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Signed-off-by: Evgenii Stratonikov <stratonikov@runbox.com>
This commit is contained in:
Evgenii Stratonikov 2023-08-16 20:10:49 +03:00
commit b92dae991b
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3
Makefile Normal file
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test:
# TODO figure out needed capabilities
sudo go test -count=1 -v ./...

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README.md Normal file
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# Source-based routing in Golang
Consider this routing table:
```
10.11.70.0/23 dev data0 proto kernel scope link src 10.11.70.42
10.11.70.0/23 dev data1 proto kernel scope link src 10.11.71.42
192.168.123.0/24 dev internal0 proto kernel scope link src 192.168.123.42
192.168.123.0/24 dev internal1 proto kernel scope link src 192.168.123.142
```
Simple `net.Dial` to either `10.11.70.42` or `10.11.71.42` will match the first subnet and be routed via data0.
This problems is usually solved by bonds.
But sometimes you need to invent a bicycle.
## Usage
```golang
import "git.frostfs.info/TrueCloudLab/multinet"
d, err := multinet.NewDialer(Config{
Subnets: []string{"10.11.70.0/23", "192.168.123.0/24"},
Balancer: multinet.BalancerTypeRoundRobin,
})
if err != nil {
// handle error
}
conn, err := d.DialContext(ctx, "tcp", "10.11.70.42")
if err != nil {
// handle error
}
// do stuff
```
### Updating interface state
`Multidialer` exposes `UpdateInterface()` method for updating state of a single link.
`NetlinkWatcher` can wrap `Multidialer` type and perform all updates automatically.
TODO: describe needed capabilities here.

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balancer.go Normal file
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package multinet
import (
"context"
"errors"
"net"
"sync/atomic"
)
// BalancerType reperents the algorithm which is used to pick source address.
type BalancerType string
const (
// BalancerTypeNoop picks first address for which link is up.
BalancerTypeNoop BalancerType = ""
// BalancerTypeNoop implements simple round-robin between up links.
// It is not fair in case some links are down.
BalancerTypeRoundRobin BalancerType = "roundrobin"
)
type balancer interface {
DialContext(ctx context.Context, s *Subnet, network, address string) (net.Conn, error)
}
type roundRobin struct {
d *dialer
i atomic.Uint32
}
func (r *roundRobin) DialContext(ctx context.Context, s *Subnet, network, address string) (net.Conn, error) {
next := int(r.i.Add(1))
for i := range s.Interfaces {
ii := s.Interfaces[(i+next)%len(s.Interfaces)]
if ii.Down {
continue
}
dd := r.d.dialer
dd.LocalAddr = ii.LocalAddr
return r.d.dialContext(&dd, ctx, "tcp", address)
}
return nil, errors.New("(*roundRobin).DialContext: no suitale node found")
}
type firstEnabled struct {
d *dialer
}
func (r *firstEnabled) DialContext(ctx context.Context, s *Subnet, network, address string) (net.Conn, error) {
for i := range s.Interfaces {
ii := s.Interfaces[i%len(s.Interfaces)]
if ii.Down {
continue
}
dd := r.d.dialer
dd.LocalAddr = ii.LocalAddr
return r.d.dialContext(&dd, ctx, "tcp", address)
}
return nil, errors.New("(*firstEnabled).DialContext: no suitale node found")
}

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dialer.go Normal file
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package multinet
import (
"bytes"
"context"
"fmt"
"net"
"net/netip"
"sort"
"sync"
)
// Dialer contains the single most important method from the net.Dialer.
type Dialer interface {
DialContext(ctx context.Context, network, address string) (net.Conn, error)
}
// Multidialer is like Dialer, but supports link state updates.
type Multidialer interface {
Dialer
UpdateInterface(name string, addr netip.Addr, status bool) error
}
var (
_ Dialer = (*net.Dialer)(nil)
_ Dialer = (*dialer)(nil)
)
type dialer struct {
// Protects subnets field (recursively).
mtx sync.RWMutex
subnets []Subnet
// Default options for the net.Dialer.
dialer net.Dialer
// If true, allow to dial only configured subnets.
restrict bool
// Algorithm to which picks source address for each ip.
balancer balancer
// Hook used in tests, overrides `net.Dialer.DialContext()`
testHookDialContext func(d *net.Dialer, ctx context.Context, network, address string) (net.Conn, error)
}
// Subnet represents a single subnet, possibly routable from multiple interfaces.
type Subnet struct {
Mask netip.Prefix
Interfaces []Source
}
// Source represents a single source IP belonging to a particular subnet.
type Source struct {
Name string
LocalAddr *net.TCPAddr
Down bool
}
// Config contains Multidialer configuration.
type Config struct {
// Routable subnets to prioritize in CIDR format.
