resources: net: Add net resource

This patch adds a net resource for managing nework interfaces, based
around netlink.

examples/lang/net1.mcl

@@ -0,0 +1,5 @@
+net "eth0" {
+	state => "up",
+	addrs => ["192.168.42.13/24",],
+	gateway => "192.168.42.1",
+}

examples/lang/net2.mcl

@@ -0,0 +1,3 @@
+net "eth0" {
+	state => "up",
+}

examples/lang/net3.mcl

@@ -0,0 +1,3 @@
+net "eth0" {
+	state => "down",
+}

resources/net.go

@@ -0,0 +1,879 @@
+// Mgmt
+// Copyright (C) 2013-2018+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package resources
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net"
+	"os"
+	"path"
+	"strings"
+	"sync"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+
+	"github.com/purpleidea/mgmt/recwatch"
+
+	multierr "github.com/hashicorp/go-multierror"
+	errwrap "github.com/pkg/errors"
+	// XXX: Do NOT use subscribe methods from this lib, as they are racey and
+	// do not clean up spawned goroutines. Should be replaced when a suitable
+	// alternative is available.
+	"github.com/vishvananda/netlink"
+)
+
+func init() {
+	RegisterResource("net", func() Res { return &NetRes{} })
+}
+
+const (
+	// IfacePrefix is the prefix used to identify unit files for managed links.
+	IfacePrefix = "mgmt-"
+	// networkdUnitFileDir is the location of networkd unit files which define
+	// the systemd network connections.
+	networkdUnitFileDir = "/etc/systemd/network/"
+	// networkdUnitFileExt is the file extension for networkd unit files.
+	networkdUnitFileExt = ".network"
+	// networkdUnitFileUmask sets the permissions on the systemd unit file.
+	networkdUnitFileUmask = 0644
+
+	// ifaceUp is the up (on) interface state.
+	ifaceUp = "up"
+	// ifaceDown is the down (off) interface state.
+	ifaceDown = "down"
+
+	// Netlink multicast groups to watch for events. For all groups see:
+	// https://github.com/torvalds/linux/blob/master/include/uapi/linux/rtnetlink.h
+	rtmGrps           = rtmGrpLink | rtmGrpIPv4IfAddr | rtmGrpIPv6IfAddr | rtmGrpIPv4IfRoute
+	rtmGrpLink        = 0x1   // interface create/delete/up/down
+	rtmGrpIPv4IfAddr  = 0x10  // add/delete IPv4 addresses
+	rtmGrpIPv6IfAddr  = 0x100 // add/delete IPv6 addresses
+	rtmGrpIPv4IfRoute = 0x40  // add delete routes
+
+	// IP routing protocols for used for netlink route messages. For all
+	// protocols see:
+	// https://github.com/torvalds/linux/blob/master/include/uapi/linux/rtnetlink.h
+	rtProtoKernel = 2 // kernel
+	rtProtoStatic = 4 // static
+)
+
+// NetRes is a network interface resource based on netlink. It manages the
+// state of a network link. Configuration is also stored in a networkd
+// configuration file, so the network is available upon reboot.
+type NetRes struct {
+	BaseRes `yaml:",inline"`
+	State   string   `yaml:"state"`   // up, down, or empty
+	Addrs   []string `yaml:"addrs"`   // list of addresses in cidr format
+	Gateway string   `yaml:"gateway"` // gateway address
+
+	iface        *iface // a struct containing the net.Interface and netlink.Link
+	unitFilePath string // the interface unit file path
+	// XXX: replace TempDir with VarDir
+	tempDir string // temporary directory for storing the pipe socket file
+}
+
+// nlChanStruct defines the channel used to send netlink messages and errors
+// to the event processing loop in Watch.
+type nlChanStruct struct {
+	msg []syscall.NetlinkMessage
+	err error
+}
+
+// Default returns some sensible defaults for this resource.
+func (obj *NetRes) Default() Res {
+	return &NetRes{
+		BaseRes: BaseRes{
+			MetaParams: DefaultMetaParams, // force a default
+		},
+	}
+}
+
+// Validate if the params passed in are valid data.
+func (obj *NetRes) Validate() error {
+	// validate state
+	if obj.State != ifaceUp && obj.State != ifaceDown && obj.State != "" {
+		return fmt.Errorf("state must be up, down or empty")
