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package rewrite
import (
"fmt"
"strings"
"github.com/coredns/coredns/middleware"
"github.com/miekg/dns"
"golang.org/x/net/context"
)
// Result is the result of a rewrite
type Result int
const (
// RewriteIgnored is returned when rewrite is not done on request.
RewriteIgnored Result = iota
// RewriteDone is returned when rewrite is done on request.
RewriteDone
// RewriteStatus is returned when rewrite is not needed and status code should be set
// for the request.
RewriteStatus
)
// Rewrite is middleware to rewrite requests internally before being handled.
type Rewrite struct {
Next middleware.Handler
Rules []Rule
noRevert bool
}
// ServeDNS implements the middleware.Handler interface.
func (rw Rewrite) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
wr := NewResponseReverter(w, r)
for _, rule := range rw.Rules {
switch result := rule.Rewrite(w, r); result {
case RewriteDone:
if rw.noRevert {
return middleware.NextOrFailure(rw.Name(), rw.Next, ctx, w, r)
}
return middleware.NextOrFailure(rw.Name(), rw.Next, ctx, wr, r)
case RewriteIgnored:
break
case RewriteStatus:
// only valid for complex rules.
// if cRule, ok := rule.(*ComplexRule); ok && cRule.Status != 0 {
// return cRule.Status, nil
// }
}
}
return middleware.NextOrFailure(rw.Name(), rw.Next, ctx, w, r)
}
// Name implements the Handler interface.
func (rw Rewrite) Name() string { return "rewrite" }
// Rule describes a rewrite rule.
type Rule interface {
// Rewrite rewrites the current request.
Rewrite(dns.ResponseWriter, *dns.Msg) Result
}
func newRule(args ...string) (Rule, error) {
if len(args) == 0 {
return nil, fmt.Errorf("no rule type specified for rewrite")
}
ruleType := strings.ToLower(args[0])
if ruleType != "edns0" && len(args) != 3 {
return nil, fmt.Errorf("%s rules must have exactly two arguments", ruleType)
}
switch ruleType {
case "name":
return newNameRule(args[1], args[2])
case "class":
return newClassRule(args[1], args[2])
case "type":
return newTypeRule(args[1], args[2])
case "edns0":
return newEdns0Rule(args[1:]...)
default:
return nil, fmt.Errorf("invalid rule type %q", args[0])
}
}
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