TUN-10388 Implement dialers for connectivity checks

This PR implements all the dialers and resolvers needed to make pre-checks happen. So this task focuses on the following:

1. Implement the DNS probe: call DNSResolver.Resolve(region)
2. Implement the QUIC probe: call QUICDialer.DialQuic (handshake only, no stream opened) and record the result.
3. Implement the HTTP/2 probe: call TCPDialer.DialEdge (TCP + TLS handshake only, no frames sent) and record the result.
4. Implement the Management API probe: call ManagementDialer.DialContext to api.cloudflare.com:443 and record the result.
5. Export edgeDiscovery as EdgeDiscovery in edgediscovery/allregions/discovery.go so the pre-check can reuse the production DNS path.

This sets up the main components to implement the checker.

cmd/cloudflared/tunnel/cmd.go

@@ -912,6 +912,7 @@ and virtualized host network stacks from each other`,
 }
 
 func configureProxyFlags(shouldHide bool) []cli.Flag {
+	//nolint: prealloc
 	flags := []cli.Flag{
 		altsrc.NewStringFlag(&cli.StringFlag{
 			Name:    "url",

edgediscovery/allregions/discovery.go

@@ -109,7 +109,7 @@ var friendlyDNSErrorLines = []string{
 }
 
 // EdgeDiscovery implements HA service discovery lookup.
-func edgeDiscovery(log *zerolog.Logger, srvService string) ([][]*EdgeAddr, error) {
+func EdgeDiscovery(log *zerolog.Logger, srvService string) ([][]*EdgeAddr, error) {
 	logger := log.With().Int(management.EventTypeKey, int(management.Cloudflared)).Logger()
 	logger.Debug().
 		Int(management.EventTypeKey, int(management.Cloudflared)).

edgediscovery/allregions/discovery_test.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/rs/zerolog"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func (ea *EdgeAddr) String() string {
@@ -25,8 +26,8 @@ func TestEdgeDiscovery(t *testing.T) {
 	}
 
 	l := zerolog.Nop()
-	addrLists, err := edgeDiscovery(&l, "")
+	addrLists, err := EdgeDiscovery(&l, "")
-	assert.NoError(t, err)
+	require.NoError(t, err)
 	actualAddrSet := map[string]bool{}
 	for _, addrs := range addrLists {
 		for _, addr := range addrs {

edgediscovery/allregions/regions.go

@@ -20,7 +20,7 @@ type Regions struct {
 
 // ResolveEdge resolves the Cloudflare edge, returning all regions discovered.
 func ResolveEdge(log *zerolog.Logger, region string, overrideIPVersion ConfigIPVersion) (*Regions, error) {
-	edgeAddrs, err := edgeDiscovery(log, getRegionalServiceName(region))
+	edgeAddrs, err := EdgeDiscovery(log, RegionalServiceName(region))
 	if err != nil {
 		return nil, err
 	}
@@ -91,6 +91,7 @@ func (rs *Regions) GetUnusedAddr(excluding *EdgeAddr, connID int) *EdgeAddr {
 	// evenly across both regions.
 	if rs.region1.AvailableAddrs() == rs.region2.AvailableAddrs() {
 		regions := []Region{rs.region1, rs.region2}
+		//nolint:gosec
 		firstChoice := rand.Intn(2)
 		return getAddrs(excluding, connID, &regions[firstChoice], &regions[1-firstChoice])
 	}
@@ -131,11 +132,13 @@ func (rs *Regions) GiveBack(addr *EdgeAddr, hasConnectivityError bool) bool {
 	return rs.region2.GiveBack(addr, hasConnectivityError)
 }
 
-// Return regionalized service name if `region` isn't empty, otherwise return the global service name for origintunneld
+// RegionalServiceName returns the SRV service name for the given region.
-func getRegionalServiceName(region string) string {
+// When region is empty it returns the global service name ("v2-origintunneld").
+// Otherwise, it prepends the region, e.g. "us-v2-origintunneld".
+func RegionalServiceName(region string) string {
 	if region != "" {
-		return region + "-" + srvService // Example: `us-v2-origintunneld`
+		return region + "-" + srvService
 	}
 
-	return srvService // Global service is just `v2-origintunneld`
+	return srvService
 }

edgediscovery/allregions/regions_test.go

@@ -237,21 +237,19 @@ func TestNewNoResolveBalancesRegions(t *testing.T) {
 	}
 }
 
-func TestGetRegionalServiceName(t *testing.T) {
+func TestRegionalServiceName(t *testing.T) {
 	// Empty region should just go to origintunneld
-	globalServiceName := getRegionalServiceName("")
+	assert.Equal(t, srvService, RegionalServiceName(""))
-	assert.Equal(t, srvService, globalServiceName)
 
 	// Non-empty region should go to the regional origintunneld variant
 	for _, region := range []string{"us", "pt", "am"} {
-		regionalServiceName := getRegionalServiceName(region)
+		assert.Equal(t, region+"-"+srvService, RegionalServiceName(region))
-		assert.Equal(t, region+"-"+srvService, regionalServiceName)
 	}
 }
 
 func RegionsIsBalanced(t *testing.T, rs *Regions) {
 	delta := rs.region1.AvailableAddrs() - rs.region2.AvailableAddrs()
-	assert.True(t, abs(delta) <= 1)
+	assert.LessOrEqual(t, abs(delta), 1)
 }
 
