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derp: remove the mutex around and closing of send channel

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Makes it less complicated.

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2020-03-21 20:43:50 -07:00 committed by Brad Fitzpatrick
parent 77921a31b1
commit c34b350efa
1 changed files with 21 additions and 41 deletions
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62
derp/derp_server.go
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@ -252,15 +252,6 @@ func (s *Server) accept(nc Conn, brw *bufio.ReadWriter, remoteAddr string) error
}
func (c *sclient) run() error {
defer func() {
// Atomically close+remove send queue, so racing writers don't
// send to closed channel.
c.mu.Lock()
close(c.sendQueue)
c.sendQueue = nil
c.mu.Unlock()
}()
go c.sender()
for {
@ -320,16 +311,6 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
return nil
}
dst.mu.RLock()
defer dst.mu.RUnlock()
if dst.sendQueue == nil {
s.packetsDropped.Add(1)
s.packetsDroppedGone.Add(1)
if debug {
c.logf("dropping packet for shutdown client %x", dstKey)
}
}
msg := sendMsg{
bs: contents,
}
@ -340,6 +321,16 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
// the queue is full, try to drop from queue head to prioritize
// fresher packets.
for attempt := 0; attempt < 3; attempt++ {
select {
case <-dst.done:
s.packetsDropped.Add(1)
s.packetsDroppedGone.Add(1)
if debug {
c.logf("dropping packet for shutdown client %x", dstKey)
}
return nil
default:
}
select {
case dst.sendQueue <- msg:
return nil
@ -480,6 +471,7 @@ type sclient struct {
logf logger.Logf
done <-chan struct{} // closed when connection closes
remoteAddr string // usually ip:port from net.Conn.RemoteAddr().String()
sendQueue chan sendMsg // messages (packets) queued to this client; never closed
// Owned by run, not thread-safe.
br *bufio.Reader
@ -488,9 +480,6 @@ type sclient struct {
// Owned by sender, not thread-safe.
bw *bufio.Writer
mu sync.RWMutex // guards access to sendQueue for shutdown.
sendQueue chan sendMsg // messages (packets) queued to this client
}
// sendMsg is a request to write a frame to an sclient (usually a data packet).
@ -540,27 +529,18 @@ func (c *sclient) sender() {
}
func (c *sclient) sendLoop() error {
c.mu.RLock()
queue := c.sendQueue
c.mu.RUnlock()
if queue == nil {
// Uncommon race, sclient shut down before this loop ever
// started. Nothing to do here, move along.
return nil
}
defer func() {
// Drain the send queue to count dropped packets
for {
_, ok := <-queue
if !ok {
break
}
c.s.packetsDropped.Add(1)
c.s.packetsDroppedGone.Add(1)
if debug {
c.logf("dropping packet for shutdown %x", c.key)
select {
case <-c.sendQueue:
c.s.packetsDropped.Add(1)
c.s.packetsDroppedGone.Add(1)
if debug {
c.logf("dropping packet for shutdown %x", c.key)
}
default:
return
}
}
}()
@ -578,7 +558,7 @@ func (c *sclient) sendLoop() error {
case <-c.done:
return nil
case msg, ok := <-queue:
case msg, ok := <-c.sendQueue:
if !ok {
return nil
}