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coordinator.go
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coordinator.go
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package tailnet
import (
"context"
"encoding/json"
"errors"
"io"
"net"
"net/netip"
"sync"
"time"
"github.com/google/uuid"
"golang.org/x/xerrors"
"tailscale.com/tailcfg"
"tailscale.com/types/key"
)
// Coordinator exchanges nodes with agents to establish connections.
// ┌──────────────────┐ ┌────────────────────┐ ┌───────────────────┐ ┌──────────────────┐
// │tailnet.Coordinate├──►│tailnet.AcceptClient│◄─►│tailnet.AcceptAgent│◄──┤tailnet.Coordinate│
// └──────────────────┘ └────────────────────┘ └───────────────────┘ └──────────────────┘
// Coordinators have different guarantees for HA support.
type Coordinator interface {
// Node returns an in-memory node by ID.
Node(id uuid.UUID) *Node
// ServeClient accepts a WebSocket connection that wants to connect to an agent
// with the specified ID.
ServeClient(conn net.Conn, id uuid.UUID, agent uuid.UUID) error
// ServeAgent accepts a WebSocket connection to an agent that listens to
// incoming connections and publishes node updates.
ServeAgent(conn net.Conn, id uuid.UUID) error
// Close closes the coordinator.
Close() error
}
// Node represents a node in the network.
type Node struct {
// ID is used to identify the connection.
ID tailcfg.NodeID `json:"id"`
// AsOf is the time the node was created.
AsOf time.Time `json:"as_of"`
// Key is the Wireguard public key of the node.
Key key.NodePublic `json:"key"`
// DiscoKey is used for discovery messages over DERP to establish peer-to-peer connections.
DiscoKey key.DiscoPublic `json:"disco"`
// PreferredDERP is the DERP server that peered connections
// should meet at to establish.
PreferredDERP int `json:"preferred_derp"`
// DERPLatency is the latency in seconds to each DERP server.
DERPLatency map[string]float64 `json:"derp_latency"`
// Addresses are the IP address ranges this connection exposes.
Addresses []netip.Prefix `json:"addresses"`
// AllowedIPs specify what addresses can dial the connection.
// We allow all by default.
AllowedIPs []netip.Prefix `json:"allowed_ips"`
// Endpoints are ip:port combinations that can be used to establish
// peer-to-peer connections.
Endpoints []string `json:"endpoints"`
}
// ServeCoordinator matches the RW structure of a coordinator to exchange node messages.
func ServeCoordinator(conn net.Conn, updateNodes func(node []*Node) error) (func(node *Node), <-chan error) {
errChan := make(chan error, 1)
sendErr := func(err error) {
select {
case errChan <- err:
default:
}
}
go func() {
decoder := json.NewDecoder(conn)
for {
var nodes []*Node
err := decoder.Decode(&nodes)
if err != nil {
sendErr(xerrors.Errorf("read: %w", err))
return
}
err = updateNodes(nodes)
if err != nil {
sendErr(xerrors.Errorf("update nodes: %w", err))
}
}
}()
return func(node *Node) {
data, err := json.Marshal(node)
if err != nil {
sendErr(xerrors.Errorf("marshal node: %w", err))
return
}
_, err = conn.Write(data)
if err != nil {
sendErr(xerrors.Errorf("write: %w", err))
}
}, errChan
}
// NewCoordinator constructs a new in-memory connection coordinator. This
// coordinator is incompatible with multiple Coder replicas as all node data is
// in-memory.
func NewCoordinator() Coordinator {
return &coordinator{
closed: false,
nodes: map[uuid.UUID]*Node{},
agentSockets: map[uuid.UUID]net.Conn{},
agentToConnectionSockets: map[uuid.UUID]map[uuid.UUID]net.Conn{},
}
}
// coordinator exchanges nodes with agents to establish connections entirely in-memory.
// The Enterprise implementation provides this for high-availability.
// ┌──────────────────┐ ┌────────────────────┐ ┌───────────────────┐ ┌──────────────────┐
// │tailnet.Coordinate├──►│tailnet.AcceptClient│◄─►│tailnet.AcceptAgent│◄──┤tailnet.Coordinate│
// └──────────────────┘ └────────────────────┘ └───────────────────┘ └──────────────────┘
// This coordinator is incompatible with multiple Coder
// replicas as all node data is in-memory.
type coordinator struct {
mutex sync.Mutex
closed bool
// 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
// 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
}
// 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 {
c.mutex.Lock()
defer c.mutex.Unlock()
return c.nodes[id]
}
// ServeClient accepts a WebSocket connection that wants to connect to an agent
// with the specified ID.
func (c *coordinator) ServeClient(conn net.Conn, id uuid.UUID, agent uuid.UUID) error {
c.mutex.Lock()
if c.closed {
c.mutex.Unlock()
return xerrors.New("coordinator is closed")
}
// When a new connection is requested, we update it with the latest
// node of the agent. This allows the connection to establish.
