// Copyright (c) Tailscale Inc & AUTHORS // SPDX-License-Identifier: BSD-3-Clause package dns import ( "errors" "io/fs" "os" "strings" "testing" "tailscale.com/tstest" "tailscale.com/util/cmpver" ) func TestLinuxDNSMode(t *testing.T) { tests := []struct { name string env newOSConfigEnv wantLog string want string }{ { name: "no_obvious_resolv.conf_owner", env: env(resolvDotConf("nameserver 10.0.0.1")), wantLog: "dns: [rc=unknown ret=direct]", want: "direct", }, { name: "network_manager", env: env( resolvDotConf( "# Managed by NetworkManager", "nameserver 10.0.0.1")), wantLog: "dns: resolvedIsActuallyResolver error: resolv.conf doesn't point to systemd-resolved; points to [10.0.0.1]\n" + "dns: [rc=nm resolved=not-in-use ret=direct]", want: "direct", }, { name: "resolvconf_but_no_resolvconf_binary", env: env(resolvDotConf("# Managed by resolvconf", "nameserver 10.0.0.1")), wantLog: "dns: [rc=resolvconf resolvconf=no ret=direct]", want: "direct", }, { name: "debian_resolvconf", env: env( resolvDotConf("# Managed by resolvconf", "nameserver 10.0.0.1"), resolvconf("debian")), wantLog: "dns: [rc=resolvconf resolvconf=debian ret=debian-resolvconf]", want: "debian-resolvconf", }, { name: "openresolv", env: env( resolvDotConf("# Managed by resolvconf", "nameserver 10.0.0.1"), resolvconf("openresolv")), wantLog: "dns: [rc=resolvconf resolvconf=openresolv ret=openresolv]", want: "openresolv", }, { name: "unknown_resolvconf_flavor", env: env( resolvDotConf("# Managed by resolvconf", "nameserver 10.0.0.1"), resolvconf("daves-discount-resolvconf")), wantLog: "[unexpected] got unknown flavor of resolvconf \"daves-discount-resolvconf\", falling back to direct manager\ndns: [rc=resolvconf resolvconf=daves-discount-resolvconf ret=direct]", want: "direct", }, { name: "resolved_alone_without_ping", env: env(resolvDotConf("# Managed by systemd-resolved", "nameserver 127.0.0.53")), wantLog: "dns: ResolvConfMode error: dbus property not found\ndns: [rc=resolved resolved=file nm=no resolv-conf-mode=error ret=systemd-resolved]", want: "systemd-resolved", }, { name: "resolved_alone_with_ping", env: env( resolvDotConf("# Managed by systemd-resolved", "nameserver 127.0.0.53"), resolvedRunning()), wantLog: "dns: [resolved-ping=yes rc=resolved resolved=file nm=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, { name: "resolved_and_nsswitch_resolve", env: env( resolvDotConf("# Managed by systemd-resolved", "nameserver 1.1.1.1"), resolvedRunning(), nsswitchDotConf("hosts: files resolve [!UNAVAIL=return] dns"), ), wantLog: "dns: [resolved-ping=yes rc=resolved resolved=nss nm=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, { name: "resolved_and_nsswitch_dns", env: env( resolvDotConf("# Managed by systemd-resolved", "nameserver 1.1.1.1"), resolvedRunning(), nsswitchDotConf("hosts: files dns resolve [!UNAVAIL=return]"), ), wantLog: "dns: resolvedIsActuallyResolver error: resolv.conf doesn't point to systemd-resolved; points to [1.1.1.1]\ndns: [resolved-ping=yes rc=resolved resolved=not-in-use ret=direct]", want: "direct", }, { name: "resolved_and_nsswitch_none", env: env( resolvDotConf("# Managed by systemd-resolved", "nameserver 1.1.1.1"), resolvedRunning(), nsswitchDotConf("hosts:"), ), wantLog: "dns: resolvedIsActuallyResolver error: resolv.conf doesn't point to systemd-resolved; points to [1.1.1.1]\ndns: [resolved-ping=yes rc=resolved resolved=not-in-use ret=direct]", want: "direct", }, { name: "resolved_and_networkmanager_not_using_resolved", env: env( resolvDotConf("# Managed by systemd-resolved", "nameserver 127.0.0.53"), resolvedRunning(), nmRunning("1.2.3", false)), wantLog: "dns: [resolved-ping=yes rc=resolved resolved=file nm=yes nm-resolved=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, { name: "resolved_and_mid_2020_networkmanager", env: env( resolvDotConf("# Managed by systemd-resolved", "nameserver 127.0.0.53"), resolvedRunning(), nmRunning("1.26.2", true)), wantLog: "dns: [resolved-ping=yes rc=resolved resolved=file nm=yes nm-resolved=yes nm-safe=yes ret=network-manager]", want: "network-manager", }, { name: "resolved_and_2021_networkmanager", env: env( resolvDotConf("# Managed by systemd-resolved", "nameserver 127.0.0.53"), resolvedRunning(), nmRunning("1.27.0", true)), wantLog: "dns: [resolved-ping=yes rc=resolved resolved=file nm=yes nm-resolved=yes nm-safe=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, { name: "resolved_and_ancient_networkmanager", env: env( resolvDotConf("# Managed by systemd-resolved", "nameserver 127.0.0.53"), resolvedRunning(), nmRunning("1.22.0", true)), wantLog: "dns: [resolved-ping=yes rc=resolved resolved=file nm=yes nm-resolved=yes nm-safe=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, // Regression tests for extreme corner cases below. { // One user reported a configuration whose comment string // alleged that it was managed by systemd-resolved, but it // was actually a completely static config file pointing // elsewhere. name: "allegedly_resolved_but_not_in_resolv.conf", env: env(resolvDotConf("# Managed by systemd-resolved", "nameserver 10.0.0.1")), wantLog: "dns: resolvedIsActuallyResolver error: resolv.conf doesn't point to systemd-resolved; points to [10.0.0.1]\n" + "dns: [rc=resolved resolved=not-in-use ret=direct]", want: "direct", }, { // We used to incorrectly decide that resolved wasn't in // charge when handed this (admittedly weird and bugged) // resolv.conf. name: "resolved_with_duplicates_in_resolv.conf", env: env( resolvDotConf( "# Managed by systemd-resolved", "nameserver 127.0.0.53", "nameserver 127.0.0.53"), resolvedRunning()), wantLog: "dns: [resolved-ping=yes rc=resolved resolved=file nm=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, { // More than one user has had resolvconf write a config that points to // systemd-resolved. We're better off using systemd-resolved. // regression test for https://github.com/tailscale/tailscale/issues/3026 name: "allegedly_resolvconf_but_actually_systemd-resolved", env: env(resolvDotConf( "# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)", "# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN", "# 127.0.0.53 is the systemd-resolved stub resolver.", "# run \"systemd-resolve --status\" to see details about the actual nameservers.", "nameserver 127.0.0.53"), resolvedRunning()), wantLog: "dns: [resolved-ping=yes rc=resolved resolved=file nm=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, { // More than one user has had resolvconf write a config that points to // systemd-resolved. We're better off using systemd-resolved. // and assuming that even if the ping doesn't show that env is correct // regression test for https://github.com/tailscale/tailscale/issues/3026 name: "allegedly_resolvconf_but_actually_systemd-resolved_but_no_ping", env: env(resolvDotConf( "# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)", "# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN", "# 127.0.0.53 is the systemd-resolved stub resolver.", "# run \"systemd-resolve --status\" to see details about the actual nameservers.", "nameserver 127.0.0.53")), wantLog: "dns: ResolvConfMode error: dbus property not found\ndns: [rc=resolved resolved=file nm=no