Pull request: 2704 local resolvers vol.1

Merge in DNS/adguard-home from 2704-local-addresses-vol.1 to master Updates #2704. Updates #2829. Updates #2846. Squashed commit of the following: commit 9a49b3d27edcb30da7f16a065226907833b1dc81 Author: Eugene Burkov <e.burkov@adguard.com> Date: Mon Mar 22 15:39:17 2021 +0300 aghnet: imp docs and logging commit 74f95a29c55b9e732276601b0ecc63fb7c3a9f9e Author: Eugene Burkov <e.burkov@adguard.com> Date: Fri Mar 19 20:56:51 2021 +0300 all: fix friday evening mistakes commit 0e2066bc5c16ed807fa601780b99e154502361a9 Author: Eugene Burkov <e.burkov@adguard.com> Date: Fri Mar 19 20:51:15 2021 +0300 all: upd testify, imp code quality commit 8237c50b670c58361ccf7adec3ff2452b1196677 Author: Eugene Burkov <e.burkov@adguard.com> Date: Fri Mar 19 20:19:29 2021 +0300 aghnet: imp test naming commit 14eb1e189339554c0a6d38e2ba7a93917774ebab Author: Eugene Burkov <e.burkov@adguard.com> Date: Fri Mar 19 19:41:43 2021 +0300 aghnet: isolate windows-specific functionality commit d461ac8b18c187999da3e3aba116571b7ebe6785 Author: Eugene Burkov <e.burkov@adguard.com> Date: Fri Mar 19 14:50:05 2021 +0300 aghnet: imp code quality commit d0ee01cb1f8613de2085c0f2f2f396e46beb52a5 Author: Eugene Burkov <e.burkov@adguard.com> Date: Fri Mar 19 11:59:10 2021 +0300 all: mv funcs to agherr, mk system resolvers getter
2021-03-22 16:46:36 +03:00
parent eb9526cc92
commit 3b2f5d7842
19 changed files with 568 additions and 48 deletions
--- a/internal/aghnet/systemresolvers_windows.go
+++ b/internal/aghnet/systemresolvers_windows.go
@@ -0,0 +1,158 @@
+// +build windows
+
+package aghnet
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net"
+	"os/exec"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/AdguardTeam/AdGuardHome/internal/agherr"
+	"github.com/AdguardTeam/AdGuardHome/internal/aghio"
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// systemResolvers implementation differs for Windows since Go's resolver
+// doesn't work there.
+//
+// See https://github.com/golang/go/issues/33097.
+type systemResolvers struct {
+	// addrs is the slice of cached local resolvers' addresses.
+	addrs     []string
+	addrsLock sync.RWMutex
+}
+
+func newSystemResolvers(refreshIvl time.Duration, _ HostGenFunc) (sr SystemResolvers) {
+	return &systemResolvers{}
+}
+
+func (sr *systemResolvers) Get() (rs []string) {
+	sr.addrsLock.RLock()
+	defer sr.addrsLock.RUnlock()
+
+	addrs := sr.addrs
+	rs = make([]string, len(addrs))
+	copy(rs, addrs)
+
+	return rs
+}
+
+// getAddrs gets local resolvers' addresses from OS in a special Windows way.
+//
+// TODO(e.burkov): This whole function needs more detailed research on getting
+// local resolvers addresses on Windows.  We execute the external command for
+// now that is not the most accurate way.
+func (sr *systemResolvers) getAddrs() (addrs []string, err error) {
+	cmd := exec.Command("nslookup")
+
+	var stdin io.WriteCloser
+	stdin, err = cmd.StdinPipe()
+	if err != nil {
+		return nil, fmt.Errorf("getting the command's stdin pipe: %w", err)
+	}
+
+	var stdout io.ReadCloser
+	stdout, err = cmd.StdoutPipe()
+	if err != nil {
+		return nil, fmt.Errorf("getting the command's stdout pipe: %w", err)
+	}
+
+	var stdoutLimited io.ReadCloser
+	stdoutLimited, err = aghio.LimitReadCloser(stdout, aghos.MaxCmdOutputSize)
+	if err != nil {
+		return nil, fmt.Errorf("limiting stdout reader: %w", err)
+	}
+
+	go func() {
+		defer agherr.LogPanic("systemResolvers")
+		defer func() {
+			derr := stdin.Close()
+			if derr != nil {
+				log.Error("systemResolvers: closing stdin pipe: %s", derr)
+			}
+		}()
+
+		_, werr := io.WriteString(stdin, "exit")
+		if werr != nil {
+			log.Error("systemResolvers: writing to command pipe: %s", werr)
+		}
+	}()
+
+	err = cmd.Start()
+	if err != nil {
+		return nil, fmt.Errorf("start command executing: %w", err)
+	}
+
+	// The output of nslookup looks like this:
+	//
+	// Default Server:  192-168-1-1.qualified.domain.ru
+	// Address:  192.168.1.1
+
+	var possibleIPs []string
+	s := bufio.NewScanner(stdoutLimited)
+	for s.Scan() {
+		line := s.Text()
+		if len(line) == 0 {
+			continue
+		}
+
+		fields := strings.Fields(line)
+		if len(fields) != 2 || fields[0] != "Address:" {
+			continue
+		}
+
+		// If the address contains port then it is separated with '#'.
+		ipStrs := strings.Split(fields[1], "#")
+		if len(ipStrs) == 0 {
+			continue
+		}
+
+		possibleIPs = append(possibleIPs, ipStrs[0])
+	}
+
+	err = cmd.Wait()
+	if err != nil {
+		return nil, fmt.Errorf("executing the command: %w", err)
+	}
+
+	// Don't close StdoutPipe since Wait do it for us in ¿most? cases.
+	//
+	// See go doc os/exec.Cmd.StdoutPipe.
+
+	for _, addr := range possibleIPs {
+		if net.ParseIP(addr) == nil {
+			log.Debug("systemResolvers: %q is not a valid ip", addr)
+
+			continue
+		}
+
+		addrs = append(addrs, addr)
+	}
+
+	return addrs, nil
+}
+
+func (sr *systemResolvers) Refresh() (err error) {
+	defer agherr.Annotate("systemResolvers: %w", &err)
+
+	got, err := sr.getAddrs()
+	if err != nil {
+		return fmt.Errorf("can't get addresses: %w", err)
+	}
+	if len(got) == 0 {
+		return nil
+	}
+
+	sr.addrsLock.Lock()
+	defer sr.addrsLock.Unlock()
+
+	sr.addrs = got
+
+	return nil
+}