+			}
+		}
+		res = append(res, route)
+	}
+	return res, nil
+}
+
+// deserializeRoute decodes a binary netlink message into a Route struct
+func deserializeRoute(m []byte) (Route, error) {
+	msg := nl.DeserializeRtMsg(m)
+	attrs, err := nl.ParseRouteAttr(m[msg.Len():])
+	if err != nil {
+		return Route{}, err
+	}
+	route := Route{
+		Scope:    Scope(msg.Scope),
+		Protocol: int(msg.Protocol),
+		Table:    int(msg.Table),
+		Type:     int(msg.Type),
+		Tos:      int(msg.Tos),
+		Flags:    int(msg.Flags),
+	}
+
+	native := nl.NativeEndian()
+	var encap, encapType syscall.NetlinkRouteAttr
+	for _, attr := range attrs {
+		switch attr.Attr.Type {
+		case syscall.RTA_GATEWAY:
+			route.Gw = net.IP(attr.Value)
+		case syscall.RTA_PREFSRC:
+			route.Src = net.IP(attr.Value)
+		case syscall.RTA_DST:
+			if msg.Family == nl.FAMILY_MPLS {
+				stack := nl.DecodeMPLSStack(attr.Value)
+				if len(stack) == 0 || len(stack) > 1 {
+					return route, fmt.Errorf("invalid MPLS RTA_DST")
+				}
+				route.MPLSDst = &stack[0]
+			} else {
+				route.Dst = &net.IPNet{
+					IP:   attr.Value,
+					Mask: net.CIDRMask(int(msg.Dst_len), 8*len(attr.Value)),
+				}
+			}
+		case syscall.RTA_OIF:
+			route.LinkIndex = int(native.Uint32(attr.Value[0:4]))
+		case syscall.RTA_IIF:
+			route.ILinkIndex = int(native.Uint32(attr.Value[0:4]))
+		case syscall.RTA_PRIORITY:
+			route.Priority = int(native.Uint32(attr.Value[0:4]))
+		case syscall.RTA_TABLE:
+			route.Table = int(native.Uint32(attr.Value[0:4]))
+		case syscall.RTA_MULTIPATH:
+			parseRtNexthop := func(value []byte) (*NexthopInfo, []byte, error) {
+				if len(value) < syscall.SizeofRtNexthop {
+					return nil, nil, fmt.Errorf("Lack of bytes")
+				}
+				nh := nl.DeserializeRtNexthop(value)
+				if len(value) < int(nh.RtNexthop.Len) {
+					return nil, nil, fmt.Errorf("Lack of bytes")
+				}
+				info := &NexthopInfo{
+					LinkIndex: int(nh.RtNexthop.Ifindex),
+					Hops:      int(nh.RtNexthop.Hops),
+					Flags:     int(nh.RtNexthop.Flags),
+				}
+				attrs, err := nl.ParseRouteAttr(value[syscall.SizeofRtNexthop:int(nh.RtNexthop.Len)])
+				if err != nil {
+					return nil, nil, err
+				}
+				var encap, encapType syscall.NetlinkRouteAttr
+				for _, attr := range attrs {
+					switch attr.Attr.Type {
+					case syscall.RTA_GATEWAY:
+						info.Gw = net.IP(attr.Value)
+					case nl.RTA_NEWDST:
+						var d Destination
+						switch msg.Family {
+						case nl.FAMILY_MPLS:
+							d = &MPLSDestination{}
+						}
+						if err := d.Decode(attr.Value); err != nil {
+							return nil, nil, err
+						}
+						info.NewDst = d
+					case nl.RTA_ENCAP_TYPE:
+						encapType = attr
+					case nl.RTA_ENCAP:
+						encap = attr
+					}
+				}
+
+				if len(encap.Value) != 0 && len(encapType.Value) != 0 {
+					typ := int(native.Uint16(encapType.Value[0:2]))
+					var e Encap
+					switch typ {
+					case nl.LWTUNNEL_ENCAP_MPLS:
+						e = &MPLSEncap{}
+						if err := e.Decode(encap.Value); err != nil {
+							return nil, nil, err
+						}
+					}
+					info.Encap = e
+				}
+
+				return info, value[int(nh.RtNexthop.Len):], nil
+			}
+			rest := attr.Value
+			for len(rest) > 0 {
+				info, buf, err := parseRtNexthop(rest)
+				if err != nil {
+					return route, err
+				}
+				route.MultiPath = append(route.MultiPath, info)
+				rest = buf
+			}
+		case nl.RTA_NEWDST:
+			var d Destination
+			switch msg.Family {
+			case nl.FAMILY_MPLS:
+				d = &MPLSDestination{}
+			}
+			if err := d.Decode(attr.Value); err != nil {
+				return route, err
+			}
+			route.NewDst = d
+		case nl.RTA_ENCAP_TYPE:
+			encapType = attr
+		case nl.RTA_ENCAP:
+			encap = attr
+		}
+	}
+
+	if len(encap.Value) != 0 && len(encapType.Value) != 0 {
+		typ := int(native.Uint16(encapType.Value[0:2]))
+		var e Encap
+		switch typ {
+		case nl.LWTUNNEL_ENCAP_MPLS:
+			e = &MPLSEncap{}
+			if err := e.Decode(encap.Value); err != nil {
+				return route, err
+			}
+		}
+		route.Encap = e
+	}
+
+	return route, nil
+}
+
+// RouteGet gets a route to a specific destination from the host system.