 func abs(x int) int {

mocks/mock_resolvers.go

@@ -0,0 +1,278 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: ../prechecks/resolvers.go
+//
+// Generated by this command:
+//
+//	mockgen -typed -build_flags=-tags=gomock -package mocks -destination mock_resolvers.go -source=../prechecks/resolvers.go
+//
+
+// Package mocks is a generated GoMock package.
+package mocks
+
+import (
+	context "context"
+	tls "crypto/tls"
+	net "net"
+	netip "net/netip"
+	reflect "reflect"
+	time "time"
+
+	quic "github.com/quic-go/quic-go"
+	zerolog "github.com/rs/zerolog"
+	gomock "go.uber.org/mock/gomock"
+
+	dialopts "github.com/cloudflare/cloudflared/connection/dialopts"
+	allregions "github.com/cloudflare/cloudflared/edgediscovery/allregions"
+)
+
+// MockDNSResolver is a mock of DNSResolver interface.
+type MockDNSResolver struct {
+	ctrl     *gomock.Controller
+	recorder *MockDNSResolverMockRecorder
+	isgomock struct{}
+}
+
+// MockDNSResolverMockRecorder is the mock recorder for MockDNSResolver.
+type MockDNSResolverMockRecorder struct {
+	mock *MockDNSResolver
+}
+
+// NewMockDNSResolver creates a new mock instance.
+func NewMockDNSResolver(ctrl *gomock.Controller) *MockDNSResolver {
+	mock := &MockDNSResolver{ctrl: ctrl}
+	mock.recorder = &MockDNSResolverMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockDNSResolver) EXPECT() *MockDNSResolverMockRecorder {
+	return m.recorder
+}
+
+// Resolve mocks base method.
+func (m *MockDNSResolver) Resolve(region string) ([][]*allregions.EdgeAddr, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Resolve", region)
+	ret0, _ := ret[0].([][]*allregions.EdgeAddr)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Resolve indicates an expected call of Resolve.
+func (mr *MockDNSResolverMockRecorder) Resolve(region any) *MockDNSResolverResolveCall {
+	mr.mock.ctrl.T.Helper()
+	call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Resolve", reflect.TypeOf((*MockDNSResolver)(nil).Resolve), region)
+	return &MockDNSResolverResolveCall{Call: call}
+}
+
+// MockDNSResolverResolveCall wrap *gomock.Call
+type MockDNSResolverResolveCall struct {
+	*gomock.Call
+}
+
+// Return rewrite *gomock.Call.Return
+func (c *MockDNSResolverResolveCall) Return(arg0 [][]*allregions.EdgeAddr, arg1 error) *MockDNSResolverResolveCall {
+	c.Call = c.Call.Return(arg0, arg1)
+	return c
+}
+
+// Do rewrite *gomock.Call.Do
+func (c *MockDNSResolverResolveCall) Do(f func(string) ([][]*allregions.EdgeAddr, error)) *MockDNSResolverResolveCall {
+	c.Call = c.Call.Do(f)
+	return c
+}
+
+// DoAndReturn rewrite *gomock.Call.DoAndReturn
+func (c *MockDNSResolverResolveCall) DoAndReturn(f func(string) ([][]*allregions.EdgeAddr, error)) *MockDNSResolverResolveCall {
+	c.Call = c.Call.DoAndReturn(f)
+	return c
+}
+
+// MockTCPDialer is a mock of TCPDialer interface.
+type MockTCPDialer struct {
+	ctrl     *gomock.Controller
+	recorder *MockTCPDialerMockRecorder
+	isgomock struct{}
+}
+
+// MockTCPDialerMockRecorder is the mock recorder for MockTCPDialer.
+type MockTCPDialerMockRecorder struct {
+	mock *MockTCPDialer
+}
+
+// NewMockTCPDialer creates a new mock instance.
+func NewMockTCPDialer(ctrl *gomock.Controller) *MockTCPDialer {
+	mock := &MockTCPDialer{ctrl: ctrl}
+	mock.recorder = &MockTCPDialerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockTCPDialer) EXPECT() *MockTCPDialerMockRecorder {
+	return m.recorder
+}
+
+// DialEdge mocks base method.
+func (m *MockTCPDialer) DialEdge(ctx context.Context, timeout time.Duration, tlsConfig *tls.Config, addr *net.TCPAddr, localIP net.IP) (net.Conn, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "DialEdge", ctx, timeout, tlsConfig, addr, localIP)
+	ret0, _ := ret[0].(net.Conn)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// DialEdge indicates an expected call of DialEdge.
+func (mr *MockTCPDialerMockRecorder) DialEdge(ctx, timeout, tlsConfig, addr, localIP any) *MockTCPDialerDialEdgeCall {
+	mr.mock.ctrl.T.Helper()
+	call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "DialEdge", reflect.TypeOf((*MockTCPDialer)(nil).DialEdge), ctx, timeout, tlsConfig, addr, localIP)
+	return &MockTCPDialerDialEdgeCall{Call: call}
+}
+
+// MockTCPDialerDialEdgeCall wrap *gomock.Call
+type MockTCPDialerDialEdgeCall struct {
+	*gomock.Call
+}
+
+// Return rewrite *gomock.Call.Return
+func (c *MockTCPDialerDialEdgeCall) Return(arg0 net.Conn, arg1 error) *MockTCPDialerDialEdgeCall {
+	c.Call = c.Call.Return(arg0, arg1)
+	return c
+}
+
+// Do rewrite *gomock.Call.Do
+func (c *MockTCPDialerDialEdgeCall) Do(f func(context.Context, time.Duration, *tls.Config, *net.TCPAddr, net.IP) (net.Conn, error)) *MockTCPDialerDialEdgeCall {
+	c.Call = c.Call.Do(f)
+	return c
+}
+
+// DoAndReturn rewrite *gomock.Call.DoAndReturn
+func (c *MockTCPDialerDialEdgeCall) DoAndReturn(f func(context.Context, time.Duration, *tls.Config, *net.TCPAddr, net.IP) (net.Conn, error)) *MockTCPDialerDialEdgeCall {
