1package smtpserver

2

3import (

4 "context"

5 "errors"

6 "sync"

7 "time"

8

9 "github.com/mjl-/mox/dns"

10 "github.com/mjl-/mox/dnsbl"

11 "github.com/mjl-/mox/mlog"

12)

13

14var dnsblHealth = struct {

15 sync.Mutex

16 zones map[dns.Domain]dnsblStatus

17}{

18 zones: map[dns.Domain]dnsblStatus{},

19}

20

21type dnsblStatus struct {

22 last time.Time

23 err error // nil, dnsbl.ErrDNS or other

24}

25

26// checkDNSBLHealth checks healthiness of DNSBL "zone", keeping the result cached for 4 hours.

27func checkDNSBLHealth(ctx context.Context, log mlog.Log, resolver dns.Resolver, zone dns.Domain) (rok bool) {

28 dnsblHealth.Lock()

29 defer dnsblHealth.Unlock()

30 status, ok := dnsblHealth.zones[zone]

31 if !ok || time.Since(status.last) > 4*time.Hour {

32 status.err = dnsbl.CheckHealth(ctx, log.Logger, resolver, zone)

33 status.last = time.Now()

34 dnsblHealth.zones[zone] = status

35 }

36 return status.err == nil || errors.Is(status.err, dnsbl.ErrDNS)

37}

38