+	}
+
+	// validate network address input
+	if (obj.Addrs == nil) != (obj.Gateway == "") {
+		return fmt.Errorf("addrs and gateway must both be set or both be empty")
+	}
+	if obj.Addrs != nil {
+		for _, addr := range obj.Addrs {
+			if _, _, err := net.ParseCIDR(addr); err != nil {
+				return errwrap.Wrapf(err, "error parsing address: %s", addr)
+			}
+		}
+	}
+	if obj.Gateway != "" {
+		if g := net.ParseIP(obj.Gateway); g == nil {
+			return fmt.Errorf("error parsing gateway: %s", obj.Gateway)
+		}
+	}
+
+	// validate the interface name
+	_, err := net.InterfaceByName(obj.GetName())
+	if err != nil {
+		return errwrap.Wrapf(err, "error finding interface: %s", obj.GetName())
+	}
+
+	return obj.BaseRes.Validate()
+}
+
+// Init runs some startup code for this resource.
+func (obj *NetRes) Init() error {
+	var err error
+	// tmp directory for pipe socket
+	// XXX: Replace with obj.VarDir
+	if obj.tempDir, err = ioutil.TempDir("", "pipe"); err != nil {
+		return errwrap.Wrapf(err, "could not get TempDir")
+	}
+
+	// store the network interface in the struct
+	obj.iface = &iface{}
+	if obj.iface.iface, err = net.InterfaceByName(obj.GetName()); err != nil {
+		return errwrap.Wrapf(err, "error finding interface: %s", obj.GetName())
+	}
+	// store the netlink link to use as interface input in netlink functions
+	if obj.iface.link, err = netlink.LinkByName(obj.GetName()); err != nil {
+		return errwrap.Wrapf(err, "error finding link: %s", obj.GetName())
+	}
+
+	// build the path to the networkd configuration file
+	obj.unitFilePath = networkdUnitFileDir + IfacePrefix + obj.GetName() + networkdUnitFileExt
+
+	return obj.BaseRes.Init()
+}
+
+// Watch listens for events from the specified interface via a netlink socket.
+// TODO: currently gets events from ALL interfaces, would be nice to reject
+// events from other interfaces.
+func (obj *NetRes) Watch() error {
+	// waitgroup for netlink receive goroutine
+	wg := &sync.WaitGroup{}
+	defer wg.Wait()
+
+	// create a netlink socket for receiving network interface events
+	conn, err := newSocketSet(rtmGrps, path.Join(obj.tempDir, "pipe.sock"))
+	if err != nil {
+		return errwrap.Wrapf(err, "error creating socket set")
+	}
+	defer conn.shutdown() // close the netlink socket and unblock conn.receive()
+
+	// watch the systemd-networkd configuration file
+	recWatcher, err := recwatch.NewRecWatcher(obj.unitFilePath, false)
+	if err != nil {
+		return err
+	}
+	// close the recwatcher when we're done
+	defer recWatcher.Close()
+
+	// channel for netlink messages
+	nlChan := make(chan *nlChanStruct) // closed from goroutine
+
+	// channel to unblock selects in goroutine
+	closeChan := make(chan struct{})
+	defer close(closeChan)
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		defer conn.close() // close the pipe when we're done with it
+		defer close(nlChan)
+		for {
+			// receive messages from the socket set
+			msgs, err := conn.receive()
+			if err != nil {
+				select {
+				case nlChan <- &nlChanStruct{
+					err: errwrap.Wrapf(err, "error receiving messages"),
+				}:
+				case <-closeChan:
+					return
+				}
+			}
+			select {
+			case nlChan <- &nlChanStruct{
+				msg: msgs,
+			}:
+			case <-closeChan:
+				return
+			}
+		}
+	}()
+
+	// notify engine that we're running
+	if err := obj.Running(); err != nil {
+		return err // bubble up a NACK...
+	}
+
+	var exit *error
+	var send bool
+	var done bool
+
+	for {
+		select {
+		case s, ok := <-nlChan:
+			if !ok {
+				if done {
+					return nil
+				}
+				done = true
+				continue
+			}
+			if err := s.err; err != nil {
+				return errwrap.Wrapf(s.err, "unknown netlink error")
+			}
+			if obj.debug {
+				log.Printf("%s: Event: %+v", obj, s.msg)
+			}
+
+			send = true
+			obj.StateOK(false)