+	c.Call = c.Call.DoAndReturn(f)
+	return c
+}
+
+// MockQUICDialer is a mock of QUICDialer interface.
+type MockQUICDialer struct {
+	ctrl     *gomock.Controller
+	recorder *MockQUICDialerMockRecorder
+	isgomock struct{}
+}
+
+// MockQUICDialerMockRecorder is the mock recorder for MockQUICDialer.
+type MockQUICDialerMockRecorder struct {
+	mock *MockQUICDialer
+}
+
+// NewMockQUICDialer creates a new mock instance.
+func NewMockQUICDialer(ctrl *gomock.Controller) *MockQUICDialer {
+	mock := &MockQUICDialer{ctrl: ctrl}
+	mock.recorder = &MockQUICDialerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockQUICDialer) EXPECT() *MockQUICDialerMockRecorder {
+	return m.recorder
+}
+
+// DialQuic mocks base method.
+func (m *MockQUICDialer) DialQuic(ctx context.Context, quicConfig *quic.Config, tlsConfig *tls.Config, addr netip.AddrPort, localAddr net.IP, connIndex uint8, logger *zerolog.Logger, opts dialopts.DialOpts) (quic.Connection, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "DialQuic", ctx, quicConfig, tlsConfig, addr, localAddr, connIndex, logger, opts)
+	ret0, _ := ret[0].(quic.Connection)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// DialQuic indicates an expected call of DialQuic.
+func (mr *MockQUICDialerMockRecorder) DialQuic(ctx, quicConfig, tlsConfig, addr, localAddr, connIndex, logger, opts any) *MockQUICDialerDialQuicCall {
+	mr.mock.ctrl.T.Helper()
+	call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "DialQuic", reflect.TypeOf((*MockQUICDialer)(nil).DialQuic), ctx, quicConfig, tlsConfig, addr, localAddr, connIndex, logger, opts)
+	return &MockQUICDialerDialQuicCall{Call: call}
+}
+
+// MockQUICDialerDialQuicCall wrap *gomock.Call
+type MockQUICDialerDialQuicCall struct {
+	*gomock.Call
+}
+
+// Return rewrite *gomock.Call.Return
+func (c *MockQUICDialerDialQuicCall) Return(arg0 quic.Connection, arg1 error) *MockQUICDialerDialQuicCall {
+	c.Call = c.Call.Return(arg0, arg1)
+	return c
+}
+
+// Do rewrite *gomock.Call.Do
+func (c *MockQUICDialerDialQuicCall) Do(f func(context.Context, *quic.Config, *tls.Config, netip.AddrPort, net.IP, uint8, *zerolog.Logger, dialopts.DialOpts) (quic.Connection, error)) *MockQUICDialerDialQuicCall {
+	c.Call = c.Call.Do(f)
+	return c
+}
+
+// DoAndReturn rewrite *gomock.Call.DoAndReturn
+func (c *MockQUICDialerDialQuicCall) DoAndReturn(f func(context.Context, *quic.Config, *tls.Config, netip.AddrPort, net.IP, uint8, *zerolog.Logger, dialopts.DialOpts) (quic.Connection, error)) *MockQUICDialerDialQuicCall {
+	c.Call = c.Call.DoAndReturn(f)
+	return c
+}
+
+// MockManagementDialer is a mock of ManagementDialer interface.
+type MockManagementDialer struct {
+	ctrl     *gomock.Controller
+	recorder *MockManagementDialerMockRecorder
+	isgomock struct{}
+}
+
+// MockManagementDialerMockRecorder is the mock recorder for MockManagementDialer.
+type MockManagementDialerMockRecorder struct {
+	mock *MockManagementDialer
+}
+
+// NewMockManagementDialer creates a new mock instance.
+func NewMockManagementDialer(ctrl *gomock.Controller) *MockManagementDialer {
+	mock := &MockManagementDialer{ctrl: ctrl}
+	mock.recorder = &MockManagementDialerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockManagementDialer) EXPECT() *MockManagementDialerMockRecorder {
+	return m.recorder
+}
+
+// DialContext mocks base method.
+func (m *MockManagementDialer) DialContext(ctx context.Context, network, addr string) (net.Conn, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "DialContext", ctx, network, addr)
+	ret0, _ := ret[0].(net.Conn)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// DialContext indicates an expected call of DialContext.
+func (mr *MockManagementDialerMockRecorder) DialContext(ctx, network, addr any) *MockManagementDialerDialContextCall {
+	mr.mock.ctrl.T.Helper()
+	call := mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "DialContext", reflect.TypeOf((*MockManagementDialer)(nil).DialContext), ctx, network, addr)
+	return &MockManagementDialerDialContextCall{Call: call}
+}
+
+// MockManagementDialerDialContextCall wrap *gomock.Call
+type MockManagementDialerDialContextCall struct {
+	*gomock.Call
+}
+
+// Return rewrite *gomock.Call.Return
+func (c *MockManagementDialerDialContextCall) Return(arg0 net.Conn, arg1 error) *MockManagementDialerDialContextCall {
+	c.Call = c.Call.Return(arg0, arg1)
+	return c
+}
+
+// Do rewrite *gomock.Call.Do
+func (c *MockManagementDialerDialContextCall) Do(f func(context.Context, string, string) (net.Conn, error)) *MockManagementDialerDialContextCall {
+	c.Call = c.Call.Do(f)
+	return c
+}
+
+// DoAndReturn rewrite *gomock.Call.DoAndReturn
+func (c *MockManagementDialerDialContextCall) DoAndReturn(f func(context.Context, string, string) (net.Conn, error)) *MockManagementDialerDialContextCall {
+	c.Call = c.Call.DoAndReturn(f)
+	return c
+}

