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|
package rewrite
import (
"context"
"fmt"
"regexp"
"strconv"
"strings"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
)
type ttlResponseRule struct {
TTL uint32
}
func (r *ttlResponseRule) RewriteResponse(rr dns.RR) {
rr.Header().Ttl = r.TTL
}
type ttlRuleBase struct {
nextAction string
response ttlResponseRule
}
func newTTLRuleBase(nextAction string, ttl uint32) ttlRuleBase {
return ttlRuleBase{
nextAction: nextAction,
response: ttlResponseRule{TTL: ttl},
}
}
func (rule *ttlRuleBase) responseRule(match bool) (ResponseRules, Result) {
if match {
return ResponseRules{&rule.response}, RewriteDone
}
return nil, RewriteIgnored
}
// Mode returns the processing nextAction
func (rule *ttlRuleBase) Mode() string { return rule.nextAction }
type exactTTLRule struct {
ttlRuleBase
From string
}
type prefixTTLRule struct {
ttlRuleBase
Prefix string
}
type suffixTTLRule struct {
ttlRuleBase
Suffix string
}
type substringTTLRule struct {
ttlRuleBase
Substring string
}
type regexTTLRule struct {
ttlRuleBase
Pattern *regexp.Regexp
}
// Rewrite rewrites the current request based upon exact match of the name
// in the question section of the request.
func (rule *exactTTLRule) Rewrite(ctx context.Context, state request.Request) (ResponseRules, Result) {
return rule.responseRule(rule.From == state.Name())
}
// Rewrite rewrites the current request when the name begins with the matching string.
func (rule *prefixTTLRule) Rewrite(ctx context.Context, state request.Request) (ResponseRules, Result) {
return rule.responseRule(strings.HasPrefix(state.Name(), rule.Prefix))
}
// Rewrite rewrites the current request when the name ends with the matching string.
func (rule *suffixTTLRule) Rewrite(ctx context.Context, state request.Request) (ResponseRules, Result) {
return rule.responseRule(strings.HasSuffix(state.Name(), rule.Suffix))
}
// Rewrite rewrites the current request based upon partial match of the
// name in the question section of the request.
func (rule *substringTTLRule) Rewrite(ctx context.Context, state request.Request) (ResponseRules, Result) {
return rule.responseRule(strings.Contains(state.Name(), rule.Substring))
}
// Rewrite rewrites the current request when the name in the question
// section of the request matches a regular expression.
func (rule *regexTTLRule) Rewrite(ctx context.Context, state request.Request) (ResponseRules, Result) {
return rule.responseRule(len(rule.Pattern.FindStringSubmatch(state.Name())) != 0)
}
// newTTLRule creates a name matching rule based on exact, partial, or regex match
func newTTLRule(nextAction string, args ...string) (Rule, error) {
if len(args) < 2 {
return nil, fmt.Errorf("too few (%d) arguments for a ttl rule", len(args))
}
var s string
if len(args) == 2 {
s = args[1]
}
if len(args) == 3 {
s = args[2]
}
ttl, valid := isValidTTL(s)
if !valid {
return nil, fmt.Errorf("invalid TTL '%s' for a ttl rule", s)
}
if len(args) == 3 {
switch strings.ToLower(args[0]) {
case ExactMatch:
return &exactTTLRule{
newTTLRuleBase(nextAction, ttl),
plugin.Name(args[1]).Normalize(),
}, nil
case PrefixMatch:
return &prefixTTLRule{
newTTLRuleBase(nextAction, ttl),
plugin.Name(args[1]).Normalize(),
}, nil
case SuffixMatch:
return &suffixTTLRule{
newTTLRuleBase(nextAction, ttl),
plugin.Name(args[1]).Normalize(),
}, nil
case SubstringMatch:
return &substringTTLRule{
newTTLRuleBase(nextAction, ttl),
plugin.Name(args[1]).Normalize(),
}, nil
case RegexMatch:
regexPattern, err := regexp.Compile(args[1])
if err != nil {
return nil, fmt.Errorf("invalid regex pattern in a ttl rule: %s", args[1])
}
return ®exTTLRule{
newTTLRuleBase(nextAction, ttl),
regexPattern,
}, nil
default:
return nil, fmt.Errorf("ttl rule supports only exact, prefix, suffix, substring, and regex name matching")
}
}
if len(args) > 3 {
return nil, fmt.Errorf("many few arguments for a ttl rule")
}
return &exactTTLRule{
newTTLRuleBase(nextAction, ttl),
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
}
if i > 2147483647 {
return uint32(0), false
}
if i < 0 {
return uint32(0), false
}
return uint32(i), true
}
|
