Pull request 312: 6321 boot ttl vol.1

Updates AdguardTeam/AdGuardHome#6321.

Squashed commit of the following:

commit fb8f98b
Merge: 329e3e3 a87a3df
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Jan 11 14:14:06 2024 +0300

    Merge branch 'master' into 6321-boot-ttl-vol.1

commit 329e3e3
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Jan 9 23:27:41 2024 +0300

    all: imp docs

commit 91cc3f0
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Dec 29 17:59:36 2023 +0500

    all: imp code, rm redundant changes

commit f0df8c2
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Dec 28 19:20:07 2023 +0500

    all: imp code

commit c1fd087
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Dec 27 18:23:38 2023 +0300

    all: move code, use new types

commit e1d9405
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Dec 27 18:17:08 2023 +0300

    upstream: add separate test

internal/bootstrap/bootstrap.go

@@ -14,20 +14,42 @@ import (
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/netutil"
+	"golang.org/x/exp/slices"
+)
+
+// Network is a network type for use in [Resolver]'s methods.
+type Network = string
+
+const (
+	// NetworkIP is a network type for both address families.
+	NetworkIP Network = "ip"
+
+	// NetworkIP4 is a network type for IPv4 address family.
+	NetworkIP4 Network = "ip4"
+
+	// NetworkIP6 is a network type for IPv6 address family.
+	NetworkIP6 Network = "ip6"
+
+	// NetworkTCP is a network type for TCP connections.
+	NetworkTCP Network = "tcp"
+
+	// NetworkUDP is a network type for UDP connections.
+	NetworkUDP Network = "udp"
 )
 
 // DialHandler is a dial function for creating unencrypted network connections
 // to the upstream server.  It establishes the connection to the server
-// specified at initialization and ignores the addr.
-type DialHandler func(ctx context.Context, network, addr string) (conn net.Conn, err error)
+// specified at initialization and ignores the addr.  network must be one of
+// [NetworkTCP] or [NetworkUDP].
+type DialHandler func(ctx context.Context, network Network, addr string) (conn net.Conn, err error)
 
 // ResolveDialContext returns a DialHandler that uses addresses resolved from u
 // using resolver.  u must not be nil.
 func ResolveDialContext(
 	u *url.URL,
 	timeout time.Duration,
-	resolver Resolver,
-	preferIPv6 bool,
+	r Resolver,
+	preferV6 bool,
 ) (h DialHandler, err error) {
 	defer func() { err = errors.Annotate(err, "dialing %q: %w", u.Host) }()
 
@@ -38,7 +60,7 @@ func ResolveDialContext(
 		return nil, err
 	}
 
-	if resolver == nil {
+	if r == nil {
 		return nil, fmt.Errorf("resolver is nil: %w", ErrNoResolvers)
 	}
 
@@ -49,36 +71,28 @@ func ResolveDialContext(
 		defer cancel()
 	}
 
-	ips, err := resolver.LookupNetIP(ctx, "ip", host)
+	ips, err := r.LookupNetIP(ctx, NetworkIP, host)
 	if err != nil {
 		return nil, fmt.Errorf("resolving hostname: %w", err)
 	}
 
-	proxynetutil.SortNetIPAddrs(ips, preferIPv6)
+	if preferV6 {
+		slices.SortStableFunc(ips, proxynetutil.PreferIPv6)
+	} else {
+		slices.SortStableFunc(ips, proxynetutil.PreferIPv4)
+	}
 
 	addrs := make([]string, 0, len(ips))
 	for _, ip := range ips {
-		if !ip.IsValid() {
-			// All invalid addresses should be in the tail after sorting.
-			break
-		}
-
-		addrs = append(addrs, netip.AddrPortFrom(ip, uint16(port)).String())
+		addrs = append(addrs, netip.AddrPortFrom(ip, port).String())
 	}
 
 	return NewDialContext(timeout, addrs...), nil
 }
 
 // NewDialContext returns a DialHandler that dials addrs and returns the first
 // successful connection.  At least a single addr should be specified.
-//
-// TODO(e.burkov):  Consider using [Resolver] instead of
-// [upstream.Options.Bootstrap] and [upstream.Options.ServerIPAddrs].
 func NewDialContext(timeout time.Duration, addrs ...string) (h DialHandler) {
-	dialer := &net.Dialer{
-		Timeout: timeout,
-	}
-
 	l := len(addrs)
 	if l == 0 {
 		log.Debug("bootstrap: no addresses to dial")
@@ -88,9 +102,11 @@ func NewDialContext(timeout time.Duration, addrs ...string) (h DialHandler) {
 		}
 	}
 
