TUN-2714: New edge discovery. Connections try to reconnect to the same edge IP.

edgediscovery/allregions/discovery.go

@@ -0,0 +1,135 @@
+package allregions
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+)
+
+const (
+	// Used to discover HA origintunneld servers
+	srvService = "origintunneld"
+	srvProto   = "tcp"
+	srvName    = "argotunnel.com"
+
+	// Used to fallback to DoT when we can't use the default resolver to
+	// discover HA origintunneld servers (GitHub issue #75).
+	dotServerName = "cloudflare-dns.com"
+	dotServerAddr = "1.1.1.1:853"
+	dotTimeout    = time.Duration(15 * time.Second)
+
+	// SRV record resolution TTL
+	resolveEdgeAddrTTL = 1 * time.Hour
+
+	subsystemEdgeAddrResolver = "edgeAddrResolver"
+)
+
+// Redeclare network functions so they can be overridden in tests.
+var (
+	netLookupSRV = net.LookupSRV
+	netLookupIP  = net.LookupIP
+)
+
+// If the call to net.LookupSRV fails, try to fall back to DoT from Cloudflare directly.
+//
+// Note: Instead of DoT, we could also have used DoH. Either of these:
+//     - directly via the JSON API (https://1.1.1.1/dns-query?ct=application/dns-json&name=_origintunneld._tcp.argotunnel.com&type=srv)
+//     - indirectly via `tunneldns.NewUpstreamHTTPS()`
+// But both of these cases miss out on a key feature from the stdlib:
+//     "The returned records are sorted by priority and randomized by weight within a priority."
+//     (https://golang.org/pkg/net/#Resolver.LookupSRV)
+// Does this matter? I don't know. It may someday. Let's use DoT so we don't need to worry about it.
+// See also: Go feature request for stdlib-supported DoH: https://github.com/golang/go/issues/27552
+var fallbackLookupSRV = lookupSRVWithDOT
+
+var friendlyDNSErrorLines = []string{
+	`Please try the following things to diagnose this issue:`,
+	`  1. ensure that argotunnel.com is returning "origintunneld" service records.`,
+	`     Run your system's equivalent of: dig srv _origintunneld._tcp.argotunnel.com`,
+	`  2. ensure that your DNS resolver is not returning compressed SRV records.`,
+	`     See GitHub issue https://github.com/golang/go/issues/27546`,
+	`     For example, you could use Cloudflare's 1.1.1.1 as your resolver:`,
+	`     https://developers.cloudflare.com/1.1.1.1/setting-up-1.1.1.1/`,
+}
+
+// EdgeDiscovery implements HA service discovery lookup.
+func edgeDiscovery(logger *logrus.Entry) ([][]*net.TCPAddr, error) {
+	_, addrs, err := netLookupSRV(srvService, srvProto, srvName)
+	if err != nil {
+		_, fallbackAddrs, fallbackErr := fallbackLookupSRV(srvService, srvProto, srvName)
+		if fallbackErr != nil || len(fallbackAddrs) == 0 {
+			// use the original DNS error `err` in messages, not `fallbackErr`
+			logger.Errorln("Error looking up Cloudflare edge IPs: the DNS query failed:", err)
+			for _, s := range friendlyDNSErrorLines {
+				logger.Errorln(s)
+			}
+			return nil, errors.Wrapf(err, "Could not lookup srv records on _%v._%v.%v", srvService, srvProto, srvName)
+		}
+		// Accept the fallback results and keep going
+		addrs = fallbackAddrs
+	}
+
+	var resolvedIPsPerCNAME [][]*net.TCPAddr
+	for _, addr := range addrs {
+		ips, err := resolveSRVToTCP(addr)
+		if err != nil {
+			return nil, err
+		}
+		resolvedIPsPerCNAME = append(resolvedIPsPerCNAME, ips)
+	}
+
+	return resolvedIPsPerCNAME, nil
+}
+
+func lookupSRVWithDOT(service, proto, name string) (cname string, addrs []*net.SRV, err error) {
+	// Inspiration: https://github.com/artyom/dot/blob/master/dot.go
+	r := &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, _ string, _ string) (net.Conn, error) {
+			var dialer net.Dialer
+			conn, err := dialer.DialContext(ctx, "tcp", dotServerAddr)
+			if err != nil {
+				return nil, err
+			}
+			tlsConfig := &tls.Config{ServerName: dotServerName}
+			return tls.Client(conn, tlsConfig), nil
+		},
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), dotTimeout)
+	defer cancel()
+	return r.LookupSRV(ctx, srvService, srvProto, srvName)
+}
+
+func resolveSRVToTCP(srv *net.SRV) ([]*net.TCPAddr, error) {
+	ips, err := netLookupIP(srv.Target)
+	if err != nil {
+		return nil, errors.Wrapf(err, "Couldn't resolve SRV record %v", srv)
+	}
+	if len(ips) == 0 {
+		return nil, fmt.Errorf("SRV record %v had no IPs", srv)
+	}
+	addrs := make([]*net.TCPAddr, len(ips))
+	for i, ip := range ips {
+		addrs[i] = &net.TCPAddr{IP: ip, Port: int(srv.Port)}
+	}
+	return addrs, nil
+}
+
+// ResolveAddrs resolves TCP address given a list of addresses. Address can be a hostname, however, it will return at most one
+// of the hostname's IP addresses
+func ResolveAddrs(addrs []string) ([]*net.TCPAddr, error) {
+	var tcpAddrs []*net.TCPAddr
+	for _, addr := range addrs {
+		tcpAddr, err := net.ResolveTCPAddr("tcp", addr)
+		if err != nil {
+			return nil, err
+		}
+		tcpAddrs = append(tcpAddrs, tcpAddr)
+	}
+	return tcpAddrs, nil
+}