Subnets []string
// If true, the only configurd subnets available through this dialer.
// Otherwise, a failback to the net.DefaultDialer.
Restrict bool
// Dialer containes default options for the net.Dialer to use.
// LocalAddr is overriden.
Dialer net.Dialer
// Balancer specifies algorithm used to pick source address.
Balancer BalancerType
}
// NewDialer ...
func NewDialer(c Config) (Multidialer, error) {
ifaces, err := net.Interfaces()
if err != nil {
return nil, err
}
sort.Slice(ifaces, func(i, j int) bool {
return ifaces[i].Name < ifaces[j].Name
})
var sources []iface
for i := range ifaces {
info, err := processIface(ifaces[i])
if err != nil {
return nil, err
}
sources = append(sources, info)
}
var d dialer
for _, subnet := range c.Subnets {
s, err := processSubnet(subnet, sources)
if err != nil {
return nil, err
}
d.subnets = append(d.subnets, s)
}
switch c.Balancer {
case BalancerTypeNoop:
d.balancer = &firstEnabled{d: &d}
case BalancerTypeRoundRobin:
d.balancer = &roundRobin{d: &d}
default:
return nil, fmt.Errorf("invalid balancer type: %s", c.Balancer)
}
d.restrict = c.Restrict
return &d, nil
}
type iface struct {
info net.Interface
addrs []netip.Prefix
}
func processIface(info net.Interface) (iface, error) {
ips, err := info.Addrs()
if err != nil {
return iface{}, err
}
var addrs []netip.Prefix
for i := range ips {
p, err := netip.ParsePrefix(ips[i].String())
if err != nil {
return iface{}, err
}
addrs = append(addrs, p)
}
return iface{info: info, addrs: addrs}, nil
}
func processSubnet(subnet string, sources []iface) (Subnet, error) {
s, err := netip.ParsePrefix(subnet)
if err != nil {
return Subnet{}, err
}
var ifs []Source
for _, source := range sources {
for i := range source.addrs {
src := source.addrs[i].Addr()
if s.Contains(src) {
ifs = append(ifs, Source{
Name: source.info.Name,
LocalAddr: &net.TCPAddr{IP: net.IP(src.AsSlice())},
})
}
}
}
sort.Slice(ifs, func(i, j int) bool {
if ifs[i].Name != ifs[j].Name {
return ifs[i].Name < ifs[j].Name
}
return bytes.Compare(ifs[i].LocalAddr.IP, ifs[j].LocalAddr.IP) == -1
})
return Subnet{
Mask: s,
Interfaces: ifs,
}, nil
}
// DialContext implements the Dialer interface.
// Hostnames for address are currently not supported.
func (d *dialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
addr, err := netip.ParseAddrPort(address)
if err != nil {
return nil, err
}
d.mtx.RLock()
defer d.mtx.RUnlock()
for i := range d.subnets {
if d.subnets[i].Mask.Contains(addr.Addr()) {
return d.balancer.DialContext(ctx, &d.subnets[i], network, address)
}
}
if d.restrict {
return nil, fmt.Errorf("no suitable interface for: [%s]%s", network, address)
}
return d.dialer.DialContext(ctx, network, address)
}
func (d *dialer) dialContext(nd *net.Dialer, ctx context.Context, network, address string) (net.Conn, error) {
if h := d.testHookDialContext; h != nil {
return h(nd, ctx, "tcp", address)
}
return nd.DialContext(ctx, "tcp", address)
}
// UpdateInterface implements the Multidialer interface.
