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net: use contexts for cgo-based DNS resolution

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Although calls to getaddrinfo can't be portably interrupted,
we still benefit from more granular resource management by
pushing the context downwards.

Fixes #15321

Change-Id: I5506195fc6493080410e3d46aaa3fe02018a24fe
Reviewed-on: https://go-review.googlesource.com/22961
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Scott Bell 2016-05-08 18:17:59 -07:00 committed by Brad Fitzpatrick
parent 9edb27e76f
commit 636670b8db
5 changed files with 180 additions and 46 deletions
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12
src/net/cgo_stub.go
View File

@ -6,6 +6,8 @@
package net
import "context"
func init() { netGo = true }
type addrinfoErrno int
@ -14,22 +16,22 @@ func (eai addrinfoErrno) Error() string { return "<nil>" }
func (eai addrinfoErrno) Temporary() bool { return false }
func (eai addrinfoErrno) Timeout() bool { return false }
func cgoLookupHost(name string) (addrs []string, err error, completed bool) {
func cgoLookupHost(ctx context.Context, name string) (addrs []string, err error, completed bool) {
return nil, nil, false
}
func cgoLookupPort(network, service string) (port int, err error, completed bool) {
func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
return 0, nil, false
}
func cgoLookupIP(name string) (addrs []IPAddr, err error, completed bool) {
func cgoLookupIP(ctx context.Context, name string) (addrs []IPAddr, err error, completed bool) {
return nil, nil, false
}
func cgoLookupCNAME(name string) (cname string, err error, completed bool) {
func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
return "", nil, false
}
func cgoLookupPTR(addr string) (ptrs []string, err error, completed bool) {
func cgoLookupPTR(ctx context.Context, addr string) (ptrs []string, err error, completed bool) {
return nil, nil, false
}

