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tailscale/derp/derphttp/derphttp_client.go

1130 lines
31 KiB
Go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// Package derphttp implements DERP-over-HTTP.
//
// This makes DERP look exactly like WebSockets.
// A server can implement DERP over HTTPS and even if the TLS connection
// intercepted using a fake root CA, unless the interceptor knows how to
// detect DERP packets, it will look like a web socket.
package derphttp
import (
"bufio"
"cmp"
"context"
"crypto/rand"
"crypto/tls"
"crypto/x509"
"errors"
"fmt"
"io"
"net"
"net/http"
"net/netip"
"net/url"
"runtime"
"strings"
"sync"
"time"
"go4.org/mem"
"tailscale.com/derp"
"tailscale.com/envknob"
"tailscale.com/health"
"tailscale.com/net/dnscache"
"tailscale.com/net/netmon"
"tailscale.com/net/netns"
"tailscale.com/net/sockstats"
"tailscale.com/net/tlsdial"
"tailscale.com/net/tshttpproxy"
"tailscale.com/syncs"
"tailscale.com/tailcfg"
"tailscale.com/tstime"
"tailscale.com/types/key"
"tailscale.com/types/logger"
)
// Client is a DERP-over-HTTP client.
//
// It automatically reconnects on error retry. That is, a failed Send or
// Recv will report the error and not retry, but subsequent calls to
// Send/Recv will completely re-establish the connection (unless Close
// has been called).
type Client struct {
TLSConfig *tls.Config // optional; nil means default
HealthTracker *health.Tracker // optional; used if non-nil only
DNSCache *dnscache.Resolver // optional; nil means no caching
MeshKey string // optional; for trusted clients
IsProber bool // optional; for probers to optional declare themselves as such
// WatchConnectionChanges is whether the client wishes to subscribe to
// notifications about clients connecting & disconnecting.
//
// Only trusted connections (using MeshKey) are allowed to use this.
WatchConnectionChanges bool
// BaseContext, if non-nil, returns the base context to use for dialing a
// new derp server. If nil, context.Background is used.
// In either case, additional timeouts may be added to the base context.
BaseContext func() context.Context
privateKey key.NodePrivate
logf logger.Logf
netMon *netmon.Monitor // always non-nil
dialer func(ctx context.Context, network, addr string) (net.Conn, error)
// Either url or getRegion is non-nil:
url *url.URL
getRegion func() *tailcfg.DERPRegion
ctx context.Context // closed via cancelCtx in Client.Close
cancelCtx context.CancelFunc
// addrFamSelAtomic is the last AddressFamilySelector set
// by SetAddressFamilySelector. It's an atomic because it needs
// to be accessed by multiple racing routines started while
// Client.conn holds mu.
addrFamSelAtomic syncs.AtomicValue[AddressFamilySelector]
mu sync.Mutex
atomicState syncs.AtomicValue[ConnectedState] // hold mu to write
started bool // true upon first connect, never transitions to false
preferred bool
canAckPings bool
closed bool
netConn io.Closer
client *derp.Client
connGen int // incremented once per new connection; valid values are >0
serverPubKey key.NodePublic
tlsState *tls.ConnectionState
pingOut map[derp.PingMessage]chan<- bool // chan to send to on pong
clock tstime.Clock
}
// ConnectedState describes the state of a derphttp Client.
type ConnectedState struct {
Connected bool
Connecting bool
Closed bool
LocalAddr netip.AddrPort // if Connected
}
derp: add optional debug logging for prober clients This allows tracking packet flow via logs for prober clients. Note that the new sclient.debug() function is called on every received packet, but will do nothing for most clients. I have adjusted sclient logging to print public keys in short format rather than full. This takes effect even for existing non-debug logging (mostly client disconnect messages). Example logs for a packet being sent from client [SbsJn] (connected to derper [dM2E3]) to client [10WOo] (connected to derper [AVxvv]): ``` derper [dM2E3]: derp client 10.0.0.1:35470[SbsJn]: register single client mesh("10.0.1.1"): 4 peers derp client 10.0.0.1:35470[SbsJn]: read frame type 4 len 40 err <nil> derp client 10.0.0.1:35470[SbsJn]: SendPacket for [10WOo], forwarding via <derphttp_client.Client [AVxvv] url=https://10.0.1.1/derp>: <nil> derp client 10.0.0.1:35470[SbsJn]: read frame type 0 len 0 err EOF derp client 10.0.0.1:35470[SbsJn]: read EOF derp client 10.0.0.1:35470[SbsJn]: sender failed: