net: net remove completed return from cgo lookup functions

After CL 487196 there is no need anymore to return
completed == false from the cgo lookup functions and
then fallback to to go resolver.  (Before CL 487196 this
change would cause the (only?) tests to fail)
Now the cgoAvailable constant guards that correctly.

This change will cause a panic when the cgo resolver is being
used without the cgo support, so it will be easier to
detect bug while changing the code in the net package.

I am leaving the completed return from cgoLookupCNAME,
because it is super broken now.

Change-Id: I2661b9a3725de2b1a229847c12adf64b3f62b136
GitHub-Last-Rev: 2a6501a53e
GitHub-Pull-Request: golang/go#59925
Reviewed-on: https://go-review.googlesource.com/c/go/+/491275
Run-TryBot: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Mateusz Poliwczak <mpoliwczak34@gmail.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

src/net/cgo_stub.go

@@ -18,22 +18,22 @@ import "context"
 // is not available on this system.
 const cgoAvailable = false
 
-func cgoLookupHost(ctx context.Context, name string) (addrs []string, err error, completed bool) {
+func cgoLookupHost(ctx context.Context, name string) (addrs []string, err error) {
-	return nil, nil, false
+	panic("cgo stub: cgo not available")
 }
 
-func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
+func cgoLookupPort(ctx context.Context, network, service string) (port int, err error) {
-	return 0, nil, false
+	panic("cgo stub: cgo not available")
 }
 
-func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error, completed bool) {
+func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error) {
-	return nil, nil, false
+	panic("cgo stub: cgo not available")
 }
 
 func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
-	return "", nil, false
+	panic("cgo stub: cgo not available")
 }
 
-func cgoLookupPTR(ctx context.Context, addr string) (ptrs []string, err error, completed bool) {
+func cgoLookupPTR(ctx context.Context, addr string) (ptrs []string, err error) {
-	return nil, nil, false
+	panic("cgo stub: cgo not available")
 }

src/net/cgo_unix.go

@@ -66,15 +66,18 @@ func doBlockingWithCtx[T any](ctx context.Context, blocking func() (T, error)) (
 	}
 }
 
-func cgoLookupHost(ctx context.Context, name string) (hosts []string, err error, completed bool) {
+func cgoLookupHost(ctx context.Context, name string) (hosts []string, err error) {
-	addrs, err, completed := cgoLookupIP(ctx, "ip", name)
+	addrs, err := cgoLookupIP(ctx, "ip", name)
+	if err != nil {
+		return nil, err
+	}
 	for _, addr := range addrs {
 		hosts = append(hosts, addr.String())
 	}
-	return
+	return hosts, nil
 }
 
-func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
+func cgoLookupPort(ctx context.Context, network, service string) (port int, err error) {
 	var hints _C_struct_addrinfo
 	switch network {
 	case "": // no hints
@@ -85,7 +88,7 @@ func cgoLookupPort(ctx context.Context, network, service string) (port int, err
 		*_C_ai_socktype(&hints) = _C_SOCK_DGRAM
 		*_C_ai_protocol(&hints) = _C_IPPROTO_UDP
 	default:
-		return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}, true
+		return 0, &DNSError{Err: "unknown network", Name: network + "/" + service}
 	}
 	switch ipVersion(network) {
 	case '4':
@@ -94,10 +97,9 @@ func cgoLookupPort(ctx context.Context, network, service string) (port int, err
 		*_C_ai_family(&hints) = _C_AF_INET6
 	}
 
-	port, err = doBlockingWithCtx(ctx, func() (int, error) {
+	return doBlockingWithCtx(ctx, func() (int, error) {
 		return cgoLookupServicePort(&hints, network, service)
 	})
-	return port, err, true
 }
 
 func cgoLookupServicePort(hints *_C_struct_addrinfo, network, service string) (port int, err error) {
@@ -208,11 +210,10 @@ func cgoLookupHostIP(network, name string) (addrs []IPAddr, err error) {
 	return addrs, nil
 }
 