136
src/net/cgo_unix.go
View File

@ -19,6 +19,7 @@ package net
import "C"
import (
"context"
"syscall"
"unsafe"
)
@ -32,18 +33,31 @@ func (eai addrinfoErrno) Error() string { return C.GoString(C.gai_strerror(C.i
func (eai addrinfoErrno) Temporary() bool { return eai == C.EAI_AGAIN }
func (eai addrinfoErrno) Timeout() bool { return false }
func cgoLookupHost(name string) (hosts []string, err error, completed bool) {
addrs, err, completed := cgoLookupIP(name)
type portLookupResult struct {
port int
err error
}
type ipLookupResult struct {
addrs []IPAddr
cname string
err error
}
type reverseLookupResult struct {
names []string
err error
}
func cgoLookupHost(ctx context.Context, name string) (hosts []string, err error, completed bool) {
addrs, err, completed := cgoLookupIP(ctx, name)
for _, addr := range addrs {
hosts = append(hosts, addr.String())
}
return
}
func cgoLookupPort(network, service string) (port int, err error, completed bool) {
acquireThread()
defer releaseThread()
func cgoLookupPort(ctx context.Context, network, service string) (port int, err error, completed bool) {
var hints C.struct_addrinfo
switch network {
case "": // no hints
@ -64,11 +78,27 @@ func cgoLookupPort(network, service string) (port int, err error, completed bool
hints.ai_family = C.AF_INET6
}
}
if ctx.Done() == nil {
port, err := cgoLookupServicePort(&hints, network, service)
return port, err, true
}
result := make(chan portLookupResult, 1)
go cgoPortLookup(result, &hints, network, service)
select {
case r := <-result:
return r.port, r.err, true
case <-ctx.Done():
// Since there isn't a portable way to cancel the lookup,
// we just let it finish and write to the buffered channel.
return 0, mapErr(ctx.Err()), false
}
}
func cgoLookupServicePort(hints *C.struct_addrinfo, network, service string) (port int, err error) {
s := C.CString(service)
var res *C.struct_addrinfo
defer C.free(unsafe.Pointer(s))
gerrno, err := C.getaddrinfo(nil, s, &hints, &res)
gerrno, err := C.getaddrinfo(nil, s, hints, &res)
if gerrno != 0 {
switch gerrno {
case C.EAI_SYSTEM:
@ -78,7 +108,7 @@ func cgoLookupPort(network, service string) (port int, err error, completed bool
default:
err = addrinfoErrno(gerrno)
}
return 0, &DNSError{Err: err.Error(), Name: network + "/" + service}, true
return 0, &DNSError{Err: err.Error(), Name: network + "/" + service}
}
defer C.freeaddrinfo(res)
@ -87,17 +117,22 @@ func cgoLookupPort(network, service string) (port int, err error, completed bool
case C.AF_INET:
sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.ai_addr))
p := (*[2]byte)(unsafe.Pointer(&sa.Port))
return int(p[0])<<8 | int(p[1]), nil, true
return int(p[0])<<8 | int(p[1]), nil
case C.AF_INET6:
sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.ai_addr))
p := (*[2]byte)(unsafe.Pointer(&sa.Port))
return int(p[0])<<8 | int(p[1]), nil, true
return int(p[0])<<8 | int(p[1]), nil
}
}
return 0, &DNSError{Err: "unknown port", Name: network + "/" + service}, true
return 0, &DNSError{Err: "unknown port", Name: network + "/" + service}
}
func cgoLookupIPCNAME(name string) (addrs []IPAddr, cname string, err error, completed bool) {
func cgoPortLookup(result chan<- portLookupResult, hints *C.struct_addrinfo, network, service string) {
port, err := cgoLookupServicePort(hints, network, service)
result <- portLookupResult{port, err}
}
func cgoLookupIPCNAME(name string) (addrs []IPAddr, cname string, err error) {
acquireThread()
defer releaseThread()
@ -127,7 +162,7 @@ func cgoLookupIPCNAME(name string) (addrs []IPAddr, cname string, err error, com
default:
err = addrinfoErrno(gerrno)
}
return nil, "", &DNSError{Err: err.Error(), Name: name}, true
return nil, "", &DNSError{Err: err.Error(), Name: name}
}
defer C.freeaddrinfo(res)
@ -156,17 +191,42 @@ func cgoLookupIPCNAME(name string) (addrs []IPAddr, cname string, err error, com
addrs = append(addrs, addr)
}
}
return addrs, cname, nil, true
return addrs, cname, nil
}
func cgoLookupIP(name string) (addrs []IPAddr, err error, completed bool) {
addrs, _, err, completed = cgoLookupIPCNAME(name)
return
func cgoIPLookup(result chan<- ipLookupResult, name string) {
addrs, cname, err := cgoLookupIPCNAME(name)
result <- ipLookupResult{addrs, cname, err}
}
func cgoLookupCNAME(name string) (cname string, err error, completed bool) {
_, cname, err, completed = cgoLookupIPCNAME(name)
return
func cgoLookupIP(ctx context.Context, name string) (addrs []IPAddr, err error, completed bool) {
if ctx.Done() == nil {
addrs, _, err = cgoLookupIPCNAME(name)
return addrs, err, true
}
result := make(chan ipLookupResult, 1)
go cgoIPLookup(result, name)
select {
case r := <-result:
return r.addrs, r.err, true
case <-ctx.Done():
return nil, mapErr(ctx.Err()), false
}
}
func cgoLookupCNAME(ctx context.Context, name string) (cname string, err error, completed bool) {
if ctx.Done() == nil {
_, cname, err = cgoLookupIPCNAME(name)
return cname, err, true
}
result := make(chan ipLookupResult, 1)
go cgoIPLookup(result, name)
select {
case r := <-result:
return r.cname, r.err, true
case <-ctx.Done():
return "", mapErr(ctx.Err()), false
}
}
// These are roughly enough for the following:
@ -182,10 +242,7 @@ const (
maxNameinfoLen = 4096
)
func cgoLookupPTR(addr string) ([]string, error, bool) {
acquireThread()
defer releaseThread()
func cgoLookupPTR(ctx context.Context, addr string) (names []string, err error, completed bool) {
var zone string
ip := parseIPv4(addr)
if ip == nil {
@ -198,9 +255,26 @@ func cgoLookupPTR(addr string) ([]string, error, bool) {
if sa == nil {
return nil, &DNSError{Err: "invalid address " + ip.String(), Name: addr}, true
}
var err error
var b []byte
if ctx.Done() == nil {
names, err := cgoLookupAddrPTR(addr, sa, salen)
return names, err, true
}
result := make(chan reverseLookupResult, 1)
go cgoReverseLookup(result, addr, sa, salen)
select {
case r := <-result:
return r.names, r.err, true
case <-ctx.Done():
return nil, mapErr(ctx.Err()), false
}
}
func cgoLookupAddrPTR(addr string, sa *C.struct_sockaddr, salen C.socklen_t) (names []string, err error) {
acquireThread()
defer releaseThread()
var gerrno int
var b []byte
for l := nameinfoLen; l <= maxNameinfoLen; l *= 2 {
b = make([]byte, l)
gerrno, err = cgoNameinfoPTR(b, sa, salen)
@ -217,16 +291,20 @@ func cgoLookupPTR(addr string) ([]string, error, bool) {
default:
err = addrinfoErrno(gerrno)
}
return nil, &DNSError{Err: err.Error(), Name: addr}, true
return nil, &DNSError{Err: err.Error(), Name: addr}
}
for i := 0; i < len(b); i++ {
if b[i] == 0 {
b = b[:i]
break
}
}
return []string{absDomainName(b)}, nil, true
return []string{absDomainName(b)}, nil
}
func cgoReverseLookup(result chan<- reverseLookupResult, addr string, sa *C.struct_sockaddr, salen C.socklen_t) {
names, err := cgoLookupAddrPTR(addr, sa, salen)
result <- reverseLookupResult{names, err}
}
func cgoSockaddr(ip IP, zone string) (*C.struct_sockaddr, C.socklen_t) {

