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netcheck: address some HTTP fallback measurement TODOs

This commit is contained in:
Brad Fitzpatrick 2020-05-29 13:31:08 -07:00
parent db2a216561
commit 3fa58303d0
2 changed files with 78 additions and 26 deletions
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17
derp/derphttp/derphttp_client.go
View File

@ -75,6 +75,12 @@ func NewRegionClient(privateKey key.Private, logf logger.Logf, getRegion func()
return c
}
// NewNetcheckClient returns a Client that's only able to have its DialRegion method called.
// It's used by the netcheck package.
func NewNetcheckClient(logf logger.Logf) *Client {
return &Client{logf: logf}
}
// NewClient returns a new DERP-over-HTTP client. It connects lazily.
// To trigger a connection, use Connect.
func NewClient(privateKey key.Private, serverURL string, logf logger.Logf) (*Client, error) {
@ -136,7 +142,8 @@ func (c *Client) useHTTPS() bool {
return true
}
func (c *Client) tlsServerName(node *tailcfg.DERPNode) string {
// TLSServerName returns which TLS cert name to expect for the given node.
func (c *Client) TLSServerName(node *tailcfg.DERPNode) string {
if c.url != nil {
return c.url.Host
}
@ -210,7 +217,7 @@ func (c *Client) connect(ctx context.Context, caller string) (client *derp.Clien
tcpConn, err = c.dialURL(ctx)
} else {
c.logf("%s: connecting to derp-%d (%v)", caller, reg.RegionID, reg.RegionCode)
tcpConn, node, err = c.dialRegion(ctx, reg)
tcpConn, node, err = c.DialRegion(ctx, reg)
}
if err != nil {
return nil, err
@ -242,7 +249,7 @@ func (c *Client) connect(ctx context.Context, caller string) (client *derp.Clien
var httpConn net.Conn // a TCP conn or a TLS conn; what we speak HTTP to
if c.useHTTPS() {
tlsConf := tlsdial.Config(c.tlsServerName(node), c.TLSConfig)
tlsConf := tlsdial.Config(c.TLSServerName(node), c.TLSConfig)
if node != nil && node.DERPTestPort != 0 {
tlsConf.InsecureSkipVerify = true
}
@ -322,10 +329,10 @@ func (c *Client) dialURL(ctx context.Context) (net.Conn, error) {
return tcpConn, nil
}
// dialRegion returns a TCP connection to the provided region, trying
// 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) {
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))
}

