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|
package main
import (
"context"
"fmt"
"log"
dns "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",
"cs",
"dash",
"music",
"unifi",
}
func main() {
ctx := context.Background()
// we only care about IPv4 for now
tsIpV4Addresses, _, err := getTsIpsDevice(ctx, TS_DEVICE_NAME)
if err != nil {
log.Fatalf("failed to get the IP addresses for %s: %v", TS_DEVICE_NAME, err)
}
svc, err := dns.NewService(ctx)
if err != nil {
log.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 {
log.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 {
log.Fatalf("failed to get the list of records: %+v", err)
}
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 {
log.Printf("will delete %s (incorrect IPv4 addresses)\n", subdomain)
recordSetsToDelete = append(recordSetsToDelete, r)
}
}
}
if !found {
log.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 {
log.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 {
log.Fatalf("failed to apply the change: %+v", err)
}
}
}
|