resolv-conf-mode=error ret=systemd-resolved]", want: "systemd-resolved", }, { // regression test for https://github.com/tailscale/tailscale/issues/3304 name: "networkmanager_but_pointing_at_systemd-resolved", env: env(resolvDotConf( "# Generated by NetworkManager", "nameserver 127.0.0.53", "options edns0 trust-ad"), resolvedRunning(), nmRunning("1.32.12", true)), wantLog: "dns: [resolved-ping=yes rc=nm resolved=file nm-resolved=yes nm-safe=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, { // regression test for https://github.com/tailscale/tailscale/issues/3304 name: "networkmanager_but_pointing_at_systemd-resolved_but_no_resolved_ping", env: env(resolvDotConf( "# Generated by NetworkManager", "nameserver 127.0.0.53", "options edns0 trust-ad"), nmRunning("1.32.12", true)), wantLog: "dns: ResolvConfMode error: dbus property not found\ndns: [rc=nm resolved=file nm-resolved=yes nm-safe=no resolv-conf-mode=error ret=systemd-resolved]", want: "systemd-resolved", }, { // regression test for https://github.com/tailscale/tailscale/issues/3304 name: "networkmanager_but_pointing_at_systemd-resolved_and_safe_nm", env: env(resolvDotConf( "# Generated by NetworkManager", "nameserver 127.0.0.53", "options edns0 trust-ad"), resolvedRunning(), nmRunning("1.26.3", true)), wantLog: "dns: [resolved-ping=yes rc=nm resolved=file nm-resolved=yes nm-safe=yes ret=network-manager]", want: "network-manager", }, { // regression test for https://github.com/tailscale/tailscale/issues/3304 name: "networkmanager_but_pointing_at_systemd-resolved_and_no_networkmanager", env: env(resolvDotConf( "# Generated by NetworkManager", "nameserver 127.0.0.53", "options edns0 trust-ad"), resolvedRunning()), wantLog: "dns: [resolved-ping=yes rc=nm resolved=file nm-resolved=yes nm=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, { // regression test for https://github.com/tailscale/tailscale/issues/3531 name: "networkmanager_but_systemd-resolved_with_search_domain", env: env(resolvDotConf( "# Generated by NetworkManager", "search lan", "nameserver 127.0.0.53"), resolvedRunning()), wantLog: "dns: [resolved-ping=yes rc=nm resolved=file nm-resolved=yes nm=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, { // Make sure that we ping systemd-resolved to let it start up and write its resolv.conf // before we read its file. env: env(resolvedStartOnPingAndThen( resolvDotConf("# Managed by systemd-resolved", "nameserver 127.0.0.53"), resolvedDbusProperty(), )), wantLog: "dns: [resolved-ping=yes rc=resolved resolved=file nm=no resolv-conf-mode=fortests ret=systemd-resolved]", want: "systemd-resolved", }, } for _, tt := range tests { t.Run(tt.name, func(t *testing.T) { var logBuf tstest.MemLogger got, err := dnsMode(logBuf.Logf, tt.env) if err != nil { t.Fatal(err) } if got != tt.want { t.Errorf("got %s; want %s", got, tt.want) } if got := strings.TrimSpace(logBuf.String()); got != tt.wantLog { t.Errorf("log output mismatch:\n got: %q\nwant: %q\n", got, tt.wantLog) } }) } } type memFS map[string]any // full path => string for regular files func (m memFS) Stat(name string) (isRegular bool, err error) { v, ok := m[name] if !ok { return false, fs.ErrNotExist } if _, ok := v.(string); ok { return true, nil } return false, nil } func (m memFS) Rename(oldName, newName string) error { panic("TODO") } func (m memFS) Remove(name string) error { panic("TODO") } func (m memFS) ReadFile(name string) ([]byte, error) { v, ok := m[name] if !ok { return nil, fs.ErrNotExist } if s, ok := v.(string); ok { return []byte(s), nil } panic("TODO") } func (m memFS) Truncate(name string) error { v, ok := m[name] if !ok { return fs.ErrNotExist } if s, ok := v.