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dns: parse answers only when query type is A or AAAA

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nadoo 2018-01-05 12:29:06 +08:00
parent 8e8361bc42
commit 52a1c35b01
1 changed files with 7 additions and 2 deletions
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9
dns.go
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@ -139,7 +139,8 @@ func (s *DNS) ListenAndServe() {
// SEE RFC1035, section 4.2.2 TCP: The message is prefixed with a two byte length field which gives the message length, excluding the two byte length field. // SEE RFC1035, section 4.2.2 TCP: The message is prefixed with a two byte length field which gives the message length, excluding the two byte length field.
if respLen > 0 { if respLen > 0 {
query := parseQuery(respMsg) query := parseQuery(respMsg)
if len(respMsg) > query.Offset { if (query.QueryType == DNSQueryTypeA || query.QueryType == DNSQueryTypeAAAA) &&
len(respMsg) > query.Offset {
answers := parseAnswers(respMsg[query.Offset:]) answers := parseAnswers(respMsg[query.Offset:])
for _, answer := range answers { for _, answer := range answers {
if answer.IP != "" { if answer.IP != "" {
@ -160,7 +161,7 @@ func (s *DNS) ListenAndServe() {
} }
} }
logf("proxy-dns %s <-> %s, %s: %s", clientAddr.String(), dnsServer, domain, ip) logf("proxy-dns %s <-> %s, type: %d, %s: %s", clientAddr.String(), dnsServer, query.QueryType, domain, ip)
}() }()
} }
@ -231,6 +232,10 @@ func parseAnswers(p []byte) []*dnsAnswer {
} }
answer := &dnsAnswer{} answer := &dnsAnswer{}
// https://tools.ietf.org/html/rfc1035#section-4.1.4
// i+2 assumes the ANSWER always using "Message compression", start with 2 bytes offset of the query domain.
// TODO: check here
answer.QueryType = binary.BigEndian.Uint16(p[i+2:]) answer.QueryType = binary.BigEndian.Uint16(p[i+2:])
answer.QueryClass = binary.BigEndian.Uint16(p[i+4:]) answer.QueryClass = binary.BigEndian.Uint16(p[i+4:])
answer.TTL = binary.BigEndian.Uint32(p[i+6:]) answer.TTL = binary.BigEndian.Uint32(p[i+6:])