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plugin/rewrite: Allow configuring min and max TTL values when rewriting TTL (#5508)

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This commit is contained in:
AndreasHuber-CH
2022-08-17 21:33:51 +02:00
committed by GitHub
parent 1a31b35b34
commit b55cee4d1a
3 changed files with 93 additions and 23 deletions
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75
plugin/rewrite/ttl.go
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@@ -14,11 +14,16 @@ import (
)
type ttlResponseRule struct {
TTL uint32
minTTL uint32
maxTTL uint32
}
func (r *ttlResponseRule) RewriteResponse(rr dns.RR) {
rr.Header().Ttl = r.TTL
if rr.Header().Ttl < r.minTTL {
rr.Header().Ttl = r.minTTL
} else if rr.Header().Ttl > r.maxTTL {
rr.Header().Ttl = r.maxTTL
}
}
type ttlRuleBase struct {
@@ -26,10 +31,10 @@ type ttlRuleBase struct {
response ttlResponseRule
}
func newTTLRuleBase(nextAction string, ttl uint32) ttlRuleBase {
func newTTLRuleBase(nextAction string, minTtl, maxTtl uint32) ttlRuleBase {
return ttlRuleBase{
nextAction: nextAction,
response: ttlResponseRule{TTL: ttl},
response: ttlResponseRule{minTTL: minTtl, maxTTL: maxTtl},
}
}
@@ -108,7 +113,7 @@ func newTTLRule(nextAction string, args ...string) (Rule, error) {
if len(args) == 3 {
s = args[2]
}
ttl, valid := isValidTTL(s)
minTtl, maxTtl, valid := isValidTTL(s)
if !valid {
return nil, fmt.Errorf("invalid TTL '%s' for a ttl rule", s)
}
@@ -116,22 +121,22 @@ func newTTLRule(nextAction string, args ...string) (Rule, error) {
switch strings.ToLower(args[0]) {
case ExactMatch:
return &exactTTLRule{
newTTLRuleBase(nextAction, ttl),
newTTLRuleBase(nextAction, minTtl, maxTtl),
plugin.Name(args[1]).Normalize(),
}, nil
case PrefixMatch:
return &prefixTTLRule{
newTTLRuleBase(nextAction, ttl),
newTTLRuleBase(nextAction, minTtl, maxTtl),
plugin.Name(args[1]).Normalize(),
}, nil
case SuffixMatch:
return &suffixTTLRule{
newTTLRuleBase(nextAction, ttl),
newTTLRuleBase(nextAction, minTtl, maxTtl),
plugin.Name(args[1]).Normalize(),
}, nil
case SubstringMatch:
return &substringTTLRule{
newTTLRuleBase(nextAction, ttl),
newTTLRuleBase(nextAction, minTtl, maxTtl),
plugin.Name(args[1]).Normalize(),
}, nil
case RegexMatch:
@@ -140,7 +145,7 @@ func newTTLRule(nextAction string, args ...string) (Rule, error) {
return nil, fmt.Errorf("invalid regex pattern in a ttl rule: %s", args[1])
}
return &regexTTLRule{
newTTLRuleBase(nextAction, ttl),
newTTLRuleBase(nextAction, minTtl, maxTtl),
regexPattern,
}, nil
default:
@@ -151,22 +156,50 @@ func newTTLRule(nextAction string, args ...string) (Rule, error) {
return nil, fmt.Errorf("many few arguments for a ttl rule")
}
return &exactTTLRule{
newTTLRuleBase(nextAction, ttl),
newTTLRuleBase(nextAction, minTtl, maxTtl),
plugin.Name(args[0]).Normalize(),
}, nil
}
// validTTL returns true if v is valid TTL value.
func isValidTTL(v string) (uint32, bool) {
i, err := strconv.Atoi(v)
if err != nil {
return uint32(0), false
func isValidTTL(v string) (uint32, uint32, bool) {
s := strings.Split(v, "-")
if len(s) == 1 {
i, err := strconv.ParseUint(s[0], 10, 32)
if err != nil {
return 0, 0, false
}
return uint32(i), uint32(i), true
}
if i > 2147483647 {
return uint32(0), false
if len(s) == 2 {
var min, max uint64
var err error
if s[0] == "" {
min = 0
} else {
min, err = strconv.ParseUint(s[0], 10, 32)
if err != nil {
return 0, 0, false
}
}
if s[1] == "" {
if s[0] == "" {
// explicitly reject ttl directive "-" that would otherwise be interpreted
// as 0-2147483647 which is pretty useless
return 0, 0, false
}
max = 2147483647
} else {
max, err = strconv.ParseUint(s[1], 10, 32)
if err != nil {
return 0, 0, false
}
}
if min > max {
// reject invalid range
return 0, 0, false
}
return uint32(min), uint32(max), true
}
if i < 0 {
return uint32(0), false
}
return uint32(i), true
return 0, 0, false
}