net: properly wrap error and return DNSError consistently

src/net/cgo_unix.go

@@ -47,11 +47,7 @@ func (eai addrinfoErrno) isAddrinfoErrno() {}
 func doBlockingWithCtx[T any](ctx context.Context, lookupName string, blocking func() (T, error)) (T, error) {
 	if err := acquireThread(ctx); err != nil {
 		var zero T
-		return zero, &DNSError{
+		return zero, newDNSError(mapErr(err), lookupName, "")
-			Name:      lookupName,
-			Err:       mapErr(err).Error(),
-			IsTimeout: err == context.DeadlineExceeded,
-		}
 	}
 
 	if ctx.Done() == nil {
@@ -77,11 +73,7 @@ func doBlockingWithCtx[T any](ctx context.Context, lookupName string, blocking f
 		return r.res, r.err
 	case <-ctx.Done():
 		var zero T
-		return zero, &DNSError{
+		return zero, newDNSError(mapErr(ctx.Err()), lookupName, "")
-			Name:      lookupName,
-			Err:       mapErr(ctx.Err()).Error(),
-			IsTimeout: ctx.Err() == context.DeadlineExceeded,
-		}
 	}
 }
 

src/net/ipsock_plan9.go

@@ -10,6 +10,7 @@ import (
 	"internal/itoa"
 	"io/fs"
 	"os"
+	"strconv"
 	"syscall"
 )
 
@@ -128,6 +129,7 @@ func startPlan9(ctx context.Context, net string, addr Addr) (ctl *os.File, dest,
 
 	clone, dest, err := queryCS1(ctx, proto, ip, port)
 	if err != nil {
+		err = handlePlan9DNSError(err, net+":"+ip.String()+":"+strconv.Itoa(port))
 		return
 	}
 	f, err := os.OpenFile(clone, os.O_RDWR, 0)

src/net/lookup_plan9.go

@@ -65,11 +65,7 @@ func query(ctx context.Context, filename, query string, bufSize int) (addrs []st
 	case r := <-ch:
 		return r.addrs, r.err
 	case <-ctx.Done():
-		return nil, &DNSError{
+		return nil, mapErr(err)
-			Name:      query,
-			Err:       ctx.Err().Error(),
-			IsTimeout: ctx.Err() == context.DeadlineExceeded,
-		}
 	}
 }
 
@@ -143,7 +139,7 @@ func toLower(in string) string {
 func lookupProtocol(ctx context.Context, name string) (proto int, err error) {
 	lines, err := query(ctx, netdir+"/cs", "!protocol="+toLower(name), 128)
 	if err != nil {
-		return 0, err
+		return 0, newDNSError(err, name, "")
 	}
 	if len(lines) == 0 {
 		return 0, UnknownNetworkError(name)
@@ -229,16 +225,16 @@ func (*Resolver) lookupPortWithNetwork(ctx context.Context, network, errNetwork,
 	lines, err := queryCS(ctx, network, "127.0.0.1", toLower(service))
 	if err != nil {
 		if stringslite.HasSuffix(err.Error(), "can't translate service") {
-			return 0, &DNSError{Err: "unknown port", Name: errNetwork + "/" + service, IsNotFound: true}
+			return 0, newDNSError(errUnknownPort, errNetwork+"/"+service, "")
 		}
-		return
+		return 0, newDNSError(err, errNetwork+"/"+service, "")
 	}
 	if len(lines) == 0 {
-		return 0, &DNSError{Err: "unknown port", Name: errNetwork + "/" + service, IsNotFound: true}
+		return 0, newDNSError(errUnknownPort, errNetwork+"/"+service, "")
 	}
 	f := getFields(lines[0])
 	if len(f) < 2 {
-		return 0, &DNSError{Err: "unknown port", Name: errNetwork + "/" + service, IsNotFound: true}
+		return 0, newDNSError(errUnknownPort, errNetwork+"/"+service, "")
 	}
 	s := f[1]
 	if i := bytealg.IndexByteString(s, '!'); i >= 0 {
@@ -247,7 +243,7 @@ func (*Resolver) lookupPortWithNetwork(ctx context.Context, network, errNetwork,
 	if n, _, ok := dtoi(s); ok {
 		return n, nil
 	}
-	return 0, &DNSError{Err: "unknown port", Name: errNetwork + "/" + service, IsNotFound: true}
+	return 0, newDNSError(errUnknownPort, errNetwork+"/"+service, "")
 }
 
 func (r *Resolver) lookupCNAME(ctx context.Context, name string) (cname string, err error) {
@@ -269,7 +265,7 @@ func (r *Resolver) lookupCNAME(ctx context.Context, name string) (cname string,
 			return f[2] + ".", nil
 		}
 	}
-	return "", errors.New("bad response from ndb/dns")
+	return "", &DNSError{Err: "bad response from ndb/dns", Name: name}
 }
 
 func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error) {

src/net/lookup_windows.go

@@ -77,7 +77,7 @@ func lookupProtocol(ctx context.Context, name string) (int, error) {
 		}
 		return r.proto, r.err
 	case <-ctx.Done():
-		return 0, mapErr(ctx.Err())
+		return 0, newDNSError(mapErr(ctx.Err()), name, "")
 	}
 }
 
