mirrors/tailscale
1
0
Fork 0
Code Issues Pull Requests Projects Wiki Activity

net/dns: exhaustively test DNS selection paths for linux.

Browse Source 
Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson
2021-09-04 23:40:48 -07:00
parent c071bcda33
commit 10547d989d
4 changed files with 290 additions and 73 deletions
Download Patch File Download Diff File Expand all files Collapse all files

108
net/dns/manager_linux.go
View File

@ -5,11 +5,11 @@
package dns
import (
"bytes"
"context"
"errors"
"fmt"
"os"
"os/exec"
"time"
"github.com/godbus/dbus/v5"
@ -27,36 +27,52 @@ func (kv kv) String() string {
}
func NewOSConfigurator(logf logger.Logf, interfaceName string) (ret OSConfigurator, err error) {
return newOSConfigurator(logf, interfaceName, newOSConfigEnv{
fs: directFS{},
resolvOwner: resolvOwner,
resolvedIsActuallyResolver: resolvedIsActuallyResolver,
dbusPing: dbusPing,
nmIsUsingResolved: nmIsUsingResolved,
nmVersionBetween: nmVersionBetween,
getResolvConfVersion: getResolvConfVersion,
})
env := newOSConfigEnv{
fs: directFS{},
dbusPing: dbusPing,
nmIsUsingResolved: nmIsUsingResolved,
nmVersionBetween: nmVersionBetween,
resolvconfStyle: resolvconfStyle,
}
mode, err := dnsMode(logf, env)
if err != nil {
return nil, err
}
switch mode {
case "direct":
return newDirectManagerOnFS(env.fs), nil
case "systemd-resolved":
return newResolvedManager(logf, interfaceName)
case "network-manager":
return newNMManager(interfaceName)
case "debian-resolvconf":
return newDebianResolvconfManager(logf)
case "openresolv":
return newOpenresolvManager()
default:
logf("[unexpected] detected unknown DNS mode %q, using direct manager as last resort", mode)
return newDirectManagerOnFS(env.fs), nil
}
}
// newOSConfigEnv are the funcs newOSConfigurator needs, pulled out for testing.
type newOSConfigEnv struct {
fs wholeFileFS
resolvOwner func(resolvConfContents []byte) string
resolvedIsActuallyResolver func(wholeFileFS) error
dbusPing func(string, string) error
nmIsUsingResolved func() error
nmVersionBetween func(v1, v2 string) (safe bool, err error)
getResolvConfVersion func() ([]byte, error)
fs wholeFileFS
dbusPing func(string, string) error
nmIsUsingResolved func() error
nmVersionBetween func(v1, v2 string) (safe bool, err error)
resolvconfStyle func() string
isResolvconfDebianVersion func() bool
}
func newOSConfigurator(logf logger.Logf, interfaceName string, env newOSConfigEnv) (ret OSConfigurator, err error) {
func dnsMode(logf logger.Logf, env newOSConfigEnv) (ret string, err error) {
var debug []kv
dbg := func(k, v string) {
debug = append(debug, kv{k, v})
}
defer func() {
if ret != nil {
dbg("ret", fmt.Sprintf("%T", ret))
if ret != "" {
dbg("ret", ret)
}
logf("dns: %v", debug)
}()
@ -64,13 +80,13 @@ func newOSConfigurator(logf logger.Logf, interfaceName string, env newOSConfigEn
bs, err := env.fs.ReadFile(resolvConf)
if os.IsNotExist(err) {
dbg("rc", "missing")
return newDirectManager(), nil
return "direct", nil
}
if err != nil {
return nil, fmt.Errorf("reading /etc/resolv.conf: %w", err)
return "", fmt.Errorf("reading /etc/resolv.conf: %w", err)
}
switch env.resolvOwner(bs) {
switch resolvOwner(bs) {
case "systemd-resolved":
dbg("rc", "resolved")
// Some systems, for reasons known only to them, have a