edgediscovery/allregions/discovery_test.go

@@ -0,0 +1,32 @@
+package allregions
+
+import (
+	"testing"
+
+	"github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestEdgeDiscovery(t *testing.T) {
+	mockAddrs := newMockAddrs(19, 2, 5)
+	netLookupSRV = mockNetLookupSRV(mockAddrs)
+	netLookupIP = mockNetLookupIP(mockAddrs)
+
+	expectedAddrSet := map[string]bool{}
+	for _, addrs := range mockAddrs.addrMap {
+		for _, addr := range addrs {
+			expectedAddrSet[addr.String()] = true
+		}
+	}
+
+	addrLists, err := edgeDiscovery(logrus.New().WithFields(logrus.Fields{}))
+	assert.NoError(t, err)
+	actualAddrSet := map[string]bool{}
+	for _, addrs := range addrLists {
+		for _, addr := range addrs {
+			actualAddrSet[addr.String()] = true
+		}
+	}
+
+	assert.Equal(t, expectedAddrSet, actualAddrSet)
+}

edgediscovery/allregions/mocks_for_test.go

@@ -0,0 +1,89 @@
+package allregions
+
+import (
+	"fmt"
+	"math"
+	"math/rand"
+	"net"
+	"reflect"
+	"testing/quick"
+)
+
+type mockAddrs struct {
+	// a set of synthetic SRV records
+	addrMap map[net.SRV][]*net.TCPAddr
+	// the total number of addresses, aggregated across addrMap.
+	// For the convenience of test code that would otherwise have to compute
+	// this by hand every time.
+	numAddrs int
+}
+
+func newMockAddrs(port uint16, numRegions uint8, numAddrsPerRegion uint8) mockAddrs {
+	addrMap := make(map[net.SRV][]*net.TCPAddr)
+	numAddrs := 0
+
+	for r := uint8(0); r < numRegions; r++ {
+		var (
+			srv   = net.SRV{Target: fmt.Sprintf("test-region-%v.example.com", r), Port: port}
+			addrs []*net.TCPAddr
+		)
+		for a := uint8(0); a < numAddrsPerRegion; a++ {
+			addrs = append(addrs, &net.TCPAddr{
+				IP:   net.ParseIP(fmt.Sprintf("10.0.%v.%v", r, a)),
+				Port: int(port),
+			})
+		}
+		addrMap[srv] = addrs
+		numAddrs += len(addrs)
+	}
+	return mockAddrs{addrMap: addrMap, numAddrs: numAddrs}
+}
+
+var _ quick.Generator = mockAddrs{}
+
+func (mockAddrs) Generate(rand *rand.Rand, size int) reflect.Value {
+	port := uint16(rand.Intn(math.MaxUint16))
+	numRegions := uint8(1 + rand.Intn(10))
+	numAddrsPerRegion := uint8(1 + rand.Intn(32))
+	result := newMockAddrs(port, numRegions, numAddrsPerRegion)
+	return reflect.ValueOf(result)
+}
+
+// Returns a function compatible with net.LookupSRV that will return the SRV
+// records from mockAddrs.
+func mockNetLookupSRV(
+	m mockAddrs,
+) func(service, proto, name string) (cname string, addrs []*net.SRV, err error) {
+	var addrs []*net.SRV
+	for k := range m.addrMap {
+		addr := k
+		addrs = append(addrs, &addr)
+		// We can't just do
+		//   addrs = append(addrs, &k)
+		// `k` will be reused by subsequent loop iterations,
+		// so all the copies of `&k` would point to the same location.
+	}
