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derp: support client->server ping (and server->client pong)

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In prep for a future change to have client ping derp connections
when their state is questionable, rather than aggressively tearing
them down and doing a heavy reconnect when their state is unknown.

We already support ping/pong in the other direction (servers probing
clients) so we already had the two frame types, but I'd never finished
this direction.

Updates #3619

Change-Id: I024b815d9db1bc57c20f82f80f95fb55fc9e2fcc
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick
2021-12-27 11:58:09 -08:00
committed by Brad Fitzpatrick
parent bc537adb1a
commit 434af15a04
4 changed files with 136 additions and 2 deletions
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25
derp/derp_client.go
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@ -261,10 +261,18 @@ func (c *Client) ForwardPacket(srcKey, dstKey key.NodePublic, pkt []byte) (err e
func (c *Client) writeTimeoutFired() { c.nc.Close() }
func (c *Client) SendPing(data [8]byte) error {
return c.sendPingOrPong(framePing, data)
}
func (c *Client) SendPong(data [8]byte) error {
return c.sendPingOrPong(framePong, data)
}
func (c *Client) sendPingOrPong(typ frameType, data [8]byte) error {
c.wmu.Lock()
defer c.wmu.Unlock()
if err := writeFrameHeader(c.bw, framePong, 8); err != nil {
if err := writeFrameHeader(c.bw, typ, 8); err != nil {
return err
}
if _, err := c.bw.Write(data[:]); err != nil {
@ -375,6 +383,12 @@ type PingMessage [8]byte
func (PingMessage) msg() {}
// PongMessage is a reply to a PingMessage from a client or server
// with the payload sent previously in a PingMessage.
type PongMessage [8]byte
func (PongMessage) msg() {}
// KeepAliveMessage is a one-way empty message from server to client, just to
// keep the connection alive. It's like a PingMessage, but doesn't solicit
// a reply from the client.
@ -536,6 +550,15 @@ func (c *Client) recvTimeout(timeout time.Duration) (m ReceivedMessage, err erro
copy(pm[:], b[:])
return pm, nil
case framePong:
var pm PongMessage
if n < 8 {
c.logf("[unexpected] dropping short ping frame")
continue
}
copy(pm[:], b[:])
return pm, nil
case frameHealth:
return HealthMessage{Problem: string(b[:])}, nil