mirror of https://github.com/docker/cli.git
439 lines
12 KiB
Go
439 lines
12 KiB
Go
/*
|
|
*
|
|
* Copyright 2018 gRPC authors.
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*
|
|
*/
|
|
|
|
// Package dns implements a dns resolver to be installed as the default resolver
|
|
// in grpc.
|
|
package dns
|
|
|
|
import (
|
|
"context"
|
|
"encoding/json"
|
|
"errors"
|
|
"fmt"
|
|
"net"
|
|
"os"
|
|
"strconv"
|
|
"strings"
|
|
"sync"
|
|
"time"
|
|
|
|
"google.golang.org/grpc/grpclog"
|
|
"google.golang.org/grpc/internal/backoff"
|
|
"google.golang.org/grpc/internal/grpcrand"
|
|
"google.golang.org/grpc/resolver"
|
|
)
|
|
|
|
func init() {
|
|
resolver.Register(NewBuilder())
|
|
}
|
|
|
|
const (
|
|
defaultPort = "443"
|
|
defaultFreq = time.Minute * 30
|
|
defaultDNSSvrPort = "53"
|
|
golang = "GO"
|
|
// txtPrefix is the prefix string to be prepended to the host name for txt record lookup.
|
|
txtPrefix = "_grpc_config."
|
|
// In DNS, service config is encoded in a TXT record via the mechanism
|
|
// described in RFC-1464 using the attribute name grpc_config.
|
|
txtAttribute = "grpc_config="
|
|
)
|
|
|
|
var (
|
|
errMissingAddr = errors.New("dns resolver: missing address")
|
|
|
|
// Addresses ending with a colon that is supposed to be the separator
|
|
// between host and port is not allowed. E.g. "::" is a valid address as
|
|
// it is an IPv6 address (host only) and "[::]:" is invalid as it ends with
|
|
// a colon as the host and port separator
|
|
errEndsWithColon = errors.New("dns resolver: missing port after port-separator colon")
|
|
)
|
|
|
|
var (
|
|
defaultResolver netResolver = net.DefaultResolver
|
|
)
|
|
|
|
var customAuthorityDialler = func(authority string) func(ctx context.Context, network, address string) (net.Conn, error) {
|
|
return func(ctx context.Context, network, address string) (net.Conn, error) {
|
|
var dialer net.Dialer
|
|
return dialer.DialContext(ctx, network, authority)
|
|
}
|
|
}
|
|
|
|
var customAuthorityResolver = func(authority string) (netResolver, error) {
|
|
host, port, err := parseTarget(authority, defaultDNSSvrPort)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
authorityWithPort := net.JoinHostPort(host, port)
|
|
|
|
return &net.Resolver{
|
|
PreferGo: true,
|
|
Dial: customAuthorityDialler(authorityWithPort),
|
|
}, nil
|
|
}
|
|
|
|
// NewBuilder creates a dnsBuilder which is used to factory DNS resolvers.
|
|
func NewBuilder() resolver.Builder {
|
|
return &dnsBuilder{minFreq: defaultFreq}
|
|
}
|
|
|
|
type dnsBuilder struct {
|
|
// minimum frequency of polling the DNS server.
|
|
minFreq time.Duration
|
|
}
|
|
|
|
// Build creates and starts a DNS resolver that watches the name resolution of the target.
|
|
func (b *dnsBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOption) (resolver.Resolver, error) {
|
|
host, port, err := parseTarget(target.Endpoint, defaultPort)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// IP address.
|
|
if net.ParseIP(host) != nil {
|
|
host, _ = formatIP(host)
|
|
addr := []resolver.Address{{Addr: host + ":" + port}}
|
|
i := &ipResolver{
|
|
cc: cc,
|
|
ip: addr,
|
|
rn: make(chan struct{}, 1),
|
|
q: make(chan struct{}),
|
|
}
|
|
cc.NewAddress(addr)
|
|
go i.watcher()
|
|
return i, nil
|
|
}
|
|
|
|
// DNS address (non-IP).