+
+		case event, ok := <-recWatcher.Events():
+			if !ok {
+				if done {
+					return nil
+				}
+				done = true
+				continue
+			}
+			if err := event.Error; err != nil {
+				return errwrap.Wrapf(err, "unknown recwatcher error")
+			}
+			if obj.debug {
+				log.Printf("%s: Event(%s): %v", obj, event.Body.Name, event.Body.Op)
+			}
+
+			send = true
+			obj.StateOK(false) // dirty
+
+		case event := <-obj.Events():
+			if exit, send = obj.ReadEvent(event); exit != nil {
+				return *exit // exit
+			}
+		}
+
+		// do all our event sending all together to avoid duplicate msgs
+		if send {
+			send = false
+			obj.Event()
+		}
+	}
+}
+
+// ifaceCheckApply checks the state of the network device and brings it up or
+// down as necessary.
+func (obj *NetRes) ifaceCheckApply(apply bool) (bool, error) {
+	// check the interface state
+	state, err := obj.iface.state()
+	if err != nil {
+		return false, errwrap.Wrapf(err, "error checking %s state", obj.GetName())
+	}
+	// if the state is correct or unspecified, we're done
+	if obj.State == state || obj.State == "" {
+		return true, nil
+	}
+
+	// end of state checking
+	if !apply {
+		return false, nil
+	}
+	log.Printf("%s: ifaceCheckApply(%t)", obj, apply)
+
+	// ip link set up/down
+	if err := obj.iface.linkUpDown(obj.State); err != nil {
+		return false, errwrap.Wrapf(err, "error setting %s up or down", obj.GetName())
+	}
+
+	return false, nil
+}
+
+// addrCheckApply checks if the interface has the correct addresses and then
+// adds/deletes addresses as necessary.
+func (obj *NetRes) addrCheckApply(apply bool) (bool, error) {
+	// get the link's addresses
+	ifaceAddrs, err := obj.iface.getAddrs()
+	if err != nil {
+		return false, errwrap.Wrapf(err, "error getting addresses from %s", obj.GetName())
+	}
+	// if state is not defined
+	if obj.Addrs == nil {
+		// send addrs
+		obj.Addrs = ifaceAddrs
+		return true, nil
+	}
+	// check if all addrs have a kernel route needed for first hop
+	kernelOK, err := obj.iface.kernelCheck(obj.Addrs)
+	if err != nil {
+		return false, errwrap.Wrapf(err, "error checking kernel routes")
+	}
+
+	// if the kernel routes are intact and the addrs match, we're done
+	err = StrSortedSliceCompare(obj.Addrs, ifaceAddrs)
+	if err == nil && kernelOK {
+		return true, nil
+	}
+
+	// end of state checking
+	if !apply {
+		return false, nil
+	}
+	log.Printf("%s: addrCheckApply(%t)", obj, apply)
+
+	// check each address and delete the ones that aren't in the definition
+	if err := obj.iface.addrApplyDelete(obj.Addrs); err != nil {
+		return false, errwrap.Wrapf(err, "error checking or deleting addresses")
+	}
+	// check each address and add the ones that are defined but do not exist
+	if err := obj.iface.addrApplyAdd(obj.Addrs); err != nil {
+		return false, errwrap.Wrapf(err, "error checking or adding addresses")
+	}
+	// make sure all the addrs have the appropriate kernel routes
+	if err := obj.iface.kernelApply(obj.Addrs); err != nil {
+		return false, errwrap.Wrapf(err, "error adding kernel routes")
+	}
+
+	return false, nil
+}
+
+// gatewayCheckApply checks if the interface has the correct default gateway
+// and adds/deletes routes as necessary.
+func (obj *NetRes) gatewayCheckApply(apply bool) (bool, error) {
+	// get all routes from the interface
+	routes, err := netlink.RouteList(obj.iface.link, netlink.FAMILY_V4)
+	if err != nil {
+		return false, errwrap.Wrapf(err, "error getting default routes")
+	}
+	// add default routes to a slice
+	defRoutes := []netlink.Route{}
+	for _, route := range routes {
+		if route.Dst == nil { // route is default
+			defRoutes = append(defRoutes, route)
+		}
+	}
+	// if the gateway is already set, we're done
+	if len(defRoutes) == 1 && defRoutes[0].Gw.String() == obj.Gateway {
+		return true, nil
