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Fix: adjust DNS TTL values based on minimum value (#2706)

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This commit adds an updated function that adjusts
the TTL values of DNS records are based on the minimum TTL
the value found in the records list so that all records share the
same TTL value. This ensures consistency in the cache
expiry time for all records to prevent caching issues.
This commit is contained in:
KaitoHH 2023-04-30 12:18:20 +08:00 committed by GitHub
parent 7f1b50f4a7
commit 257fcef0b8
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 28 additions and 4 deletions
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3
dns/resolver.go
View File

@ -143,7 +143,8 @@ func (r *Resolver) ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg, e
setMsgTTL(msg, uint32(1)) // Continue fetch
go r.exchangeWithoutCache(ctx, m)
} else {
setMsgTTL(msg, uint32(time.Until(expireTime).Seconds()))
// updating TTL by subtracting common delta time from each DNS record
updateMsgTTL(msg, uint32(time.Until(expireTime).Seconds()))
}
return
}

29
dns/util.go
View File

@ -14,8 +14,25 @@ import (
"github.com/Dreamacro/clash/log"
D "github.com/miekg/dns"
"github.com/samber/lo"
)
func minimalTTL(records []D.RR) uint32 {
return lo.MinBy(records, func(r1 D.RR, r2 D.RR) bool {
return r1.Header().Ttl < r2.Header().Ttl
}).Header().Ttl
}
func updateTTL(records []D.RR, ttl uint32) {
if len(records) == 0 {
return
}
delta := minimalTTL(records) - ttl
for i := range records {
records[i].Header().Ttl = lo.Clamp(records[i].Header().Ttl-delta, 1, records[i].Header().Ttl)
}
}
func putMsgToCache(c *cache.LruCache, key string, q D.Question, msg *D.Msg) {
// skip dns cache for acme challenge
if q.Qtype == D.TypeTXT && strings.HasPrefix(q.Name, "_acme-challenge.") {
@ -26,11 +43,11 @@ func putMsgToCache(c *cache.LruCache, key string, q D.Question, msg *D.Msg) {
var ttl uint32
switch {
case len(msg.Answer) != 0:
ttl = msg.Answer[0].Header().Ttl
ttl = minimalTTL(msg.Answer)
case len(msg.Ns) != 0:
ttl = msg.Ns[0].Header().Ttl
ttl = minimalTTL(msg.Ns)
case len(msg.Extra) != 0:
ttl = msg.Extra[0].Header().Ttl
ttl = minimalTTL(msg.Extra)
default:
log.Debugln("[DNS] response msg empty: %#v", msg)
return
@ -53,6 +70,12 @@ func setMsgTTL(msg *D.Msg, ttl uint32) {
}
}
func updateMsgTTL(msg *D.Msg, ttl uint32) {
updateTTL(msg.Answer, ttl)
updateTTL(msg.Ns, ttl)
updateTTL(msg.Extra, ttl)
}
func isIPRequest(q D.Question) bool {
return q.Qclass == D.ClassINET && (q.Qtype == D.TypeA || q.Qtype == D.TypeAAAA)
}