|
|
ctx, cancel := context.WithCancel(context.Background())
|
|
d := &dnsResolver{
|
|
freq: b.minFreq,
|
|
backoff: backoff.Exponential{MaxDelay: b.minFreq},
|
|
host: host,
|
|
port: port,
|
|
ctx: ctx,
|
|
cancel: cancel,
|
|
cc: cc,
|
|
t: time.NewTimer(0),
|
|
rn: make(chan struct{}, 1),
|
|
disableServiceConfig: opts.DisableServiceConfig,
|
|
}
|
|
|
|
if target.Authority == "" {
|
|
d.resolver = defaultResolver
|
|
} else {
|
|
d.resolver, err = customAuthorityResolver(target.Authority)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
|
|
d.wg.Add(1)
|
|
go d.watcher()
|
|
return d, nil
|
|
}
|
|
|
|
// Scheme returns the naming scheme of this resolver builder, which is "dns".
|
|
func (b *dnsBuilder) Scheme() string {
|
|
return "dns"
|
|
}
|
|
|
|
type netResolver interface {
|
|
LookupHost(ctx context.Context, host string) (addrs []string, err error)
|
|
LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*net.SRV, err error)
|
|
LookupTXT(ctx context.Context, name string) (txts []string, err error)
|
|
}
|
|
|
|
// ipResolver watches for the name resolution update for an IP address.
|
|
type ipResolver struct {
|
|
cc resolver.ClientConn
|
|
ip []resolver.Address
|
|
// rn channel is used by ResolveNow() to force an immediate resolution of the target.
|
|
rn chan struct{}
|
|
q chan struct{}
|
|
}
|
|
|
|
// ResolveNow resend the address it stores, no resolution is needed.
|
|
func (i *ipResolver) ResolveNow(opt resolver.ResolveNowOption) {
|
|
select {
|
|
case i.rn <- struct{}{}:
|
|
default:
|
|
}
|
|
}
|
|
|
|
// Close closes the ipResolver.
|
|
func (i *ipResolver) Close() {
|
|
close(i.q)
|
|
}
|
|
|
|
func (i *ipResolver) watcher() {
|
|
for {
|
|
select {
|
|
case <-i.rn:
|
|
i.cc.NewAddress(i.ip)
|
|
case <-i.q:
|
|
return
|
|
}
|
|
}
|
|
}
|
|
|
|
// dnsResolver watches for the name resolution update for a non-IP target.
|
|
type dnsResolver struct {
|
|
freq time.Duration
|
|
backoff backoff.Exponential
|
|
retryCount int
|
|
host string
|
|
port string
|
|
resolver netResolver
|
|
ctx context.Context
|
|
cancel context.CancelFunc
|
|
cc resolver.ClientConn
|
|
// rn channel is used by ResolveNow() to force an immediate resolution of the target.
|
|
rn chan struct{}
|
|
t *time.Timer
|
|
// wg is used to enforce Close() to return after the watcher() goroutine has finished.
|
|
// Otherwise, data race will be possible. [Race Example] in dns_resolver_test we
|
|
// replace the real lookup functions with mocked ones to facilitate testing.
|
|
// If Close() doesn't wait for watcher() goroutine finishes, race detector sometimes
|
|
// will warns lookup (READ the lookup function pointers) inside watcher() goroutine
|
|
// has data race with replaceNetFunc (WRITE the lookup function pointers).
|
|
wg sync.WaitGroup
|
|
disableServiceConfig bool
|
|
}
|
|
|
|
// ResolveNow invoke an immediate resolution of the target that this dnsResolver watches.
|
|
func (d *dnsResolver) ResolveNow(opt resolver.ResolveNowOption) {
|
|
select {
|
|
case d.rn <- struct{}{}:
|
|
default:
|
|
}
|
|
}
|
|
|
|
// Close closes the dnsResolver.
