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NfNitLoop ("Cody Casterline 🏳️🌈") wrote:
#TIL: #glibc's resolv.conf has an option, single-request, which disables parallel DNS requests for IPv4/6 and makes them sequential. This is a fix for "DNS servers [that] cannot handle these queries properly".
But, after a bit of digging w/ #wireshark, the issue seems to be that by default glibc makes those parallel requests USING THE SAME UDP SOURCE PORT. 🤦♂️ So buggy or overzealous NAT/firewall rules are likely causing the 2nd response to get dropped.
+1 port >> +1 network round trip latency.