/usr/share/gocode/src/google.golang.org/grpc/transport/control.go is in golang-google-grpc-dev 1.6.0-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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*
* Copyright 2014 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 transport
import (
"fmt"
"math"
"sync"
"time"
"golang.org/x/net/http2"
)
const (
// The default value of flow control window size in HTTP2 spec.
defaultWindowSize = 65535
// The initial window size for flow control.
initialWindowSize = defaultWindowSize // for an RPC
infinity = time.Duration(math.MaxInt64)
defaultClientKeepaliveTime = infinity
defaultClientKeepaliveTimeout = time.Duration(20 * time.Second)
defaultMaxStreamsClient = 100
defaultMaxConnectionIdle = infinity
defaultMaxConnectionAge = infinity
defaultMaxConnectionAgeGrace = infinity
defaultServerKeepaliveTime = time.Duration(2 * time.Hour)
defaultServerKeepaliveTimeout = time.Duration(20 * time.Second)
defaultKeepalivePolicyMinTime = time.Duration(5 * time.Minute)
// max window limit set by HTTP2 Specs.
maxWindowSize = math.MaxInt32
)
// The following defines various control items which could flow through
// the control buffer of transport. They represent different aspects of
// control tasks, e.g., flow control, settings, streaming resetting, etc.
type windowUpdate struct {
streamID uint32
increment uint32
flush bool
}
func (*windowUpdate) item() {}
type settings struct {
ack bool
ss []http2.Setting
}
func (*settings) item() {}
type resetStream struct {
streamID uint32
code http2.ErrCode
}
func (*resetStream) item() {}
type goAway struct {
code http2.ErrCode
debugData []byte
headsUp bool
closeConn bool
}
func (*goAway) item() {}
type flushIO struct {
}
func (*flushIO) item() {}
type ping struct {
ack bool
data [8]byte
}
func (*ping) item() {}
// quotaPool is a pool which accumulates the quota and sends it to acquire()
// when it is available.
type quotaPool struct {
c chan int
mu sync.Mutex
quota int
}
// newQuotaPool creates a quotaPool which has quota q available to consume.
func newQuotaPool(q int) *quotaPool {
qb := "aPool{
c: make(chan int, 1),
}
if q > 0 {
qb.c <- q
} else {
qb.quota = q
}
return qb
}
// add cancels the pending quota sent on acquired, incremented by v and sends
// it back on acquire.
func (qb *quotaPool) add(v int) {
qb.mu.Lock()
defer qb.mu.Unlock()
select {
case n := <-qb.c:
qb.quota += n
default:
}
qb.quota += v
if qb.quota <= 0 {
return
}
// After the pool has been created, this is the only place that sends on
// the channel. Since mu is held at this point and any quota that was sent
// on the channel has been retrieved, we know that this code will always
// place any positive quota value on the channel.
select {
case qb.c <- qb.quota:
qb.quota = 0
default:
}
}
// acquire returns the channel on which available quota amounts are sent.
func (qb *quotaPool) acquire() <-chan int {
return qb.c
}
// inFlow deals with inbound flow control
type inFlow struct {
mu sync.Mutex
// The inbound flow control limit for pending data.
limit uint32
// pendingData is the overall data which have been received but not been
// consumed by applications.
pendingData uint32
// The amount of data the application has consumed but grpc has not sent
// window update for them. Used to reduce window update frequency.
pendingUpdate uint32
// delta is the extra window update given by receiver when an application
// is reading data bigger in size than the inFlow limit.
delta uint32
}
// newLimit updates the inflow window to a new value n.
// It assumes that n is always greater than the old limit.
func (f *inFlow) newLimit(n uint32) uint32 {
f.mu.Lock()
defer f.mu.Unlock()
d := n - f.limit
f.limit = n
return d
}
func (f *inFlow) maybeAdjust(n uint32) uint32 {
if n > uint32(math.MaxInt32) {
n = uint32(math.MaxInt32)
}
f.mu.Lock()
defer f.mu.Unlock()
// estSenderQuota is the receiver's view of the maximum number of bytes the sender
// can send without a window update.
estSenderQuota := int32(f.limit - (f.pendingData + f.pendingUpdate))
// estUntransmittedData is the maximum number of bytes the sends might not have put
// on the wire yet. A value of 0 or less means that we have already received all or
// more bytes than the application is requesting to read.
estUntransmittedData := int32(n - f.pendingData) // Casting into int32 since it could be negative.
// This implies that unless we send a window update, the sender won't be able to send all the bytes
// for this message. Therefore we must send an update over the limit since there's an active read
// request from the application.
if estUntransmittedData > estSenderQuota {
// Sender's window shouldn't go more than 2^31 - 1 as speecified in the HTTP spec.
if f.limit+n > maxWindowSize {
f.delta = maxWindowSize - f.limit
} else {
// Send a window update for the whole message and not just the difference between
// estUntransmittedData and estSenderQuota. This will be helpful in case the message
// is padded; We will fallback on the current available window(at least a 1/4th of the limit).
f.delta = n
}
return f.delta
}
return 0
}
// onData is invoked when some data frame is received. It updates pendingData.
func (f *inFlow) onData(n uint32) error {
f.mu.Lock()
defer f.mu.Unlock()
f.pendingData += n
if f.pendingData+f.pendingUpdate > f.limit+f.delta {
return fmt.Errorf("received %d-bytes data exceeding the limit %d bytes", f.pendingData+f.pendingUpdate, f.limit)
}
return nil
}
// onRead is invoked when the application reads the data. It returns the window size
// to be sent to the peer.
func (f *inFlow) onRead(n uint32) uint32 {
f.mu.Lock()
defer f.mu.Unlock()
if f.pendingData == 0 {
return 0
}
f.pendingData -= n
if n > f.delta {
n -= f.delta
f.delta = 0
} else {
f.delta -= n
n = 0
}
f.pendingUpdate += n
if f.pendingUpdate >= f.limit/4 {
wu := f.pendingUpdate
f.pendingUpdate = 0
return wu
}
return 0
}
func (f *inFlow) resetPendingUpdate() uint32 {
f.mu.Lock()
defer f.mu.Unlock()
n := f.pendingUpdate
f.pendingUpdate = 0
return n
}
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