mocks/mockgen.go

@@ -3,3 +3,5 @@
 package mocks
 
 //go:generate sh -c "go run go.uber.org/mock/mockgen -typed -build_flags=\"-tags=gomock\" -package mocks -destination mock_limiter.go -source=../flow/limiter.go Limiter"
+
+//go:generate sh -c "go run go.uber.org/mock/mockgen -typed -build_flags=\"-tags=gomock\" -package mocks -destination mock_resolvers.go -source=../prechecks/resolvers.go"

prechecks/probes.go

@@ -0,0 +1,338 @@
+package prechecks
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"math"
+	"net"
+	"net/netip"
+	"time"
+
+	"github.com/quic-go/quic-go"
+	"github.com/rs/zerolog"
+
+	"github.com/cloudflare/cloudflared/connection/dialopts"
+
+	"github.com/cloudflare/cloudflared/connection"
+	edgedial "github.com/cloudflare/cloudflared/edgediscovery"
+	"github.com/cloudflare/cloudflared/edgediscovery/allregions"
+)
+
+const (
+	perProbeDialTimeout = 5 * time.Second
+
+	// Action messages for each probe outcome.
+	actionDNSFail        = "Ensure your DNS resolver can resolve '%s'. Run: dig A %s @1.1.1.1. If that fails, contact your network administrator."
+	actionQUICBlocked    = "QUIC traffic failed to connect to port 7844."
+	actionHTTP2Blocked   = "Allow outbound TCP on port 7844."
+	actionAPIUnreachable = "cloudflared will still run, but automatic software updates are unavailable. " +
+		"Ensure port 443 TCP to api.cloudflare.com is open if you want auto-updates."
+
+	// Component names for CheckResult.
+	componentDNSResolution   = "DNS Resolution"
+	componentUDPConnectivity = "UDP Connectivity"
+	componentTCPConnectivity = "TCP Connectivity"
+	componentCloudflareAPI   = "Cloudflare API"
+
+	// Target identifiers for CheckResult.
+	targetPortQUIC  = "Port 7844 (QUIC)"
+	targetPortHTTP2 = "Port 7844 (HTTP/2)"
+	targetAPI       = "api.cloudflare.com:443"
+
+	// Details messages for CheckResult.
+	detailsNoAddressesReturned    = "No addresses returned"
+	detailsResolvedSuccessfully   = "Resolved successfully"
+	detailsHandshakeFailed        = "Handshake failed"
+	detailsHandshakeSuccessful    = "Handshake successful"
+	detailsBlockedOrUnreachable   = "Blocked or unreachable"
+	detailsTLSHandshakeSuccessful = "TLS handshake successful"
+	detailsConnectionFailed       = "Connection failed"
+	detailsTCPPortReachable       = "TCP port reachable (TLS not validated)"
+	detailsDNSPrerequisiteFailed  = "DNS prerequisite failed"
+
+	// Region hostname templates.
+	region1Global = "region1.v2.argotunnel.com"
+	region2Global = "region2.v2.argotunnel.com"
+	region1US     = "us-region1.v2.argotunnel.com"
+	region2US     = "us-region2.v2.argotunnel.com"
+	region1Fed    = "fed-region1.v2.argotunnel.com"
+	region2Fed    = "fed-region2.v2.argotunnel.com"
+)
+
+type EdgeDNSResolver struct {
+	Log *zerolog.Logger
+}
+
+func (r *EdgeDNSResolver) Resolve(region string) ([][]*allregions.EdgeAddr, error) {
+	return allregions.EdgeDiscovery(r.Log, allregions.RegionalServiceName(region))
+}
+
+type EdgeTCPDialer struct{}
+
+func (d *EdgeTCPDialer) DialEdge(
+	ctx context.Context,
+	timeout time.Duration,
+	tlsConfig *tls.Config,
+	addr *net.TCPAddr,
+	localIP net.IP,
+) (net.Conn, error) {
+	return edgedial.DialEdge(ctx, timeout, tlsConfig, addr, localIP)
+}
+
+type EdgeQUICDialer struct{}
+
+func (d *EdgeQUICDialer) DialQuic(
+	ctx context.Context,
+	quicConfig *quic.Config,
+	tlsConfig *tls.Config,
+	addr netip.AddrPort,
+	localAddr net.IP,
+	connIndex uint8,
+	logger *zerolog.Logger,
+	opts dialopts.DialOpts,
+) (quic.Connection, error) {
+	return connection.DialQuic(ctx, quicConfig, tlsConfig, addr, localAddr, connIndex, logger, opts)
+}
+
+type NetManagementDialer struct {
+	Dialer net.Dialer
+}
+
+func (d *NetManagementDialer) DialContext(ctx context.Context, network, addr string) (net.Conn, error) {
+	return d.Dialer.DialContext(ctx, network, addr)
+}
+
+// probeDNS resolves edge addresses for the given region via the supplied
+// DNSResolver and returns a CheckResult for each region discovered. If
+// resolution fails for all regions, every result will carry StatusFail.
+func probeDNS(
+	resolver DNSResolver,
+	region string,
+) ([][]*allregions.EdgeAddr, []CheckResult) {
+	addrGroups, err := resolver.Resolve(region)
+	if err != nil || len(addrGroups) == 0 {
+		detail := detailsNoAddressesReturned
+		if err != nil {
+			detail = err.Error()
+		}
+		region1Target, region2Target := regionTargets(region)
+		return nil, []CheckResult{
+			{
+				Type:        ProbeTypeDNS,
+				Component:   componentDNSResolution,
+				Target:      region1Target,
+				ProbeStatus: Fail,
+				Details:     detail,
+				Action:      fmt.Sprintf(actionDNSFail, region1Target, region1Target),
+			},
+			{
+				Type:        ProbeTypeDNS,
+				Component:   componentDNSResolution,
+				Target:      region2Target,
+				ProbeStatus: Fail,
+				Details:     detail,
+				Action:      fmt.Sprintf(actionDNSFail, region2Target, region2Target),
+			},
+		}
+	}
+
+	region1Target, region2Target := regionTargets(region)
+	targets := []string{region1Target, region2Target}
+
+	results := make([]CheckResult, 0, len(addrGroups))
+	for i, group := range addrGroups {
+		target := fmt.Sprintf("region%d.v2.argotunnel.com", i+1)
+		if i < len(targets) {
+			target = targets[i]
+		}
+		if len(group) == 0 {
+			results = append(results, CheckResult{
+				Type:        ProbeTypeDNS,
+				Component:   componentDNSResolution,
+				Target:      target,
+				ProbeStatus: Fail,
+				Details:     detailsNoAddressesReturned,
+				Action:      fmt.Sprintf(actionDNSFail, target, target),
+			})
+		} else {
+			results = append(results, CheckResult{
+				Type:        ProbeTypeDNS,
+				Component:   componentDNSResolution,
+				Target:      target,
+				ProbeStatus: Pass,
+				Details:     detailsResolvedSuccessfully,