// Updating address on a specific interface is currently not supported.
func (d *dialer) UpdateInterface(iface string, addr netip.Addr, up bool) error {
d.mtx.Lock()
defer d.mtx.Unlock()
for i := range d.subnets {
for j := range d.subnets[i].Interfaces {
matchIface := d.subnets[i].Interfaces[j].Name == iface
if matchIface {
d.subnets[i].Interfaces[j].Down = !up
continue
}
a, _ := netip.AddrFromSlice(d.subnets[i].Interfaces[j].LocalAddr.IP)
matchAddr := a.IsUnspecified() || addr == a
if matchAddr {
d.subnets[i].Interfaces[j].Down = !up
}
}
}
return nil
}

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package multinet
import (
"net"
"net/netip"
"runtime"
"testing"
"github.com/stretchr/testify/require"
"github.com/vishvananda/netlink"
"github.com/vishvananda/netns"
)
func TestDialer(t *testing.T) {
runInNewNamespace(t, "2 interfaces with multiple routes in different subnets", func(t *testing.T, ns netns.NsHandle) {
setup(t, map[string][]string{
"testdev1": {"1.2.30.10/23", "4.4.4.4/8"},
"testdev2": {"1.2.30.11/23", "4.4.4.5/8"},
})
// Do not use `t.Run` because everything should be executed in a single OS thread.
{ // Restrict to a single subnet.
d, err := NewDialer(Config{
Subnets: []string{"1.2.30.0/23"},
})
require.NoError(t, err)
require.Equal(t, []Subnet{
{
Mask: netip.MustParsePrefix("1.2.30.0/23"),
Interfaces: []Source{
{Name: "testdev1", LocalAddr: &net.TCPAddr{IP: net.IP{1, 2, 30, 10}}},
{Name: "testdev2", LocalAddr: &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}},
},
},
}, d.(*dialer).subnets)
}
{ // Restrict to two subnets.
d, err := NewDialer(Config{
Subnets: []string{"1.2.30.0/23", "4.0.0.0/8"},
})
require.NoError(t, err)
require.Equal(t, []Subnet{
{
Mask: netip.MustParsePrefix("1.2.30.0/23"),
Interfaces: []Source{
{Name: "testdev1", LocalAddr: &net.TCPAddr{IP: net.IP{1, 2, 30, 10}}},
{Name: "testdev2", LocalAddr: &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}},
},
},
{
Mask: netip.MustParsePrefix("4.0.0.0/8"),
Interfaces: []Source{
{Name: "testdev1", LocalAddr: &net.TCPAddr{IP: net.IP{4, 4, 4, 4}}},
{Name: "testdev2", LocalAddr: &net.TCPAddr{IP: net.IP{4, 4, 4, 5}}},
},
},
}, d.(*dialer).subnets)
}
})
runInNewNamespace(t, "4 interfaces, 2 for data, 2 internal", func(t *testing.T, ns netns.NsHandle) {
setup(t, map[string][]string{
"internal1": {"192.168.0.1/16"},
"internal2": {"192.168.0.2/16"},
"data1": {"10.11.12.101/24"},
"data2": {"10.11.12.102/24"},
})
d, err := NewDialer(Config{
Subnets: []string{"10.11.12.0/24", "192.168.0.0/16"},
})
require.NoError(t, err)
require.Equal(t, []Subnet{
{
Mask: netip.MustParsePrefix("10.11.12.0/24"),
Interfaces: []Source{
{Name: "data1", LocalAddr: &net.TCPAddr{IP: net.IP{10, 11, 12, 101}}},
{Name: "data2", LocalAddr: &net.TCPAddr{IP: net.IP{10, 11, 12, 102}}},
},
},
{
Mask: netip.MustParsePrefix("192.168.0.0/16"),
Interfaces: []Source{
{Name: "internal1", LocalAddr: &net.TCPAddr{IP: net.IP{192, 168, 0, 1}}},
{Name: "internal2", LocalAddr: &net.TCPAddr{IP: net.IP{192, 168, 0, 2}}},
},
},
}, d.(*dialer).subnets)
})
runInNewNamespace(t, "with ipv6", func(t *testing.T, ns netns.NsHandle) {
addr1 := "2001:db8:85a3:8d3:1319:8a2e:370:7348/64"
addr2 := "2001:db8:85a3:8d3:1319:8a2e:370:8192/64"
setup(t, map[string][]string{
"testdev1": {addr1},
"testdev2": {addr2},
})
// Do not use `t.Run` because everything should be executed in a single OS thread.
