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Commit d32ec38f authored by Russ Cox's avatar Russ Cox
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net: remove non-cgo macOS resolver code 

The built-in Go resolver works significantly better.
In particular, the use of res_search does not support
CNAME or PTR queries and may not even be thread-safe.

This CL is essentially a revert of CL 166297 plus fixes,
including CL 180842.

See CL 180842 for additional notes about problems
with this approach.

Fixes #31705.

Change-Id: I0a30a0de2fbd04f6c461520fd34378c84aadf66c
Reviewed-on: https://go-review.googlesource.com/c/go/+/180843
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: default avatarKeith Randall <khr@golang.org>
parent 705830e2
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src/net/cgo_darwin_stub.go deleted 100644 → 0
View file @ 705830e2
// Copyright 2019 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.
// This file is intended to be used in non-cgo builds of darwin binaries,
// in particular when cross-compiling a darwin binary from a non-darwin machine.
// All OS calls on darwin have to be done via C libraries, and this code makes such
// calls with the runtime's help. (It is a C call but does not require the cgo tool to
// be compiled, and as such it is possible to build even when cross-compiling.)
//
// The specific C library calls are to res_init and res_search from /usr/lib/system/libsystem_info.dylib.
// Unfortunately, an ordinary C program calling these names would actually end up with
// res_9_init and res_9_search from /usr/lib/libresolv.dylib, not libsystem_info.
// It may well be that the libsystem_info routines are completely unused on macOS systems
// except for this code. At the least, they have the following problems:
//
// - TypeALL requests do not work, so if we want both IPv4 and IPv6 addresses,
// we have to do two requests, one for TypeA and one for TypeAAAA.
// - TypeCNAME requests hang indefinitely.
// - TypePTR requests fail unconditionally.
// - Detailed error information is stored in the global h_errno value,
// which cannot be accessed safely (it is not per-thread like errno).
// - The routines may not be safe to call from multiple threads.
// If you run net.test under lldb, that emits syslog prints to stderr
// that suggest double-free problems. (If not running under lldb,
// it is unclear where the syslog prints go, if anywhere.)
//
// This code is marked for deletion. If it is to be revived, it should be changed to use
// res_9_init and res_9_search from libresolv and special care should be paid to
// error detail and thread safety.
// +build !netgo,!cgo
// +build darwin
package net
import (
"context"
"errors"
"sync"
"golang.org/x/net/dns/dnsmessage"
)
type addrinfoErrno int
func (eai addrinfoErrno) Error() string { return "<nil>" }
func (eai addrinfoErrno) Temporary() bool { return false }
func (eai addrinfoErrno) Timeout() bool { return false }
func cgoLookupHost(ctx context.Context, name string) (addrs []string, err error, completed bool) {
// The 4-suffix indicates IPv4, TypeA lookups.
// The 6-suffix indicates IPv6, TypeAAAA lookups.
// If resSearch is updated to call the libresolv res_9_search (see comment at top of file),
// it may be possible to make one call for TypeALL
// and get both address kinds out.
r4, err4 := resSearch(ctx, name, int32(dnsmessage.TypeA), int32(dnsmessage.ClassINET))
if err4 == nil {
addrs, err4 = appendHostsFromResources(addrs, r4)
}
r6, err6 := resSearch(ctx, name, int32(dnsmessage.TypeAAAA), int32(dnsmessage.ClassINET))
if err6 == nil {
addrs, err6 = appendHostsFromResources(addrs, r6)
}
if err4 != nil && err6 != nil {
return nil, err4, false
}
return addrs, nil, true
}
func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
port, err = goLookupPort(network, service) // we can just use netgo lookup
return port, err, err == nil
}
func cgoLookupIP(ctx context.Context, network, name string) (addrs []IPAddr, err error, completed bool) {
// The 4-suffix indicates IPv4, TypeA lookups.
// The 6-suffix indicates IPv6, TypeAAAA lookups.