+	return func(_, _, _ string) (string, []*net.SRV, error) {
+		return "", addrs, nil
+	}
+}
+
+// Returns a function compatible with net.LookupIP that translates the SRV records
+// from mockAddrs into IP addresses, based on the TCP addresses in mockAddrs.
+func mockNetLookupIP(
+	m mockAddrs,
+) func(host string) ([]net.IP, error) {
+	return func(host string) ([]net.IP, error) {
+		for srv, tcpAddrs := range m.addrMap {
+			if srv.Target != host {
+				continue
+			}
+			result := make([]net.IP, len(tcpAddrs))
+			for i, tcpAddr := range tcpAddrs {
+				result[i] = tcpAddr.IP
+			}
+			return result, nil
+		}
+		return nil, fmt.Errorf("No IPs for %v", host)
+	}
+}

edgediscovery/allregions/region.go

@@ -0,0 +1,78 @@
+package allregions
+
+import (
+	"net"
+)
+
+// Region contains cloudflared edge addresses. The edge is partitioned into several regions for
+// redundancy purposes.
+type Region struct {
+	connFor map[*net.TCPAddr]UsedBy
+}
+
+// NewRegion creates a region with the given addresses, which are all unused.
+func NewRegion(addrs []*net.TCPAddr) Region {
+	// The zero value of UsedBy is Unused(), so we can just initialize the map's values with their
+	// zero values.
+	m := make(map[*net.TCPAddr]UsedBy)
+	for _, addr := range addrs {
+		m[addr] = Unused()
+	}
+	return Region{connFor: m}
+}
+
+// AddrUsedBy finds the address used by the given connection in this region.
+// Returns nil if the connection isn't using any IP.
+func (r *Region) AddrUsedBy(connID int) *net.TCPAddr {
+	for addr, used := range r.connFor {
+		if used.Used && used.ConnID == connID {
+			return addr
+		}
+	}
+	return nil
+}
+
+// AvailableAddrs counts how many unused addresses this region contains.
+func (r Region) AvailableAddrs() int {
+	n := 0
+	for _, usedby := range r.connFor {
+		if !usedby.Used {
+			n++
+		}
+	}
+	return n
+}
+
+// GetUnusedIP returns a random unused address in this region.
+// Returns nil if all addresses are in use.
+func (r Region) GetUnusedIP(excluding *net.TCPAddr) *net.TCPAddr {
+	for addr, usedby := range r.connFor {
+		if !usedby.Used && addr != excluding {
+			return addr
+		}
+	}
+	return nil
+}
+
+// Use the address, assigning it to a proxy connection.
+func (r Region) Use(addr *net.TCPAddr, connID int) {
+	r.connFor[addr] = InUse(connID)
+}
+
+// GetAnyAddress returns an arbitrary address from the region.
+func (r Region) GetAnyAddress() *net.TCPAddr {
+	for addr := range r.connFor {
+		return addr
+	}
+	return nil
+}
+
+// GiveBack the address, ensuring it is no longer assigned to an IP.
+// Returns true if the address is in this region.
+func (r Region) GiveBack(addr *net.TCPAddr) (ok bool) {
+	if _, ok := r.connFor[addr]; !ok {
+		return false
+	}
+	r.connFor[addr] = Unused()
+	return true
+}