+			})
+		}
+	}
+
+	return addrGroups, results
+}
+
+// probeQUIC performs a QUIC handshake to a single edge address and returns a
+// CheckResult. The connection is closed immediately after the handshake – no
+// streams are opened and no RPC frames are sent – to avoid triggering the OTD
+// registration timeout (TUN-6732). The probe SNI (probe.cftunnel.com) is used
+// instead of the production quic.cftunnel.com to prevent OTD log noise.
+//
+// A per-probe deadline (perProbeDialTimeout) is applied on top of the parent
+// context so that a single blocked handshake cannot consume the entire suite
+// budget.
+func probeQUIC(
+	ctx context.Context,
+	dialer QUICDialer,
+	addr *allregions.EdgeAddr,
+	logger *zerolog.Logger,
+) CheckResult {
+	dialCtx, cancel := context.WithTimeout(ctx, perProbeDialTimeout)
+	defer cancel()
+
+	tlsSettings := connection.QUIC.ProbeTLSSettings()
+	tlsConfig := &tls.Config{
+		ServerName:       tlsSettings.ServerName,
+		NextProtos:       tlsSettings.NextProtos,
+		MinVersion:       tls.VersionTLS13,
+		CurvePreferences: []tls.CurveID{tls.CurveP256},
+	}
+
+	// We call dialer.DialQuic with isProbe = true, which bypasses connIndex check.
+	// Therefore, whatever we add to connIndex will not be relevant.
+	edgeAddrPort := addr.UDP.AddrPort()
+	conn, err := dialer.DialQuic(
+		dialCtx,
+		&quic.Config{},
+		tlsConfig,
+		edgeAddrPort,
+		nil,
+		math.MaxUint8,
+		logger,
+		dialopts.DialOpts{SkipPortReuse: true},
+	)
+	if err != nil {
+		return CheckResult{
+			Type:        ProbeTypeQUIC,
+			Component:   componentUDPConnectivity,
+			Target:      targetPortQUIC,
+			ProbeStatus: Fail,
+			Details:     detailsHandshakeFailed,
+			Action:      actionQUICBlocked,
+		}
+	}
+
+	if err := conn.CloseWithError(0, "precheck complete"); err != nil {
+		logger.Debug().Err(err).Msg("Failed to close QUIC connection after successful handshake")
+	}
+
+	return CheckResult{
+		Type:        ProbeTypeQUIC,
+		Component:   componentUDPConnectivity,
+		Target:      targetPortQUIC,
+		ProbeStatus: Pass,
+		Details:     detailsHandshakeSuccessful,
+	}
+}
+
+// probeHTTP2 performs a TCP + TLS handshake to a single edge address and
+// returns a CheckResult. The connection is closed immediately after the
+// handshake – no HTTP/2 frames are sent – to keep the probe minimal. The probe
+// SNI (probe.cftunnel.com) is used instead of the production h2.cftunnel.com
+// to prevent OTD log noise.
+//
+// The dial timeout is capped at perProbeDialTimeout so that a single blocked
+// dial cannot exhaust the entire suite budget.
+func probeHTTP2(ctx context.Context, dialer TCPDialer, addr *allregions.EdgeAddr) CheckResult {
+	tlsSettings := connection.HTTP2.ProbeTLSSettings()
+	tlsConfig := &tls.Config{
+		ServerName:       tlsSettings.ServerName,
+		MinVersion:       tls.VersionTLS12,
+		CurvePreferences: []tls.CurveID{tls.CurveP256},
+	}
+
+	conn, err := dialer.DialEdge(ctx, perProbeDialTimeout, tlsConfig, addr.TCP, nil)
+	if err != nil {
+		return CheckResult{
+			Type:        ProbeTypeHTTP2,
+			Component:   componentTCPConnectivity,
+			Target:      targetPortHTTP2,
+			ProbeStatus: Fail,
+			Details:     detailsBlockedOrUnreachable,
+			Action:      actionHTTP2Blocked,
+		}
+	}
+	_ = conn.Close()
+
+	return CheckResult{
+		Type:        ProbeTypeHTTP2,
+		Component:   componentTCPConnectivity,
+		Target:      targetPortHTTP2,
+		ProbeStatus: Pass,
+		Details:     detailsTLSHandshakeSuccessful,
+	}
+}
+
+// probeManagementAPI tests TCP connectivity to api.cloudflare.com:443. A
+// successful TCP connection (no TLS handshake required) confirms the port is
+// reachable. This probe is always a soft failure: the tunnel can run without
+// it, but automatic software updates will be unavailable.
+func probeManagementAPI(ctx context.Context, dialer ManagementDialer) CheckResult {
+	dialCtx, cancel := context.WithTimeout(ctx, perProbeDialTimeout)
+	defer cancel()
+
+	conn, err := dialer.DialContext(dialCtx, "tcp", targetAPI)
+	if err != nil {
+		return CheckResult{
+			Type:        ProbeTypeManagementAPI,
+			Component:   componentCloudflareAPI,
+			Target:      targetAPI,
+			ProbeStatus: Fail,
+			Details:     detailsConnectionFailed,
+			Action:      actionAPIUnreachable,
+		}
+	}
+	_ = conn.Close()
+
+	return CheckResult{
+		Type:        ProbeTypeManagementAPI,
+		Component:   componentCloudflareAPI,
+		Target:      targetAPI,
+		ProbeStatus: Pass,
+		Details:     detailsTCPPortReachable,
+	}
+}
+
+func skipResult(probeType ProbeType, component, target string) CheckResult {
+	return CheckResult{
+		Type:        probeType,
+		Component:   component,
+		Target:      target,
+		ProbeStatus: Skip,
+		Details:     detailsDNSPrerequisiteFailed,
+	}
+}
+
+// regionTargets returns the human-readable hostnames for region1 and region2
+// based on the optional region flag value.
+func regionTargets(region string) (string, string) {
+	switch region {
+	case "us":
+		return region1US, region2US
+	case "fed":
+		return region1Fed, region2Fed
+	default:
+		return region1Global, region2Global
+	}
+}
+
+// addrsByFamily extracts one V4 and one V6 address from a resolved CNAME group
+// using allregions.NewRegion so that the IP-version preference logic matches
+// production exactly. When cfg.IPVersion restricts to a single family the
+// excluded family's pointer is nil.
+func addrsByFamily(group []*allregions.EdgeAddr, ipVersion allregions.ConfigIPVersion) (v4, v6 *allregions.EdgeAddr) {
+	if ipVersion != allregions.IPv6Only {
+		v4 = allregions.NewRegion(group, allregions.IPv4Only).GetAnyAddress()
+	}
+	if ipVersion != allregions.IPv4Only {
+		v6 = allregions.NewRegion(group, allregions.IPv6Only).GetAnyAddress()
+	}
+	return
+}