context canceled derp client 10.0.0.1:35470[SbsJn]: removing connection derper [AVxvv]: derp client 10.0.1.1:50650[10WOo]: register single client derp client 10.0.1.1:50650[10WOo]: received forwarded packet from [SbsJn] via [dM2E3] derp client 10.0.1.1:50650[10WOo]: sendPkt attempt 0 enqueued derp client 10.0.1.1:50650[10WOo]: sendPacket from [SbsJn]: <nil> derp client 10.0.1.1:50650[10WOo]: read frame type 0 len 0 err EOF derp client 10.0.1.1:50650[10WOo]: read EOF derp client 10.0.1.1:50650[10WOo]: sender failed: context canceled derp client 10.0.1.1:50650[10WOo]: removing connection ``` Signed-off-by: Anton Tolchanov <anton@tailscale.com>
2 years ago
func (c *Client) String() string {
return fmt.Sprintf("<derphttp_client.Client %s url=%s>", c.ServerPublicKey().ShortString(), c.url)
derp: add optional debug logging for prober clients This allows tracking packet flow via logs for prober clients. Note that the new sclient.debug() function is called on every received packet, but will do nothing for most clients. I have adjusted sclient logging to print public keys in short format rather than full. This takes effect even for existing non-debug logging (mostly client disconnect messages). Example logs for a packet being sent from client [SbsJn] (connected to derper [dM2E3]) to client [10WOo] (connected to derper [AVxvv]): ``` derper [dM2E3]: derp client 10.0.0.1:35470[SbsJn]: register single client mesh("10.0.1.1"): 4 peers derp client 10.0.0.1:35470[SbsJn]: read frame type 4 len 40 err <nil> derp client 10.0.0.1:35470[SbsJn]: SendPacket for [10WOo], forwarding via <derphttp_client.Client [AVxvv] url=https://10.0.1.1/derp>: <nil> derp client 10.0.0.1:35470[SbsJn]: read frame type 0 len 0 err EOF derp client 10.0.0.1:35470[SbsJn]: read EOF derp client 10.0.0.1:35470[SbsJn]: sender failed: context canceled derp client 10.0.0.1:35470[SbsJn]: removing connection derper [AVxvv]: derp client 10.0.1.1:50650[10WOo]: register single client derp client 10.0.1.1:50650[10WOo]: received forwarded packet from [SbsJn] via [dM2E3] derp client 10.0.1.1:50650[10WOo]: sendPkt attempt 0 enqueued derp client 10.0.1.1:50650[10WOo]: sendPacket from [SbsJn]: <nil> derp client 10.0.1.1:50650[10WOo]: read frame type 0 len 0 err EOF derp client 10.0.1.1:50650[10WOo]: read EOF derp client 10.0.1.1:50650[10WOo]: sender failed: context canceled derp client 10.0.1.1:50650[10WOo]: removing connection ``` Signed-off-by: Anton Tolchanov <anton@tailscale.com>
2 years ago
}
// NewRegionClient returns a new DERP-over-HTTP client. It connects lazily.
// To trigger a connection, use Connect.
// The healthTracker parameter is also optional.
func NewRegionClient(privateKey key.NodePrivate, logf logger.Logf, netMon *netmon.Monitor, getRegion func() *tailcfg.DERPRegion) *Client {
if netMon == nil {
panic("nil netMon")
}
ctx, cancel := context.WithCancel(context.Background())
c := &Client{
privateKey: privateKey,
logf: logf,
netMon: netMon,
getRegion: getRegion,
ctx: ctx,
cancelCtx: cancel,
clock: tstime.StdClock{},
}
return c
}
// NewNetcheckClient returns a Client that's only able to have its DialRegionTLS method called.
// It's used by the netcheck package.
func NewNetcheckClient(logf logger.Logf, netMon *netmon.Monitor) *Client {
if netMon == nil {
panic("nil netMon")
}
return &Client{
logf: logf,
clock: tstime.StdClock{},
netMon: netMon,
}
}
// NewClient returns a new DERP-over-HTTP client. It connects lazily.
// To trigger a connection, use Connect.
func NewClient(privateKey key.NodePrivate, serverURL string, logf logger.Logf, netMon *netmon.Monitor) (*Client, error) {
if netMon == nil {
panic("nil netMon")
}
u, err := url.Parse(serverURL)
if err != nil {
return nil, fmt.Errorf("derphttp.NewClient: %v", err)
}
if urlPort(u) == "" {
return nil, fmt.Errorf("derphttp.NewClient: invalid URL scheme %q", u.Scheme)
}
ctx, cancel := context.WithCancel(context.Background())
c := &Client{
privateKey: privateKey,
logf: logf,
url: u,
ctx: ctx,
cancelCtx: cancel,
clock: tstime.StdClock{},
netMon: netMon,
}
return c, nil
}
// isStarted reports whether this client has been used yet.
//
// If if reports false, it may still have its exported fields configured.
func (c *Client) isStarted() bool {
c.mu.Lock()
defer c.mu.Unlock()
return c.started
}
// Connect connects or reconnects to the server, unless already connected.