+	}
+	// if no gateway was defined
+	if obj.Gateway == "" {
+		// send the gateway if there is one
+		if len(defRoutes) == 1 {
+			obj.Gateway = defRoutes[0].Gw.String()
+		}
+		return true, nil
+	}
+
+	// end of state checking
+	if !apply {
+		return false, nil
+	}
+	log.Printf("%s: gatewayCheckApply(%t)", obj, apply)
+
+	// delete all but one default route
+	for i := 1; i < len(defRoutes); i++ {
+		if err := netlink.RouteDel(&defRoutes[i]); err != nil {
+			return false, errwrap.Wrapf(err, "error deleting route: %+v", defRoutes[i])
+		}
+	}
+
+	// add or change the default route
+	if err := netlink.RouteReplace(&netlink.Route{
+		LinkIndex: obj.iface.iface.Index,
+		Gw:        net.ParseIP(obj.Gateway),
+		Protocol:  rtProtoStatic,
+	}); err != nil {
+		return false, errwrap.Wrapf(err, "error replacing default route")
+	}
+
+	return false, nil
+}
+
+// fileCheckApply checks and maintains the systemd-networkd unit file contents.
+func (obj *NetRes) fileCheckApply(apply bool) (bool, error) {
+	// check if the unit file exists
+	_, err := os.Stat(obj.unitFilePath)
+	if err != nil && !os.IsNotExist(err) {
+		return false, errwrap.Wrapf(err, "error checking file")
+	}
+	// build the unit file contents from the definition
+	contents := obj.unitFileContents()
+	// check the file contents
+	if err == nil {
+		unitFile, err := ioutil.ReadFile(obj.unitFilePath)
+		if err != nil {
+			return false, errwrap.Wrapf(err, "error reading file")
+		}
+		// return if the file is good
+		if bytes.Equal(unitFile, contents) {
+			return true, nil
+		}
+	}
+
+	if !apply {
+		return false, nil
+	}
+	log.Printf("%s: fileCheckApply(%t)", obj, apply)
+
+	// write the file
+	if err := ioutil.WriteFile(obj.unitFilePath, contents, networkdUnitFileUmask); err != nil {
+		return false, errwrap.Wrapf(err, "error writing configuration file")
+	}
+	return false, nil
+}
+
+// CheckApply is run to check the state and, if apply is true, to apply the
+// necessary changes to reach the desired state. This is run before Watch and
+// again if Watch finds a change occurring to the state.
+func (obj *NetRes) CheckApply(apply bool) (checkOK bool, err error) {
+	checkOK = true
+
+	// check the network device
+	if c, err := obj.ifaceCheckApply(apply); err != nil {
+		return false, err
+	} else if !c {
+		checkOK = false
+	}
+
+	// if the interface is supposed to be down, we're done
+	if obj.State == ifaceDown {
+		return checkOK, nil
+	}
+
+	// check the addresses
+	if c, err := obj.addrCheckApply(apply); err != nil {
+		return false, err
+	} else if !c {
+		checkOK = false
+	}
+
+	// check the gateway
+	if c, err := obj.gatewayCheckApply(apply); err != nil {
+		return false, err
+	} else if !c {
+		checkOK = false
+	}
+
+	// if the state is unspecified, we're done
+	if obj.State == "" {
+		return checkOK, nil
+	}
+
+	// check the networkd unit file
+	if c, err := obj.fileCheckApply(apply); err != nil {
+		return false, err
+	} else if !c {
+		checkOK = false
+	}
+
+	return checkOK, nil
+}
+
+// Close cleans up when we're done.
+func (obj *NetRes) Close() error {
+	var errList error
+	// XXX: replace TempDir with VarDir
+	if err := os.RemoveAll(obj.tempDir); err != nil {
+		errList = multierr.Append(errList, err)
+	}
+	if err := obj.BaseRes.Close(); err != nil {
+		errList = multierr.Append(errList, err)
+	}
+	return errList
+}
+
+// NetUID is a unique resource identifier.
+type NetUID struct {
+	// NOTE: There is also a name variable in the BaseUID struct, this is
+	// information about where this UID came from, and is unrelated to the
+	// information about the resource we're matching. That data which is
+	// used in the IFF function, is what you see in the struct fields here.
+	BaseUID
+	name string // the network interface name
+}
+
