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netcheck: DERP latency over HTTPS when UDP is blocked

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* netcheck: DERP letency over HTTPS when UDP failed

Updates #207

Signed-off-by: Zijie Lu <zijie@tailscale.com>

* netcheck: async DERP latency check over HTTPS

Updates #207

Signed-off-by: Zijie Lu <zijie@tailscale.com>

* netcheck: DERP latency check over HTTPS: fix concurrent map

Updates #207

Signed-off-by: Zijie Lu <zijie@tailscale.com>

* netcheck: DERP latency check over HTTPS: some improvements

Updates #207

Signed-off-by: Zijie Lu <zijie@tailscale.com>

* netcheck: DERP latency check over HTTPS: use timeout context

Updates #207

Signed-off-by: Zijie Lu <zijie@tailscale.com>

* netcheck: DERP latency check over HTTPS: use report mutex

Updates #207

Signed-off-by: Zijie Lu <zijie@tailscale.com>

* netcheck: DERP latency check over HTTPS if UDP is BLOCKED

Updates #207

Signed-off-by: Zijie Lu <zijie@tailscale.com>

* netcheck: DERP latency check over HTTPS: new function measureHTTPSLatency

Updates #207

Signed-off-by: Zijie Lu <zijie@tailscale.com>
This commit is contained in:
halulu 2020-05-11 11:23:09 -04:00 committed by GitHub
parent 8a3e77fc43
commit 874be6566d
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 64 additions and 7 deletions
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1
go.mod
View File

@ -19,6 +19,7 @@ require (
github.com/peterbourgon/ff/v2 v2.0.0
github.com/tailscale/winipcfg-go v0.0.0-20200413171540-609dcf2df55f
github.com/tailscale/wireguard-go v0.0.0-20200424121617-8d10f231531a
github.com/tcnksm/go-httpstat v0.2.0
github.com/toqueteos/webbrowser v1.2.0
go4.org/mem v0.0.0-20200411205429-f77f31c81751
golang.org/x/crypto v0.0.0-20200317142112-1b76d66859c6

2
go.sum
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@ -81,6 +81,8 @@ github.com/tailscale/winipcfg-go v0.0.0-20200413171540-609dcf2df55f h1:uFj5bslHs
github.com/tailscale/winipcfg-go v0.0.0-20200413171540-609dcf2df55f/go.mod h1:x880GWw5fvrl2DVTQ04ttXQD4DuppTt1Yz6wLibbjNE=
github.com/tailscale/wireguard-go v0.0.0-20200424121617-8d10f231531a h1:HMkTFyhcvZaKf7+7T76rks4HqB83fptUemBIfLGI6TM=
github.com/tailscale/wireguard-go v0.0.0-20200424121617-8d10f231531a/go.mod h1:JPm5cTfu1K+qDFRbiHy0sOlHUylYQbpl356sdYFD8V4=
github.com/tcnksm/go-httpstat v0.2.0 h1:rP7T5e5U2HfmOBmZzGgGZjBQ5/GluWUylujl0tJ04I0=
github.com/tcnksm/go-httpstat v0.2.0/go.mod h1:s3JVJFtQxtBEBC9dwcdTTXS9xFnM3SXAZwPG41aurT8=
github.com/toqueteos/webbrowser v1.2.0 h1:tVP/gpK69Fx+qMJKsLE7TD8LuGWPnEV71wBN9rrstGQ=
github.com/toqueteos/webbrowser v1.2.0/go.mod h1:XWoZq4cyp9WeUeak7w7LXRUQf1F1ATJMir8RTqb4ayM=
github.com/ulikunitz/xz v0.5.6 h1:jGHAfXawEGZQ3blwU5wnWKQJvAraT7Ftq9EXjnXYgt8=

68
netcheck/netcheck.go
View File

@ -11,12 +11,15 @@
"errors"
"fmt"
"io"
"io/ioutil"
"log"
"net"
"net/http"
"sort"
"sync"
"time"
"github.com/tcnksm/go-httpstat"
"golang.org/x/sync/errgroup"
"tailscale.com/derp/derpmap"
"tailscale.com/net/dnscache"
@ -442,8 +445,6 @@ func (c *Client) GetReport(ctx context.Context) (*Report, error) {
}
mu.Lock()
defer mu.Unlock()
// Check hairpinning.
if ret.MappingVariesByDestIP == "false" && gotEP4 != "" {
select {
@ -453,12 +454,32 @@ func (c *Client) GetReport(ctx context.Context) (*Report, error) {
ret.HairPinning.Set(false)
}
}
mu.Unlock()
// TODO: if UDP is blocked, try to measure TCP connect times
// to DERP nodes instead? So UDP-blocked users still get a
// decent DERP node, rather than being randomly assigned to
// the other side of the planet? Or try ICMP? (likely also
// blocked?)
// Try HTTPS latency check if UDP is blocked and all checkings failed
if !anyV4() {
c.logf("netcheck: UDP is blocked, try HTTPS")
var wg sync.WaitGroup
for _, server := range stuns4 {
server := server
if _, ok := ret.DERPLatency[server]; ok {
continue
}
wg.Add(1)
go func() {
defer wg.Done()
if d, err := c.measureHTTPSLatency(server); err != nil {
c.logf("netcheck: measuring HTTPS latency of %v: %v", server, err)
} else {
mu.Lock()
ret.DERPLatency[server] = d
mu.Unlock()
}
}()
}
wg.Wait()
}
report := ret.Clone()
@ -468,6 +489,39 @@ func (c *Client) GetReport(ctx context.Context) (*Report, error) {
return report, nil
}
func (c *Client) measureHTTPSLatency(server string) (time.Duration, error) {
host, _, err := net.SplitHostPort(server)
if err != nil {
return 0, err
}
var result httpstat.Result
hctx, cancel := context.WithTimeout(httpstat.WithHTTPStat(context.Background(), &result), 5*time.Second)
defer cancel()
u := fmt.Sprintf("https://%s/derp/latency-check", host)
req, err := http.NewRequestWithContext(hctx, "GET", u, nil)
if err != nil {
return 0, err
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
return 0, err
}
defer resp.Body.Close()
_, err = io.Copy(ioutil.Discard, resp.Body)
if err != nil {
return 0, err
}
result.End(c.timeNow())
// TODO: decide best timing heuristic here.
// Maybe the server should return the tcpinfo_rtt?
return result.ServerProcessing, nil
}
func (c *Client) logConciseReport(r *Report) {
buf := bytes.NewBuffer(make([]byte, 0, 256)) // empirically: 5 DERPs + IPv6 == ~233 bytes
fmt.Fprintf(buf, "udp=%v", r.UDP)