// It returns nil if there was already a good connection, or if one was made.
func (c *Client) Connect(ctx context.Context) error {
_, _, err := c.connect(ctx, "derphttp.Client.Connect")
return err
}
// newContext returns a new context for setting up a new DERP connection.
// It uses either c.BaseContext or returns context.Background.
func (c *Client) newContext() context.Context {
if c.BaseContext != nil {
ctx := c.BaseContext()
if ctx == nil {
panic("BaseContext returned nil")
}
return ctx
}
return context.Background()
}
// TLSConnectionState returns the last TLS connection state, if any.
// The client must already be connected.
func (c *Client) TLSConnectionState() (_ *tls.ConnectionState, ok bool) {
c.mu.Lock()
defer c.mu.Unlock()
if c.closed || c.client == nil {
return nil, false
}
return c.tlsState, c.tlsState != nil
}
// ServerPublicKey returns the server's public key.
//
// It only returns a non-zero value once a connection has succeeded
// from an earlier call.
func (c *Client) ServerPublicKey() key.NodePublic {
c.mu.Lock()
defer c.mu.Unlock()
return c.serverPubKey
}
// SelfPublicKey returns our own public key.
func (c *Client) SelfPublicKey() key.NodePublic {
return c.privateKey.Public()
}
func urlPort(u *url.URL) string {
if p := u.Port(); p != "" {
return p
}
switch u.Scheme {
case "https":
return "443"
case "http":
return "80"
}
return ""
}
// debugDERPUseHTTP tells clients to connect to DERP via HTTP on port
// 3340 instead of HTTPS on 443.
var debugUseDERPHTTP = envknob.RegisterBool("TS_DEBUG_USE_DERP_HTTP")
func (c *Client) targetString(reg *tailcfg.DERPRegion) string {
if c.url != nil {
return c.url.String()
}
return fmt.Sprintf("region %d (%v)", reg.RegionID, reg.RegionCode)
}
func (c *Client) useHTTPS() bool {
if c.url != nil && c.url.Scheme == "http" {
return false
}
if debugUseDERPHTTP() {
return false
}
return true
}
// tlsServerName returns the tls.Config.ServerName value (for the TLS ClientHello).
func (c *Client) tlsServerName(node *tailcfg.DERPNode) string {
if c.url != nil {
return c.url.Hostname()
}
return node.HostName
}
func (c *Client) urlString(node *tailcfg.DERPNode) string {
if c.url != nil {
return c.url.String()
}
proto := "https"
if debugUseDERPHTTP() {
proto = "http"
}
return fmt.Sprintf("%s://%s/derp", proto, node.HostName)
}
// AddressFamilySelector decides whether IPv6 is preferred for
// outbound dials.
type AddressFamilySelector interface {
// PreferIPv6 reports whether IPv4 dials should be slightly
// delayed to give IPv6 a better chance of winning dial races.
// Implementations should only return true if IPv6 is expected
// to succeed. (otherwise delaying IPv4 will delay the
// connection overall)
PreferIPv6() bool
}
// SetAddressFamilySelector sets the AddressFamilySelector that this
// connection will use. It should be called before any dials.
// The value must not be nil. If called more than once, s must
// be the same concrete type as any prior calls.
func (c *Client) SetAddressFamilySelector(s AddressFamilySelector) {
c.addrFamSelAtomic.Store(s)
}
func (c *Client) preferIPv6() bool {
if s, ok := c.addrFamSelAtomic.Load().(AddressFamilySelector); ok {
return s.PreferIPv6()
}
return false
}
// dialWebsocketFunc is non-nil (set by websocket.go's init) when compiled in.
var dialWebsocketFunc func(ctx context.Context, urlStr string) (net.Conn, error)
func useWebsockets() bool {
if runtime.GOOS == "js" {
return true
}
if dialWebsocketFunc != nil {
return envknob.Bool("TS_DEBUG_DERP_WS_CLIENT")
}
return false
}
func (c *Client) connect(ctx context.Context, caller string) (client *derp.Client, connGen int, err error) {
c.mu.Lock()
defer c.mu.Unlock()
c.started = true
if c.closed {
return nil, 0, ErrClientClosed
}
if c.client != nil {
return c.client, c.connGen, nil
}
c.atomicState.Store(ConnectedState{Connecting: true})
defer func() {
if err != nil {
c.atomicState.Store(ConnectedState{Connecting: false})
}
}()
// timeout is the fallback maximum time (if ctx doesn't limit
// it further) to do all of: DNS + TCP + TLS + HTTP Upgrade +
// DERP upgrade.
const timeout = 10 * time.Second
ctx, cancel := context.WithTimeout(ctx, timeout)
go func() {
select {
case <-ctx.Done():
// Either timeout fired (handled below), or
// we're returning via the defer cancel()
// below.