|
|
func (d *dnsResolver) Close() {
|
|
d.cancel()
|
|
d.wg.Wait()
|
|
d.t.Stop()
|
|
}
|
|
|
|
func (d *dnsResolver) watcher() {
|
|
defer d.wg.Done()
|
|
for {
|
|
select {
|
|
case <-d.ctx.Done():
|
|
return
|
|
case <-d.t.C:
|
|
case <-d.rn:
|
|
}
|
|
result, sc := d.lookup()
|
|
// Next lookup should happen within an interval defined by d.freq. It may be
|
|
// more often due to exponential retry on empty address list.
|
|
if len(result) == 0 {
|
|
d.retryCount++
|
|
d.t.Reset(d.backoff.Backoff(d.retryCount))
|
|
} else {
|
|
d.retryCount = 0
|
|
d.t.Reset(d.freq)
|
|
}
|
|
d.cc.NewServiceConfig(sc)
|
|
d.cc.NewAddress(result)
|
|
}
|
|
}
|
|
|
|
func (d *dnsResolver) lookupSRV() []resolver.Address {
|
|
var newAddrs []resolver.Address
|
|
_, srvs, err := d.resolver.LookupSRV(d.ctx, "grpclb", "tcp", d.host)
|
|
if err != nil {
|
|
grpclog.Infof("grpc: failed dns SRV record lookup due to %v.\n", err)
|
|
return nil
|
|
}
|
|
for _, s := range srvs {
|
|
lbAddrs, err := d.resolver.LookupHost(d.ctx, s.Target)
|
|
if err != nil {
|
|
grpclog.Infof("grpc: failed load balancer address dns lookup due to %v.\n", err)
|
|
continue
|
|
}
|
|
for _, a := range lbAddrs {
|
|
a, ok := formatIP(a)
|
|
if !ok {
|
|
grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
|
|
continue
|
|
}
|
|
addr := a + ":" + strconv.Itoa(int(s.Port))
|
|
newAddrs = append(newAddrs, resolver.Address{Addr: addr, Type: resolver.GRPCLB, ServerName: s.Target})
|
|
}
|
|
}
|
|
return newAddrs
|
|
}
|
|
|
|
func (d *dnsResolver) lookupTXT() string {
|
|
ss, err := d.resolver.LookupTXT(d.ctx, txtPrefix+d.host)
|
|
if err != nil {
|
|
grpclog.Infof("grpc: failed dns TXT record lookup due to %v.\n", err)
|
|
return ""
|
|
}
|
|
var res string
|
|
for _, s := range ss {
|
|
res += s
|
|
}
|
|
|
|
// TXT record must have "grpc_config=" attribute in order to be used as service config.
|
|
if !strings.HasPrefix(res, txtAttribute) {
|
|
grpclog.Warningf("grpc: TXT record %v missing %v attribute", res, txtAttribute)
|
|
return ""
|
|
}
|
|
return strings.TrimPrefix(res, txtAttribute)
|
|
}
|
|
|
|
func (d *dnsResolver) lookupHost() []resolver.Address {
|
|
var newAddrs []resolver.Address
|
|
addrs, err := d.resolver.LookupHost(d.ctx, d.host)
|
|
if err != nil {
|
|
grpclog.Warningf("grpc: failed dns A record lookup due to %v.\n", err)
|
|
return nil
|
|
}
|
|
for _, a := range addrs {
|
|
a, ok := formatIP(a)
|
|
if !ok {
|
|
grpclog.Errorf("grpc: failed IP parsing due to %v.\n", err)
|
|
continue
|
|
}
|
|
addr := a + ":" + d.port
|
|
newAddrs = append(newAddrs, resolver.Address{Addr: addr})
|
|
}
|
|
return newAddrs
|
|
}
|
|
|
|
func (d *dnsResolver) lookup() ([]resolver.Address, string) {
|
|
newAddrs := d.lookupSRV()
|
|
// Support fallback to non-balancer address.
|
|
newAddrs = append(newAddrs, d.lookupHost()...)
|
|
if d.disableServiceConfig {
|
|
return newAddrs, ""
|
|
}
|
|
sc := d.lookupTXT()
|
|
return newAddrs, canaryingSC(sc)
|
|
}
|
|
|
|
// formatIP returns ok = false if addr is not a valid textual representation of an IP address.