+// IFF aka if and only if they are equivalent, return true. If not, false.
+func (obj *NetUID) IFF(uid ResUID) bool {
+	res, ok := uid.(*NetUID)
+	if !ok {
+		return false
+	}
+	return obj.name == res.name
+}
+
+// UIDs includes all params to make a unique identification of this object.
+// Most resources only return one although some resources can return multiple.
+func (obj *NetRes) UIDs() []ResUID {
+	x := &NetUID{
+		BaseUID: BaseUID{Name: obj.GetName(), Kind: obj.GetKind()},
+		name:    obj.Name,
+	}
+	return []ResUID{x}
+}
+
+// GroupCmp returns whether two resources can be grouped together or not.
+func (obj *NetRes) GroupCmp(r Res) bool {
+	_, ok := r.(*NetRes)
+	if !ok {
+		return false
+	}
+	return false
+}
+
+// Compare two resources and return if they are equivalent.
+func (obj *NetRes) Compare(r Res) bool {
+	// we can only compare NetRes to others of the same resource kind
+	res, ok := r.(*NetRes)
+	if !ok {
+		return false
+	}
+	if !obj.BaseRes.Compare(res) {
+		return false
+	}
+	if obj.Name != res.Name {
+		return false
+	}
+	if obj.State != res.State {
+		return false
+	}
+	if (obj.Addrs == nil) != (res.Addrs == nil) {
+		return false
+	}
+	if err := StrSortedSliceCompare(obj.Addrs, res.Addrs); err != nil {
+		return false
+	}
+	if obj.Gateway != res.Gateway {
+		return false
+	}
+
+	return true
+}
+
+// UnmarshalYAML is the custom unmarshal handler for this struct.
+// It is primarily useful for setting the defaults.
+func (obj *NetRes) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	type rawRes NetRes // indirection to avoid infinite recursion
+
+	def := obj.Default()     // get the default
+	res, ok := def.(*NetRes) // put in the right format
+	if !ok {
+		return fmt.Errorf("could not convert to NetRes")
+	}
+	raw := rawRes(*res) // convert; the defaults go here
+
+	if err := unmarshal(&raw); err != nil {
+		return err
+	}
+
+	*obj = NetRes(raw) // restore from indirection with type conversion!
+	return nil
+}
+
+// unitFileContents builds the unit file contents from the definition.
+func (obj *NetRes) unitFileContents() []byte {
+	// build the unit file contents
+	u := []string{"[Match]"}
+	u = append(u, fmt.Sprintf("Name=%s", obj.GetName()))
+	u = append(u, "[Network]")
+	for _, addr := range obj.Addrs {
+		u = append(u, fmt.Sprintf("Address=%s", addr))
+	}
+	if obj.Gateway != "" {
+		u = append(u, fmt.Sprintf("Gateway=%s", obj.Gateway))
+	}
+	c := strings.Join(u, "\n")
+	return []byte(c)
+}
+
+// iface wraps net.Interface to add additional methods.
+type iface struct {
+	iface *net.Interface
+	link  netlink.Link
+}
+
+// state reports the state of the interface as up or down.
+func (obj *iface) state() (string, error) {
+	var err error
+	if obj.iface, err = net.InterfaceByName(obj.iface.Name); err != nil {
+		return "", errwrap.Wrapf(err, "error updating interface")
+	}
+	// if the interface's "up" flag is 0, it's down
+	if obj.iface.Flags&net.FlagUp == 0 {
+		return ifaceDown, nil
+	}
+	// otherwise it's up
+	return ifaceUp, nil
+}
+
+// linkUpDown brings the interface up or down, depending on input value.
+func (obj *iface) linkUpDown(state string) error {
+	if state != ifaceUp && state != ifaceDown {
+		return fmt.Errorf("state must be up or down")
+	}
+	if state == ifaceUp {
+		return netlink.LinkSetUp(obj.link)
+	}
+	return netlink.LinkSetDown(obj.link)
+}
+
+// getAddrs returns a list of strings containing all of the interface's
+// IP addresses in CIDR format.
+func (obj *iface) getAddrs() ([]string, error) {
+	var ifaceAddrs []string
+	a, err := obj.iface.Addrs()
+	if err != nil {
+		return nil, errwrap.Wrapf(err, "error getting addrs from interface: %s", obj.iface.Name)
+	}
+	// we're only interested in the strings (not the network)
+	for _, addr := range a {