prechecks/probes_test.go

@@ -0,0 +1,536 @@
+package prechecks
+
+import (
+	"context"
+	"errors"
+	"net"
+	"testing"
+
+	"github.com/quic-go/quic-go"
+	"github.com/rs/zerolog"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/mock/gomock"
+
+	"github.com/cloudflare/cloudflared/edgediscovery/allregions"
+	"github.com/cloudflare/cloudflared/mocks"
+)
+
+// Test constants for repeated string values.
+const (
+	testRegion1Global = region1Global
+	testRegion2Global = region2Global
+	testRegion1US     = region1US
+	testRegion2US     = region2US
+	testRegion1Fed    = region1Fed
+	testRegion2Fed    = region2Fed
+	testRegion1EU     = "eu-region1.v2.argotunnel.com"
+	testRegion2EU     = "eu-region2.v2.argotunnel.com"
+
+	testEdgePort = 7844
+)
+
+// mockQuicConnection is a minimal test double for quic.Connection.
+type mockQuicConnection struct {
+	closeErr error
+}
+
+func (m *mockQuicConnection) AcceptStream(_ context.Context) (quic.Stream, error) {
+	return nil, nil
+}
+
+func (m *mockQuicConnection) AcceptUniStream(_ context.Context) (quic.ReceiveStream, error) {
+	return nil, nil
+}
+
+func (m *mockQuicConnection) OpenStream() (quic.Stream, error) {
+	return nil, nil
+}
+
+func (m *mockQuicConnection) OpenStreamSync(_ context.Context) (quic.Stream, error) {
+	return nil, nil
+}
+
+func (m *mockQuicConnection) OpenUniStream() (quic.SendStream, error) {
+	return nil, nil
+}
+
+func (m *mockQuicConnection) OpenUniStreamSync(_ context.Context) (quic.SendStream, error) {
+	return nil, nil
+}
+
+func (m *mockQuicConnection) LocalAddr() net.Addr {
+	return nil
+}
+
+func (m *mockQuicConnection) RemoteAddr() net.Addr {
+	return nil
+}
+
+func (m *mockQuicConnection) CloseWithError(_ quic.ApplicationErrorCode, _ string) error {
+	return m.closeErr
+}
+
+func (m *mockQuicConnection) Context() context.Context {
+	return context.Background()
+}
+
+func (m *mockQuicConnection) ConnectionState() quic.ConnectionState {
+	return quic.ConnectionState{}
+}
+
+func (m *mockQuicConnection) SendDatagram(_ []byte) error {
+	return nil
+}
+
+func (m *mockQuicConnection) ReceiveDatagram(_ context.Context) ([]byte, error) {
+	return nil, nil
+}
+
+func (m *mockQuicConnection) AddPath(*quic.Transport) (*quic.Path, error) {
+	return nil, nil
+}
+
+// Helper to create test edge addresses.
+func createTestEdgeAddr(ip string, port int, version allregions.EdgeIPVersion) *allregions.EdgeAddr {
+	parsedIP := net.ParseIP(ip)
+	return &allregions.EdgeAddr{
+		TCP:       &net.TCPAddr{IP: parsedIP, Port: port},
+		UDP:       &net.UDPAddr{IP: parsedIP, Port: port},
+		IPVersion: version,
+	}
+}
+
+// probeDNS tests.
+
+func TestProbeDNS_Success(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	v4Addr := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+	v6Addr := createTestEdgeAddr("2001:db8::1", testEdgePort, allregions.V6)
+
+	resolver := mocks.NewMockDNSResolver(ctrl)
+	resolver.EXPECT().Resolve("").Return([][]*allregions.EdgeAddr{{v4Addr, v6Addr}}, nil)
+
+	addrs, results := probeDNS(resolver, "")
+
+	require.NotNil(t, addrs)
+	require.Len(t, results, 1)
+	assert.Len(t, addrs, 1)
+	assert.Equal(t, ProbeTypeDNS, results[0].Type)
+	assert.Equal(t, testRegion1Global, results[0].Target)
+	assert.Equal(t, Pass, results[0].ProbeStatus)
+	assert.Equal(t, detailsResolvedSuccessfully, results[0].Details)
+}
+
+func TestProbeDNS_MultipleRegions(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	v4Addr1 := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+	v4Addr2 := createTestEdgeAddr("192.0.2.2", testEdgePort, allregions.V4)
+
+	resolver := mocks.NewMockDNSResolver(ctrl)
+	resolver.EXPECT().Resolve("").Return([][]*allregions.EdgeAddr{{v4Addr1}, {v4Addr2}}, nil)
+
+	addrs, results := probeDNS(resolver, "")
+
+	require.NotNil(t, addrs)
+	require.Len(t, results, 2)
+	assert.Len(t, addrs, 2)
+
+	assert.Equal(t, testRegion1Global, results[0].Target)
+	assert.Equal(t, Pass, results[0].ProbeStatus)
+
+	assert.Equal(t, testRegion2Global, results[1].Target)
+	assert.Equal(t, Pass, results[1].ProbeStatus)
+}
+
+func TestProbeDNS_ResolverError(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	resolver := mocks.NewMockDNSResolver(ctrl)
+	resolver.EXPECT().Resolve("").Return(nil, errors.New("DNS lookup failed"))
+
+	addrs, results := probeDNS(resolver, "")
+
+	assert.Nil(t, addrs)
+	require.Len(t, results, 2)
+
+	assert.Equal(t, Fail, results[0].ProbeStatus)
+	assert.Equal(t, "DNS lookup failed", results[0].Details)
+	assert.Contains(t, results[0].Action, testRegion1Global)
+	assert.Contains(t, results[1].Action, testRegion2Global)
+
+	assert.Equal(t, Fail, results[1].ProbeStatus)
+}
+
+func TestProbeDNS_EmptyResults(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	resolver := mocks.NewMockDNSResolver(ctrl)
+	resolver.EXPECT().Resolve("").Return([][]*allregions.EdgeAddr{}, nil)
+
+	addrs, results := probeDNS(resolver, "")
+
+	assert.Nil(t, addrs)
+	require.Len(t, results, 2)
+	assert.Equal(t, Fail, results[0].ProbeStatus)
+	assert.Equal(t, "No addresses returned", results[0].Details)
+}
+
