1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
|
// 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.
// +build linux
//lint:file-ignore U1000 refactoring, temporarily unused code.
package dns
import (
"context"
"errors"
"fmt"
"net"
"github.com/godbus/dbus/v5"
"golang.org/x/sys/unix"
"inet.af/netaddr"
"tailscale.com/types/logger"
"tailscale.com/util/dnsname"
)
// resolvedListenAddr is the listen address of the resolved stub resolver.
//
// We only consider resolved to be the system resolver if the stub resolver is;
// that is, if this address is the sole nameserver in /etc/resolved.conf.
// In other cases, resolved may be managing the system DNS configuration directly.
// Then the nameserver list will be a concatenation of those for all
// the interfaces that register their interest in being a default resolver with
// SetLinkDomains([]{{"~.", true}, ...})
// which includes at least the interface with the default route, i.e. not us.
// This does not work for us: there is a possibility of getting NXDOMAIN
// from the other nameservers before we are asked or get a chance to respond.
// We consider this case as lacking resolved support and fall through to dnsDirect.
//
// While it may seem that we need to read a config option to get at this,
// this address is, in fact, hard-coded into resolved.
var resolvedListenAddr = netaddr.IPv4(127, 0, 0, 53)
var errNotReady = errors.New("interface not ready")
type resolvedLinkNameserver struct {
Family int32
Address []byte
}
type resolvedLinkDomain struct {
Domain string
RoutingOnly bool
}
// isResolvedActive determines if resolved is currently managing system DNS settings.
func isResolvedActive() bool {
ctx, cancel := context.WithTimeout(context.Background(), reconfigTimeout)
defer cancel()
conn, err := dbus.SystemBus()
if err != nil {
// Probably no DBus on the system, or we're not allowed to use
// it. Cannot control resolved.
return false
}
rd := conn.Object("org.freedesktop.resolve1", dbus.ObjectPath("/org/freedesktop/resolve1"))
call := rd.CallWithContext(ctx, "org.freedesktop.DBus.Peer.Ping", 0)
if call.Err != nil {
// Can't talk to resolved.
return false
}
config, err := readResolvConf()
if err != nil {
return false
}
// The sole nameserver must be the systemd-resolved stub.
if len(config.Nameservers) == 1 && config.Nameservers[0] == resolvedListenAddr {
return true
}
return false
}
// resolvedManager uses the systemd-resolved DBus API.
type resolvedManager struct {
logf logger.Logf
ifidx int
resolved dbus.BusObject
}
func newResolvedManager(logf logger.Logf, interfaceName string) (*resolvedManager, error) {
conn, err := dbus.SystemBus()
if err != nil {
return nil, err
}
iface, err := net.InterfaceByName(interfaceName)
if err != nil {
return nil, err
}
return &resolvedManager{
logf: logf,
ifidx: iface.Index,
resolved: conn.Object("org.freedesktop.resolve1", dbus.ObjectPath("/org/freedesktop/resolve1")),
}, nil
}
// Up implements managerImpl.
func (m *resolvedManager) SetDNS(config OSConfig) error {
ctx, cancel := context.WithTimeout(context.Background(), reconfigTimeout)
defer cancel()
var linkNameservers = make([]resolvedLinkNameserver, len(config.Nameservers))
for i, server := range config.Nameservers {
ip := server.As16()
if server.Is4() {
linkNameservers[i] = resolvedLinkNameserver{
Family: unix.AF_INET,
Address: ip[12:],
}
} else {
linkNameservers[i] = resolvedLinkNameserver{
Family: unix.AF_INET6,
Address: ip[:],
}
}
}
err := m.resolved.CallWithContext(
ctx, "org.freedesktop.resolve1.Manager.SetLinkDNS", 0,
m.ifidx, linkNameservers,
).Store()
if err != nil {
return fmt.Errorf("setLinkDNS: %w", err)
}
linkDomains := make([]resolvedLinkDomain, 0, len(config.SearchDomains)+len(config.MatchDomains))
seenDomains := map[dnsname.FQDN]bool{}
for _, domain := range config.SearchDomains {
if seenDomains[domain] {
continue
}
seenDomains[domain] = true
linkDomains = append(linkDomains, resolvedLinkDomain{
Domain: domain.WithTrailingDot(),
RoutingOnly: false,
})
}
for _, domain := range config.MatchDomains {
if seenDomains[domain] {
// Search domains act as both search and match in
// resolved, so it's correct to skip.
continue
}
seenDomains[domain] = true
linkDomains = append(linkDomains, resolvedLinkDomain{
Domain: domain.WithTrailingDot(),
RoutingOnly: true,
})
}
if len(config.MatchDomains) == 0 && len(config.Nameservers) > 0 {
// Caller requested full DNS interception, install a
// routing-only root domain.
linkDomains = append(linkDomains, resolvedLinkDomain{
Domain: ".",
RoutingOnly: true,
})
}
err = m.resolved.CallWithContext(
ctx, "org.freedesktop.resolve1.Manager.SetLinkDomains", 0,
m.ifidx, linkDomains,
).Store()
if err != nil {
return fmt.Errorf("setLinkDomains: %w", err)
}
if call := m.resolved.CallWithContext(ctx, "org.freedesktop.resolve1.Manager.SetLinkDefaultRoute", 0, m.ifidx, len(config.MatchDomains) == 0); call.Err != nil {
return fmt.Errorf("setLinkDefaultRoute: %w", err)
}
// Some best-effort setting of things, but resolved should do the
// right thing if these fail (e.g. a really old resolved version
// or something).
// Disable LLMNR, we don't do multicast.
if call := m.resolved.CallWithContext(ctx, "org.freedesktop.resolve1.Manager.SetLinkLLMNR", 0, m.ifidx, "no"); call.Err != nil {
m.logf("[v1] failed to disable LLMNR: %v", call.Err)
}
// Disable mdns.
if call := m.resolved.CallWithContext(ctx, "org.freedesktop.resolve1.Manager.SetLinkMulticastDNS", 0, m.ifidx, "no"); call.Err != nil {
m.logf("[v1] failed to disable mdns: %v", call.Err)
}
// We don't support dnssec consistently right now, force it off to
// avoid partial failures when we split DNS internally.
if call := m.resolved.CallWithContext(ctx, "org.freedesktop.resolve1.Manager.SetLinkDNSSEC", 0, m.ifidx, "no"); call.Err != nil {
m.logf("[v1] failed to disable DNSSEC: %v", call.Err)
}
if call := m.resolved.CallWithContext(ctx, "org.freedesktop.resolve1.Manager.SetLinkDNSOverTLS", 0, m.ifidx, "no"); call.Err != nil {
m.logf("[v1] failed to disable DoT: %v", call.Err)
}
if call := m.resolved.CallWithContext(ctx, "org.freedesktop.resolve1.Manager.FlushCaches", 0); call.Err != nil {
m.logf("failed to flush resolved DNS cache: %v", call.Err)
}
return nil
}
func (m *resolvedManager) SupportsSplitDNS() bool {
return true
}
func (m *resolvedManager) GetBaseConfig() (OSConfig, error) {
return OSConfig{}, ErrGetBaseConfigNotSupported
}
func (m *resolvedManager) Close() error {
ctx, cancel := context.WithTimeout(context.Background(), reconfigTimeout)
defer cancel()
if call := m.resolved.CallWithContext(ctx, "org.freedesktop.resolve1.Manager.RevertLink", 0, m.ifidx); call.Err != nil {
return fmt.Errorf("RevertLink: %w", call.Err)
}
return nil
}
|