// If resSearch is updated to call the libresolv res_9_search (see comment at top of file),
// it may be possible to make one call for TypeALL (when vers != '6' and vers != '4')
// and get both address kinds out.
var r4, r6 []dnsmessage.Resource
var err4, err6 error
vers := ipVersion(network)
if vers != '6' {
r4, err4 = resSearch(ctx, name, int32(dnsmessage.TypeA), int32(dnsmessage.ClassINET))
if err4 == nil {
addrs, err4 = appendIPsFromResources(addrs, r4)
}
}
if vers != '4' {
r6, err6 = resSearch(ctx, name, int32(dnsmessage.TypeAAAA), int32(dnsmessage.ClassINET))
if err6 == nil {
addrs, err6 = appendIPsFromResources(addrs, r6)
}
}
if err4 != nil && err6 != nil {
return nil, err4, false
}
return addrs, nil, true
}
func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
resources, err := resSearch(ctx, name, int32(dnsmessage.TypeCNAME), int32(dnsmessage.ClassINET))
if err != nil {
return
}
cname, err = parseCNAMEFromResources(resources)
if err != nil {
return "", err, false
}
return cname, nil, true
}
func cgoLookupPTR(ctx context.Context, addr string) (ptrs []string, err error, completed bool) {
resources, err := resSearch(ctx, addr, int32(dnsmessage.TypePTR), int32(dnsmessage.ClassINET))
if err != nil {
return
}
ptrs, err = parsePTRsFromResources(resources)
if err != nil {
return
}
return ptrs, nil, true
}
var (
resInitOnce sync.Once
resInitResult int32
)
// resSearch will make a call to the 'res_search' routine in libSystem
// and parse the output as a slice of resource resources which can then be parsed
func resSearch(ctx context.Context, hostname string, rtype, class int32) ([]dnsmessage.Resource, error) {
// We have to use res_init and res_search, but these do not set errno on failure.
// (They set h_errno, which is a global int shared by all threads and therefore
// racy to use.)
// https://opensource.apple.com/source/Libinfo/Libinfo-517.200.9/dns.subproj/res_query.c.auto.html
resInitOnce.Do(func() {
resInitResult = res_init()
})
if resInitResult < 0 {
return nil, errors.New("res_init failure")
}
// res_search does not set errno.
// It returns the size of the DNS response packet.
// But if the DNS response packet contains failure-like response codes,
// res_search returns -1 even though it has copied the packet into buf,
// giving us no way to find out how big the packet is.
// For now, we are willing to take res_search's word that there's nothing
// useful in the response, even though there *is* a response.
name := make([]byte, len(hostname)+1) // +1 for NUL at end for C
copy(name, hostname)
var buf [1024]byte
size, _ := res_search(&name[0], class, rtype, &buf[0], int32(len(buf)))
if size <= 0 {
return nil, errors.New("res_search failure")
}
var p dnsmessage.Parser
if _, err := p.Start(buf[:size]); err != nil {
return nil, err
}
p.SkipAllQuestions()
resources, err := p.AllAnswers()
if err != nil {
return nil, err
}
return resources, nil
}
func copyBytes(x []byte) []byte {
y := make([]byte, len(x))
copy(y, x)
return y
}
func appendHostsFromResources(answers []string, resources []dnsmessage.Resource) ([]string, error) {
for i := range resources {
switch resources[i].Header.Type {
case dnsmessage.TypeA:
b := resources[i].Body.(*dnsmessage.AResource)
answers = append(answers, IP(b.A[:]).String())
case dnsmessage.TypeAAAA:
b := resources[i].Body.(*dnsmessage.AAAAResource)
answers = append(answers, IP(b.AAAA[:]).String())
default:
return nil, errors.New("could not parse an A or AAAA response from message buffer")
}
}
return answers, nil
}
func appendIPsFromResources(answers []IPAddr, resources []dnsmessage.Resource) ([]IPAddr, error) {
for i := range resources {
switch resources[i].Header.Type {
case dnsmessage.TypeA:
b := resources[i].Body.(*dnsmessage.AResource)
answers = append(answers, IPAddr{IP: IP(copyBytes(b.A[:]))})
case dnsmessage.TypeAAAA:
b := resources[i].Body.(*dnsmessage.AAAAResource)
answers = append(answers, IPAddr{IP: IP(copyBytes(b.AAAA[:]))})
default:
return nil, errors.New("could not parse an A or AAAA response from message buffer")
}
}
return answers, nil
}
func parseCNAMEFromResources(resources []dnsmessage.Resource) (string, error) {
if len(resources) == 0 {
return "", errors.New("no CNAME record received")
}
c, ok := resources[0].Body.(*dnsmessage.CNAMEResource)
if !ok {
return "", errors.New("could not parse CNAME record")
}
return c.CNAME.String(), nil
}
func parsePTRsFromResources(resources []dnsmessage.Resource) ([]string, error) {
var answers []string
for i := range resources {
switch resources[i].Header.Type {
case dnsmessage.TypePTR:
p := resources[0].Body.(*dnsmessage.PTRResource)
answers = append(answers, p.PTR.String())
default:
return nil, errors.New("could not parse a PTR response from message buffer")
}
}
return answers, nil
}
// res_init and res_search are defined in runtime/lookup_darwin.go
func res_init() int32
func res_search(dname *byte, class int32, rtype int32, answer *byte, anslen int32) (int32, int32)
src/net/cgo_darwin_stub_test.go deleted 100644 → 0
View file @ 705830e2
// Copyright 2019 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.
