feat: publish standalone worker

Separate worker packaging and service lifecycle from the control plane.

checks/cdns/a_records.go

@@ -0,0 +1,39 @@
+// Package cdns provides functionality.
+package cdns
+
+import (
+	"errors"
+	"strconv"
+
+	"github.com/miekg/dns"
+
+	"rsgit.ru/rsmon/rsmon/internal/netaddr"
+)
+
+// FetchARecords provides functionality.
+func FetchARecords(zone, ns string) ([]NSRecord, error) {
+	config := dns.ClientConfig{Servers: []string{ns}}
+	c := new(dns.Client)
+	m := new(dns.Msg)
+	m.SetQuestion(zone, dns.TypeA)
+	m.RecursionDesired = true
+	r, _, err := c.Exchange(m, config.Servers[0]+":53")
+	if err != nil {
+		return nil, err
+	}
+	if r.Rcode != dns.RcodeSuccess {
+		return nil, errors.New("bad rcode: " + strconv.Itoa(r.Rcode))
+	}
+
+	var result []NSRecord
+	for _, a := range r.Answer {
+		if ar, ok := a.(*dns.A); ok {
+			// spew.Dump(ar)
+			val := netaddr.Inet{Inet: ar.A}
+			result = append(result, NSRecord{Name: a.Header().Name, Kind: "A", Value: val})
+			// fmt.Printf("%s\n", mx.String())
+		}
+	}
+
+	return result, nil
+}