61
src/net/cgo_unix_test.go
View File

@ -13,15 +13,70 @@ import (
)
func TestCgoLookupIP(t *testing.T) {
host := "localhost"
_, err, ok := cgoLookupIP(host)
ctx := context.Background()
_, err, ok := cgoLookupIP(ctx, "localhost")
if !ok {
t.Errorf("cgoLookupIP must not be a placeholder")
}
if err != nil {
t.Error(err)
}
if _, err := goLookupIP(context.Background(), host); err != nil {
}
func TestCgoLookupIPWithCancel(t *testing.T) {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
_, err, ok := cgoLookupIP(ctx, "localhost")
if !ok {
t.Errorf("cgoLookupIP must not be a placeholder")
}
if err != nil {
t.Error(err)
}
}
func TestCgoLookupPort(t *testing.T) {
ctx := context.Background()
_, err, ok := cgoLookupPort(ctx, "tcp", "smtp")
if !ok {
t.Errorf("cgoLookupPort must not be a placeholder")
}
if err != nil {
t.Error(err)
}
}
func TestCgoLookupPortWithCancel(t *testing.T) {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
_, err, ok := cgoLookupPort(ctx, "tcp", "smtp")
if !ok {
t.Errorf("cgoLookupPort must not be a placeholder")
}
if err != nil {
t.Error(err)
}
}
func TestCgoLookupPTR(t *testing.T) {
ctx := context.Background()
_, err, ok := cgoLookupPTR(ctx, "127.0.0.1")
if !ok {
t.Errorf("cgoLookupPTR must not be a placeholder")
}
if err != nil {
t.Error(err)
}
}
func TestCgoLookupPTRWithCancel(t *testing.T) {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
_, err, ok := cgoLookupPTR(ctx, "127.0.0.1")
if !ok {
t.Errorf("cgoLookupPTR must not be a placeholder")
}
if err != nil {
t.Error(err)
}
}

12
src/net/lookup_unix.go
View File

@ -55,7 +55,7 @@ func lookupProtocol(_ context.Context, name string) (int, error) {
func lookupHost(ctx context.Context, host string) (addrs []string, err error) {
order := systemConf().hostLookupOrder(host)
if order == hostLookupCgo {
if addrs, err, ok := cgoLookupHost(host); ok {
if addrs, err, ok := cgoLookupHost(ctx, host); ok {
return addrs, err
}
// cgo not available (or netgo); fall back to Go's DNS resolver
@ -67,8 +67,7 @@ func lookupHost(ctx context.Context, host string) (addrs []string, err error) {
func lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) {
order := systemConf().hostLookupOrder(host)
if order == hostLookupCgo {
// TODO(bradfitz): push down ctx, or at least its deadline to start
if addrs, err, ok := cgoLookupIP(host); ok {
if addrs, err, ok := cgoLookupIP(ctx, host); ok {
return addrs, err
}
// cgo not available (or netgo); fall back to Go's DNS resolver
@ -84,7 +83,7 @@ func lookupPort(ctx context.Context, network, service string) (int, error) {
// files might be on a remote filesystem, though. This should
// probably race goroutines if ctx != context.Background().
if systemConf().canUseCgo() {
if port, err, ok := cgoLookupPort(network, service); ok {
if port, err, ok := cgoLookupPort(ctx, network, service); ok {
return port, err
}
}
@ -93,8 +92,7 @@ func lookupPort(ctx context.Context, network, service string) (int, error) {
func lookupCNAME(ctx context.Context, name string) (string, error) {
if systemConf().canUseCgo() {
// TODO: use ctx. issue 15321. Or race goroutines.
if cname, err, ok := cgoLookupCNAME(name); ok {
if cname, err, ok := cgoLookupCNAME(ctx, name); ok {
return cname, err
}
}
@ -161,7 +159,7 @@ func lookupTXT(ctx context.Context, name string) ([]string, error) {
func lookupAddr(ctx context.Context, addr string) ([]string, error) {
if systemConf().canUseCgo() {
if ptrs, err, ok := cgoLookupPTR(addr); ok {
if ptrs, err, ok := cgoLookupPTR(ctx, addr); ok {
return ptrs, err
}
}

5
src/net/netgo_unix_test.go
View File

@ -14,14 +14,15 @@ import (
func TestGoLookupIP(t *testing.T) {
host := "localhost"
_, err, ok := cgoLookupIP(host)
ctx := context.Background()
_, err, ok := cgoLookupIP(ctx, host)
if ok {
t.Errorf("cgoLookupIP must be a placeholder")
}
if err != nil {
t.Error(err)
}
if _, err := goLookupIP(context.Background(), host); err != nil {
if _, err := goLookupIP(ctx, host); err != nil {
t.Error(err)
}
}