edgediscovery/allregions/region_test.go

@@ -0,0 +1,287 @@
+package allregions
+
+import (
+	"fmt"
+	"net"
+	"reflect"
+	"testing"
+)
+
+func TestRegion_New(t *testing.T) {
+	r := NewRegion([]*net.TCPAddr{&addr0, &addr1, &addr2})
+	fmt.Println(r.connFor)
+	if r.AvailableAddrs() != 3 {
+		t.Errorf("r.AvailableAddrs() == %v but want 3", r.AvailableAddrs())
+	}
+}
+
+func TestRegion_AddrUsedBy(t *testing.T) {
+	type fields struct {
+		connFor map[*net.TCPAddr]UsedBy
+	}
+	type args struct {
+		connID int
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   *net.TCPAddr
+	}{
+		{
+			name: "happy trivial test",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: InUse(0),
+			}},
+			args: args{connID: 0},
+			want: &addr0,
+		},
+		{
+			name: "sad trivial test",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: InUse(0),
+			}},
+			args: args{connID: 1},
+			want: nil,
+		},
+		{
+			name: "sad test",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: InUse(0),
+				&addr1: InUse(1),
+				&addr2: InUse(2),
+			}},
+			args: args{connID: 3},
+			want: nil,
+		},
+		{
+			name: "happy test",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: InUse(0),
+				&addr1: InUse(1),
+				&addr2: InUse(2),
+			}},
+			args: args{connID: 1},
+			want: &addr1,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := &Region{
+				connFor: tt.fields.connFor,
+			}
+			if got := r.AddrUsedBy(tt.args.connID); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Region.AddrUsedBy() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestRegion_AvailableAddrs(t *testing.T) {
+	type fields struct {
+		connFor map[*net.TCPAddr]UsedBy
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   int
+	}{
+		{
+			name: "contains addresses",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: InUse(0),
+				&addr1: Unused(),
+				&addr2: InUse(2),
+			}},
+			want: 1,
+		},
+		{
+			name: "all free",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: Unused(),
+				&addr1: Unused(),
+				&addr2: Unused(),
+			}},
+			want: 3,
+		},
+		{
+			name: "all used",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: InUse(0),
+				&addr1: InUse(1),
+				&addr2: InUse(2),
+			}},
+			want: 0,
+		},
+		{
+			name:   "empty",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{}},
+			want:   0,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := Region{
+				connFor: tt.fields.connFor,
+			}
+			if got := r.AvailableAddrs(); got != tt.want {
+				t.Errorf("Region.AvailableAddrs() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestRegion_GetUnusedIP(t *testing.T) {
+	type fields struct {
+		connFor map[*net.TCPAddr]UsedBy
+	}
+	type args struct {
+		excluding *net.TCPAddr
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   *net.TCPAddr
+	}{
+		{
+			name: "happy test with excluding set",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: Unused(),
+				&addr1: Unused(),
+				&addr2: InUse(2),
+			}},
+			args: args{excluding: &addr0},
+			want: &addr1,