{ // Restrict to a single subnet.
d, err := NewDialer(Config{
Subnets: []string{"2001:db8:85a3:8d3::/64"},
})
require.NoError(t, err)
require.Equal(t, []Subnet{
{
Mask: netip.MustParsePrefix("2001:db8:85a3:8d3::/64"),
Interfaces: []Source{
{Name: "testdev1", LocalAddr: mustParseIPv6(t, addr1)},
{Name: "testdev2", LocalAddr: mustParseIPv6(t, addr2)},
},
},
}, d.(*dialer).subnets)
}
})
}
func mustParseIPv6(t *testing.T, s string) *net.TCPAddr {
ip, _, err := net.ParseCIDR(s)
require.NoError(t, err)
return &net.TCPAddr{IP: ip}
}
func setup(t *testing.T, config map[string][]string) {
for name, ips := range config {
link := createLink(t, name)
for i := range ips {
ip, err := netlink.ParseIPNet(ips[i])
require.NoError(t, err)
require.NoError(t, netlink.AddrAdd(link, &netlink.Addr{IPNet: ip}))
}
}
}
func createLink(t *testing.T, name string) netlink.Link {
require.NoError(t, netlink.LinkAdd(&netlink.Dummy{LinkAttrs: netlink.LinkAttrs{Name: name}}))
link, err := netlink.LinkByName(name)
require.NoError(t, err)
require.NoError(t, netlink.LinkSetUp(link))
return link
}
func runInNewNamespace(t *testing.T, name string, f func(t *testing.T, ns netns.NsHandle)) {
t.Run(name, func(t *testing.T) {
// To avoid messing with host network settings,
// we create a new names space and execute tests in it.
// Switching thread can move us to a different namespace, thus this line.
runtime.LockOSThread()
defer runtime.UnlockOSThread()
origns, err := netns.Get()
require.NoError(t, err)
defer origns.Close()
defer netns.Set(origns)
newns, err := netns.New()
require.NoError(t, err)
defer newns.Close()
f(t, newns)
})
}

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module git.frostfs.info/TrueCloudLab/multinet
go 1.21.0
require (
github.com/stretchr/testify v1.8.4
github.com/vishvananda/netlink v1.1.0
github.com/vishvananda/netns v0.0.4
golang.org/x/sys v0.2.0
)
require (
github.com/davecgh/go-spew v1.1.1 // indirect
github.com/pmezard/go-difflib v1.0.0 // indirect
gopkg.in/yaml.v3 v3.0.1 // indirect
)

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package multinet
import (
"net/netip"
"sync"
"github.com/vishvananda/netlink"
"github.com/vishvananda/netns"
"golang.org/x/sys/unix"
)
type NetlinkWatcher struct {
d Multidialer
linkUpdates chan netlink.LinkUpdate
addrUpdates chan netlink.AddrUpdate
done chan struct{}
wg sync.WaitGroup
}
func NewNetlinkWatcher(d Multidialer) *NetlinkWatcher {
return &NetlinkWatcher{
d: d,
addrUpdates: make(chan netlink.AddrUpdate, 1),
linkUpdates: make(chan netlink.LinkUpdate, 1),
done: make(chan struct{}),
}
}
func (w *NetlinkWatcher) Start() error {
ns, err := netns.Get()
if err != nil {
return err
}
if err := netlink.LinkSubscribe(w.linkUpdates, w.done); err != nil {
return err
}
if err := netlink.AddrSubscribe(w.addrUpdates, w.done); err != nil {
close(w.done)
return err
}
w.wg.Add(1)
go w.watch(ns)
return nil
}
func (w *NetlinkWatcher) watch(ns netns.NsHandle) {
defer w.wg.Done()
for {
select {
case <-w.done:
return
case update := <-w.addrUpdates:
// Wont work if an multiple interfaces share IP address.
// Should not happen in practice.
