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
|
package main
import (
"context"
"flag"
"fmt"
"log"
"os"
"strings"
"google.golang.org/api/dns/v1"
)
const (
GCP_PROJECT_NAME = "fcuny-homelab"
GCP_MANAGED_ZONE = "fcuny-xyz"
TS_DEVICE_NAME = "tahoe"
TTL = 300
)
var desiredRecords = []string{
"bt",
"dash",
"music",
"unifi",
}
const usage = `Usage:
dns-updater [OPTIONS] <COMMAND>
Options:
-ts-api-key API key for tailscale
Examples:
$ dns-updater -ts-api-key $(passage credentials/tailscale)
$ dns-updater -ts-api-key $(passage credentials/tailscale) update
`
var l = log.New(os.Stderr, "", 0)
func main() {
var (
tsAPIKeyFlag string
command string
)
flag.Usage = func() { fmt.Fprintf(os.Stderr, "%s\n", usage) }
flag.StringVar(&tsAPIKeyFlag, "ts-api-key", "", "the API key for tailscale")
flag.Parse()
if flag.NArg() > 1 {
flag.Usage()
os.Exit(1)
} else {
command = flag.Arg(0)
if command != "" && command != "update" {
flag.Usage()
os.Exit(1)
}
}
ctx := context.Background()
// we only care about IPv4 for now
tsIpV4Addresses, _, err := getTsIpsDevice(ctx, tsAPIKeyFlag, TS_DEVICE_NAME)
if err != nil {
l.Fatalf("failed to get the IP addresses for %s: %v", TS_DEVICE_NAME, err)
}
svc, err := dns.NewService(ctx)
if err != nil {
l.Fatalf("failed to create the client for Google Cloud DNS: %v", err)
}
zone, err := svc.ManagedZones.Get(GCP_PROJECT_NAME, GCP_MANAGED_ZONE).Context(ctx).Do()
if err != nil {
l.Fatalf("failed to get information about the managed zone %s: %+v", GCP_MANAGED_ZONE, err)
}
recordSets, err := svc.ResourceRecordSets.List(GCP_PROJECT_NAME, GCP_MANAGED_ZONE).Context(ctx).Do()
if err != nil {
l.Fatalf("failed to get the list of records: %+v", err)
}
switch command {
case "update":
updateRecords(ctx, svc, recordSets, zone, tsIpV4Addresses)
default:
listRecords(recordSets)
}
}
func listRecords(recordSets *dns.ResourceRecordSetsListResponse) {
for _, record := range recordSets.Rrsets {
switch record.Type {
case "A":
ips := strings.Join(record.Rrdatas[:], ",")
fmt.Printf("%-25s %4d %s\n", record.Name, record.Ttl, ips)
}
}
}
func updateRecords(ctx context.Context, svc *dns.Service, recordSets *dns.ResourceRecordSetsListResponse, zone *dns.ManagedZone, tsIpV4Addresses []string) {
var (
existingRecordSets = []*dns.ResourceRecordSet{}
recordSetsToAdd = []*dns.ResourceRecordSet{}
recordSetsToDelete = []*dns.ResourceRecordSet{}
)
for _, record := range recordSets.Rrsets {
if record.Type == "A" {
existingRecordSets = append(existingRecordSets, record)
}
}
// first pass: create what's missing
for _, subdomain := range desiredRecords {
found := false
subdomain = fmt.Sprintf("%s.%s", subdomain, zone.DnsName)
for _, r := range existingRecordSets {
if subdomain == r.Name && r.Type == "A" {
// check that the IP addresses are correct
ipsFound := 0
for _, rr := range r.Rrdatas {
for _, ip := range tsIpV4Addresses {
if rr == ip {
ipsFound += 1
continue
}
}
}
// while we found the subdomain with the correct type,
// we also need to make sure the list of IPs is
// correct. If they are not, we delete the record and
// add it again with the correct values.
if ipsFound == len(tsIpV4Addresses) {
found = true
continue
} else {
l.Printf("will delete %s (incorrect IPv4 addresses)\n", subdomain)
recordSetsToDelete = append(recordSetsToDelete, r)
}
}
}
if !found {
l.Printf("will add %s\n", subdomain)
r := &dns.ResourceRecordSet{
Name: subdomain,
Type: "A",
Ttl: TTL,
Rrdatas: tsIpV4Addresses,
}
recordSetsToAdd = append(recordSetsToAdd, r)
}
}
// second pass: delete what's not needed
for _, r := range existingRecordSets {
found := false
for _, subdomain := range desiredRecords {
subdomain = fmt.Sprintf("%s.%s", subdomain, zone.DnsName)
if subdomain == r.Name && r.Type == "A" {
found = true
continue
}
}
if !found {
l.Printf("will delete %s\n", r.Name)
recordSetsToDelete = append(recordSetsToDelete, r)
}
}
if len(recordSetsToAdd) > 0 || len(recordSetsToDelete) > 0 {
change := &dns.Change{Additions: recordSetsToAdd, Deletions: recordSetsToDelete}
if _, err := svc.Changes.Create(GCP_PROJECT_NAME, GCP_MANAGED_ZONE, change).Context(ctx).Do(); err != nil {
l.Fatalf("failed to apply the change: %+v", err)
}
}
}
|
