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plugin/rewrite: streamline the ResponseRule handling. (#4473)

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* plugin/rewrite: streamline the ResponseRule handling.

The functionality of a response rule is now completely encapsulated behind
a `ResponseRule` interface. This significantly simplifies the complete
processing flow, it enables more flexible response handling and it is possible
to eliminate lots of state flags, ifs and switches.

Based on the new flexibility the pull request also enables to support a
response name rewrite for all name rewrite types.
To be compatible, an explicit `answer auto` option is added to support
a best effort response rewrite (name and value).
Additionally now all name rewrite rules support additional name and value
reponse rewrite options.

Using this feature it is also possible now to rewrite a complete sub domain
hierarchy to a single domain name combined with a correct rewrite (#2389).

Signed-off-by: Uwe Krueger <uwe.krueger@sap.com>

* revert policy

Signed-off-by: Uwe Krueger <uwe.krueger@sap.com>

Co-authored-by: Miek Gieben <miek@miek.nl>
This commit is contained in:
Uwe Krueger
2021-05-04 10:05:45 +02:00
committed by GitHub
parent 696c8731d6
commit 40edf1e566
13 changed files with 889 additions and 521 deletions
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34
plugin/rewrite/rewrite.go
View File

@@ -31,40 +31,34 @@ const (
// Rewrite is a plugin to rewrite requests internally before being handled.
type Rewrite struct {
Next plugin.Handler
Rules []Rule
noRevert bool
Next plugin.Handler
Rules []Rule
RevertPolicy
}
// ServeDNS implements the plugin.Handler interface.
func (rw Rewrite) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
wr := NewResponseReverter(w, r)
if rw.RevertPolicy == nil {
rw.RevertPolicy = NewRevertPolicy(false, false)
}
wr := NewResponseReverter(w, r, rw.RevertPolicy)
state := request.Request{W: w, Req: r}
for _, rule := range rw.Rules {
switch result := rule.Rewrite(ctx, state); result {
case RewriteDone:
respRules, result := rule.Rewrite(ctx, state)
if result == RewriteDone {
if _, ok := dns.IsDomainName(state.Req.Question[0].Name); !ok {
err := fmt.Errorf("invalid name after rewrite: %s", state.Req.Question[0].Name)
state.Req.Question[0] = wr.originalQuestion
return dns.RcodeServerFailure, err
}
for _, respRule := range rule.GetResponseRules() {
if respRule.Active {
wr.ResponseRewrite = true
wr.ResponseRules = append(wr.ResponseRules, respRule)
}
}
wr.ResponseRules = append(wr.ResponseRules, respRules...)
if rule.Mode() == Stop {
if rw.noRevert {
return plugin.NextOrFailure(rw.Name(), rw.Next, ctx, w, r)
}
return plugin.NextOrFailure(rw.Name(), rw.Next, ctx, wr, r)
break
}
case RewriteIgnored:
}
}
if rw.noRevert || len(wr.ResponseRules) == 0 {
if !rw.RevertPolicy.DoRevert() || len(wr.ResponseRules) == 0 {
return plugin.NextOrFailure(rw.Name(), rw.Next, ctx, w, r)
}
return plugin.NextOrFailure(rw.Name(), rw.Next, ctx, wr, r)
@@ -76,11 +70,9 @@ func (rw Rewrite) Name() string { return "rewrite" }
// Rule describes a rewrite rule.
type Rule interface {
// Rewrite rewrites the current request.
Rewrite(ctx context.Context, state request.Request) Result
Rewrite(ctx context.Context, state request.Request) (ResponseRules, Result)
// Mode returns the processing mode stop or continue.
Mode() string
// GetResponseRules returns rules to rewrite response with, if any.
GetResponseRules() []ResponseRule
}
func newRule(args ...string) (Rule, error) {