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fix: ensure agent websocket only removes its own conn #5828

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Merged
merged 4 commits into from
Jan 23, 2023
Merged

fix: ensure agent websocket only removes its own conn #5828

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bda160c
fix: ensure agent websocket only removes its own conn from the map
coadler Jan 23, 2023
4b67adf
add test
coadler Jan 23, 2023
c080b7c
fixup! add test
coadler Jan 23, 2023
fd0509d
fixup! add test
coadler Jan 23, 2023
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42 changes: 31 additions & 11 deletions tailnet/coordinator.go
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Original file line number Diff line number Diff line change
Expand Up @@ -104,7 +104,7 @@ func NewCoordinator() Coordinator {
return &coordinator{
closed: false,
nodes: map[uuid.UUID]*Node{},
agentSockets: map[uuid.UUID]net.Conn{},
agentSockets: map[uuid.UUID]idConn{},
agentToConnectionSockets: map[uuid.UUID]map[uuid.UUID]net.Conn{},
}
}
Expand All @@ -123,12 +123,19 @@ type coordinator struct {
// nodes maps agent and connection IDs their respective node.
nodes map[uuid.UUID]*Node
// agentSockets maps agent IDs to their open websocket.
agentSockets map[uuid.UUID]net.Conn
agentSockets map[uuid.UUID]idConn
// agentToConnectionSockets maps agent IDs to connection IDs of conns that
// are subscribed to updates for that agent.
agentToConnectionSockets map[uuid.UUID]map[uuid.UUID]net.Conn
}

type idConn struct {
// id is an ephemeral UUID used to uniquely identify the owner of the
// connection.
id uuid.UUID
conn net.Conn
}

// Node returns an in-memory node by ID.
// If the node does not exist, nil is returned.
func (c *coordinator) Node(id uuid.UUID) *Node {
Expand Down Expand Up @@ -224,7 +231,7 @@ func (c *coordinator) handleNextClientMessage(id, agent uuid.UUID, decoder *json
return xerrors.Errorf("marshal nodes: %w", err)
}

_, err = agentSocket.Write(data)
_, err = agentSocket.conn.Write(data)
if err != nil {
if errors.Is(err, io.EOF) {
return nil
Expand Down Expand Up @@ -268,20 +275,33 @@ func (c *coordinator) ServeAgent(conn net.Conn, id uuid.UUID) error {
c.mutex.Lock()
}

// If an old agent socket is connected, we close it
// to avoid any leaks. This shouldn't ever occur because
// we expect one agent to be running.
// This uniquely identifies a connection that belongs to this goroutine.
unique := uuid.New()

// If an old agent socket is connected, we close it to avoid any leaks. This
// shouldn't ever occur because we expect one agent to be running, but it's
// possible for a race condition to happen when an agent is disconnected and
// attempts to reconnect before the server realizes the old connection is
// dead.
oldAgentSocket, ok := c.agentSockets[id]
if ok {
_ = oldAgentSocket.Close()
_ = oldAgentSocket.conn.Close()
}
c.agentSockets[id] = idConn{
id: unique,
conn: conn,
}
c.agentSockets[id] = conn
c.mutex.Unlock()
defer func() {
c.mutex.Lock()
defer c.mutex.Unlock()
delete(c.agentSockets, id)
delete(c.nodes, id)

// Only delete the connection if it's ours. It could have been
// overwritten.
if idConn := c.agentSockets[id]; idConn.id == unique {
delete(c.agentSockets, id)
delete(c.nodes, id)
}
}()

decoder := json.NewDecoder(conn)
Expand Down Expand Up @@ -349,7 +369,7 @@ func (c *coordinator) Close() error {
for _, socket := range c.agentSockets {
socket := socket
go func() {
_ = socket.Close()
_ = socket.conn.Close()
wg.Done()
}()
}
Expand Down