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Created by Jim Pirzyk@pirzyk

dig +tcp does not honor +tries=1 nor +retry=0

Summary

When using dig in a test suite and the resolver closes the TCP connection early in the process, due to being rate limited or on a blocked list, dig will retry the TCP connection even though +tries=1 and +retry=0 are on the command line. I believe this is due to 14afc8425b7e034b714ebff896a9b5aab9b0fe12

BIND version used

37>dig -v
DiG 9.16.1-Ubuntu

Steps to reproduce

Setup a DNS resolver that will drop the connection after the accept() call before any data is read. In my test I have 2 queries sent right after each other. The first query should succeed (and does) and the second one should be dropped.

dig @127.0.0.1 -p 5354 +time=1 +tries=1 -b 127.0.3.15 +tcp +nokeepopen example.com example.com

What is the current bug behavior?

20210213 184035.278 T     36738 ------ 6       - accept4(fd=8, sock.sa=127.0.3.15:33601, ss_len=16, SOCK_NONBLOCK){}
20210213 184035.278 T     36738 ------ 6       - CLIENT: accept4(sockfd=8, ...): tcp open 127.0.3.15:33601, using descriptor sockfd=14
20210213 184035.280 T     36738 ------ 6       - accept4(fd=8, sock.sa=127.0.3.15:40929, ss_len=16, SOCK_NONBLOCK){}
20210213 184035.280 T     36738 ------ 6         - ratelimit_ip4_bucket[00003678=hash(ip=127.0.3.15)].counts[7].item[0]: count=2 >= limit=2; dropping query
20210213 184035.280 T     36738 ------ 6       - accept4(fd=8, sock.sa=127.0.3.15:56039, ss_len=16, SOCK_NONBLOCK){}
20210213 184035.280 T     36738 ------ 6         - ratelimit_ip4_bucket[00003678=hash(ip=127.0.3.15)].counts[7].item[0]: count=3 >= limit=2; dropping query

What is the expected correct behavior?

20210213 184035.278 T     36738 ------ 6       - accept4(fd=8, sock.sa=127.0.3.15:33601, ss_len=16, SOCK_NONBLOCK){}
20210213 184035.278 T     36738 ------ 6       - CLIENT: accept4(sockfd=8, ...): tcp open 127.0.3.15:33601, using descriptor sockfd=14
20210213 184035.280 T     36738 ------ 6       - accept4(fd=8, sock.sa=127.0.3.15:40929, ss_len=16, SOCK_NONBLOCK){}
20210213 184035.280 T     36738 ------ 6         - ratelimit_ip4_bucket[00003678=hash(ip=127.0.3.15)].counts[7].item[0]: count=2 >= limit=2; dropping query
Edited by Jim Pirzyk