UDP issue - queries with udp port 53 / dns #52
Description
hi all,
I'm running into issues with UDP based DNS resolution (getting consistent but 'random' timeouts). I'm using pen from github / compiled source (it says "pen 0.35.0").
I've added basic packet captures. It represents 3 concurrent "nslookup www.cname.myserver.guy" attempts, nothing fancy - just start the pen process and try three times. the first two work fine, the last does not.
In the first transaction, the source port of the udp request 46590 matches in the return packet. The nslookup works fine.
17:52:51.692302 IP dnssource.myserver.guy.46590 > resolver.myserver.guy.domain: 25463+ A? www.cname.myserver.guy. (36)
17:52:51.693977 IP resolver.myserver.guy.domain > dnssource.myserver.guy.46590: 25463* 1/2/2 A www.myserver.guy (120)
The same for the second transaction, the source port 35253 matches in the return packet, and the nslookup works fine..
17:52:57.551415 IP dnssource.myserver.guy.35253 > resolver.myserver.guy.domain: 22653+ A? www.cname.myserver.guy. (36)
17:52:57.552963 IP resolver.myserver.guy.domain > dnssource.myserver.guy.35253: 22653* 1/2/2 A www.myserver.guy (120)
however! in the third request, the source port is 39939 but the return packet has the port of the previous packet 35253. This packet never gets back to the nslookup and so fails with a timeout.
17:53:00.740266 IP dnssource.myserver.guy.39939 > resolver.myserver.guy.domain: 4360+ A? www.cname.myserver.guy. (36)
17:53:00.741555 IP resolver.myserver.guy.domain > dnssource.myserver.guy.35253: 4360* 1/2/2 A www.myserver.guy (120)
For what it's worth... if I change the config to use TCP for DNS requests, it all works wonderfully!
oh, another interesting point is that the exact same configuration with pen 0.25.1 also works with no issues.