136 lines
4.6 KiB
Go
136 lines
4.6 KiB
Go
package allregions
|
|
|
|
import (
|
|
"context"
|
|
"crypto/tls"
|
|
"fmt"
|
|
"net"
|
|
"time"
|
|
|
|
"github.com/cloudflare/cloudflared/logger"
|
|
"github.com/pkg/errors"
|
|
)
|
|
|
|
const (
|
|
// Used to discover HA origintunneld servers
|
|
srvService = "origintunneld"
|
|
srvProto = "tcp"
|
|
srvName = "argotunnel.com"
|
|
|
|
// Used to fallback to DoT when we can't use the default resolver to
|
|
// discover HA origintunneld servers (GitHub issue #75).
|
|
dotServerName = "cloudflare-dns.com"
|
|
dotServerAddr = "1.1.1.1:853"
|
|
dotTimeout = time.Duration(15 * time.Second)
|
|
|
|
// SRV record resolution TTL
|
|
resolveEdgeAddrTTL = 1 * time.Hour
|
|
|
|
subsystemEdgeAddrResolver = "edgeAddrResolver"
|
|
)
|
|
|
|
// Redeclare network functions so they can be overridden in tests.
|
|
var (
|
|
netLookupSRV = net.LookupSRV
|
|
netLookupIP = net.LookupIP
|
|
)
|
|
|
|
// If the call to net.LookupSRV fails, try to fall back to DoT from Cloudflare directly.
|
|
//
|
|
// Note: Instead of DoT, we could also have used DoH. Either of these:
|
|
// - directly via the JSON API (https://1.1.1.1/dns-query?ct=application/dns-json&name=_origintunneld._tcp.argotunnel.com&type=srv)
|
|
// - indirectly via `tunneldns.NewUpstreamHTTPS()`
|
|
// But both of these cases miss out on a key feature from the stdlib:
|
|
// "The returned records are sorted by priority and randomized by weight within a priority."
|
|
// (https://golang.org/pkg/net/#Resolver.LookupSRV)
|
|
// Does this matter? I don't know. It may someday. Let's use DoT so we don't need to worry about it.
|
|
// See also: Go feature request for stdlib-supported DoH: https://github.com/golang/go/issues/27552
|
|
var fallbackLookupSRV = lookupSRVWithDOT
|
|
|
|
var friendlyDNSErrorLines = []string{
|
|
`Please try the following things to diagnose this issue:`,
|
|
` 1. ensure that argotunnel.com is returning "origintunneld" service records.`,
|
|
` Run your system's equivalent of: dig srv _origintunneld._tcp.argotunnel.com`,
|
|
` 2. ensure that your DNS resolver is not returning compressed SRV records.`,
|
|
` See GitHub issue https://github.com/golang/go/issues/27546`,
|
|
` For example, you could use Cloudflare's 1.1.1.1 as your resolver:`,
|
|
` https://developers.cloudflare.com/1.1.1.1/setting-up-1.1.1.1/`,
|
|
}
|
|
|
|
// EdgeDiscovery implements HA service discovery lookup.
|
|
func edgeDiscovery(logger logger.Service) ([][]*net.TCPAddr, error) {
|
|
_, addrs, err := netLookupSRV(srvService, srvProto, srvName)
|
|
if err != nil {
|
|
_, fallbackAddrs, fallbackErr := fallbackLookupSRV(srvService, srvProto, srvName)
|
|
if fallbackErr != nil || len(fallbackAddrs) == 0 {
|
|
// use the original DNS error `err` in messages, not `fallbackErr`
|
|
logger.Errorf("Error looking up Cloudflare edge IPs: the DNS query failed: %s", err)
|
|
for _, s := range friendlyDNSErrorLines {
|
|
logger.Error(s)
|
|
}
|
|
return nil, errors.Wrapf(err, "Could not lookup srv records on _%v._%v.%v", srvService, srvProto, srvName)
|
|
}
|
|
// Accept the fallback results and keep going
|
|
addrs = fallbackAddrs
|
|
}
|
|
|
|
var resolvedIPsPerCNAME [][]*net.TCPAddr
|
|
for _, addr := range addrs {
|
|
ips, err := resolveSRVToTCP(addr)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
resolvedIPsPerCNAME = append(resolvedIPsPerCNAME, ips)
|
|
}
|
|
|
|
return resolvedIPsPerCNAME, nil
|
|
}
|
|
|
|
func lookupSRVWithDOT(service, proto, name string) (cname string, addrs []*net.SRV, err error) {
|
|
// Inspiration: https://github.com/artyom/dot/blob/master/dot.go
|
|
r := &net.Resolver{
|
|
PreferGo: true,
|
|
Dial: func(ctx context.Context, _ string, _ string) (net.Conn, error) {
|
|
var dialer net.Dialer
|
|
conn, err := dialer.DialContext(ctx, "tcp", dotServerAddr)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
tlsConfig := &tls.Config{ServerName: dotServerName}
|
|
return tls.Client(conn, tlsConfig), nil
|
|
},
|
|
}
|
|
ctx, cancel := context.WithTimeout(context.Background(), dotTimeout)
|
|
defer cancel()
|
|
return r.LookupSRV(ctx, srvService, srvProto, srvName)
|
|
}
|
|
|
|
func resolveSRVToTCP(srv *net.SRV) ([]*net.TCPAddr, error) {
|
|
ips, err := netLookupIP(srv.Target)
|
|
if err != nil {
|
|
return nil, errors.Wrapf(err, "Couldn't resolve SRV record %v", srv)
|
|
}
|
|
if len(ips) == 0 {
|
|
return nil, fmt.Errorf("SRV record %v had no IPs", srv)
|
|
}
|
|
addrs := make([]*net.TCPAddr, len(ips))
|
|
for i, ip := range ips {
|
|
addrs[i] = &net.TCPAddr{IP: ip, Port: int(srv.Port)}
|
|
}
|
|
return addrs, nil
|
|
}
|
|
|
|
// ResolveAddrs resolves TCP address given a list of addresses. Address can be a hostname, however, it will return at most one
|
|
// of the hostname's IP addresses.
|
|
func ResolveAddrs(addrs []string, logger logger.Service) (resolved []*net.TCPAddr) {
|
|
for _, addr := range addrs {
|
|
tcpAddr, err := net.ResolveTCPAddr("tcp", addr)
|
|
if err != nil {
|
|
logger.Errorf("Failed to resolve %s, err: %v", addr, err)
|
|
} else {
|
|
resolved = append(resolved, tcpAddr)
|
|
}
|
|
}
|
|
return
|
|
}
|