-	// TODO(e.burkov):  Check IPv6 preference here.
+	dialer := &net.Dialer{
+		Timeout: timeout,
+	}
 
-	return func(ctx context.Context, network, _ string) (conn net.Conn, err error) {
+	return func(ctx context.Context, network Network, _ string) (conn net.Conn, err error) {
 		var errs []error
 
 		// Return first succeeded connection.  Note that we're using addrs
@@ -101,17 +117,18 @@ func NewDialContext(timeout time.Duration, addrs ...string) (h DialHandler) {
 			start := time.Now()
 			conn, err = dialer.DialContext(ctx, network, addr)
 			elapsed := time.Since(start)
-			if err == nil {
-				log.Debug("bootstrap: connection to %s succeeded in %s", addr, elapsed)
+			if err != nil {
+				log.Debug("bootstrap: connection to %s failed in %s: %s", addr, elapsed, err)
+				errs = append(errs, err)
 
-				return conn, nil
+				continue
 			}
 
-			log.Debug("bootstrap: connection to %s failed in %s: %s", addr, elapsed, err)
-			errs = append(errs, err)
+			log.Debug("bootstrap: connection to %s succeeded in %s", addr, elapsed)
+
+			return conn, nil
 		}
 
-		// TODO(e.burkov):  Use errors.Join in Go 1.20.
-		return nil, errors.List("all dialers failed", errs...)
+		return nil, errors.Join(errs...)
 	}
 }

internal/bootstrap/bootstrap_test.go

@@ -87,7 +87,7 @@ func TestResolveDialContext(t *testing.T) {
 				network string,
 				host string,
 			) (addrs []netip.Addr, err error) {
-				require.Equal(pt, "ip", network)
+				require.Equal(pt, bootstrap.NetworkIP, network)
 				require.Equal(pt, hostname, host)
 
 				return tc.addresses, nil
@@ -103,7 +103,7 @@ func TestResolveDialContext(t *testing.T) {
 			)
 			require.NoError(t, err)
 
-			conn, err := dialContext(context.Background(), "tcp", "")
+			conn, err := dialContext(context.Background(), bootstrap.NetworkTCP, "")
 			require.NoError(t, err)
 
 			expected, ok := testutil.RequireReceive(t, sig, testTimeout)
@@ -120,7 +120,7 @@ func TestResolveDialContext(t *testing.T) {
 				network string,
 				host string,
 			) (addrs []netip.Addr, err error) {
-				require.Equal(pt, "ip", network)
+				require.Equal(pt, bootstrap.NetworkIP, network)
 				require.Equal(pt, hostname, host)
 
 				return nil, nil
@@ -135,7 +135,7 @@ func TestResolveDialContext(t *testing.T) {
 		)
 		require.NoError(t, err)
 
-		_, err = dialContext(context.Background(), "tcp", "")
+		_, err = dialContext(context.Background(), bootstrap.NetworkTCP, "")
 		testutil.AssertErrorMsg(t, "no addresses", err)
 	})
 

internal/bootstrap/error.go

@@ -0,0 +1,6 @@
+package bootstrap
+
+import "github.com/AdguardTeam/golibs/errors"
+
+// ErrNoResolvers is returned when zero resolvers specified.
+const ErrNoResolvers errors.Error = "no resolvers specified"

internal/bootstrap/resolver.go

@@ -8,22 +8,21 @@ import (
 
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
+	"golang.org/x/exp/slices"
 )
 
-// Resolver resolves the hostnames to IP addresses.
+// Resolver resolves the hostnames to IP addresses.  Note, that [net.Resolver]
+// from standard library also implements this interface.
 type Resolver interface {
-	// LookupNetIP looks up the IP addresses for the given host.  network must
-	// be one of "ip", "ip4" or "ip6".  The response may be empty even if err is
-	// nil.
-	LookupNetIP(ctx context.Context, network, host string) (addrs []netip.Addr, err error)
+	// LookupNetIP looks up the IP addresses for the given host.  network should
+	// be one of [NetworkIP], [NetworkIP4] or [NetworkIP6].  The response may be
+	// empty even if err is nil.  All the addrs must be valid.
+	LookupNetIP(ctx context.Context, network Network, host string) (addrs []netip.Addr, err error)
 }
 