+func TestProbeDNS_EmptyGroup(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	resolver := mocks.NewMockDNSResolver(ctrl)
+	resolver.EXPECT().Resolve("").Return([][]*allregions.EdgeAddr{{}}, nil)
+
+	addrs, results := probeDNS(resolver, "")
+
+	require.NotNil(t, addrs)
+	require.Len(t, results, 1)
+	assert.Equal(t, Fail, results[0].ProbeStatus)
+	assert.Equal(t, "No addresses returned", results[0].Details)
+}
+
+func TestProbeDNS_RegionFlag(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	v4Addr := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+	resolver := mocks.NewMockDNSResolver(ctrl)
+	resolver.EXPECT().Resolve("us").Return([][]*allregions.EdgeAddr{{v4Addr}}, nil)
+
+	_, results := probeDNS(resolver, "us")
+
+	require.Len(t, results, 1)
+	assert.Equal(t, testRegion1US, results[0].Target)
+}
+
+// probeQUIC tests.
+
+func TestProbeQUIC_Success(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	mockConn := &mockQuicConnection{}
+	dialer := mocks.NewMockQUICDialer(ctrl)
+	dialer.EXPECT().DialQuic(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(mockConn, nil)
+
+	addr := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+	logger := zerolog.New(nil)
+
+	result := probeQUIC(context.Background(), dialer, addr, &logger)
+
+	assert.Equal(t, ProbeTypeQUIC, result.Type)
+	assert.Equal(t, Pass, result.ProbeStatus)
+	assert.Equal(t, detailsHandshakeSuccessful, result.Details)
+}
+
+func TestProbeQUIC_DialError(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	dialer := mocks.NewMockQUICDialer(ctrl)
+	dialer.EXPECT().DialQuic(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(nil, errors.New("connection refused"))
+
+	addr := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+	logger := zerolog.New(nil)
+
+	result := probeQUIC(context.Background(), dialer, addr, &logger)
+
+	assert.Equal(t, ProbeTypeQUIC, result.Type)
+	assert.Equal(t, Fail, result.ProbeStatus)
+	assert.Equal(t, detailsHandshakeFailed, result.Details)
+	assert.Equal(t, actionQUICBlocked, result.Action)
+}
+
+func TestProbeQUIC_CloseErrorDoesNotAffectResult(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	mockConn := &mockQuicConnection{closeErr: errors.New("close failed")}
+	dialer := mocks.NewMockQUICDialer(ctrl)
+	dialer.EXPECT().DialQuic(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(mockConn, nil)
+
+	addr := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+	logger := zerolog.New(nil)
+
+	result := probeQUIC(context.Background(), dialer, addr, &logger)
+
+	assert.Equal(t, ProbeTypeQUIC, result.Type)
+	assert.Equal(t, Pass, result.ProbeStatus)
+	assert.Equal(t, detailsHandshakeSuccessful, result.Details)
+}
+
+func TestProbeQUIC_ContextTimeout(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	dialer := mocks.NewMockQUICDialer(ctrl)
+	dialer.EXPECT().DialQuic(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(nil, context.DeadlineExceeded)
+
+	addr := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+	logger := zerolog.New(nil)
+
+	result := probeQUIC(context.Background(), dialer, addr, &logger)
+
+	assert.Equal(t, Fail, result.ProbeStatus)
+	assert.Equal(t, detailsHandshakeFailed, result.Details)
+}
+
+// probeHTTP2 tests.
+
+func TestProbeHTTP2_Success(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	dialer := mocks.NewMockTCPDialer(ctrl)
+	dialer.EXPECT().DialEdge(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(&net.TCPConn{}, nil)
+
+	addr := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+
+	result := probeHTTP2(context.Background(), dialer, addr)
+
+	assert.Equal(t, ProbeTypeHTTP2, result.Type)
+	assert.Equal(t, Pass, result.ProbeStatus)
+	assert.Equal(t, detailsTLSHandshakeSuccessful, result.Details)
+}
+
+func TestProbeHTTP2_DialError(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	dialer := mocks.NewMockTCPDialer(ctrl)
+	dialer.EXPECT().DialEdge(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(nil, errors.New("connection refused"))
+
+	addr := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+
+	result := probeHTTP2(context.Background(), dialer, addr)
+
+	assert.Equal(t, ProbeTypeHTTP2, result.Type)
+	assert.Equal(t, Fail, result.ProbeStatus)
+	assert.Equal(t, detailsBlockedOrUnreachable, result.Details)
+	assert.Equal(t, actionHTTP2Blocked, result.Action)
+}
+
+// probeManagementAPI tests.
+
+func TestProbeManagementAPI_Success(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	dialer := mocks.NewMockManagementDialer(ctrl)
+	dialer.EXPECT().DialContext(gomock.Any(), "tcp", "api.cloudflare.com:443").Return(&net.TCPConn{}, nil)
+
+	result := probeManagementAPI(context.Background(), dialer)
+
+	assert.Equal(t, ProbeTypeManagementAPI, result.Type)
+	assert.Equal(t, "Cloudflare API", result.Component)
+	assert.Equal(t, "api.cloudflare.com:443", result.Target)
+	assert.Equal(t, Pass, result.ProbeStatus)
+	assert.Equal(t, detailsTCPPortReachable, result.Details)
+}
+
+func TestProbeManagementAPI_DialError(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	dialer := mocks.NewMockManagementDialer(ctrl)
+	dialer.EXPECT().DialContext(gomock.Any(), "tcp", "api.cloudflare.com:443").Return(nil, errors.New("connection refused"))