+		},
+		{
+			name: "happy test with no excluding",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: InUse(0),
+				&addr1: Unused(),
+				&addr2: InUse(2),
+			}},
+			args: args{excluding: nil},
+			want: &addr1,
+		},
+		{
+			name: "sad test with no excluding",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: InUse(0),
+				&addr1: InUse(1),
+				&addr2: InUse(2),
+			}},
+			args: args{excluding: nil},
+			want: nil,
+		},
+		{
+			name: "sad test with excluding",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: Unused(),
+				&addr1: InUse(1),
+				&addr2: InUse(2),
+			}},
+			args: args{excluding: &addr0},
+			want: nil,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := Region{
+				connFor: tt.fields.connFor,
+			}
+			if got := r.GetUnusedIP(tt.args.excluding); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Region.GetUnusedIP() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestRegion_GiveBack(t *testing.T) {
+	type fields struct {
+		connFor map[*net.TCPAddr]UsedBy
+	}
+	type args struct {
+		addr *net.TCPAddr
+	}
+	tests := []struct {
+		name           string
+		fields         fields
+		args           args
+		wantOk         bool
+		availableAfter int
+	}{
+		{
+			name: "sad test with excluding",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr1: InUse(1),
+			}},
+			args:           args{addr: &addr1},
+			wantOk:         true,
+			availableAfter: 1,
+		},
+		{
+			name: "sad test with excluding",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr1: InUse(1),
+			}},
+			args:           args{addr: &addr2},
+			wantOk:         false,
+			availableAfter: 0,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := Region{
+				connFor: tt.fields.connFor,
+			}
+			if gotOk := r.GiveBack(tt.args.addr); gotOk != tt.wantOk {
+				t.Errorf("Region.GiveBack() = %v, want %v", gotOk, tt.wantOk)
+			}
+			if tt.availableAfter != r.AvailableAddrs() {
+				t.Errorf("Region.AvailableAddrs() = %v, want %v", r.AvailableAddrs(), tt.availableAfter)
+			}
+		})
+	}
+}
+
+func TestRegion_GetAnyAddress(t *testing.T) {
+	type fields struct {
+		connFor map[*net.TCPAddr]UsedBy
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		wantNil bool
+	}{
+		{
+			name:    "Sad test -- GetAnyAddress should only fail if the region is empty",
+			fields:  fields{connFor: map[*net.TCPAddr]UsedBy{}},
+			wantNil: true,
+		},
+		{
+			name: "Happy test (all addresses unused)",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: Unused(),
+			}},
+			wantNil: false,
+		},
+		{
+			name: "Happy test (GetAnyAddress can still return addresses used by proxy conns)",
+			fields: fields{connFor: map[*net.TCPAddr]UsedBy{
+				&addr0: InUse(2),
+			}},
+			wantNil: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := Region{
+				connFor: tt.fields.connFor,
+			}
+			if got := r.GetAnyAddress(); tt.wantNil != (got == nil) {
+				t.Errorf("Region.GetAnyAddress() = %v, but should it return nil? %v", got, tt.wantNil)
+			}
+		})
+	}
+}