// +build !netgo,!cgo
// +build darwin
package net
import (
"context"
"strings"
"testing"
)
func TestPseudoCgoLookupHost(t *testing.T) {
addrs, err, ok := cgoLookupHost(context.Background(), "google.com")
t.Logf("cgoLookupHost google.com: %v %v %v", addrs, err, ok)
if !ok {
t.Fatal("cgoLookupHost ok=false")
}
if err != nil {
t.Fatalf("cgoLookupHost: %v", err)
}
// cgoLookupHost need not return IPv4 before IPv6 in general,
// but for the current implementation it does.
// If that changes, this test will need updating.
if len(addrs) < 1 || strings.Count(addrs[0], ".") != 3 || !strings.Contains(addrs[len(addrs)-1], "::") {
t.Fatalf("cgoLookupHost google.com = %v, want IPv4 and IPv6", addrs)
}
}
func TestPseudoCgoLookupIP(t *testing.T) {
ips, err, ok := cgoLookupIP(context.Background(), "ip", "google.com")
t.Logf("cgoLookupIP google.com: %v %v %v", ips, err, ok)
if !ok {
t.Fatal("cgoLookupIP ok=false")
}
if err != nil {
t.Fatalf("cgoLookupIP: %v", err)
}
// cgoLookupIP need not return IPv4 before IPv6 in general,
// but for the current implementation it does.
// If that changes, this test will need updating.
if len(ips) < 1 || len(ips[0].IP) != 4 || len(ips[len(ips)-1].IP) != 16 {
t.Fatalf("cgoLookupIP google.com = %v, want IPv4 and IPv6", ips)
}
}
func TestPseudoCgoLookupCNAME(t *testing.T) {
t.Skip("res_search on macOS hangs in TypeCNAME queries (even in plain C programs)")
cname, err, ok := cgoLookupCNAME(context.Background(), "redirect.swtch.com")
t.Logf("cgoLookupCNAME redirect.swtch.com: %v %v %v", cname, err, ok)
if !ok {
t.Fatal("cgoLookupCNAME ok=false")
}
if err != nil {
t.Fatalf("cgoLookupCNAME: %v", err)
}
if !strings.HasSuffix(cname, ".com") {
t.Fatalf("cgoLookupCNAME redirect.swtch.com = %v, want *.com", cname)
}
}
func TestPseudoCgoLookupPTR(t *testing.T) {
t.Skip("res_search on macOS does not support TypePTR")
ptrs, err, ok := cgoLookupPTR(context.Background(), "8.8.8.8")
t.Logf("cgoLookupPTR 8.8.8.8: %v %v %v", ptrs, err, ok)
if !ok {
t.Fatal("cgoLookupPTR ok=false")
}
if err != nil {
t.Fatalf("cgoLookupPTR: %v", err)
}
if len(ptrs) < 1 || ptrs[0] != "google-public-dns-a.google.com" {
t.Fatalf("cgoLookupPTR = %v, want google-public-dns-a.google.com", ptrs)
}
}
src/net/cgo_stub.go
View file @ d32ec38f
......@@ -3,7 +3,6 @@
// license that can be found in the LICENSE file.
// +build !cgo netgo
// +build !darwin
package net
......
src/net/conf.go
View file @ d32ec38f
......@@ -70,11 +70,6 @@ func initConfVal() {
// their own DNS requests. So always use cgo instead, which
// avoids that.
if runtime.GOOS == "darwin" {
// Normally we force netGo to be true if building without cgo enabled.