|
|
// If addr is an IPv4 address, return the addr and ok = true.
|
|
// If addr is an IPv6 address, return the addr enclosed in square brackets and ok = true.
|
|
func formatIP(addr string) (addrIP string, ok bool) {
|
|
ip := net.ParseIP(addr)
|
|
if ip == nil {
|
|
return "", false
|
|
}
|
|
if ip.To4() != nil {
|
|
return addr, true
|
|
}
|
|
return "[" + addr + "]", true
|
|
}
|
|
|
|
// parseTarget takes the user input target string and default port, returns formatted host and port info.
|
|
// If target doesn't specify a port, set the port to be the defaultPort.
|
|
// If target is in IPv6 format and host-name is enclosed in square brackets, brackets
|
|
// are stripped when setting the host.
|
|
// examples:
|
|
// target: "www.google.com" defaultPort: "443" returns host: "www.google.com", port: "443"
|
|
// target: "ipv4-host:80" defaultPort: "443" returns host: "ipv4-host", port: "80"
|
|
// target: "[ipv6-host]" defaultPort: "443" returns host: "ipv6-host", port: "443"
|
|
// target: ":80" defaultPort: "443" returns host: "localhost", port: "80"
|
|
func parseTarget(target, defaultPort string) (host, port string, err error) {
|
|
if target == "" {
|
|
return "", "", errMissingAddr
|
|
}
|
|
if ip := net.ParseIP(target); ip != nil {
|
|
// target is an IPv4 or IPv6(without brackets) address
|
|
return target, defaultPort, nil
|
|
}
|
|
if host, port, err = net.SplitHostPort(target); err == nil {
|
|
if port == "" {
|
|
// If the port field is empty (target ends with colon), e.g. "[::1]:", this is an error.
|
|
return "", "", errEndsWithColon
|
|
}
|
|
// target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port
|
|
if host == "" {
|
|
// Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed.
|
|
host = "localhost"
|
|
}
|
|
return host, port, nil
|
|
}
|
|
if host, port, err = net.SplitHostPort(target + ":" + defaultPort); err == nil {
|
|
// target doesn't have port
|
|
return host, port, nil
|
|
}
|
|
return "", "", fmt.Errorf("invalid target address %v, error info: %v", target, err)
|
|
}
|
|
|
|
type rawChoice struct {
|
|
ClientLanguage *[]string `json:"clientLanguage,omitempty"`
|
|
Percentage *int `json:"percentage,omitempty"`
|
|
ClientHostName *[]string `json:"clientHostName,omitempty"`
|
|
ServiceConfig *json.RawMessage `json:"serviceConfig,omitempty"`
|
|
}
|
|
|
|
func containsString(a *[]string, b string) bool {
|
|
if a == nil {
|
|
return true
|
|
}
|
|
for _, c := range *a {
|
|
if c == b {
|
|
return true
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
func chosenByPercentage(a *int) bool {
|
|
if a == nil {
|
|
return true
|
|
}
|
|
return grpcrand.Intn(100)+1 <= *a
|
|
}
|
|
|
|
func canaryingSC(js string) string {
|
|
if js == "" {
|
|
return ""
|
|
}
|
|
var rcs []rawChoice
|
|
err := json.Unmarshal([]byte(js), &rcs)
|
|
if err != nil {
|
|
grpclog.Warningf("grpc: failed to parse service config json string due to %v.\n", err)
|
|
return ""
|
|
}
|
|
cliHostname, err := os.Hostname()
|
|
if err != nil {
|
|
grpclog.Warningf("grpc: failed to get client hostname due to %v.\n", err)
|
|
return ""
|
|
}
|
|
var sc string
|
|
for _, c := range rcs {
|
|
if !containsString(c.ClientLanguage, golang) ||
|
|
!chosenByPercentage(c.Percentage) ||
|
|
!containsString(c.ClientHostName, cliHostname) ||
|
|
c.ServiceConfig == nil {
|
|
continue
|
|
}
|
|
sc = string(*c.ServiceConfig)
|
|
break
|
|
}
|
|
return sc
|
|
}
|