case <-c.ctx.Done():
// Propagate a Client.Close call into
// cancelling this context.
cancel()
}
}()
defer cancel()
var reg *tailcfg.DERPRegion // nil when using c.url to dial
if c.getRegion != nil {
reg = c.getRegion()
if reg == nil {
return nil, 0, errors.New("DERP region not available")
}
}
var tcpConn net.Conn
defer func() {
if err != nil {
if ctx.Err() != nil {
err = fmt.Errorf("%v: %v", ctx.Err(), err)
}
err = fmt.Errorf("%s connect to %v: %v", caller, c.targetString(reg), err)
if tcpConn != nil {
go tcpConn.Close()
}
}
}()
var node *tailcfg.DERPNode // nil when using c.url to dial
switch {
case useWebsockets():
var urlStr string
if c.url != nil {
urlStr = c.url.String()
} else {
urlStr = c.urlString(reg.Nodes[0])
}
c.logf("%s: connecting websocket to %v", caller, urlStr)
conn, err := dialWebsocketFunc(ctx, urlStr)
if err != nil {
c.logf("%s: websocket to %v error: %v", caller, urlStr, err)
return nil, 0, err
}
brw := bufio.NewReadWriter(bufio.NewReader(conn), bufio.NewWriter(conn))
derpClient, err := derp.NewClient(c.privateKey, conn, brw, c.logf,
derp.MeshKey(c.MeshKey),
derp.CanAckPings(c.canAckPings),
derp.IsProber(c.IsProber),
)
if err != nil {
return nil, 0, err
}
if c.preferred {
if err := derpClient.NotePreferred(true); err != nil {
go conn.Close()
return nil, 0, err
}
}
c.serverPubKey = derpClient.ServerPublicKey()
c.client = derpClient
c.netConn = conn
c.connGen++
return c.client, c.connGen, nil
case c.url != nil:
c.logf("%s: connecting to %v", caller, c.url)
tcpConn, err = c.dialURL(ctx)
default:
c.logf("%s: connecting to derp-%d (%v)", caller, reg.RegionID, reg.RegionCode)
tcpConn, node, err = c.dialRegion(ctx, reg)
}
if err != nil {
return nil, 0, err
}
// Now that we have a TCP connection, force close it if the
// TLS handshake + DERP setup takes too long.
done := make(chan struct{})
defer close(done)
go func() {
select {
case <-done:
// Normal path. Upgrade occurred in time.
case <-ctx.Done():
select {
case <-done:
// Normal path. Upgrade occurred in time.
// But the ctx.Done() is also done because
// the "defer cancel()" above scheduled
// before this goroutine.
default:
// The TLS or HTTP or DERP exchanges didn't complete
// in time. Force close the TCP connection to force
// them to fail quickly.
tcpConn.Close()
}
}
}()
var httpConn net.Conn // a TCP conn or a TLS conn; what we speak HTTP to
var serverPub key.NodePublic // or zero if unknown (if not using TLS or TLS middlebox eats it)
var serverProtoVersion int
var tlsState *tls.ConnectionState
if c.useHTTPS() {
tlsConn := c.tlsClient(tcpConn, node)
httpConn = tlsConn
// Force a handshake now (instead of waiting for it to
// be done implicitly on read/write) so we can check
// the ConnectionState.
if err := tlsConn.Handshake(); err != nil {
return nil, 0, err
}
// We expect to be using TLS 1.3 to our own servers, and only
// starting at TLS 1.3 are the server's returned certificates
// encrypted, so only look for and use our "meta cert" if we're
// using TLS 1.3. If we're not using TLS 1.3, it might be a user
// running cmd/derper themselves with a different configuration,
// in which case we can avoid this fast-start optimization.
// (If a corporate proxy is MITM'ing TLS 1.3 connections with
// corp-mandated TLS root certs than all bets are off anyway.)
// Note that we're not specifically concerned about TLS downgrade
// attacks. TLS handles that fine:
// https://blog.gypsyengineer.com/en/security/how-does-tls-1-3-protect-against-downgrade-attacks.html
cs := tlsConn.ConnectionState()
tlsState = &cs
if cs.Version >= tls.VersionTLS13 {
serverPub, serverProtoVersion = parseMetaCert(cs.PeerCertificates)
}
} else {
httpConn = tcpConn
}
brw := bufio.NewReadWriter(bufio.NewReader(httpConn), bufio.NewWriter(httpConn))
var derpClient *derp.Client
req, err := http.NewRequest("GET", c.urlString(node), nil)
if err != nil {
return nil, 0, err
}
req.Header.Set("Upgrade", "DERP")
req.Header.Set("Connection", "Upgrade")
if !serverPub.IsZero() && serverProtoVersion != 0 {
// parseMetaCert found the server's public key (no TLS
// middlebox was in the way), so skip the HTTP upgrade
// exchange. See https://github.com/tailscale/tailscale/issues/693
// for an overview. We still send the HTTP request
// just to get routed into the server's HTTP Handler so it
// can Hijack the request, but we signal with a special header
// that we don't want to deal with its HTTP response.
req.Header.Set(fastStartHeader, "1") // suppresses the server's HTTP response
if err := req.Write(brw); err != nil {
return nil, 0, err
}
// No need to flush the HTTP request. the derp.Client's initial
// client auth frame will flush it.