87
net/netcheck/netcheck.go
View File

@ -21,6 +21,7 @@ import (
"github.com/tcnksm/go-httpstat"
"inet.af/netaddr"
"tailscale.com/derp/derphttp"
"tailscale.com/net/dnscache"
"tailscale.com/net/interfaces"
"tailscale.com/net/netns"
@ -611,10 +612,15 @@ func newReport() *Report {
//
// It may not be called concurrently with itself.
func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (*Report, error) {
// Wait for STUN for 3 seconds, but then give HTTP probing
// another 2 seconds if all UDP failed.
const overallTimeout = 5 * time.Second
const stunTimeout = 3 * time.Second
// Mask user context with ours that we guarantee to cancel so
// we can depend on it being closed in goroutines later.
// (User ctx might be context.Background, etc)
ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
ctx, cancel := context.WithTimeout(ctx, overallTimeout)
defer cancel()
if dm == nil {
@ -707,7 +713,11 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (*Report, e
}(probeSet)
}
stunTimer := time.NewTimer(stunTimeout)
defer stunTimer.Stop()
select {
case <-stunTimer.C:
case <-ctx.Done():
case <-wg.DoneChan():
case <-rs.stopProbeCh:
@ -719,7 +729,8 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (*Report, e
rs.stopTimers()
// Try HTTPS latency check if all STUN probes failed due to UDP presumably being blocked.
if !rs.anyUDP() {
// TODO: this should be moved into the probePlan, using probeProto probeHTTPS.
if !rs.anyUDP() && ctx.Err() == nil {
var wg sync.WaitGroup
var need []*tailcfg.DERPRegion
for rid, reg := range dm.Regions {
@ -734,11 +745,22 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (*Report, e
for _, reg := range need {
go func(reg *tailcfg.DERPRegion) {
defer wg.Done()
if d, err := c.measureHTTPSLatency(reg); err != nil {
if d, ip, err := c.measureHTTPSLatency(ctx, reg); err != nil {
c.logf("netcheck: measuring HTTPS latency of %v (%d): %v", reg.RegionCode, reg.RegionID, err)
} else {
rs.mu.Lock()
rs.report.RegionLatency[reg.RegionID] = d
// We set these IPv4 and IPv6 but they're not really used
// and we don't necessarily set them both. If UDP is blocked
// and both IPv4 and IPv6 are available over TCP, it's basically
// random which fields end up getting set here.
// Since they're not needed, that's fine for now.
if ip.Is4() {
rs.report.IPv4 = true
}
if ip.Is6() {
rs.report.IPv6 = true
}
rs.mu.Unlock()
}
}(reg)
@ -756,41 +778,64 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (*Report, e
return report, nil
}
// TODO: have caller pass in context
func (c *Client) measureHTTPSLatency(reg *tailcfg.DERPRegion) (time.Duration, error) {
if len(reg.Nodes) == 0 {
return 0, errors.New("no nodes")
}
node := reg.Nodes[0] // TODO: use all nodes per region
host := node.HostName
// TODO: connect using provided IPv4/IPv6; use a Trasport & set the dialer
// TODO: also have the caller set the Report.IPv4 or Report.IPv6 bool
func (c *Client) measureHTTPSLatency(ctx context.Context, reg *tailcfg.DERPRegion) (time.Duration, netaddr.IP, error) {
var result httpstat.Result
hctx, cancel := context.WithTimeout(httpstat.WithHTTPStat(context.Background(), &result), 5*time.Second)
ctx, cancel := context.WithTimeout(httpstat.WithHTTPStat(ctx, &result), 5*time.Second)
defer cancel()
u := fmt.Sprintf("https://%s/derp/latency-check", host)
req, err := http.NewRequestWithContext(hctx, "GET", u, nil)
var ip netaddr.IP
dc := derphttp.NewNetcheckClient(c.logf)
nc, node, err := dc.DialRegion(ctx, reg)
if err != nil {
return 0, err
return 0, ip, err
}
defer nc.Close()
if ta, ok := nc.RemoteAddr().(*net.TCPAddr); ok {
ip, _ = netaddr.FromStdIP(ta.IP)
}
if ip == (netaddr.IP{}) {
return 0, ip, fmt.Errorf("no unexpected RemoteAddr %#v", nc.RemoteAddr())
}
resp, err := http.DefaultClient.Do(req)
connc := make(chan net.Conn, 1)
connc <- nc
tr := &http.Transport{
DialTLSContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
select {
case nc := <-connc:
return nc, nil
default:
return nil, errors.New("only one conn expected")
}
},
}
hc := &http.Client{Transport: tr}
host := dc.TLSServerName(node)
u := fmt.Sprintf("https://%s/derp/latency-check", host)
req, err := http.NewRequestWithContext(ctx, "GET", u, nil)
if err != nil {
return 0, err
return 0, ip, err
}
resp, err := hc.Do(req)
if err != nil {
return 0, ip, err
}
defer resp.Body.Close()
_, err = io.Copy(ioutil.Discard, resp.Body)
if err != nil {
return 0, err
return 0, ip, err
}
result.End(c.timeNow())
// TODO: decide best timing heuristic here.
// Maybe the server should return the tcpinfo_rtt?
return result.ServerProcessing, nil
return result.ServerProcessing, ip, nil
}
func (c *Client) logConciseReport(r *Report, dm *tailcfg.DERPMap) {