edgediscovery/allregions/regions.go

@@ -0,0 +1,118 @@
+package allregions
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Regions stores Cloudflare edge network IPs, partitioned into two regions.
+// This is NOT thread-safe. Users of this package should use it with a lock.
+type Regions struct {
+	region1 Region
+	region2 Region
+}
+
+// ------------------------------------
+// Constructors
+// ------------------------------------
+
+// ResolveEdge resolves the Cloudflare edge, returning all regions discovered.
+func ResolveEdge(logger *logrus.Entry) (*Regions, error) {
+	addrLists, err := edgeDiscovery(logger)
+	if err != nil {
+		return nil, err
+	}
+	if len(addrLists) < 2 {
+		return nil, fmt.Errorf("expected at least 2 Cloudflare Regions regions, but SRV only returned %v", len(addrLists))
+	}
+	return &Regions{
+		region1: NewRegion(addrLists[0]),
+		region2: NewRegion(addrLists[1]),
+	}, nil
+}
+
+// StaticEdge creates a list of edge addresses from the list of hostnames.
+// Mainly used for testing connectivity.
+func StaticEdge(hostnames []string) (*Regions, error) {
+	addrs, err := ResolveAddrs(hostnames)
+	if err != nil {
+		return nil, err
+	}
+	return NewNoResolve(addrs), nil
+}
+
+// NewNoResolve doesn't resolve the edge. Instead it just uses the given addresses.
+// You probably only need this for testing.
+func NewNoResolve(addrs []*net.TCPAddr) *Regions {
+	region1 := make([]*net.TCPAddr, 0)
+	region2 := make([]*net.TCPAddr, 0)
+	for i, v := range addrs {
+		if i%2 == 0 {
+			region1 = append(region1, v)
+		} else {
+			region2 = append(region2, v)
+		}
+	}
+
+	return &Regions{
+		region1: NewRegion(region1),
+		region2: NewRegion(region2),
+	}
+}
+
+// ------------------------------------
+// Methods
+// ------------------------------------
+
+// GetAnyAddress returns an arbitrary address from the larger region.
+func (rs *Regions) GetAnyAddress() *net.TCPAddr {
+	if rs.region1.AvailableAddrs() > rs.region2.AvailableAddrs() {
+		return rs.region1.GetAnyAddress()
+	}
+	return rs.region2.GetAnyAddress()
+}
+
+// AddrUsedBy finds the address used by the given connection.
+// Returns nil if the connection isn't using an address.
+func (rs *Regions) AddrUsedBy(connID int) *net.TCPAddr {
+	if addr := rs.region1.AddrUsedBy(connID); addr != nil {
+		return addr
+	}
+	return rs.region2.AddrUsedBy(connID)
+}
+
+// GetUnusedAddr gets an unused addr from the edge, excluding the given addr. Prefer to use addresses
+// evenly across both regions.
+func (rs *Regions) GetUnusedAddr(excluding *net.TCPAddr, connID int) *net.TCPAddr {
+	var addr *net.TCPAddr
+	if rs.region1.AvailableAddrs() > rs.region2.AvailableAddrs() {
+		addr = rs.region1.GetUnusedIP(excluding)
+		rs.region1.Use(addr, connID)
+	} else {
+		addr = rs.region2.GetUnusedIP(excluding)
+		rs.region2.Use(addr, connID)
+	}
+
+	if addr == nil {
+		return nil
+	}
+
+	// Mark the address as used and return it
+	return addr
+}
+
+// AvailableAddrs returns how many edge addresses aren't used.
+func (rs *Regions) AvailableAddrs() int {
+	return rs.region1.AvailableAddrs() + rs.region2.AvailableAddrs()
+}
+
+// GiveBack the address so that other connections can use it.
+// Returns true if the address is in this edge.
+func (rs *Regions) GiveBack(addr *net.TCPAddr) bool {
+	if found := rs.region1.GiveBack(addr); found {
+		return found
+	}
+	return rs.region2.GiveBack(addr)
+}