} else {
if err := req.Write(brw); err != nil {
return nil, 0, err
}
if err := brw.Flush(); err != nil {
return nil, 0, err
}
resp, err := http.ReadResponse(brw.Reader, req)
if err != nil {
return nil, 0, err
}
if resp.StatusCode != http.StatusSwitchingProtocols {
b, _ := io.ReadAll(resp.Body)
resp.Body.Close()
return nil, 0, fmt.Errorf("GET failed: %v: %s", err, b)
}
}
derpClient, err = derp.NewClient(c.privateKey, httpConn, brw, c.logf,
derp.MeshKey(c.MeshKey),
derp.ServerPublicKey(serverPub),
derp.CanAckPings(c.canAckPings),
derp.IsProber(c.IsProber),
)
if err != nil {
return nil, 0, err
}
if c.preferred {
if err := derpClient.NotePreferred(true); err != nil {
go httpConn.Close()
return nil, 0, err
}
}
if c.WatchConnectionChanges {
if err := derpClient.WatchConnectionChanges(); err != nil {
go httpConn.Close()
return nil, 0, err
}
}
c.serverPubKey = derpClient.ServerPublicKey()
c.client = derpClient
c.netConn = tcpConn
c.tlsState = tlsState
c.connGen++
localAddr, _ := c.client.LocalAddr()
c.atomicState.Store(ConnectedState{
Connected: true,
LocalAddr: localAddr,
})
return c.client, c.connGen, nil
}
// SetURLDialer sets the dialer to use for dialing URLs.
// This dialer is only use for clients created with NewClient, not NewRegionClient.
// If unset or nil, the default dialer is used.
//
// The primary use for this is the derper mesh mode to connect to each
// other over a VPC network.
func (c *Client) SetURLDialer(dialer func(ctx context.Context, network, addr string) (net.Conn, error)) {
c.dialer = dialer
}
func (c *Client) dialURL(ctx context.Context) (net.Conn, error) {
host := c.url.Hostname()
if c.dialer != nil {
return c.dialer(ctx, "tcp", net.JoinHostPort(host, urlPort(c.url)))
}
hostOrIP := host
dialer := netns.NewDialer(c.logf, c.netMon)
if c.DNSCache != nil {
ip, _, _, err := c.DNSCache.LookupIP(ctx, host)
if err == nil {
hostOrIP = ip.String()
}
if err != nil && netns.IsSOCKSDialer(dialer) {
// Return an error if we're not using a dial
// proxy that can do DNS lookups for us.
return nil, err
}
}
tcpConn, err := dialer.DialContext(ctx, "tcp", net.JoinHostPort(hostOrIP, urlPort(c.url)))
if err != nil {
return nil, fmt.Errorf("dial of %v: %v", host, err)
}
return tcpConn, nil
}
// dialRegion returns a TCP connection to the provided region, trying
// each node in order (with dialNode) until one connects or ctx is
// done.
func (c *Client) dialRegion(ctx context.Context, reg *tailcfg.DERPRegion) (net.Conn, *tailcfg.DERPNode, error) {
if len(reg.Nodes) == 0 {
return nil, nil, fmt.Errorf("no nodes for %s", c.targetString(reg))
}
var firstErr error
for _, n := range reg.Nodes {
if n.STUNOnly {
if firstErr == nil {
firstErr = fmt.Errorf("no non-STUNOnly nodes for %s", c.targetString(reg))
}
continue
}
c, err := c.dialNode(ctx, n)
if err == nil {
return c, n, nil
}
if firstErr == nil {
firstErr = err
}
}
return nil, nil, firstErr
}
func (c *Client) tlsClient(nc net.Conn, node *tailcfg.DERPNode) *tls.Conn {
tlsConf := tlsdial.Config(c.tlsServerName(node), c.HealthTracker, c.TLSConfig)
if node != nil {
if node.InsecureForTests {
tlsConf.InsecureSkipVerify = true
tlsConf.VerifyConnection = nil
}
if node.CertName != "" {
tlsdial.SetConfigExpectedCert(tlsConf, node.CertName)
}
}
return tls.Client(nc, tlsConf)
}
// DialRegionTLS returns a TLS connection to a DERP node in the given region.