+		ifaceAddrs = append(ifaceAddrs, addr.String())
+	}
+	return ifaceAddrs, nil
+}
+
+// kernelCheck checks if all addresses in the list have a corresponding kernel
+// route, without which the network would be unreachable.
+func (obj *iface) kernelCheck(addrs []string) (bool, error) {
+	var routeOK bool
+
+	// get a list of all the routes associated with the interface
+	routes, err := netlink.RouteList(obj.link, netlink.FAMILY_V4)
+	if err != nil {
+		return false, errwrap.Wrapf(err, "error getting routes")
+	}
+	// check each route against each addr
+	for _, addr := range addrs {
+		routeOK = false
+		ip, ipNet, err := net.ParseCIDR(addr)
+		if err != nil {
+			return false, errwrap.Wrapf(err, "error parsing addr: %s", addr)
+		}
+		for _, r := range routes {
+			// if src, dst and protocol are correct, the kernel route exists
+			if r.Src.Equal(ip) && r.Dst.String() == ipNet.String() && r.Protocol == rtProtoKernel {
+				routeOK = true
+				break
+			}
+		}
+		// if any addr is missing a kernel route return early
+		if !routeOK {
+			break
+		}
+	}
+	return routeOK, nil
+}
+
+// kernelApply adds or replaces each address' kernel route as necessary.
+func (obj *iface) kernelApply(addrs []string) error {
+	// for each addr, add or replace the corresponding kernel route
+	for _, addr := range addrs {
+		ip, ipNet, err := net.ParseCIDR(addr)
+		if err != nil {
+			return errwrap.Wrapf(err, "error parsing addr: %s", addr)
+		}
+		// kernel route needed for the network to be reachable from a given ip
+		if err := netlink.RouteReplace(&netlink.Route{
+			LinkIndex: obj.iface.Index,
+			Dst:       ipNet,
+			Src:       ip,
+			Protocol:  rtProtoKernel,
+			Scope:     netlink.SCOPE_LINK,
+		}); err != nil {
+			return errwrap.Wrapf(err, "error replacing first hop route")
+		}
+	}
+	return nil
+}
+
+// addrApplyDelete, checks the interface's addresses and deletes any that are not
+// in the list/definition.
+func (obj *iface) addrApplyDelete(objAddrs []string) error {
+	ifaceAddrs, err := obj.getAddrs()
+	if err != nil {
+		return errwrap.Wrapf(err, "error getting addrs from interface: %s", obj.iface.Name)
+	}
+	for _, ifaceAddr := range ifaceAddrs {
+		addrOK := false
+		for _, objAddr := range objAddrs {
+			if ifaceAddr == objAddr {
+				addrOK = true
+			}
+		}
+		if addrOK {
+			continue
+		}
+		addr, err := netlink.ParseAddr(ifaceAddr)
+		if err != nil {
+			return errwrap.Wrapf(err, "error parsing netlink address: %s", ifaceAddr)
+		}
+		if err := netlink.AddrDel(obj.link, addr); err != nil {
+			return errwrap.Wrapf(err, "error deleting addr: %s from %s", ifaceAddr, obj.iface.Name)
+		}
+	}
+	return nil
+}
+
+// addrApplyAdd checks if the interface has each address in the supplied list,
+// and if it doesn't, it adds them.
+func (obj *iface) addrApplyAdd(objAddrs []string) error {
+	ifaceAddrs, err := obj.getAddrs()
+	if err != nil {
+		return errwrap.Wrapf(err, "error getting addrs from interface: %s", obj.iface.Name)
+	}
+	for _, objAddr := range objAddrs {
+		addrOK := false
+		for _, ifaceAddr := range ifaceAddrs {
+			if ifaceAddr == objAddr {
+				addrOK = true
+			}
+		}
+		if addrOK {
+			continue
+		}
+		addr, err := netlink.ParseAddr(objAddr)
+		if err != nil {
+			return errwrap.Wrapf(err, "error parsing cidr address: %s", objAddr)
+		}
+		if err := netlink.AddrAdd(obj.link, addr); err != nil {
+			return errwrap.Wrapf(err, "error adding addr: %s to %s", objAddr, obj.iface.Name)
+		}
+	}
+	return nil
+}
+
+// socketSet is used to receive events from a socket and shut it down cleanly
+// when asked. It contains a socket for events and a pipe socket to unblock
+// receive on shutdown.
+type socketSet struct {
+	fdEvents int
+	fdPipe   int
+	pipeFile string
+}
+
+// newSocketSet returns a socketSet, initialized with the given parameters.