// On Darwin, we can call libc even if cgo is not enabled, so only set netGo to true
// if explicitly requested.
confVal.netGo = dnsMode == "go"
confVal.forceCgoLookupHost = true
return
}
......
src/runtime/lookup_darwin.go deleted 100644 → 0
View file @ 705830e2
// Copyright 2019 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.
package runtime
import (
"unsafe"
)
//go:linkname res_init net.res_init
//go:nosplit
//go:cgo_unsafe_args
func res_init() int32 {
return libcCall(unsafe.Pointer(funcPC(res_init_trampoline)), nil)
}
func res_init_trampoline()
//go:linkname res_search net.res_search
//go:nosplit
//go:cgo_unsafe_args
func res_search(dname *byte, class int32, rtype int32, answer *byte, anslen int32) (int32, int32) {
args := struct {
dname *byte
class, rtype int32
answer *byte
anslen, retSize, retErr int32
}{dname, class, rtype, answer, anslen, 0, 0}
libcCall(unsafe.Pointer(funcPC(res_search_trampoline)), unsafe.Pointer(&args))
return args.retSize, args.retErr
}
func res_search_trampoline()
//go:cgo_import_dynamic libc_res_search res_search "/usr/lib/libSystem.B.dylib"
//go:cgo_import_dynamic libc_res_init res_init "/usr/lib/libSystem.B.dylib"
src/runtime/lookup_darwin_386.s deleted 100644 → 0
View file @ 705830e2
// Copyright 2019 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.
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
TEXT runtime·res_init_trampoline(SB),NOSPLIT,$0
PUSHL BP
MOVL SP, BP
SUBL $8, SP
CALL libc_res_init(SB)
CMPL AX, $-1
JNE ok
CALL libc_error(SB)
ok:
MOVL BP, SP
POPL BP
RET
TEXT runtime·res_search_trampoline(SB),NOSPLIT,$0
PUSHL BP
MOVL SP, BP
SUBL $24, SP
MOVL 32(SP), CX
MOVL 16(CX), AX // arg 5 anslen
MOVL AX, 16(SP)
MOVL 12(CX), AX // arg 4 answer
MOVL AX, 12(SP)
MOVL 8(CX), AX // arg 3 type
MOVL AX, 8(SP)
MOVL 4(CX), AX // arg 2 class
MOVL AX, 4(SP)
MOVL 0(CX), AX // arg 1 name
MOVL AX, 0(SP)
CALL libc_res_search(SB)
XORL DX, DX
CMPL AX, $-1
JNE ok
CALL libc_error(SB)
MOVL (AX), DX
XORL AX, AX
ok:
MOVL 32(SP), CX
MOVL AX, 20(CX)
MOVL DX, 24(CX)
MOVL BP, SP
POPL BP
RET
src/runtime/lookup_darwin_amd64.s deleted 100644 → 0
View file @ 705830e2
// Copyright 2019 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.
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
TEXT runtime·res_init_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
CALL libc_res_init(SB)
CMPL AX, $-1
JNE ok
CALL libc_error(SB)
ok:
POPQ BP
RET
TEXT runtime·res_search_trampoline(SB),NOSPLIT,$0
PUSHQ BP
MOVQ SP, BP
MOVQ DI, BX // move DI into BX to preserve struct addr
MOVL 24(BX), R8 // arg 5 anslen
MOVQ 16(BX), CX // arg 4 answer
MOVL 12(BX), DX // arg 3 type
MOVL 8(BX), SI // arg 2 class
MOVQ 0(BX), DI // arg 1 name
CALL libc_res_search(SB)
XORL DX, DX
CMPL AX, $-1
JNE ok
CALL libc_error(SB)
MOVLQSX (AX), DX // move return from libc_error into DX
XORL AX, AX // size on error is 0
ok:
MOVL AX, 28(BX) // size
MOVL DX, 32(BX) // error code
POPQ BP
RET
src/runtime/lookup_darwin_arm.s deleted 100644 → 0
View file @ 705830e2
// Copyright 2015 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.
// System calls and other sys.stuff for ARM64, Darwin
// System calls are implemented in libSystem, this file contains
// trampolines that convert from Go to C calling convention.
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
// On darwin/arm, the runtime always uses runtime/cgo
// for resolution. This will just exit with a nominal
// exit code.
TEXT runtime·res_search_trampoline(SB),NOSPLIT,$0
MOVW $90, R0
BL libc_exit(SB)
RET
TEXT runtime·res_init_trampoline(SB),NOSPLIT,$0
MOVW $91, R0
BL libc_exit(SB)
RET
src/runtime/lookup_darwin_arm64.s deleted 100644 → 0
View file @ 705830e2
// Copyright 2019 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.
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
// On darwin/arm, the runtime always uses runtime/cgo
// for resolution. This will just exit with a nominal
// exit code.
TEXT runtime·res_search_trampoline(SB),NOSPLIT,$0
MOVW $90, R0
BL libc_exit(SB)
RET
TEXT runtime·res_init_trampoline(SB),NOSPLIT,$0
MOVW $91, R0
BL libc_exit(SB)
RET
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