//
// DERP nodes for a region are tried in sequence according to their order
// in the DERP map. TLS is initiated on the first node where a socket is
// established.
func (c *Client) DialRegionTLS(ctx context.Context, reg *tailcfg.DERPRegion) (tlsConn *tls.Conn, connClose io.Closer, node *tailcfg.DERPNode, err error) {
tcpConn, node, err := c.dialRegion(ctx, reg)
if err != nil {
return nil, nil, nil, err
}
done := make(chan bool) // unbuffered
defer close(done)
tlsConn = c.tlsClient(tcpConn, node)
go func() {
select {
case <-done:
case <-ctx.Done():
tcpConn.Close()
}
}()
err = tlsConn.Handshake()
if err != nil {
return nil, nil, nil, err
}
select {
case done <- true:
return tlsConn, tcpConn, node, nil
case <-ctx.Done():
return nil, nil, nil, ctx.Err()
}
}
func (c *Client) dialContext(ctx context.Context, proto, addr string) (net.Conn, error) {
return netns.NewDialer(c.logf, c.netMon).DialContext(ctx, proto, addr)
}
// shouldDialProto reports whether an explicitly provided IPv4 or IPv6
// address (given in s) is valid. An empty value means to dial, but to
// use DNS. The predicate function reports whether the non-empty
// string s contained a valid IP address of the right family.
func shouldDialProto(s string, pred func(netip.Addr) bool) bool {
if s == "" {
return true
}
ip, _ := netip.ParseAddr(s)
return pred(ip)
}
const dialNodeTimeout = 1500 * time.Millisecond
// dialNode returns a TCP connection to node n, racing IPv4 and IPv6
// (both as applicable) against each other.
// A node is only given dialNodeTimeout to connect.
//
// TODO(bradfitz): longer if no options remain perhaps? ... Or longer
// overall but have dialRegion start overlapping races?
func (c *Client) dialNode(ctx context.Context, n *tailcfg.DERPNode) (net.Conn, error) {
// First see if we need to use an HTTP proxy.
proxyReq := &http.Request{
Method: "GET", // doesn't really matter
URL: &url.URL{
Scheme: "https",
Host: c.tlsServerName(n),
Path: "/", // unused
},
}
if proxyURL, err := tshttpproxy.ProxyFromEnvironment(proxyReq); err == nil && proxyURL != nil {
return c.dialNodeUsingProxy(ctx, n, proxyURL)
}
type res struct {
c net.Conn
err error
}
resc := make(chan res) // must be unbuffered
ctx, cancel := context.WithTimeout(ctx, dialNodeTimeout)
defer cancel()
ctx = sockstats.WithSockStats(ctx, sockstats.LabelDERPHTTPClient, c.logf)
nwait := 0
startDial := func(dstPrimary, proto string) {
nwait++
go func() {
if proto == "tcp4" && c.preferIPv6() {
t, tChannel := c.clock.NewTimer(200 * time.Millisecond)
select {
case <-ctx.Done():
// Either user canceled original context,
// it timed out, or the v6 dial succeeded.
t.Stop()
return
case <-tChannel:
// Start v4 dial
}
}
dst := cmp.Or(dstPrimary, n.HostName)
port := "443"
if n.DERPPort != 0 {
port = fmt.Sprint(n.DERPPort)
}
c, err := c.dialContext(ctx, proto, net.JoinHostPort(dst, port))
select {
case resc <- res{c, err}:
case <-ctx.Done():
if c != nil {
c.Close()
}
}
}()
}
if shouldDialProto(n.IPv4, netip.Addr.Is4) {
startDial(n.IPv4, "tcp4")
}
if shouldDialProto(n.IPv6, netip.Addr.Is6) {
startDial(n.IPv6, "tcp6")
}
if nwait == 0 {
return nil, errors.New("both IPv4 and IPv6 are explicitly disabled for node")
}
var firstErr error
for {
select {
case res := <-resc:
nwait--
if res.err == nil {
return res.c, nil
}
if firstErr == nil {
firstErr = res.err
}
if nwait == 0 {
return nil, firstErr
}
case <-ctx.Done():
return nil, ctx.Err()
}
}
}
func firstStr(a, b string) string {
if a != "" {
return a
}
return b
}
// dialNodeUsingProxy connects to n using a CONNECT to the HTTP(s) proxy in proxyURL.
