4e63d0be35
This fix enables goimports check and fixes several imports format
so that the import sections are prettier, e.g.:
```
import (
- "github.com/miekg/dns"
"regexp"
"strconv"
"strings"
+
+ "github.com/miekg/dns"
)
```
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
74 lines
2 KiB
Go
74 lines
2 KiB
Go
package rewrite
|
|
|
|
import (
|
|
"regexp"
|
|
"strconv"
|
|
"strings"
|
|
|
|
"github.com/miekg/dns"
|
|
)
|
|
|
|
// ResponseRule contains a rule to rewrite a response with.
|
|
type ResponseRule struct {
|
|
Active bool
|
|
Pattern *regexp.Regexp
|
|
Replacement string
|
|
}
|
|
|
|
// ResponseReverter reverses the operations done on the question section of a packet.
|
|
// This is need because the client will otherwise disregards the response, i.e.
|
|
// dig will complain with ';; Question section mismatch: got miek.nl/HINFO/IN'
|
|
type ResponseReverter struct {
|
|
dns.ResponseWriter
|
|
originalQuestion dns.Question
|
|
ResponseRewrite bool
|
|
ResponseRules []ResponseRule
|
|
}
|
|
|
|
// NewResponseReverter returns a pointer to a new ResponseReverter.
|
|
func NewResponseReverter(w dns.ResponseWriter, r *dns.Msg) *ResponseReverter {
|
|
return &ResponseReverter{
|
|
ResponseWriter: w,
|
|
originalQuestion: r.Question[0],
|
|
}
|
|
}
|
|
|
|
// WriteMsg records the status code and calls the
|
|
// underlying ResponseWriter's WriteMsg method.
|
|
func (r *ResponseReverter) WriteMsg(res *dns.Msg) error {
|
|
res.Question[0] = r.originalQuestion
|
|
if r.ResponseRewrite {
|
|
for _, rr := range res.Answer {
|
|
name := rr.Header().Name
|
|
for _, rule := range r.ResponseRules {
|
|
regexGroups := rule.Pattern.FindStringSubmatch(name)
|
|
if len(regexGroups) == 0 {
|
|
continue
|
|
}
|
|
s := rule.Replacement
|
|
for groupIndex, groupValue := range regexGroups {
|
|
groupIndexStr := "{" + strconv.Itoa(groupIndex) + "}"
|
|
if strings.Contains(s, groupIndexStr) {
|
|
s = strings.Replace(s, groupIndexStr, groupValue, -1)
|
|
}
|
|
}
|
|
name = s
|
|
}
|
|
rr.Header().Name = name
|
|
}
|
|
}
|
|
return r.ResponseWriter.WriteMsg(res)
|
|
}
|
|
|
|
// Write is a wrapper that records the size of the message that gets written.
|
|
func (r *ResponseReverter) Write(buf []byte) (int, error) {
|
|
n, err := r.ResponseWriter.Write(buf)
|
|
return n, err
|
|
}
|
|
|
|
// Hijack implements dns.Hijacker. It simply wraps the underlying
|
|
// ResponseWriter's Hijack method if there is one, or returns an error.
|
|
func (r *ResponseReverter) Hijack() {
|
|
r.ResponseWriter.Hijack()
|
|
return
|
|
}
|