/
reuse.go
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/
reuse.go
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/*
* Copyright (C) 2020-2022, IrineSistiana
*
* This file is part of mosdns.
*
* mosdns is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* mosdns is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package transport
import (
"context"
"errors"
"net"
"sync"
"time"
"github.com/IrineSistiana/mosdns/v5/pkg/dnsutils"
"github.com/IrineSistiana/mosdns/v5/pkg/pool"
"go.uber.org/zap"
)
const (
// Most servers will send SERVFAIL after 3~5s. If no resp, connection may be dead.
reuseConnQueryTimeout = time.Second * 6
)
// ReuseConnTransport is for old tcp protocol. (no pipelining)
type ReuseConnTransport struct {
dialFunc func(ctx context.Context) (NetConn, error)
dialTimeout time.Duration
idleTimeout time.Duration
logger *zap.Logger // non-nil
ctx context.Context
ctxCancel context.CancelCauseFunc
m sync.Mutex // protect following fields
closed bool
idleConns map[*reusableConn]struct{}
conns map[*reusableConn]struct{}
// for testing
testWaitRespTimeout time.Duration
}
type ReuseConnOpts struct {
// DialContext specifies the method to dial a connection to the server.
// DialContext MUST NOT be nil.
DialContext func(ctx context.Context) (NetConn, error)
// DialTimeout specifies the timeout for DialFunc.
// Default is defaultDialTimeout.
DialTimeout time.Duration
// Default is defaultIdleTimeout
IdleTimeout time.Duration
Logger *zap.Logger
}
func NewReuseConnTransport(opt ReuseConnOpts) *ReuseConnTransport {
ctx, cancel := context.WithCancelCause(context.Background())
t := &ReuseConnTransport{
ctx: ctx,
ctxCancel: cancel,
idleConns: make(map[*reusableConn]struct{}),
conns: make(map[*reusableConn]struct{}),
}
t.dialFunc = opt.DialContext
setDefaultGZ(&t.dialTimeout, opt.DialTimeout, defaultDialTimeout)
setDefaultGZ(&t.idleTimeout, opt.IdleTimeout, defaultIdleTimeout)
setNonNilLogger(&t.logger, opt.Logger)
return t
}
func (t *ReuseConnTransport) ExchangeContext(ctx context.Context, m []byte) (*[]byte, error) {
const maxRetry = 2
retry := 0
for {
var isNewConn bool
c, err := t.getIdleConn()
if err != nil {
return nil, err
}
if c == nil {
isNewConn = true
c, err = t.getNewConn(ctx)
if err != nil {
return nil, err
}
}
queryPayload, err := copyMsgWithLenHdr(m)
if err != nil {
return nil, err
}
resp, err := c.exchange(ctx, queryPayload)
if err != nil {
if !isNewConn && retry <= maxRetry {
retry++
continue // retry if c is a reused connection.
}
return nil, err
}
return resp, nil
}
}
// getNewConn dial a *reusableConn.
// The caller must call releaseReusableConn to release the reusableConn.
func (t *ReuseConnTransport) getNewConn(ctx context.Context) (*reusableConn, error) {
callCtx, cancel := context.WithCancel(ctx)
defer cancel()
type dialRes struct {
c *reusableConn
err error
}
dialChan := make(chan dialRes)
go func() {
dialCtx, cancelDial := context.WithTimeout(t.ctx, t.dialTimeout)
defer cancelDial()
var rc *reusableConn
c, err := t.dialFunc(dialCtx)
if err != nil {
t.logger.Check(zap.WarnLevel, "fail to dial reusable conn").Write(zap.Error(err))
}
if c != nil {
rc = t.newReusableConn(c)
if rc == nil { // transport closed
c.Close()
rc = nil
err = ErrClosedTransport
}
}
select {
case dialChan <- dialRes{c: rc, err: err}:
case <-callCtx.Done(): // caller canceled getNewConn() call
if rc != nil { // put this conn to pool
t.setIdle(rc)
}
}
}()
select {
case <-callCtx.Done():
return nil, context.Cause(ctx)
case <-t.ctx.Done():
return nil, context.Cause(t.ctx)
case res := <-dialChan:
return res.c, res.err
}
}
func (t *ReuseConnTransport) setIdle(c *reusableConn) {
t.m.Lock()
defer t.m.Unlock()
if t.closed {
return
}
if _, ok := t.conns[c]; ok {
t.idleConns[c] = struct{}{}
}
}
// getIdleConn returns a *reusableConn from conn pool, or nil if no conn
// is idle.
