Pull request #1558: add-dnssvc

Merge in DNS/adguard-home from add-dnssvc to master

Squashed commit of the following:

commit 55f4f114bab65a03c0d65383e89020a7356cff32
Merge: 95dc28d9 6e63757f
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Aug 15 20:53:07 2022 +0300

    Merge branch 'master' into add-dnssvc

commit 95dc28d9d77d06e8ac98c1e6772557bffbf1705b
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Aug 15 20:52:50 2022 +0300

    all: imp tests, docs

commit 0d9d02950d84afd160b4b1c118da856cee6f12e5
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Aug 11 19:27:59 2022 +0300

    all: imp docs

commit 8990e038a81da4430468da12fcebedf79fe14df6
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Aug 11 19:05:29 2022 +0300

    all: imp tests more

commit 92730d93a2a1ac77888c2655508e43efaf0e9fde
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Aug 11 18:37:48 2022 +0300

    all: imp tests more

commit 8cd45ba30da7ac310e9dc666fb2af438e577b02d
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu Aug 11 18:11:15 2022 +0300

    all: add v1 dnssvc stub; refactor tests

internal/v1/dnssvc/dnssvc.go

@@ -0,0 +1,193 @@
+// Package dnssvc contains the AdGuard Home DNS service.
+//
+// TODO(a.garipov): Define, if all methods of a *Service should work with a nil
+// receiver.
+package dnssvc
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/netip"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/v1/agh"
+	// TODO(a.garipov): Add a “dnsproxy proxy” package to shield us from changes
+	// and replacement of module dnsproxy.
+	"github.com/AdguardTeam/dnsproxy/proxy"
+	"github.com/AdguardTeam/dnsproxy/upstream"
+)
+
+// Config is the AdGuard Home DNS service configuration structure.
+//
+// TODO(a.garipov): Add timeout for incoming requests.
+type Config struct {
+	// Addresses are the addresses on which to serve plain DNS queries.
+	Addresses []netip.AddrPort
+
+	// Upstreams are the DNS upstreams to use.  If not set, upstreams are
+	// created using data from BootstrapServers, UpstreamServers, and
+	// UpstreamTimeout.
+	//
+	// TODO(a.garipov): Think of a better scheme.  Those other three parameters
+	// are here only to make Config work properly.
+	Upstreams []upstream.Upstream
+
+	// BootstrapServers are the addresses for bootstrapping the upstream DNS
+	// server addresses.
+	BootstrapServers []string
+
+	// UpstreamServers are the upstream DNS server addresses to use.
+	UpstreamServers []string
+
+	// UpstreamTimeout is the timeout for upstream requests.
+	UpstreamTimeout time.Duration
+}
+
+// Service is the AdGuard Home DNS service.  A nil *Service is a valid
+// [agh.Service] that does nothing.
+type Service struct {
+	proxy      *proxy.Proxy
+	bootstraps []string
+	upstreams  []string
+	upsTimeout time.Duration
+}
+
+// New returns a new properly initialized *Service.  If c is nil, svc is a nil
+// *Service that does nothing.  The fields of c must not be modified after
+// calling New.
+func New(c *Config) (svc *Service, err error) {
+	if c == nil {
+		return nil, nil
+	}
+
+	svc = &Service{
+		bootstraps: c.BootstrapServers,
+		upstreams:  c.UpstreamServers,
+		upsTimeout: c.UpstreamTimeout,
+	}
+
+	var upstreams []upstream.Upstream
+	if len(c.Upstreams) > 0 {
+		upstreams = c.Upstreams
+	} else {
+		upstreams, err = addressesToUpstreams(
+			c.UpstreamServers,
+			c.BootstrapServers,
+			c.UpstreamTimeout,
+		)
+		if err != nil {
+			return nil, fmt.Errorf("converting upstreams: %w", err)
+		}
+	}
+
+	svc.proxy = &proxy.Proxy{
+		Config: proxy.Config{
+			UDPListenAddr: udpAddrs(c.Addresses),
+			TCPListenAddr: tcpAddrs(c.Addresses),
+			UpstreamConfig: &proxy.UpstreamConfig{
+				Upstreams: upstreams,
+			},
+		},
+	}
+
+	err = svc.proxy.Init()
+	if err != nil {
+		return nil, fmt.Errorf("proxy: %w", err)
+	}
+
+	return svc, nil
+}
+
+// addressesToUpstreams is a wrapper around [upstream.AddressToUpstream].  It
+// accepts a slice of addresses and other upstream parameters, and returns a
+// slice of upstreams.
+func addressesToUpstreams(
+	upsStrs []string,
+	bootstraps []string,
+	timeout time.Duration,
+) (upstreams []upstream.Upstream, err error) {
+	upstreams = make([]upstream.Upstream, len(upsStrs))
+	for i, upsStr := range upsStrs {
+		upstreams[i], err = upstream.AddressToUpstream(upsStr, &upstream.Options{
+			Bootstrap: bootstraps,
+			Timeout:   timeout,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("upstream at index %d: %w", i, err)
+		}
+	}
+
+	return upstreams, nil
+}
+
+// tcpAddrs converts []netip.AddrPort into []*net.TCPAddr.
+func tcpAddrs(addrPorts []netip.AddrPort) (tcpAddrs []*net.TCPAddr) {
+	if addrPorts == nil {
+		return nil
+	}
+
+	tcpAddrs = make([]*net.TCPAddr, len(addrPorts))
+	for i, a := range addrPorts {
+		tcpAddrs[i] = net.TCPAddrFromAddrPort(a)
+	}
+
+	return tcpAddrs
+}
+
+// udpAddrs converts []netip.AddrPort into []*net.UDPAddr.
+func udpAddrs(addrPorts []netip.AddrPort) (udpAddrs []*net.UDPAddr) {
+	if addrPorts == nil {
+		return nil
+	}
+
+	udpAddrs = make([]*net.UDPAddr, len(addrPorts))
+	for i, a := range addrPorts {
+		udpAddrs[i] = net.UDPAddrFromAddrPort(a)
+	}
+
+	return udpAddrs
+}
+
+// type check
+var _ agh.Service = (*Service)(nil)
+
+// Start implements the [agh.Service] interface for *Service.  svc may be nil.
+// After Start exits, all DNS servers have tried to start, but there is no
+// guarantee that they did.  Errors from the servers are written to the log.
+func (svc *Service) Start() (err error) {
+	if svc == nil {
+		return nil
+	}
+
+	return svc.proxy.Start()
+}
+
+// Shutdown implements the [agh.Service] interface for *Service.  svc may be
+// nil.
+func (svc *Service) Shutdown(ctx context.Context) (err error) {
+	if svc == nil {
+		return nil
+	}
+
+	return svc.proxy.Stop()
+}
+
+// Config returns the current configuration of the web service.
+func (svc *Service) Config() (c *Config) {
+	// TODO(a.garipov): Do we need to get the TCP addresses separately?
+	udpAddrs := svc.proxy.Addrs(proxy.ProtoUDP)
+	addrs := make([]netip.AddrPort, len(udpAddrs))
+	for i, a := range udpAddrs {
+		addrs[i] = a.(*net.UDPAddr).AddrPort()
+	}
+
+	c = &Config{
+		Addresses:        addrs,
+		BootstrapServers: svc.bootstraps,
+		UpstreamServers:  svc.upstreams,
+		UpstreamTimeout:  svc.upsTimeout,
+	}
+
+	return c
+}