+
+	result := probeManagementAPI(context.Background(), dialer)
+
+	assert.Equal(t, ProbeTypeManagementAPI, result.Type)
+	assert.Equal(t, Fail, result.ProbeStatus)
+	assert.Equal(t, detailsConnectionFailed, result.Details)
+	assert.Equal(t, actionAPIUnreachable, result.Action)
+}
+
+// skipResult tests.
+
+func TestSkipResult(t *testing.T) {
+	t.Parallel()
+
+	result := skipResult(ProbeTypeQUIC, "UDP Connectivity", "Port 7844 (QUIC)")
+
+	assert.Equal(t, ProbeTypeQUIC, result.Type)
+	assert.Equal(t, "UDP Connectivity", result.Component)
+	assert.Equal(t, "Port 7844 (QUIC)", result.Target)
+	assert.Equal(t, Skip, result.ProbeStatus)
+	assert.Equal(t, detailsDNSPrerequisiteFailed, result.Details)
+}
+
+// regionTargets tests.
+
+func TestRegionTargets(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name        string
+		region      string
+		wantRegion1 string
+		wantRegion2 string
+		description string
+	}{
+		{
+			name:        "empty region returns global hostnames",
+			region:      "",
+			wantRegion1: testRegion1Global,
+			wantRegion2: testRegion2Global,
+		},
+		{
+			name:        "us region returns US hostnames",
+			region:      "us",
+			wantRegion1: testRegion1US,
+			wantRegion2: testRegion2US,
+		},
+		{
+			name:        "fed region returns fed hostnames",
+			region:      "fed",
+			wantRegion1: testRegion1Fed,
+			wantRegion2: testRegion2Fed,
+		},
+		{
+			name:        "unknown region defaults to global hostnames",
+			region:      "eu",
+			wantRegion1: testRegion1Global,
+			wantRegion2: testRegion2Global,
+			description: "Unknown regions should default to global hostnames",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			gotR1, gotR2 := regionTargets(tt.region)
+			assert.Equal(t, tt.wantRegion1, gotR1)
+			assert.Equal(t, tt.wantRegion2, gotR2)
+		})
+	}
+}
+
+// addrsByFamily tests.
+
+func TestAddrsByFamily(t *testing.T) {
+	t.Parallel()
+
+	v4Addr := createTestEdgeAddr("192.0.2.1", testEdgePort, allregions.V4)
+	v6Addr := createTestEdgeAddr("2001:db8::1", testEdgePort, allregions.V6)
+
+	tests := []struct {
+		name      string
+		group     []*allregions.EdgeAddr
+		ipVersion allregions.ConfigIPVersion
+		wantV4    bool
+		wantV6    bool
+	}{
+		{
+			name:      "auto returns both v4 and v6",
+			group:     []*allregions.EdgeAddr{v4Addr, v6Addr},
+			ipVersion: allregions.Auto,
+			wantV4:    true,
+			wantV6:    true,
+		},
+		{
+			name:      "ipv4 only returns v4 and nil v6",
+			group:     []*allregions.EdgeAddr{v4Addr, v6Addr},
+			ipVersion: allregions.IPv4Only,
+			wantV4:    true,
+			wantV6:    false,
+		},
+		{
+			name:      "ipv6 only returns nil v4 and v6",
+			group:     []*allregions.EdgeAddr{v4Addr, v6Addr},
+			ipVersion: allregions.IPv6Only,
+			wantV4:    false,
+			wantV6:    true,
+		},
+		{
+			name:      "empty group returns nil for both",
+			group:     []*allregions.EdgeAddr{},
+			ipVersion: allregions.Auto,
+			wantV4:    false,
+			wantV6:    false,
+		},
+		{
+			name:      "only v4 available returns v4 and nil v6",
+			group:     []*allregions.EdgeAddr{v4Addr},
+			ipVersion: allregions.Auto,
+			wantV4:    true,
+			wantV6:    false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			gotV4, gotV6 := addrsByFamily(tt.group, tt.ipVersion)
+			if tt.wantV4 {
+				assert.NotNil(t, gotV4)
+			} else {
+				assert.Nil(t, gotV4)
+			}
+			if tt.wantV6 {
+				assert.NotNil(t, gotV6)
+			} else {
+				assert.Nil(t, gotV6)
+			}
+		})
+	}
+}
+
+// IPv6 address tests for probeQUIC.
+
+func TestProbeQUIC_IPv6Address(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	mockConn := &mockQuicConnection{}
+	dialer := mocks.NewMockQUICDialer(ctrl)
+	dialer.EXPECT().DialQuic(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(mockConn, nil)
+
+	addr := createTestEdgeAddr("2001:db8::1", testEdgePort, allregions.V6)
+	logger := zerolog.New(nil)
+
+	result := probeQUIC(context.Background(), dialer, addr, &logger)
+
+	assert.Equal(t, Pass, result.ProbeStatus)
+	assert.Equal(t, detailsHandshakeSuccessful, result.Details)
+}
+
+// IPv6 address tests for probeHTTP2.
+
+func TestProbeHTTP2_IPv6Address(t *testing.T) {
+	t.Parallel()
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	dialer := mocks.NewMockTCPDialer(ctrl)
+	dialer.EXPECT().DialEdge(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).Return(&net.TCPConn{}, nil)
+
+	addr := createTestEdgeAddr("2001:db8::1", testEdgePort, allregions.V6)
+
+	result := probeHTTP2(context.Background(), dialer, addr)
+
+	assert.Equal(t, Pass, result.ProbeStatus)
+}

prechecks/resolvers.go

@@ -23,9 +23,6 @@ import (
 // system resolver fails, and resolves each discovered hostname via
 // net.LookupIP. The returned slice already has each address tagged with
 // .IPVersion = V4 or V6.
-//
-// Note: allregions.EdgeDiscovery must be exported (currently unexported as
-// edgeDiscovery) before a production adapter can be wired up.
 type DNSResolver interface {
 	// Resolve performs edge discovery for the given region string (empty for
 	// global, "us" / "fed" for regional endpoints) and returns the resolved