-func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error, completed bool) {
+func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error) {
-	addrs, err = doBlockingWithCtx(ctx, func() ([]IPAddr, error) {
+	return doBlockingWithCtx(ctx, func() ([]IPAddr, error) {
 		return cgoLookupHostIP(network, name)
 	})
-	return addrs, err, true
 }
 
 // These are roughly enough for the following:
@@ -228,20 +229,19 @@ const (
 	maxNameinfoLen = 4096
 )
 
-func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error, completed bool) {
+func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error) {
 	ip, err := netip.ParseAddr(addr)
 	if err != nil {
-		return nil, &DNSError{Err: "invalid address", Name: addr}, true
+		return nil, &DNSError{Err: "invalid address", Name: addr}
 	}
 	sa, salen := cgoSockaddr(IP(ip.AsSlice()), ip.Zone())
 	if sa == nil {
-		return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}, true
+		return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}
 	}
 
-	names, err = doBlockingWithCtx(ctx, func() ([]string, error) {
+	return doBlockingWithCtx(ctx, func() ([]string, error) {
 		return cgoLookupAddrPTR(addr, sa, salen)
 	})
-	return names, err, true
 }
 
 func cgoLookupAddrPTR(addr string, sa *_C_struct_sockaddr, salen _C_socklen_t) (names []string, err error) {

src/net/cgo_unix_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (cgo || darwin) && !netgo && unix
+//go:build !netgo && ((cgo && unix) || darwin)
 
 package net
 
@@ -14,10 +14,7 @@ import (
 func TestCgoLookupIP(t *testing.T) {
 	defer dnsWaitGroup.Wait()
 	ctx := context.Background()
-	_, err, ok := cgoLookupIP(ctx, "ip", "localhost")
+	_, err := cgoLookupIP(ctx, "ip", "localhost")
-	if !ok {
-		t.Errorf("cgoLookupIP must not be a placeholder")
-	}
 	if err != nil {
 		t.Error(err)
 	}
@@ -27,10 +24,7 @@ func TestCgoLookupIPWithCancel(t *testing.T) {
 	defer dnsWaitGroup.Wait()
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
-	_, err, ok := cgoLookupIP(ctx, "ip", "localhost")
+	_, err := cgoLookupIP(ctx, "ip", "localhost")
-	if !ok {
-		t.Errorf("cgoLookupIP must not be a placeholder")
-	}
 	if err != nil {
 		t.Error(err)
 	}
@@ -39,10 +33,7 @@ func TestCgoLookupIPWithCancel(t *testing.T) {
 func TestCgoLookupPort(t *testing.T) {
 	defer dnsWaitGroup.Wait()
 	ctx := context.Background()
-	_, err, ok := cgoLookupPort(ctx, "tcp", "smtp")
+	_, err := cgoLookupPort(ctx, "tcp", "smtp")
-	if !ok {
-		t.Errorf("cgoLookupPort must not be a placeholder")
-	}
 	if err != nil {
 		t.Error(err)
 	}
@@ -52,10 +43,7 @@ func TestCgoLookupPortWithCancel(t *testing.T) {
 	defer dnsWaitGroup.Wait()
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
-	_, err, ok := cgoLookupPort(ctx, "tcp", "smtp")
+	_, err := cgoLookupPort(ctx, "tcp", "smtp")
-	if !ok {
-		t.Errorf("cgoLookupPort must not be a placeholder")
-	}
 	if err != nil {
 		t.Error(err)
 	}
@@ -64,10 +52,7 @@ func TestCgoLookupPortWithCancel(t *testing.T) {
 func TestCgoLookupPTR(t *testing.T) {
 	defer dnsWaitGroup.Wait()
 	ctx := context.Background()
-	_, err, ok := cgoLookupPTR(ctx, "127.0.0.1")
+	_, err := cgoLookupPTR(ctx, "127.0.0.1")
-	if !ok {
-		t.Errorf("cgoLookupPTR must not be a placeholder")
-	}
 	if err != nil {
 		t.Error(err)
 	}
@@ -77,10 +62,7 @@ func TestCgoLookupPTRWithCancel(t *testing.T) {
 	defer dnsWaitGroup.Wait()
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
-	_, err, ok := cgoLookupPTR(ctx, "127.0.0.1")
+	_, err := cgoLookupPTR(ctx, "127.0.0.1")
-	if !ok {
-		t.Errorf("cgoLookupPTR must not be a placeholder")
-	}
 	if err != nil {
 		t.Error(err)
 	}