(string); ok { m[name] = s[:0] } return nil } func (m memFS) WriteFile(name string, contents []byte, perm os.FileMode) error { m[name] = string(contents) return nil } type dbusService struct { name, path string hook func() // if non-nil, run on ping } type dbusProperty struct { name, path string iface, member string hook func() (string, error) // what to return } type envBuilder struct { fs memFS dbus []dbusService dbusProperties []dbusProperty nmUsingResolved bool nmVersion string resolvconfStyle string } type envOption interface { apply(*envBuilder) } type envOpt func(*envBuilder) func (e envOpt) apply(b *envBuilder) { e(b) } func env(opts ...envOption) newOSConfigEnv { b := &envBuilder{ fs: memFS{}, } for _, opt := range opts { opt.apply(b) } return newOSConfigEnv{ fs: b.fs, dbusPing: func(name, path string) error { for _, svc := range b.dbus { if svc.name == name && svc.path == path { if svc.hook != nil { svc.hook() } return nil } } return errors.New("dbus service not found") }, dbusReadString: func(name, path, iface, member string) (string, error) { for _, svc := range b.dbusProperties { if svc.name == name && svc.path == path && svc.iface == iface && svc.member == member { return svc.hook() } } return "", errors.New("dbus property not found") }, nmIsUsingResolved: func() error { if !b.nmUsingResolved { return errors.New("networkmanager not using resolved") } return nil }, nmVersionBetween: func(first, last string) (bool, error) { outside := cmpver.Compare(b.nmVersion, first) < 0 || cmpver.Compare(b.nmVersion, last) > 0 return !outside, nil }, resolvconfStyle: func() string { return b.resolvconfStyle }, } } func resolvDotConf(ss ...string) envOption { return envOpt(func(b *envBuilder) { b.fs["/etc/resolv.conf"] = strings.Join(ss, "\n") }) } func nsswitchDotConf(ss ...string) envOption { return envOpt(func(b *envBuilder) { b.fs["/etc/nsswitch.conf"] = strings.Join(ss, "\n") }) } // resolvedRunning returns an option that makes resolved reply to a dbusPing // and the ResolvConfMode property. func resolvedRunning() envOption { return resolvedStartOnPingAndThen(resolvedDbusProperty()) } // resolvedDbusProperty returns an option that responds to the ResolvConfMode // property that resolved exposes. func resolvedDbusProperty() envOption { return setDbusProperty("org.freedesktop.resolve1", "/org/freedesktop/resolve1", "org.freedesktop.resolve1.Manager", "ResolvConfMode", "fortests") } // resolvedStartOnPingAndThen returns an option that makes resolved be // active but not yet running. On a dbus ping, it then applies the // provided options. func resolvedStartOnPingAndThen(opts ...envOption) envOption { return envOpt(func(b *envBuilder) { b.dbus = append(b.dbus, dbusService{ name: "org.freedesktop.resolve1", path: "/org/freedesktop/resolve1", hook: func() { for _, opt := range opts { opt.apply(b) } }, }) }) } func nmRunning(version string, usingResolved bool) envOption { return envOpt(func(b *envBuilder) { b.nmUsingResolved = usingResolved b.nmVersion = version b.dbus = append(b.dbus, dbusService{name: "org.freedesktop.NetworkManager", path: "/org/freedesktop/NetworkManager/DnsManager"}) }) } func resolvconf(s string) envOption { return envOpt(func(b *envBuilder) { b.resolvconfStyle = s }) } func setDbusProperty(name, path, iface, member, value string) envOption { return envOpt(func(b *envBuilder) { b.dbusProperties = append(b.dbusProperties, dbusProperty{ name: name, path: path, iface: iface, member: member, hook: func() (string, error) { return value, nil }, }) }) }