@@ -110,11 +110,7 @@ func (r *Resolver) lookupIP(ctx context.Context, network, name string) ([]IPAddr
 
 	getaddr := func() ([]IPAddr, error) {
 		if err := acquireThread(ctx); err != nil {
-			return nil, &DNSError{
+			return nil, newDNSError(mapErr(err), name, "")
-				Name:      name,
-				Err:       mapErr(err).Error(),
-				IsTimeout: ctx.Err() == context.DeadlineExceeded,
-			}
 		}
 		defer releaseThread()
 		hints := syscall.AddrinfoW{
@@ -197,11 +193,7 @@ func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int
 
 	// TODO(bradfitz): finish ctx plumbing
 	if err := acquireThread(ctx); err != nil {
-		return 0, &DNSError{
+		return 0, newDNSError(mapErr(err), network+"/"+service, "")
-			Name:      network + "/" + service,
-			Err:       mapErr(err).Error(),
-			IsTimeout: ctx.Err() == context.DeadlineExceeded,
-		}
 	}
 	defer releaseThread()
 
@@ -265,11 +257,7 @@ func (r *Resolver) lookupCNAME(ctx context.Context, name string) (string, error)
 
 	// TODO(bradfitz): finish ctx plumbing
 	if err := acquireThread(ctx); err != nil {
-		return "", &DNSError{
+		return "", newDNSError(mapErr(err), name, "")
-			Name:      name,
-			Err:       mapErr(err).Error(),
-			IsTimeout: ctx.Err() == context.DeadlineExceeded,
-		}
 	}
 	defer releaseThread()
 	var rec *syscall.DNSRecord
@@ -295,11 +283,7 @@ func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (
 	}
 	// TODO(bradfitz): finish ctx plumbing
 	if err := acquireThread(ctx); err != nil {
-		return "", nil, &DNSError{
+		return "", nil, newDNSError(mapErr(err), name, "")
-			Name:      name,
-			Err:       mapErr(err).Error(),
-			IsTimeout: ctx.Err() == context.DeadlineExceeded,
-		}
 	}
 	defer releaseThread()
 	var target string
@@ -330,11 +314,7 @@ func (r *Resolver) lookupMX(ctx context.Context, name string) ([]*MX, error) {
 	}
 	// TODO(bradfitz): finish ctx plumbing.
 	if err := acquireThread(ctx); err != nil {
-		return nil, &DNSError{
+		return nil, newDNSError(mapErr(err), name, "")
-			Name:      name,
-			Err:       mapErr(err).Error(),
-			IsTimeout: ctx.Err() == context.DeadlineExceeded,
-		}
 	}
 	defer releaseThread()
 	var rec *syscall.DNSRecord
@@ -359,11 +339,7 @@ func (r *Resolver) lookupNS(ctx context.Context, name string) ([]*NS, error) {
 	}
 	// TODO(bradfitz): finish ctx plumbing.
 	if err := acquireThread(ctx); err != nil {
-		return nil, &DNSError{
+		return nil, newDNSError(mapErr(err), name, "")
-			Name:      name,
-			Err:       mapErr(err).Error(),
-			IsTimeout: ctx.Err() == context.DeadlineExceeded,
-		}
 	}
 	defer releaseThread()
 	var rec *syscall.DNSRecord
@@ -387,11 +363,7 @@ func (r *Resolver) lookupTXT(ctx context.Context, name string) ([]string, error)
 	}
 	// TODO(bradfitz): finish ctx plumbing.
 	if err := acquireThread(ctx); err != nil {
-		return nil, &DNSError{
+		return nil, newDNSError(mapErr(err), name, "")
-			Name:      name,
-			Err:       mapErr(err).Error(),
-			IsTimeout: ctx.Err() == context.DeadlineExceeded,
-		}
 	}
 	defer releaseThread()
 	var rec *syscall.DNSRecord
@@ -420,11 +392,7 @@ func (r *Resolver) lookupAddr(ctx context.Context, addr string) ([]string, error
 
 	// TODO(bradfitz): finish ctx plumbing.
 	if err := acquireThread(ctx); err != nil {
-		return nil, &DNSError{
+		return nil, newDNSError(mapErr(err), addr, "")
-			Name:      addr,
-			Err:       mapErr(err).Error(),
-			IsTimeout: ctx.Err() == context.DeadlineExceeded,
-		}
 	}
 	defer releaseThread()
 	arpa, err := reverseaddr(addr)