node, ok := c.nodes[agent]
c.mutex.Unlock()
if ok {
data, err := json.Marshal([]*Node{node})
if err != nil {
return xerrors.Errorf("marshal node: %w", err)
}
_, err = conn.Write(data)
if err != nil {
return xerrors.Errorf("write nodes: %w", err)
}
}
c.mutex.Lock()
connectionSockets, ok := c.agentToConnectionSockets[agent]
if !ok {
connectionSockets = map[uuid.UUID]net.Conn{}
c.agentToConnectionSockets[agent] = connectionSockets
}
// Insert this connection into a map so the agent
// can publish node updates.
connectionSockets[id] = conn
c.mutex.Unlock()
defer func() {
c.mutex.Lock()
defer c.mutex.Unlock()
// Clean all traces of this connection from the map.
delete(c.nodes, id)
connectionSockets, ok := c.agentToConnectionSockets[agent]
if !ok {
return
}
delete(connectionSockets, id)
if len(connectionSockets) != 0 {
return
}
delete(c.agentToConnectionSockets, agent)
}()
decoder := json.NewDecoder(conn)
for {
err := c.handleNextClientMessage(id, agent, decoder)
if err != nil {
if errors.Is(err, io.EOF) {
return nil
}
return xerrors.Errorf("handle next client message: %w", err)
}
}
}
func (c *coordinator) handleNextClientMessage(id, agent uuid.UUID, decoder *json.Decoder) error {
var node Node
err := decoder.Decode(&node)
if err != nil {
return xerrors.Errorf("read json: %w", err)
}
c.mutex.Lock()
// Update the node of this client in our in-memory map. If an agent entirely
// shuts down and reconnects, it needs to be aware of all clients attempting
// to establish connections.
c.nodes[id] = &node
agentSocket, ok := c.agentSockets[agent]
if !ok {
c.mutex.Unlock()
return nil
}
c.mutex.Unlock()
// Write the new node from this client to the actively connected agent.
data, err := json.Marshal([]*Node{&node})
if err != nil {
return xerrors.Errorf("marshal nodes: %w", err)
}
_, err = agentSocket.Write(data)
if err != nil {
if errors.Is(err, io.EOF) {
return nil
}
return xerrors.Errorf("write json: %w", err)
}
return nil
}
// ServeAgent accepts a WebSocket connection to an agent that
// listens to incoming connections and publishes node updates.
func (c *coordinator) ServeAgent(conn net.Conn, id uuid.UUID) error {
c.mutex.Lock()
if c.closed {
c.mutex.Unlock()
return xerrors.New("coordinator is closed")
}
sockets, ok := c.agentToConnectionSockets[id]
if ok {
// Publish all nodes that want to connect to the
// desired agent ID.
nodes := make([]*Node, 0, len(sockets))
for targetID := range sockets {
node, ok := c.nodes[targetID]
if !ok {
continue
}
nodes = append(nodes, node)
}
c.mutex.Unlock()
data, err := json.Marshal(nodes)
if err != nil {
return xerrors.Errorf("marshal json: %w", err)
}
_, err = conn.Write(data)
if err != nil {
return xerrors.Errorf("write nodes: %w", err)
}
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.
oldAgentSocket, ok := c.agentSockets[id]
if ok {
_ = oldAgentSocket.Close()
}
c.agentSockets[id] = conn
c.mutex.Unlock()
defer func() {
c.mutex.Lock()
defer c.mutex.Unlock()
delete(c.agentSockets, id)
delete(c.nodes, id)
}()
decoder := json.NewDecoder(conn)
for {
err := c.handleNextAgentMessage(id, decoder)
if err != nil {
if errors.Is(err, io.EOF) || errors.Is(err, context.Canceled) {
return nil
}
return xerrors.Errorf("handle next agent message: %w", err)
}
}
}
func (c *coordinator) handleNextAgentMessage(id uuid.UUID, decoder *json.Decoder) error {
var node Node
err := decoder.Decode(&node)
if err != nil {
return xerrors.Errorf("read json: %w", err)
}
c.mutex.Lock()
c.nodes[id] = &node
connectionSockets, ok := c.agentToConnectionSockets[id]
if !ok {
c.mutex.Unlock()
return nil
}
data, err := json.Marshal([]*Node{&node})
if err != nil {
c.mutex.Unlock()
return xerrors.Errorf("marshal nodes: %w", err)
}
// Publish the new node to every listening socket.
var wg sync.WaitGroup
wg.Add(len(connectionSockets))
for _, connectionSocket := range connectionSockets {
connectionSocket := connectionSocket
go func() {
_ = connectionSocket.SetWriteDeadline(time.Now().Add(5 * time.Second))
_, _ = connectionSocket.Write(data)
wg.Done()
}()
}
c.mutex.Unlock()
wg.Wait()
return nil
}
// Close closes all of the open connections in the coordinator and stops the
// coordinator from accepting new connections.
func (c *coordinator) Close() error {
c.mutex.Lock()
if c.closed {
c.mutex.Unlock()
return nil
}
c.closed = true
wg := sync.WaitGroup{}
wg.Add(len(c.agentSockets))
for _, socket := range c.agentSockets {
socket := socket
go func() {
_ = socket.Close()
wg.Done()
}()
}
for _, connMap := range c.agentToConnectionSockets {
wg.Add(len(connMap))
for _, socket := range connMap {
socket := socket
go func() {
_ = socket.Close()
wg.Done()
}()
}
}
c.mutex.Unlock()
wg.Wait()
return nil
}