// +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 }