src/net/lookup_unix.go

@@ -56,11 +56,7 @@ func lookupProtocol(_ context.Context, name string) (int, error) {
 func (r *Resolver) lookupHost(ctx context.Context, host string) (addrs []string, err error) {
 	order, conf := systemConf().hostLookupOrder(r, host)
 	if order == hostLookupCgo {
-		if addrs, err, ok := cgoLookupHost(ctx, host); ok {
+		return cgoLookupHost(ctx, host)
-			return addrs, err
-		}
-		// cgo not available (or netgo); fall back to Go's DNS resolver
-		order = hostLookupFilesDNS
 	}
 	return r.goLookupHostOrder(ctx, host, order, conf)
 }
@@ -71,11 +67,7 @@ func (r *Resolver) lookupIP(ctx context.Context, network, host string) (addrs []
 	}
 	order, conf := systemConf().hostLookupOrder(r, host)
 	if order == hostLookupCgo {
-		if addrs, err, ok := cgoLookupIP(ctx, network, host); ok {
+		return cgoLookupIP(ctx, network, host)
-			return addrs, err
-		}
-		// cgo not available (or netgo); fall back to Go's DNS resolver
-		order = hostLookupFilesDNS
 	}
 	ips, _, err := r.goLookupIPCNAMEOrder(ctx, network, host, order, conf)
 	return ips, err
@@ -85,16 +77,15 @@ func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int
 	// Port lookup is not a DNS operation.
 	// Prefer the cgo resolver if possible.
 	if !systemConf().mustUseGoResolver(r) {
-		if port, err, ok := cgoLookupPort(ctx, network, service); ok {
+		port, err := cgoLookupPort(ctx, network, service)
-			if err != nil {
+		if err != nil {
-				// Issue 18213: if cgo fails, first check to see whether we
+			// Issue 18213: if cgo fails, first check to see whether we
-				// have the answer baked-in to the net package.
+			// have the answer baked-in to the net package.
-				if port, err := goLookupPort(network, service); err == nil {
+			if port, err := goLookupPort(network, service); err == nil {
-					return port, nil
+				return port, nil
-				}
 			}
-			return port, err
 		}
+		return port, err
 	}
 	return goLookupPort(network, service)
 }
@@ -128,9 +119,7 @@ func (r *Resolver) lookupTXT(ctx context.Context, name string) ([]string, error)
 func (r *Resolver) lookupAddr(ctx context.Context, addr string) ([]string, error) {
 	order, conf := systemConf().hostLookupOrder(r, "")
 	if order == hostLookupCgo {
-		if ptrs, err, ok := cgoLookupPTR(ctx, addr); ok {
+		return cgoLookupPTR(ctx, addr)
-			return ptrs, err
-		}
 	}
 	return r.goLookupPTR(ctx, addr, conf)
 }

src/net/netgo_unix_test.go

@@ -1,28 +0,0 @@
-// Copyright 2013 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build (!cgo || netgo) && (dragonfly || freebsd || linux || netbsd || openbsd || solaris)
-
-package net
-
-import (
-	"context"
-	"testing"
-)
-
-func TestGoLookupIP(t *testing.T) {
-	defer dnsWaitGroup.Wait()
-	host := "localhost"
-	ctx := context.Background()
-	_, err, ok := cgoLookupIP(ctx, "ip", host)
-	if ok {
-		t.Errorf("cgoLookupIP must be a placeholder")
-	}
-	if err != nil {
-		t.Error(err)
-	}
-	if _, err := DefaultResolver.goLookupIP(ctx, "ip", host); err != nil {
-		t.Error(err)
-	}
-}