tailscale/cmd/derper/mesh.go

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// 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 main
import (
"context"
"errors"
"fmt"
"log"
"net"
"strings"
"time"
"tailscale.com/derp"
"tailscale.com/derp/derphttp"
"tailscale.com/types/key"
"tailscale.com/types/logger"
)
func startMesh(s *derp.Server) error {
if *meshWith == "" {
return nil
}
if !s.HasMeshKey() {
return errors.New("--mesh-with requires --mesh-psk-file")
}
for _, host := range strings.Split(*meshWith, ",") {
if err := startMeshWithHost(s, host); err != nil {
return err
}
}
return nil
}
func startMeshWithHost(s *derp.Server, host string) error {
logf := logger.WithPrefix(log.Printf, fmt.Sprintf("mesh(%q): ", host))
c, err := derphttp.NewClient(s.PrivateKey(), "https://"+host+"/derp", logf)
if err != nil {
return err
}
c.MeshKey = s.MeshKey()
// For meshed peers within a region, connect via VPC addresses.
c.SetURLDialer(func(ctx context.Context, network, addr string) (net.Conn, error) {
host, port, err := net.SplitHostPort(addr)
if err != nil {
return nil, err
}
var d net.Dialer
var r net.Resolver
if port == "443" && strings.HasSuffix(host, ".tailscale.com") {
base := strings.TrimSuffix(host, ".tailscale.com")
subCtx, cancel := context.WithTimeout(ctx, 2*time.Second)
defer cancel()
vpcHost := base + "-vpc.tailscale.com"
ips, _ := r.LookupIP(subCtx, "ip", vpcHost)
if len(ips) > 0 {
vpcAddr := net.JoinHostPort(ips[0].String(), port)
c, err := d.DialContext(subCtx, network, vpcAddr)
if err == nil {
log.Printf("connected to %v (%v) instead of %v", vpcHost, ips[0], base)
return c, nil
}
log.Printf("failed to connect to %v (%v): %v; trying non-VPC route", vpcHost, ips[0], err)
}
}
return d.DialContext(ctx, network, addr)
})
add := func(k key.Public) { s.AddPacketForwarder(k, c) }
remove := func(k key.Public) { s.RemovePacketForwarder(k, c) }
go c.RunWatchConnectionLoop(context.Background(), s.PublicKey(), logf, add, remove)
return nil
}