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send_queue.go
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send_queue.go
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package quic
import "github.com/quic-go/quic-go/internal/protocol"
type sender interface {
Send(p *packetBuffer, gsoSize uint16, ecn protocol.ECN)
Run() error
WouldBlock() bool
Available() <-chan struct{}
Close()
}
type queueEntry struct {
buf *packetBuffer
gsoSize uint16
ecn protocol.ECN
}
type sendQueue struct {
queue chan queueEntry
closeCalled chan struct{} // runStopped when Close() is called
runStopped chan struct{} // runStopped when the run loop returns
available chan struct{}
conn sendConn
}
var _ sender = &sendQueue{}
const sendQueueCapacity = 8
func newSendQueue(conn sendConn) sender {
return &sendQueue{
conn: conn,
runStopped: make(chan struct{}),
closeCalled: make(chan struct{}),
available: make(chan struct{}, 1),
queue: make(chan queueEntry, sendQueueCapacity),
}
}
// Send sends out a packet. It's guaranteed to not block.
// Callers need to make sure that there's actually space in the send queue by calling WouldBlock.
// Otherwise Send will panic.
func (h *sendQueue) Send(p *packetBuffer, gsoSize uint16, ecn protocol.ECN) {
select {
case h.queue <- queueEntry{buf: p, gsoSize: gsoSize, ecn: ecn}:
// clear available channel if we've reached capacity
if len(h.queue) == sendQueueCapacity {
select {
case <-h.available:
default:
}
}
case <-h.runStopped:
default:
panic("sendQueue.Send would have blocked")
}
}
func (h *sendQueue) WouldBlock() bool {
return len(h.queue) == sendQueueCapacity
}
func (h *sendQueue) Available() <-chan struct{} {
return h.available
}
func (h *sendQueue) Run() error {
defer close(h.runStopped)
var shouldClose bool
for {
if shouldClose && len(h.queue) == 0 {
return nil
}
select {
case <-h.closeCalled:
h.closeCalled = nil // prevent this case from being selected again
// make sure that all queued packets are actually sent out
shouldClose = true
case e := <-h.queue:
if err := h.conn.Write(e.buf.Data, e.gsoSize, e.ecn); err != nil {
// This additional check enables:
// 1. Checking for "datagram too large" message from the kernel, as such,
// 2. Path MTU discovery,and
// 3. Eventual detection of loss PingFrame.
if !isSendMsgSizeErr(err) {
return err
}
}
e.buf.Release()
select {
case h.available <- struct{}{}:
default:
}
}
}
}
func (h *sendQueue) Close() {
close(h.closeCalled)
// wait until the run loop returned
<-h.runStopped
}