+func newSocketSet(groups uint32, file string) (*socketSet, error) {
+	// make a netlink socket file descriptor
+	fdEvents, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW, unix.NETLINK_ROUTE)
+	if err != nil {
+		return nil, errwrap.Wrapf(err, "error creating netlink socket")
+	}
+	// bind to the socket and add add the netlink groups we need to get events
+	if err := unix.Bind(fdEvents, &unix.SockaddrNetlink{
+		Family: unix.AF_NETLINK,
+		Groups: groups,
+	}); err != nil {
+		return nil, errwrap.Wrapf(err, "error binding netlink socket")
+	}
+
+	// create a pipe socket to unblock unix.Select when we close
+	fdPipe, err := unix.Socket(unix.AF_UNIX, unix.SOCK_RAW, unix.PROT_NONE)
+	if err != nil {
+		return nil, errwrap.Wrapf(err, "error creating pipe socket")
+	}
+	// bind the pipe to a file
+	if err = unix.Bind(fdPipe, &unix.SockaddrUnix{
+		Name: file,
+	}); err != nil {
+		return nil, errwrap.Wrapf(err, "error binding pipe socket")
+	}
+	return &socketSet{
+		fdEvents: fdEvents,
+		fdPipe:   fdPipe,
+		pipeFile: file,
+	}, nil
+}
+
+// shutdown closes the event file descriptor and unblocks receive by sending
+// a message to the pipe file descriptor. It must be called before close, and
+// should only be called once.
+func (obj *socketSet) shutdown() error {
+	// close the event socket so no more events are produced
+	if err := unix.Close(obj.fdEvents); err != nil {
+		return err
+	}
+	// send a message to the pipe to unblock select
+	return unix.Sendto(obj.fdPipe, nil, 0, &unix.SockaddrUnix{
+		Name: path.Join(obj.pipeFile),
+	})
+}
+
+// close closes the pipe file descriptor. It must only be called after
+// shutdown has closed fdEvents, and unblocked receive. It should only be
+// called once.
+func (obj *socketSet) close() error {
+	return unix.Close(obj.fdPipe)
+}
+
+// receive waits for bytes from fdEvents and parses them into a slice of
+// netlink messages. It will block until an event is produced, or shutdown
+// is called.
+func (obj *socketSet) receive() ([]syscall.NetlinkMessage, error) {
+	// Select will return when any fd in fdSet (fdEvents and fdPipe) is ready
+	// to read.
+	_, err := unix.Select(obj.nfd(), obj.fdSet(), nil, nil, nil)
+	if err != nil {
+		// if a system interrupt is caught
+		if err == unix.EINTR { // signal interrupt
+			return nil, nil
+		}
+		return nil, errwrap.Wrapf(err, "error selecting on fd")
+	}
+	// receive the message from the netlink socket into b
+	b := make([]byte, os.Getpagesize())
+	n, _, err := unix.Recvfrom(obj.fdEvents, b, unix.MSG_DONTWAIT) // non-blocking receive
+	if err != nil {
+		// if fdEvents is closed
+		if err == unix.EBADF { // bad file descriptor
+			return nil, nil
+		}
+		return nil, errwrap.Wrapf(err, "error receiving messages")
+	}
+	// if we didn't get enough bytes for a header, something went wrong
+	if n < unix.NLMSG_HDRLEN {
+		return nil, fmt.Errorf("received short header")
+	}
+	b = b[:n] // truncate b to message length
+	// use syscall to parse, as func does not exist in x/sys/unix
+	return syscall.ParseNetlinkMessage(b)
+}
+
+// nfd returns one more than the highest fd value in the struct, for use as as
+// the nfds parameter in select. It represents the file descriptor set maximum
+// size. See man select for more info.
+func (obj *socketSet) nfd() int {
+	if obj.fdEvents > obj.fdPipe {
+		return obj.fdEvents + 1
+	}
+	return obj.fdPipe + 1
+}
+
+// fdSet returns a bitmask representation of the integer values of fdEvents
+// and fdPipe. See man select for more info.
+func (obj *socketSet) fdSet() *unix.FdSet {
+	fdSet := &unix.FdSet{}
+	fdSet.Bits[obj.fdEvents/64] |= 1 << uint(obj.fdEvents)
+	fdSet.Bits[obj.fdPipe/64] |= 1 << uint(obj.fdPipe) // fd = 3 becomes 100 if we add 5, we get 10100
+	return fdSet
+}