func (c *Client) dialNodeUsingProxy(ctx context.Context, n *tailcfg.DERPNode, proxyURL *url.URL) (_ net.Conn, err error) {
pu := proxyURL
var proxyConn net.Conn
if pu.Scheme == "https" {
var d tls.Dialer
proxyConn, err = d.DialContext(ctx, "tcp", net.JoinHostPort(pu.Hostname(), firstStr(pu.Port(), "443")))
} else {
var d net.Dialer
proxyConn, err = d.DialContext(ctx, "tcp", net.JoinHostPort(pu.Hostname(), firstStr(pu.Port(), "80")))
}
defer func() {
if err != nil && proxyConn != nil {
// In a goroutine in case it's a *tls.Conn (that can block on Close)
// TODO(bradfitz): track the underlying tcp.Conn and just close that instead.
go proxyConn.Close()
}
}()
if err != nil {
return nil, err
}
done := make(chan struct{})
defer close(done)
go func() {
select {
case <-done:
return
case <-ctx.Done():
proxyConn.Close()
}
}()
target := net.JoinHostPort(n.HostName, "443")
var authHeader string
if v, err := tshttpproxy.GetAuthHeader(pu); err != nil {
c.logf("derphttp: error getting proxy auth header for %v: %v", proxyURL, err)
} else if v != "" {
authHeader = fmt.Sprintf("Proxy-Authorization: %s\r\n", v)
}
if _, err := fmt.Fprintf(proxyConn, "CONNECT %s HTTP/1.1\r\nHost: %s\r\n%s\r\n", target, target, authHeader); err != nil {
if ctx.Err() != nil {
return nil, ctx.Err()
}
return nil, err
}
br := bufio.NewReader(proxyConn)
res, err := http.ReadResponse(br, nil)
if err != nil {
if ctx.Err() != nil {
return nil, ctx.Err()
}
c.logf("derphttp: CONNECT dial to %s: %v", target, err)
return nil, err
}
c.logf("derphttp: CONNECT dial to %s: %v", target, res.Status)
if res.StatusCode != 200 {
return nil, fmt.Errorf("invalid response status from HTTP proxy %s on CONNECT to %s: %v", pu, target, res.Status)
}
return proxyConn, nil
}
func (c *Client) Send(dstKey key.NodePublic, b []byte) error {
client, _, err := c.connect(c.newContext(), "derphttp.Client.Send")
if err != nil {
return err
}
if err := client.Send(dstKey, b); err != nil {
c.closeForReconnect(client)
}
return err
}
func (c *Client) registerPing(m derp.PingMessage, ch chan<- bool) {
c.mu.Lock()
defer c.mu.Unlock()
if c.pingOut == nil {
c.pingOut = map[derp.PingMessage]chan<- bool{}
}
c.pingOut[m] = ch
}
func (c *Client) unregisterPing(m derp.PingMessage) {
c.mu.Lock()
defer c.mu.Unlock()
delete(c.pingOut, m)
}
func (c *Client) handledPong(m derp.PongMessage) bool {
c.mu.Lock()
defer c.mu.Unlock()
k := derp.PingMessage(m)
if ch, ok := c.pingOut[k]; ok {
ch <- true
delete(c.pingOut, k)
return true
}
return false
}
// Ping sends a ping to the peer and waits for it either to be
// acknowledged (in which case Ping returns nil) or waits for ctx to
// be over and returns an error. It will wait at most 5 seconds
// before returning an error.
//
// Another goroutine must be in a loop calling Recv or
// RecvDetail or ping responses won't be handled.
func (c *Client) Ping(ctx context.Context) error {
maxDL := time.Now().Add(5 * time.Second)
if dl, ok := ctx.Deadline(); !ok || dl.After(maxDL) {
var cancel context.CancelFunc
ctx, cancel = context.WithDeadline(ctx, maxDL)
defer cancel()
}
var data derp.PingMessage
rand.Read(data[:])
gotPing := make(chan bool, 1)
c.registerPing(data, gotPing)
defer c.unregisterPing(data)
if err := c.SendPing(data); err != nil {
return err
}
select {
case <-gotPing:
return nil
case <-ctx.Done():
return ctx.Err()
}
}
// SendPing writes a ping message, without any implicit connect or
// reconnect. This is a lower-level interface that writes a frame
// without any implicit handling of the response pong, if any. For a
// higher-level interface, use Ping.
func (c *Client) SendPing(data [8]byte) error {
c.mu.Lock()
closed, client := c.closed, c.client
c.mu.Unlock()
if closed {
return ErrClientClosed
}
if client == nil {
return errors.New("client not connected")
}
return client.SendPing(data)
}
// LocalAddr reports c's local TCP address, without any implicit
// connect or reconnect.
func (c *Client) LocalAddr() (netip.AddrPort, error) {
st := c.atomicState.Load()
if st.Closed {
return netip.AddrPort{}, ErrClientClosed
}
la := st.LocalAddr
if !st.Connected && !la.IsValid() {
return netip.AddrPort{}, errors.New("client not connected")
}
return la, nil
}
func (c *Client) ForwardPacket(from, to key.NodePublic, b []byte) error {
client, _, err := c.connect(c.newContext(), "derphttp.Client.ForwardPacket")
if err != nil {
return err
}
if err := client.ForwardPacket(from, to, b); err != nil {
c.closeForReconnect(client)
}
return err
}
// SendPong sends a reply to a ping, with the ping's provided
// challenge/identifier data.