edgediscovery/allregions/regions_test.go

@@ -0,0 +1,140 @@
+package allregions
+
+import (
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	addr0 = net.TCPAddr{
+		IP:   net.ParseIP("123.4.5.0"),
+		Port: 8000,
+		Zone: "",
+	}
+	addr1 = net.TCPAddr{
+		IP:   net.ParseIP("123.4.5.1"),
+		Port: 8000,
+		Zone: "",
+	}
+	addr2 = net.TCPAddr{
+		IP:   net.ParseIP("123.4.5.2"),
+		Port: 8000,
+		Zone: "",
+	}
+	addr3 = net.TCPAddr{
+		IP:   net.ParseIP("123.4.5.3"),
+		Port: 8000,
+		Zone: "",
+	}
+)
+
+func makeRegions() Regions {
+	r1 := NewRegion([]*net.TCPAddr{&addr0, &addr1})
+	r2 := NewRegion([]*net.TCPAddr{&addr2, &addr3})
+	return Regions{region1: r1, region2: r2}
+}
+
+func TestRegions_AddrUsedBy(t *testing.T) {
+	rs := makeRegions()
+	addr1 := rs.GetUnusedAddr(nil, 1)
+	assert.Equal(t, addr1, rs.AddrUsedBy(1))
+	addr2 := rs.GetUnusedAddr(nil, 2)
+	assert.Equal(t, addr2, rs.AddrUsedBy(2))
+	addr3 := rs.GetUnusedAddr(nil, 3)
+	assert.Equal(t, addr3, rs.AddrUsedBy(3))
+}
+
+func TestRegions_Giveback_Region1(t *testing.T) {
+	rs := makeRegions()
+	rs.region1.Use(&addr0, 0)
+	rs.region1.Use(&addr1, 1)
+	rs.region2.Use(&addr2, 2)
+	rs.region2.Use(&addr3, 3)
+
+	assert.Equal(t, 0, rs.AvailableAddrs())
+
+	rs.GiveBack(&addr0)
+	assert.Equal(t, &addr0, rs.GetUnusedAddr(nil, 3))
+}
+func TestRegions_Giveback_Region2(t *testing.T) {
+	rs := makeRegions()
+	rs.region1.Use(&addr0, 0)
+	rs.region1.Use(&addr1, 1)
+	rs.region2.Use(&addr2, 2)
+	rs.region2.Use(&addr3, 3)
+
+	assert.Equal(t, 0, rs.AvailableAddrs())
+
+	rs.GiveBack(&addr2)
+	assert.Equal(t, &addr2, rs.GetUnusedAddr(nil, 2))
+}
+
+func TestRegions_GetUnusedAddr_OneAddrLeft(t *testing.T) {
+	rs := makeRegions()
+
+	rs.region1.Use(&addr0, 0)
+	rs.region1.Use(&addr1, 1)
+	rs.region2.Use(&addr2, 2)
+
+	assert.Equal(t, 1, rs.AvailableAddrs())
+	assert.Equal(t, &addr3, rs.GetUnusedAddr(nil, 3))
+}
+
+func TestRegions_GetUnusedAddr_Excluding_Region1(t *testing.T) {
+	rs := makeRegions()
+
+	rs.region1.Use(&addr0, 0)
+	rs.region1.Use(&addr1, 1)
+
+	assert.Equal(t, 2, rs.AvailableAddrs())
+	assert.Equal(t, &addr3, rs.GetUnusedAddr(&addr2, 3))
+}
+
+func TestRegions_GetUnusedAddr_Excluding_Region2(t *testing.T) {
+	rs := makeRegions()
+
+	rs.region2.Use(&addr2, 0)
+	rs.region2.Use(&addr3, 1)
+
+	assert.Equal(t, 2, rs.AvailableAddrs())
+	assert.Equal(t, &addr1, rs.GetUnusedAddr(&addr0, 1))
+}
+
+func TestNewNoResolveBalancesRegions(t *testing.T) {
+	type args struct {
+		addrs []*net.TCPAddr
+	}
+	tests := []struct {
+		name string
+		args args
+	}{
+		{
+			name: "one address",
+			args: args{addrs: []*net.TCPAddr{&addr0}},
+		},
+		{
+			name: "two addresses",
+			args: args{addrs: []*net.TCPAddr{&addr0, &addr1}},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			regions := NewNoResolve(tt.args.addrs)
+			RegionsIsBalanced(t, regions)
+		})
+	}
+}
+
+func RegionsIsBalanced(t *testing.T, rs *Regions) {
+	delta := rs.region1.AvailableAddrs() - rs.region2.AvailableAddrs()
+	assert.True(t, abs(delta) <= 1)
+}
+
+func abs(x int) int {
+	if x >= 0 {
+		return x
+	}
+	return -x
+}

edgediscovery/allregions/usedby.go

@@ -0,0 +1,14 @@
+package allregions
+
+type UsedBy struct {
+	ConnID int
+	Used   bool
+}
+
+func InUse(connID int) UsedBy {
+	return UsedBy{ConnID: connID, Used: true}
+}
+
+func Unused() UsedBy {
+	return UsedBy{}
+}