Simplified loop mechanism for openvpn and dns

- Refers to #91
- http control server starts without waiting for unbound and/or openvpn
- Trying to get rid of waiter and use channels directly
- Simpler main.go
- More robust logic overall

internal/dns/loop.go

@@ -0,0 +1,183 @@
+package dns
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/qdm12/golibs/command"
+	"github.com/qdm12/golibs/logging"
+	"github.com/qdm12/private-internet-access-docker/internal/constants"
+	"github.com/qdm12/private-internet-access-docker/internal/settings"
+)
+
+type Looper interface {
+	Run(ctx context.Context, restart <-chan struct{}, done chan<- struct{})
+	RunRestartTicker(ctx context.Context, restart chan<- struct{})
+}
+
+type looper struct {
+	conf         Configurator
+	settings     settings.DNS
+	logger       logging.Logger
+	streamMerger command.StreamMerger
+	uid          int
+	gid          int
+}
+
+func NewLooper(conf Configurator, settings settings.DNS, logger logging.Logger,
+	streamMerger command.StreamMerger, uid, gid int) Looper {
+	return &looper{
+		conf:         conf,
+		settings:     settings,
+		logger:       logger.WithPrefix("dns over tls: "),
+		uid:          uid,
+		gid:          gid,
+		streamMerger: streamMerger,
+	}
+}
+
+func (l *looper) attemptingRestart(err error) {
+	l.logger.Warn(err)
+	l.logger.Info("attempting restart in 10 seconds")
+	time.Sleep(10 * time.Second)
+}
+
+func (l *looper) Run(ctx context.Context, restart <-chan struct{}, done chan<- struct{}) {
+	l.fallbackToUnencryptedDNS()
+	select {
+	case <-restart:
+	case <-ctx.Done():
+		close(done)
+		return
+	}
+	_, unboundCancel := context.WithCancel(ctx)
+	for {
+		if !l.settings.Enabled {
+			// wait for another restart signal to recheck if it is enabled
+			select {
+			case <-restart:
+			case <-ctx.Done():
+				unboundCancel()
+				close(done)
+				return
+			}
+		}
+		if ctx.Err() == context.Canceled {
+			unboundCancel()
+			close(done)
+			return
+		}
+
+		// Setup
+		if err := l.conf.DownloadRootHints(l.uid, l.gid); err != nil {
+			l.attemptingRestart(err)
+			continue
+		}
+		if err := l.conf.DownloadRootKey(l.uid, l.gid); err != nil {
+			l.attemptingRestart(err)
+			continue
+		}
+		if err := l.conf.MakeUnboundConf(l.settings, l.uid, l.gid); err != nil {
+			l.attemptingRestart(err)
+			continue
+		}
+
+		// Start command
+		unboundCancel()
+		unboundCtx, unboundCancel := context.WithCancel(ctx)
+		stream, waitFn, err := l.conf.Start(unboundCtx, l.settings.VerbosityDetailsLevel)
+		if err != nil {
+			unboundCancel()
+			l.fallbackToUnencryptedDNS()
+			l.attemptingRestart(err)
+		}
+
+		// Started successfully
+		go l.streamMerger.Merge(unboundCtx, stream,
+			command.MergeName("unbound"), command.MergeColor(constants.ColorUnbound()))
+		l.conf.UseDNSInternally(net.IP{127, 0, 0, 1})                         // use Unbound
+		if err := l.conf.UseDNSSystemWide(net.IP{127, 0, 0, 1}); err != nil { // use Unbound
+			unboundCancel()
+			l.fallbackToUnencryptedDNS()
+			l.attemptingRestart(err)
+		}
+		if err := l.conf.WaitForUnbound(); err != nil {
+			unboundCancel()
+			l.fallbackToUnencryptedDNS()
+			l.attemptingRestart(err)
+		}
+		waitError := make(chan error)
+		go func() {
+			err := waitFn() // blocking
+			if unboundCtx.Err() != context.Canceled {
+				waitError <- fmt.Errorf("unbound: %w", err)
+			}
+		}()
+
+		// Wait for one of the three cases below
+		select {
+		case <-ctx.Done():
+			l.logger.Warn("context canceled: exiting loop")
+			unboundCancel()
+			close(waitError)
+			close(done)
+			return
+		case <-restart: // triggered restart
+			unboundCancel()
+			close(waitError)
+			l.logger.Info("restarting")
+		case err := <-waitError: // unexpected error
+			unboundCancel()
+			close(waitError)
+			l.fallbackToUnencryptedDNS()
+			l.attemptingRestart(err)
+		}
+	}
+}
+
+func (l *looper) fallbackToUnencryptedDNS() {
+	// Try with user provided plaintext ip address
+	targetIP := l.settings.PlaintextAddress
+	if targetIP != nil {
+		l.conf.UseDNSInternally(targetIP)
+		if err := l.conf.UseDNSSystemWide(targetIP); err != nil {
+			l.logger.Error(err)
+		}
+		return
+	}
+
+	// Try with any IPv4 address from the providers chosen
+	for _, provider := range l.settings.Providers {
+		data := constants.DNSProviderMapping()[provider]
+		for _, targetIP = range data.IPs {
+			if targetIP.To4() != nil {
+				l.conf.UseDNSInternally(targetIP)
+				if err := l.conf.UseDNSSystemWide(targetIP); err != nil {
+					l.logger.Error(err)
+				}
+				return
+			}
+		}
+	}
+
+	// No IPv4 address found
+	l.logger.Error("no ipv4 DNS address found for providers %s", l.settings.Providers)
+}
+
+func (l *looper) RunRestartTicker(ctx context.Context, restart chan<- struct{}) {
+	if l.settings.UpdatePeriod == 0 {
+		return
+	}
+	ticker := time.NewTicker(l.settings.UpdatePeriod)
+	for {
+		select {
+		case <-ctx.Done():
+			ticker.Stop()
+			return
+		case <-ticker.C:
+			restart <- struct{}{}
+		}
+	}
+}