+// Equivalent to: 'ip route get'.
+func RouteGet(destination net.IP) ([]Route, error) {
+	return pkgHandle.RouteGet(destination)
+}
+
+// RouteGet gets a route to a specific destination from the host system.
+// Equivalent to: 'ip route get'.
+func (h *Handle) RouteGet(destination net.IP) ([]Route, error) {
+	req := h.newNetlinkRequest(syscall.RTM_GETROUTE, syscall.NLM_F_REQUEST)
+	family := nl.GetIPFamily(destination)
+	var destinationData []byte
+	var bitlen uint8
+	if family == FAMILY_V4 {
+		destinationData = destination.To4()
+		bitlen = 32
+	} else {
+		destinationData = destination.To16()
+		bitlen = 128
+	}
+	msg := &nl.RtMsg{}
+	msg.Family = uint8(family)
+	msg.Dst_len = bitlen
+	req.AddData(msg)
+
+	rtaDst := nl.NewRtAttr(syscall.RTA_DST, destinationData)
+	req.AddData(rtaDst)
+
+	msgs, err := req.Execute(syscall.NETLINK_ROUTE, syscall.RTM_NEWROUTE)
+	if err != nil {
+		return nil, err
+	}
+
+	var res []Route
+	for _, m := range msgs {
+		route, err := deserializeRoute(m)
+		if err != nil {
+			return nil, err
+		}
+		res = append(res, route)
+	}
+	return res, nil
+
+}
+
+// RouteSubscribe takes a chan down which notifications will be sent
+// when routes are added or deleted. Close the 'done' chan to stop subscription.
+func RouteSubscribe(ch chan<- RouteUpdate, done <-chan struct{}) error {
+	return routeSubscribeAt(netns.None(), netns.None(), ch, done, nil)
+}
+
+// RouteSubscribeAt works like RouteSubscribe plus it allows the caller
+// to choose the network namespace in which to subscribe (ns).
+func RouteSubscribeAt(ns netns.NsHandle, ch chan<- RouteUpdate, done <-chan struct{}) error {
+	return routeSubscribeAt(ns, netns.None(), ch, done, nil)
+}
+
+// RouteSubscribeOptions contains a set of options to use with
+// RouteSubscribeWithOptions.
+type RouteSubscribeOptions struct {
+	Namespace     *netns.NsHandle
+	ErrorCallback func(error)
+}
+
+// RouteSubscribeWithOptions work like RouteSubscribe but enable to
+// provide additional options to modify the behavior. Currently, the
+// namespace can be provided as well as an error callback.
+func RouteSubscribeWithOptions(ch chan<- RouteUpdate, done <-chan struct{}, options RouteSubscribeOptions) error {
+	if options.Namespace == nil {
+		none := netns.None()
+		options.Namespace = &none
+	}
+	return routeSubscribeAt(*options.Namespace, netns.None(), ch, done, options.ErrorCallback)
+}
+
+func routeSubscribeAt(newNs, curNs netns.NsHandle, ch chan<- RouteUpdate, done <-chan struct{}, cberr func(error)) error {
+	s, err := nl.SubscribeAt(newNs, curNs, syscall.NETLINK_ROUTE, syscall.RTNLGRP_IPV4_ROUTE, syscall.RTNLGRP_IPV6_ROUTE)
+	if err != nil {
+		return err
+	}
+	if done != nil {
+		go func() {
+			<-done
+			s.Close()
+		}()
+	}
+	go func() {
+		defer close(ch)
+		for {
+			msgs, err := s.Receive()
+			if err != nil {
+				if cberr != nil {
+					cberr(err)
+				}
+				return
+			}
+			for _, m := range msgs {
+				route, err := deserializeRoute(m.Data)
+				if err != nil {
+					if cberr != nil {
+						cberr(err)
+					}
+					return
+				}
+				ch <- RouteUpdate{Type: m.Header.Type, Route: route}
+			}
+		}
+	}()
+
+	return nil
+}