//
// Unlike other send methods, SendPong makes no attempt to connect or
// reconnect to the peer. It's best effort. If there's a connection
// problem, the server will choose to hang up on us if we're not
// replying.
func (c *Client) SendPong(data [8]byte) error {
c.mu.Lock()
if c.closed {
c.mu.Unlock()
return ErrClientClosed
}
if c.client == nil {
c.mu.Unlock()
return errors.New("not connected")
}
dc := c.client
c.mu.Unlock()
return dc.SendPong(data)
}
// SetCanAckPings sets whether this client will reply to ping requests from the server.
//
// This only affects future connections.
func (c *Client) SetCanAckPings(v bool) {
c.mu.Lock()
defer c.mu.Unlock()
c.canAckPings = v
}
// NotePreferred notes whether this Client is the caller's preferred
// (home) DERP node. It's only used for stats.
func (c *Client) NotePreferred(v bool) {
c.mu.Lock()
if c.preferred == v {
c.mu.Unlock()
return
}
c.preferred = v
client := c.client
c.mu.Unlock()
if client != nil {
if err := client.NotePreferred(v); err != nil {
c.closeForReconnect(client)
}
}
}
// ClosePeer asks the server to close target's TCP connection.
//
// Only trusted connections (using MeshKey) are allowed to use this.
func (c *Client) ClosePeer(target key.NodePublic) error {
client, _, err := c.connect(c.newContext(), "derphttp.Client.ClosePeer")
if err != nil {
return err
}
err = client.ClosePeer(target)
if err != nil {
c.closeForReconnect(client)
}
return err
}
// Recv reads a message from c. The returned message may alias memory from Client.
// The message should only be used until the next Client call.
func (c *Client) Recv() (derp.ReceivedMessage, error) {
m, _, err := c.RecvDetail()
return m, err
}
// RecvDetail is like Recv, but additional returns the connection generation on each message.
// The connGen value is incremented every time the derphttp.Client reconnects to the server.
func (c *Client) RecvDetail() (m derp.ReceivedMessage, connGen int, err error) {
client, connGen, err := c.connect(c.newContext(), "derphttp.Client.Recv")
if err != nil {
return nil, 0, err
}
for {
m, err = client.Recv()
switch m := m.(type) {
case derp.PongMessage:
if c.handledPong(m) {
continue
}
}
if err != nil {
c.closeForReconnect(client)
if c.isClosed() {
err = ErrClientClosed
}
}
return m, connGen, err
}
}
func (c *Client) isClosed() bool {
c.mu.Lock()
defer c.mu.Unlock()
return c.closed
}
// Close closes the client. It will not automatically reconnect after
// being closed.
func (c *Client) Close() error {
if c.cancelCtx != nil {
c.cancelCtx() // not in lock, so it can cancel Connect, which holds mu
}
c.mu.Lock()
defer c.mu.Unlock()
if c.closed {
return ErrClientClosed
}
c.closed = true
if c.netConn != nil {
c.netConn.Close()
}
c.atomicState.Store(ConnectedState{Closed: true})
return nil
}
// closeForReconnect closes the underlying network connection and
// zeros out the client field so future calls to Connect will
// reconnect.
//
// The provided brokenClient is the client to forget. If current
// client is not brokenClient, closeForReconnect does nothing. (This
// prevents a send and receive goroutine from failing at the ~same
// time and both calling closeForReconnect and the caller goroutines
// forever calling closeForReconnect in lockstep endlessly;
// https://github.com/tailscale/tailscale/pull/264)
func (c *Client) closeForReconnect(brokenClient *derp.Client) {
c.mu.Lock()
defer c.mu.Unlock()
if c.client != brokenClient {
return
}
if c.netConn != nil {
c.netConn.Close()
c.netConn = nil
}
c.client = nil
}
var ErrClientClosed = errors.New("derphttp.Client closed")
func parseMetaCert(certs []*x509.Certificate) (serverPub key.NodePublic, serverProtoVersion int) {
for _, cert := range certs {
// Look for derpkey prefix added by initMetacert() on the server side.
if pubHex, ok := strings.CutPrefix(cert.Subject.CommonName, "derpkey"); ok {
var err error
serverPub, err = key.ParseNodePublicUntyped(mem.S(pubHex))
if err == nil && cert.SerialNumber.BitLen() <= 8 { // supports up to version 255
return serverPub, int(cert.SerialNumber.Int64())
}
}
}
return key.NodePublic{}, 0
}