ip, ok := netip.AddrFromSlice(update.LinkAddress.IP)
if !ok {
continue
}
w.d.UpdateInterface("", ip, update.NewAddr)
case update := <-w.linkUpdates:
up := update.Flags&unix.IFF_UP != 0
w.d.UpdateInterface(update.Link.Attrs().Name, netip.Addr{}, up)
}
}
}
func (w *NetlinkWatcher) Stop() {
close(w.done)
w.wg.Wait()
}

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package multinet
import (
"context"
"net"
"testing"
"time"
"github.com/stretchr/testify/require"
"github.com/vishvananda/netlink"
"github.com/vishvananda/netns"
)
func Test_NetlinkWatcher(t *testing.T) {
runInNewNamespace(t, "noop balancer, disable interface", func(t *testing.T, ns netns.NsHandle) {
setup(t, map[string][]string{
"testdev1": {"1.2.30.11/23"},
"testdev2": {"1.2.30.12/23"},
})
addr1 := &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}
addr2 := &net.TCPAddr{IP: net.IP{1, 2, 30, 12}}
d, err := NewDialer(Config{
Subnets: []string{"1.2.30.0/23"},
})
require.NoError(t, err)
w := NewNetlinkWatcher(d)
require.NoError(t, w.Start())
t.Cleanup(w.Stop)
result := make(chan net.Addr, 1)
d.(*dialer).testHookDialContext = func(d *net.Dialer, _ context.Context, _, _ string) (net.Conn, error) {
result <- d.LocalAddr
return nil, nil
}
checkDialAddr(t, d, result, addr1)
checkDialAddr(t, d, result, addr1)
link, err := netlink.LinkByName("testdev1")
require.NoError(t, err)
require.NoError(t, netlink.LinkSetDown(link))
time.Sleep(time.Second)
checkDialAddr(t, d, result, addr2)
checkDialAddr(t, d, result, addr2)
require.NoError(t, netlink.LinkSetUp(link))
time.Sleep(time.Second)
checkDialAddr(t, d, result, addr1)
})
runInNewNamespace(t, "noop balancer, remove address", func(t *testing.T, ns netns.NsHandle) {
setup(t, map[string][]string{
"testdev1": {"1.2.30.11/23"},
"testdev2": {"1.2.30.12/23"},
})
addr1 := &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}
addr2 := &net.TCPAddr{IP: net.IP{1, 2, 30, 12}}
d, err := NewDialer(Config{
Subnets: []string{"1.2.30.0/23"},
})
require.NoError(t, err)
w := NewNetlinkWatcher(d)
require.NoError(t, w.Start())
t.Cleanup(w.Stop)
result := make(chan net.Addr, 1)
d.(*dialer).testHookDialContext = func(d *net.Dialer, _ context.Context, _, _ string) (net.Conn, error) {
result <- d.LocalAddr
return nil, nil
}
checkDialAddr(t, d, result, addr1)
checkDialAddr(t, d, result, addr1)
link, err := netlink.LinkByName("testdev1")
require.NoError(t, err)
ip, err := netlink.ParseIPNet("1.2.30.11/23")
require.NoError(t, err)
require.NoError(t, netlink.AddrDel(link, &netlink.Addr{IPNet: ip}))
time.Sleep(time.Second)
checkDialAddr(t, d, result, addr2)
checkDialAddr(t, d, result, addr2)
require.NoError(t, netlink.AddrAdd(link, &netlink.Addr{IPNet: ip}))
time.Sleep(time.Second)
checkDialAddr(t, d, result, addr1)
})
runInNewNamespace(t, "round-robin balancer, disable interface", func(t *testing.T, ns netns.NsHandle) {
setup(t, map[string][]string{
"testdev1": {"1.2.30.11/23"},
"testdev2": {"1.2.30.12/23"},
})
addr1 := &net.TCPAddr{IP: net.IP{1, 2, 30, 11}}
addr2 := &net.TCPAddr{IP: net.IP{1, 2, 30, 12}}
d, err := NewDialer(Config{
Subnets: []string{"1.2.30.0/23"},
Balancer: BalancerTypeRoundRobin,
})
require.NoError(t, err)
w := NewNetlinkWatcher(d)
require.NoError(t, w.Start())
t.Cleanup(w.Stop)
result := make(chan net.Addr, 1)
d.(*dialer).testHookDialContext = func(d *net.Dialer, _ context.Context, _, _ string) (net.Conn, error) {
result <- d.LocalAddr
return nil, nil
}
checkDialAddr(t, d, result, addr2)
checkDialAddr(t, d, result, addr1)
checkDialAddr(t, d, result, addr2)
link, err := netlink.LinkByName("testdev1")
require.NoError(t, err)
require.NoError(t, netlink.LinkSetDown(link))
time.Sleep(time.Second)
checkDialAddr(t, d, result, addr2)
checkDialAddr(t, d, result, addr2)
require.NoError(t, netlink.LinkSetUp(link))
time.Sleep(time.Second)
checkDialAddr(t, d, result, addr1)
checkDialAddr(t, d, result, addr2)
})
}
func checkDialAddr(t *testing.T, d Multidialer, ch chan net.Addr, expected net.Addr) {
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
_, err := d.DialContext(ctx, "tcp", "1.2.30.42:12345")
require.NoError(t, err)
select {
case addr := <-ch:
require.Equal(t, expected, addr)
default:
require.Fail(t, "DialContext() was not called")
}
}