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fix(agent): guard against multiple rpty race for same id #7998

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Merged
merged 2 commits into from
Jun 13, 2023
Merged

fix(agent): guard against multiple rpty race for same id #7998

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2484e7f
fix(agent): guard against multiple rpty race for same id
mafredri Jun 13, 2023
33ba988
fix: Bonus, close process on agent close
mafredri Jun 13, 2023
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29 changes: 23 additions & 6 deletions agent/agent.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1025,16 +1025,32 @@ func (a *agent) handleReconnectingPTY(ctx context.Context, logger slog.Logger, m
}()

var rpty *reconnectingPTY
rawRPTY, ok := a.reconnectingPTYs.Load(msg.ID)
sendConnected := make(chan *reconnectingPTY, 1)
// On store, reserve this ID to prevent multiple concurrent new connections.
waitReady, ok := a.reconnectingPTYs.LoadOrStore(msg.ID, sendConnected)
if ok {
close(sendConnected) // Unused.
logger.Debug(ctx, "connecting to existing session")
rpty, ok = rawRPTY.(*reconnectingPTY)
c, ok := waitReady.(chan *reconnectingPTY)
if !ok {
return xerrors.Errorf("found invalid type in reconnecting pty map: %T", rawRPTY)
return xerrors.Errorf("found invalid type in reconnecting pty map: %T", waitReady)
}
rpty, ok = <-c
if !ok || rpty == nil {
return xerrors.Errorf("reconnecting pty closed before connection")
}
c <- rpty // Put it back for the next reconnect.
} else {
logger.Debug(ctx, "creating new session")

connected := false
defer func() {
if !connected && retErr != nil {
a.reconnectingPTYs.Delete(msg.ID)
close(sendConnected)
}
}()

// Empty command will default to the users shell!
cmd, err := a.sshServer.CreateCommand(ctx, msg.Command, nil)
if err != nil {
Expand All @@ -1055,7 +1071,7 @@ func (a *agent) handleReconnectingPTY(ctx context.Context, logger slog.Logger, m
return xerrors.Errorf("start command: %w", err)
}

ctx, cancelFunc := context.WithCancel(ctx)
ctx, cancel := context.WithCancel(ctx)
rpty = &reconnectingPTY{
activeConns: map[string]net.Conn{
// We have to put the connection in the map instantly otherwise
Expand All @@ -1064,10 +1080,9 @@ func (a *agent) handleReconnectingPTY(ctx context.Context, logger slog.Logger, m
},
ptty: ptty,
// Timeouts created with an after func can be reset!
timeout: time.AfterFunc(a.reconnectingPTYTimeout, cancelFunc),
timeout: time.AfterFunc(a.reconnectingPTYTimeout, cancel),
circularBuffer: circularBuffer,
}
a.reconnectingPTYs.Store(msg.ID, rpty)
// We don't need to separately monitor for the process exiting.
// When it exits, our ptty.OutputReader() will return EOF after
// reading all process output.
Expand Down Expand Up @@ -1117,6 +1132,8 @@ func (a *agent) handleReconnectingPTY(ctx context.Context, logger slog.Logger, m
}); err != nil {
return xerrors.Errorf("start routine: %w", err)
}
connected = true
sendConnected <- rpty
}
// Resize the PTY to initial height + width.
err := rpty.ptty.Resize(msg.Height, msg.Width)
Expand Down