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tailscale/netcheck/netcheck.go

139 lines
2.9 KiB
Go

// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package netcheck checks the network conditions from the current host.
package netcheck
import (
"context"
"io"
"net"
"strings"
"sync"
"time"
"golang.org/x/sync/errgroup"
"tailscale.com/interfaces"
"tailscale.com/stunner"
"tailscale.com/types/logger"
"tailscale.com/types/opt"
)
type Report struct {
UDP bool // UDP works
IPv6 bool // IPv6 works
MappingVariesByDestIP opt.Bool // for IPv4
DERPLatency map[string]time.Duration // keyed by STUN host:port
}
func GetReport(ctx context.Context, logf logger.Logf) (*Report, error) {
closeOnCtx := func(c io.Closer) {
<-ctx.Done()
c.Close()
}
v6, err := interfaces.HaveIPv6GlobalAddress()
if err != nil {
logf("interfaces: %v", err)
}
var (
mu sync.Mutex
ret = &Report{
DERPLatency: map[string]time.Duration{},
}
gotIP = map[string]string{} // server -> IP
)
add := func(server, ip string, d time.Duration) {
logf("%s says we are %s (in %v)", server, ip, d)
mu.Lock()
defer mu.Unlock()
ret.UDP = true
ret.DERPLatency[server] = d
if strings.Contains(server, "-v6") {
ret.IPv6 = true
}
gotIP[server] = ip
}
var pc4, pc6 net.PacketConn
pc4, err = net.ListenPacket("udp4", ":0")
if err != nil {
logf("udp4: %v", err)
return nil, err
}
go closeOnCtx(pc4)
if v6 {
pc6, err = net.ListenPacket("udp6", ":0")
if err != nil {
logf("udp6: %v", err)
v6 = false
} else {
go closeOnCtx(pc6)
}
}
reader := func(s *stunner.Stunner, pc net.PacketConn) {
var buf [64 << 10]byte
for {
n, addr, err := pc.ReadFrom(buf[:])
if err != nil {
if ctx.Err() != nil {
return
}
logf("ReadFrom: %v", err)
return
}
ua, ok := addr.(*net.UDPAddr)
if !ok {
logf("ReadFrom: unexpected addr %T", addr)
continue
}
s.Receive(buf[:n], ua)
}
}
var grp errgroup.Group
s4 := &stunner.Stunner{
Send: pc4.WriteTo,
Endpoint: add,
Servers: []string{"derp1.tailscale.com:3478", "derp2.tailscale.com:3478"},
Logf: logf,
}
grp.Go(func() error { return s4.Run(ctx) })
go reader(s4, pc4)
if v6 {
s6 := &stunner.Stunner{
Endpoint: add,
Send: pc6.WriteTo,
Servers: []string{"derp1-v6.tailscale.com:3478", "derp2-v6.tailscale.com:3478"},
Logf: logf,
OnlyIPv6: true,
}
grp.Go(func() error { return s6.Run(ctx) })
go reader(s6, pc6)
}
err = grp.Wait()
if err != nil {
return nil, err
}
mu.Lock()
defer mu.Unlock() // unnecessary, but feels weird without
// TODO: generalize this to find at least two out of N DERP
// servers (where N will be 5+).
ip1 := gotIP["derp1.tailscale.com:3478"]
ip2 := gotIP["derp2.tailscale.com:3478"]
if ip1 != "" && ip2 != "" {
ret.MappingVariesByDestIP.Set(ip1 != ip2)
}
return ret, nil
}