// The caller must call releaseReusableConn to release the reusableConn.
func (t *ReuseConnTransport) getIdleConn() (*reusableConn, error) {
t.m.Lock()
defer t.m.Unlock()
if t.closed {
return nil, ErrClosedTransport
}
for c := range t.idleConns {
delete(t.idleConns, c)
return c, nil
}
return nil, nil
}
// Close closes ReuseConnTransport and all its connections.
// It always returns a nil error.
func (t *ReuseConnTransport) Close() error {
t.m.Lock()
defer t.m.Unlock()
if t.closed {
return nil
}
t.closed = true
for c := range t.conns {
delete(t.conns, c)
delete(t.idleConns, c)
c.closeWithErrByTransport(ErrClosedTransport)
}
t.ctxCancel(ErrClosedTransport)
return nil
}
type reusableConn struct {
c NetConn
t *ReuseConnTransport
m sync.Mutex
waitingResp chan *[]byte
closeOnce sync.Once
closeNotify chan struct{}
closeErr error
}
// return nil if transport was closed
func (t *ReuseConnTransport) newReusableConn(c NetConn) *reusableConn {
rc := &reusableConn{
c: c,
t: t,
closeNotify: make(chan struct{}),
}
t.m.Lock()
if t.closed { // t was closed.
t.m.Unlock()
return nil
}
t.conns[rc] = struct{}{}
t.m.Unlock()
go rc.readLoop()
return rc
}
var (
errUnexpectedResp = errors.New("server misbehaving: unexpected response")
)
func (c *reusableConn) readLoop() {
for {
resp, err := dnsutils.ReadRawMsgFromTCP(c.c)
if err != nil {
c.closeWithErr(err)
return
}
c.m.Lock()
respChan := c.waitingResp
c.waitingResp = nil
c.m.Unlock()
if respChan == nil {
pool.ReleaseBuf(resp)
c.closeWithErr(errUnexpectedResp)
return
}
// This connection is idled again.
c.c.SetReadDeadline(time.Now().Add(c.t.idleTimeout))
// Note: calling setIdle before sending resp back to make sure this connection is idle
// before Exchange call returning. Otherwise, Test_ReuseConnTransport may fail.
c.t.setIdle(c)
select {
case respChan <- resp:
default:
panic("bug: respChan has buffer, we shouldn't reach here")
}
}
}
func (c *reusableConn) closeWithErr(err error) {
if err == nil {
err = net.ErrClosed
}
c.closeOnce.Do(func() {
c.t.m.Lock()
delete(c.t.conns, c)
delete(c.t.idleConns, c)
c.t.m.Unlock()
c.closeErr = err
c.c.Close()
close(c.closeNotify)
})
}
func (c *reusableConn) closeWithErrByTransport(err error) {
if err == nil {
err = net.ErrClosed
}
c.closeOnce.Do(func() {
c.closeErr = err
c.c.Close()
close(c.closeNotify)
})
}
func (c *reusableConn) exchange(ctx context.Context, q *[]byte) (*[]byte, error) {
respChan := make(chan *[]byte, 1)
c.m.Lock()
if c.waitingResp != nil {
c.m.Unlock()
panic("bug: reusableConn: concurrent exchange calls")
}
c.waitingResp = respChan
c.m.Unlock()
waitRespTimeout := reuseConnQueryTimeout
if c.t.testWaitRespTimeout > 0 {
waitRespTimeout = c.t.testWaitRespTimeout
}
c.c.SetDeadline(time.Now().Add(waitRespTimeout))
_, err := c.c.Write(*q)
if err != nil {
c.closeWithErr(err)
return nil, err
}
select {
case resp := <-respChan:
return resp, nil
case <-c.closeNotify:
return nil, c.closeErr
case <-ctx.Done():
return nil, context.Cause(ctx)
}
}