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Fix: DNS NCACHE TTL and OPT RRs (#2900) 

* Fix: DNS NCACHE TTL and OPT RRs

1. DNS NCACHE was not correctly implemented.
2. OPT RRs must not be cached or forwarded.

Closes #2889.
This commit is contained in:
Jiahao Lu 2023-08-24 23:28:04 +08:00 committed by GitHub
parent 8a4c46ae77
commit 45c10a17a6
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 28 additions and 6 deletions
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6
dns/resolver.go
View File

@ -16,6 +16,7 @@ import (
C "github.com/Dreamacro/clash/constant"
D "github.com/miekg/dns"
"github.com/samber/lo"
"golang.org/x/sync/singleflight"
)
@ -166,7 +167,10 @@ func (r *Resolver) exchangeWithoutCache(ctx context.Context, m *D.Msg) (msg *D.M
}
msg := result.(*D.Msg)
// OPT RRs MUST NOT be cached, forwarded, or stored in or loaded from master files.
msg.Extra = lo.Filter(msg.Extra, func(rr D.RR, index int) bool {
return rr.Header().Rrtype != D.TypeOPT
})
putMsgToCache(r.lruCache, q.String(), q, msg)
}()

28
dns/util.go
View File

@ -6,22 +6,27 @@ import (
"errors"
"fmt"
"net"
"strings"
"time"
"github.com/Dreamacro/clash/common/cache"
"github.com/Dreamacro/clash/common/picker"
"github.com/Dreamacro/clash/log"
D "github.com/miekg/dns"
"github.com/samber/lo"
)
const serverFailureCacheTTL uint32 = 5
func minimalTTL(records []D.RR) uint32 {
if len(records) == 0 {
rr := lo.MinBy(records, func(r1 D.RR, r2 D.RR) bool {
return r1.Header().Ttl < r2.Header().Ttl
})
if rr == nil {
return 0
}
return lo.MinBy(records, func(r1 D.RR, r2 D.RR) bool {
return r1.Header().Ttl < r2.Header().Ttl
}).Header().Ttl
return rr.Header().Ttl
}
func updateTTL(records []D.RR, ttl uint32) {
@ -35,7 +40,20 @@ func updateTTL(records []D.RR, ttl uint32) {
}
func putMsgToCache(c *cache.LruCache, key string, q D.Question, msg *D.Msg) {
ttl := minimalTTL(msg.Answer)
// skip dns cache for acme challenge
if q.Qtype == D.TypeTXT && strings.HasPrefix(q.Name, "_acme-challenge.") {
log.Debugln("[DNS] dns cache ignored because of acme challenge for: %s", q.Name)
return
}
var ttl uint32
if msg.Rcode == D.RcodeServerFailure {
// [...] a resolver MAY cache a server failure response.
// If it does so it MUST NOT cache it for longer than five (5) minutes [...]
ttl = serverFailureCacheTTL
} else {
ttl = minimalTTL(append(append(msg.Answer, msg.Ns...), msg.Extra...))
}
if ttl == 0 {
return
}