@ -78,22 +94,22 @@ func newOSConfigurator(logf logger.Logf, interfaceName string, env newOSConfigEn
// header, but doesn't actually point to resolved. We mustn't
// try to program resolved in that case.
// https://github.com/tailscale/tailscale/issues/2136
if err := env.resolvedIsActuallyResolver(env.fs); err != nil {
if err := resolvedIsActuallyResolver(bs); err != nil {
dbg("resolved", "not-in-use")
return newDirectManagerOnFS(env.fs), nil
return "direct", nil
}
if err := env.dbusPing("org.freedesktop.resolve1", "/org/freedesktop/resolve1"); err != nil {
dbg("resolved", "no")
return newDirectManagerOnFS(env.fs), nil
return "direct", nil
}
if err := env.dbusPing("org.freedesktop.NetworkManager", "/org/freedesktop/NetworkManager/DnsManager"); err != nil {
dbg("nm", "no")
return newResolvedManager(logf, interfaceName)
return "systemd-resolved", nil
}
dbg("nm", "yes")
if err := env.nmIsUsingResolved(); err != nil {
dbg("nm-resolved", "no")
return newResolvedManager(logf, interfaceName)
return "systemd-resolved", nil
}
dbg("nm-resolved", "yes")
@ -131,26 +147,38 @@ func newOSConfigurator(logf logger.Logf, interfaceName string, env newOSConfigEn
// that comes with it (see
// https://github.com/tailscale/tailscale/issues/1699,
// https://github.com/tailscale/tailscale/pull/1945)
safe, err := nmVersionBetween("1.26.0", "1.26.5")
safe, err := env.nmVersionBetween("1.26.0", "1.26.5")
if err != nil {
// Failed to figure out NM's version, can't make a correct
// decision.
return nil, fmt.Errorf("checking NetworkManager version: %v", err)
return "", fmt.Errorf("checking NetworkManager version: %v", err)
}
if safe {
dbg("nm-safe", "yes")
return newNMManager(interfaceName)
return "network-manager", nil
}
dbg("nm-safe", "no")
return newResolvedManager(logf, interfaceName)
return "systemd-resolved", nil
case "resolvconf":
dbg("rc", "resolvconf")
if _, err := exec.LookPath("resolvconf"); err != nil {
style := env.resolvconfStyle()
switch style {
case "":
dbg("resolvconf", "no")
return newDirectManagerOnFS(env.fs), nil
return "direct", nil
case "debian":
dbg("resolvconf", "debian")
return "debian-resolvconf", nil
case "openresolv":
dbg("resolvconf", "openresolv")
return "openresolv", nil
default:
// Shouldn't happen, that means we updated flavors of
// resolvconf without updating here.
dbg("resolvconf", style)
logf("[unexpected] got unknown flavor of resolvconf %q, falling back to direct manager", env.resolvconfStyle())
return "direct", nil
}
dbg("resolvconf", "yes")
return newResolvconfManager(logf, env.getResolvConfVersion)
case "NetworkManager":
// You'd think we would use newNMManager somewhere in
// here. However, as explained in
@ -165,10 +193,10 @@ func newOSConfigurator(logf logger.Logf, interfaceName string, env newOSConfigEn
// anyway, so you still need a fallback path that uses
// directManager.
dbg("rc", "nm")
return newDirectManagerOnFS(env.fs), nil
return "direct", nil
default:
dbg("rc", "unknown")
return newDirectManagerOnFS(env.fs), nil
return "direct", nil
}
}
@ -216,8 +244,8 @@ func nmIsUsingResolved() error {
return nil
}
func resolvedIsActuallyResolver(fs wholeFileFS) error {
cfg, err := newDirectManagerOnFS(fs).readResolvConf()
func resolvedIsActuallyResolver(bs []byte) error {
cfg, err := readResolv(bytes.NewBuffer(bs))
if err != nil {
return err
}