resources/util.go

@@ -270,3 +270,27 @@ func GetGID(group string) (int, error) {
 
 	return -1, errwrap.Wrapf(err, "group lookup error (%s)", group)
 }
+
+// StrSortedSliceCompare takes two lists of strings and returns whether or not
+// they are equivalent. It will return nil if both sets contain the same
+// elements, regardless of order, and an error if they do not.
+func StrSortedSliceCompare(a, b []string) error {
+	if len(a) != len(b) {
+		return fmt.Errorf("slices have different lengths: %d vs %d", len(a), len(b))
+	}
+
+	// make a copy of each to sort, so we don't reorder the inputs
+	x := make([]string, len(a))
+	y := make([]string, len(b))
+	copy(x, a)
+	copy(y, b)
+
+	sort.Strings(x)
+	sort.Strings(y)
+	for i := range x {
+		if x[i] != y[i] {
+			return fmt.Errorf("values do not match: %s vs %s", x[i], y[i])
+		}
+	}
+	return nil
+}

resources/util_test.go

@@ -378,3 +378,45 @@ func TestCurrentUserGroupById(t *testing.T) {
 		t.Errorf("gid didn't match current user's: %s vs %s", strconv.Itoa(gid), currentGID)
 	}
 }
+
+func TestStrSortedSliceCompare0(t *testing.T) {
+	slice1 := []string{"foo", "bar", "baz"}
+	slice2 := []string{"bar", "foo", "baz"}
+
+	if err := StrSortedSliceCompare(slice1, slice2); err != nil {
+		t.Errorf("slices were not evaluated as equivalent: %v, %v", slice1, slice2)
+	}
+}
+
+func TestStrSortedSliceCompare1(t *testing.T) {
+	slice1 := []string{"foo", "bar", "baz"}
+	slice2 := []string{"fi", "fi", "fo"}
+
+	if err := StrSortedSliceCompare(slice1, slice2); err == nil {
+		t.Errorf("slices were evaluated as equivalent: %v, %v", slice1, slice2)
+	}
+}
+
+func TestStrSortedSliceCompare2(t *testing.T) {
+	slice1 := []string{"foo", "bar", "baz"}
+	slice2 := []string{"foo", "bar"}
+
+	if err := StrSortedSliceCompare(slice1, slice2); err == nil {
+		t.Errorf("slices were evaluated as equivalent: %v, %v", slice1, slice2)
+	}
+}
+
+func TestStrSortedSliceCompare3(t *testing.T) {
+	slice0 := []string{"foo", "bar", "baz"}
+	slice1 := []string{"zip", "zap", "zop"}
+
+	_ = StrSortedSliceCompare(slice0, slice1)
+
+	if slice0[0] != "foo" || slice0[1] != "bar" || slice0[2] != "baz" {
+		t.Errorf("input slice reordered to: %v", slice0)
+	}
+
+	if slice1[0] != "zip" || slice1[1] != "zap" || slice1[2] != "zop" {
+		t.Errorf("input slice reordered to: %v", slice1)
+	}
+}

yamlgraph/gconfig.go

@@ -63,6 +63,7 @@ type Resources struct {
 	Hostname []*resources.HostnameRes `yaml:"hostname"`
 	KV       []*resources.KVRes       `yaml:"kv"`
 	Msg      []*resources.MsgRes      `yaml:"msg"`
+	Net      []*resources.NetRes      `yaml:"net"`
 	Noop     []*resources.NoopRes     `yaml:"noop"`
 	Nspawn   []*resources.NspawnRes   `yaml:"nspawn"`
 	Password []*resources.PasswordRes `yaml:"password"`