 // type check
 var _ Resolver = &net.Resolver{}
 
-// ErrNoResolvers is returned when zero resolvers specified.
-const ErrNoResolvers errors.Error = "no resolvers specified"
-
 // ParallelResolver is a slice of resolvers that are queried concurrently.  The
 // first successful response is returned.
 type ParallelResolver []Resolver
@@ -34,7 +33,7 @@ var _ Resolver = ParallelResolver(nil)
 // LookupNetIP implements the [Resolver] interface for ParallelResolver.
 func (r ParallelResolver) LookupNetIP(
 	ctx context.Context,
-	network string,
+	network Network,
 	host string,
 ) (addrs []netip.Addr, err error) {
 	resolversNum := len(r)
@@ -48,7 +47,7 @@ func (r ParallelResolver) LookupNetIP(
 	}
 
 	// Size of channel must accommodate results of lookups from all resolvers,
-	// sending into channel will be block otherwise.
+	// sending into channel will block otherwise.
 	ch := make(chan any, resolversNum)
 	for _, rslv := range r {
 		go lookupAsync(ctx, rslv, network, host, ch)
@@ -97,3 +96,50 @@ func lookup(ctx context.Context, r Resolver, network, host string) (addrs []neti
 
 	return addrs, err
 }
+
+// ConsequentResolver is a slice of resolvers that are queried in order until
+// the first successful non-empty response, as opposed to just successful
+// response requirement in [ParallelResolver].
+type ConsequentResolver []Resolver
+
+// type check
+var _ Resolver = ConsequentResolver(nil)
+
+// LookupNetIP implements the [Resolver] interface for ConsequentResolver.
+func (resolvers ConsequentResolver) LookupNetIP(
+	ctx context.Context,
+	network Network,
+	host string,
+) (addrs []netip.Addr, err error) {
+	if len(resolvers) == 0 {
+		return nil, ErrNoResolvers
+	}
+
+	var errs []error
+	for _, r := range resolvers {
+		addrs, err = r.LookupNetIP(ctx, network, host)
+		if err == nil && len(addrs) > 0 {
+			return addrs, nil
+		}
+
+		errs = append(errs, err)
+	}
+
+	return nil, errors.Join(errs...)
+}
+
+// StaticResolver is a resolver which always responds with an underlying slice
+// of IP addresses regardless of host and network.
+type StaticResolver []netip.Addr
+
+// type check
+var _ Resolver = StaticResolver(nil)
+
+// LookupNetIP implements the [Resolver] interface for StaticResolver.
+func (r StaticResolver) LookupNetIP(
+	_ context.Context,
+	_ Network,
+	_ string,
+) (addrs []netip.Addr, err error) {
+	return slices.Clone(r), nil
+}

internal/netutil/netutil.go

@@ -12,6 +12,42 @@ import (
 	"golang.org/x/exp/slices"
 )
 
+// PreferIPv4 compares two addresses, preferring IPv4 addresses over IPv6 ones.
+// Invalid addresses are sorted near the end.
+func PreferIPv4(a, b netip.Addr) (res int) {
+	if !a.IsValid() {
+		return 1
+	} else if !b.IsValid() {
+		return -1
+	}
+
+	if aIs4 := a.Is4(); aIs4 == b.Is4() {
+		return a.Compare(b)
+	} else if aIs4 {
+		return -1
+	}
+
+	return 1
+}
+
+// PreferIPv6 compares two addresses, preferring IPv6 addresses over IPv4 ones.
+// Invalid addresses are sorted near the end.
+func PreferIPv6(a, b netip.Addr) (res int) {
+	if !a.IsValid() {
+		return 1
+	} else if !b.IsValid() {
+		return -1
+	}
+
+	if aIs6 := a.Is6(); aIs6 == b.Is6() {
+		return a.Compare(b)
+	} else if aIs6 {
+		return -1
+	}
+
+	return 1
+}
+
 // SortNetIPAddrs sorts addrs in accordance with the protocol preferences.
 // Invalid addresses are sorted near the end.  Zones are ignored.
 func SortNetIPAddrs(addrs []netip.Addr, preferIPv6 bool) {

proxy/proxy_test.go

@@ -329,7 +329,7 @@ func TestExchangeWithReservedDomains(t *testing.T) {
 		upstreams,
 		&upstream.Options{
 			InsecureSkipVerify: false,
-			Bootstrap:          googleRslv,
+			Bootstrap:          upstream.NewCachingResolver(googleRslv),
 			Timeout:            1 * time.Second,
 		},
 	)
@@ -412,7 +412,7 @@ func TestOneByOneUpstreamsExchange(t *testing.T) {
 		u, err = upstream.AddressToUpstream(
 			line,
 			&upstream.Options{
-				Bootstrap: googleRslv,
+				Bootstrap: upstream.NewCachingResolver(googleRslv),
 				Timeout:   timeOut,
 			},
 		)