Pull request 2064: AG-23599 Upd proxy

Merge in DNS/adguard-home from AG-23599-upd-proxy to master

Squashed commit of the following:

commit 31a4da2fe425d648a94f13060e8786ffae0be3ca
Merge: 2c2fb253d 94bceaa84
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Nov 16 13:37:55 2023 +0300

    Merge branch 'master' into AG-23599-upd-proxy

commit 2c2fb253d489baa6b97a524b7e3327676ee6aa6f
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Wed Nov 15 19:03:20 2023 +0300

    dnsforward: imp code

commit 7384365758f80753cc4234184e7bd7311a85435d
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Nov 14 17:02:07 2023 +0300

    all: imp code

commit 9c0be82285eed0602f593f805cfb7d02ace17a64
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Fri Nov 10 20:21:00 2023 +0300

    all: imp code, docs

commit 5a47875882b5afd0264e4d473e884843745ff3f4
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Nov 9 16:50:51 2023 +0300

    all: upd proxy

internal/aghnet/hostscontainer.go

@@ -1,14 +1,17 @@
 package aghnet
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"io/fs"
 	"net/netip"
 	"path"
+	"strings"
 	"sync/atomic"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+	"github.com/AdguardTeam/dnsproxy/upstream"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/hostsfile"
 	"github.com/AdguardTeam/golibs/log"
@@ -141,13 +144,9 @@ func NewHostsContainer(
 func (hc *HostsContainer) Close() (err error) {
 	log.Debug("%s: closing", hostsContainerPrefix)
 
-	err = hc.watcher.Close()
-	if err != nil {
-		err = fmt.Errorf("closing fs watcher: %w", err)
-
-		// Go on and close the container either way.
-	}
+	err = errors.Annotate(hc.watcher.Close(), "closing fs watcher: %w")
 
+	// Go on and close the container either way.
 	close(hc.done)
 
 	return err
@@ -319,3 +318,39 @@ func (hc *HostsContainer) refresh() (err error) {
 
 	return nil
 }
+
+// type check
+var _ upstream.Resolver = (*HostsContainer)(nil)
+
+// LookupNetIP implements the [upstream.Resolver] interface for *HostsContainer.
+func (hc *HostsContainer) LookupNetIP(
+	ctx context.Context,
+	network string,
+	hostname string,
+) (addrs []netip.Addr, err error) {
+	// TODO(e.burkov):  Think of extracting this logic to a golibs function if
+	// needed anywhere else.
+	var isDesiredProto func(ip netip.Addr) (ok bool)
+	switch network {
+	case "ip4":
+		isDesiredProto = (netip.Addr).Is4
+	case "ip6":
+		isDesiredProto = (netip.Addr).Is6
+	case "ip":
+		isDesiredProto = func(ip netip.Addr) (ok bool) { return true }
+	default:
+		return nil, fmt.Errorf("unsupported network: %q", network)
+	}
+
+	idx := hc.current.Load()
+	recs := idx.names[strings.ToLower(hostname)]
+
+	addrs = make([]netip.Addr, 0, len(recs))
+	for _, rec := range recs {
+		if isDesiredProto(rec.Addr) {
+			addrs = append(addrs, rec.Addr)
+		}
+	}
+
+	return slices.Clip(addrs), nil
+}

internal/aghnet/net.go

@@ -10,9 +10,11 @@ import (
 	"net"
 	"net/netip"
 	"net/url"
+	"strings"
 	"syscall"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+	"github.com/AdguardTeam/dnsproxy/upstream"
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
 )
@@ -307,6 +309,50 @@ func ParseAddrPort(s string, defaultPort uint16) (ipp netip.AddrPort, err error)
 	return ipp, nil
 }
 
+// ParseSubnet parses s either as a CIDR prefix itself, or as an IP address,
+// returning the corresponding single-IP CIDR prefix.
+//
+// TODO(e.burkov):  Taken from dnsproxy, move to golibs.
+func ParseSubnet(s string) (p netip.Prefix, err error) {
+	if strings.Contains(s, "/") {
+		p, err = netip.ParsePrefix(s)
+		if err != nil {
+			return netip.Prefix{}, err
+		}
+	} else {
+		var ip netip.Addr
+		ip, err = netip.ParseAddr(s)
+		if err != nil {
+			return netip.Prefix{}, err
+		}
+
+		p = netip.PrefixFrom(ip, ip.BitLen())
+	}
+
+	return p, nil
+}
+
+// ParseBootstraps returns the slice of upstream resolvers parsed from addrs.
+// It additionally returns the closers for each resolver, that should be closed
+// after use.
+func ParseBootstraps(
+	addrs []string,
+	opts *upstream.Options,
+) (boots []*upstream.UpstreamResolver, err error) {
+	boots = make([]*upstream.UpstreamResolver, 0, len(boots))
+	for i, b := range addrs {
+		var r *upstream.UpstreamResolver
+		r, err = upstream.NewUpstreamResolver(b, opts)
+		if err != nil {
+			return nil, fmt.Errorf("bootstrap at index %d: %w", i, err)
+		}
+
+		boots = append(boots, r)
+	}
+
+	return boots, nil
+}
+
 // BroadcastFromPref calculates the broadcast IP address for p.
 func BroadcastFromPref(p netip.Prefix) (bc netip.Addr) {
 	bc = p.Addr().Unmap()