Bugzilla – Full Text Bug Listing
|Summary:||Receive malformed packet from authoritative name server when request with edns0, and retry with edns0 again|
|Component:||server||Assignee:||unbound team <unbound-team>|
|Attachments:||example of malformed packet|
Description chenfzh 2014-08-27 10:15:50 CEST
Created attachment 260 [details] example of malformed packet Some authoritative name server doesn't support edns well, when unbound send a request to it, it response with a malformed packet. If I request this server without edns, it response with a normal packet. unbound detect by checking NOTIMPL or FORMERR flag, but the malformed packet do not contain these flag, so function servied_udp_callback treat it like a normal packet, but unbound fail to parse this packet. Then unbound retry with edns0, and fail again, and again... I'm not sure it's a bug, but I think it's better to send to the authoritative name server a request without edns after receiving a malformed packet from the server. There's an example in the attachment.The domain name is 126.com.cn, and the authoritative name server is 188.8.131.52.
Comment 1 Wouter Wijngaards 2014-08-28 13:53:50 CEST
Hi Chenfzh, Yes that is an interesting improvement in EDNS support detection. The packet is malformed, but is good if the additional-rr-count had been 1. Best regards, Wouter
Comment 2 chenfzh 2014-08-29 04:22:37 CEST
I tried to let the serviced_query.status do not be serviced_query_UDP_EDNS any more if unbound received malformed packet before, but I didn't find out a suitable way to implement it. I modified function parse_section in util/data/msgparse.c to make it work (so far), but I think that's not a good solution.