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DNS Resolution Behavior

1 post · May 2017

What this trail covers

This post investigates and explains the differences in DNS resolution behavior between Go's native resolver, Cgo, and C, particularly concerning RFC 6724 (3484) and IPv6. It details how disabling IPv6 affects IP address sorting and identifies that Go's native resolver implements only a partial subset of RFC 6724 rules, lacking source address selection, which leads to different outcomes compared to Cgo/C resolvers.

All Grab trails
  1. DNS Resolution in Go and CgoThis post details an investigation into DNS resolution differences between Go's native resolver, Cgo, and C. It explains RFC 6724 (3484) and its impact on IP address selection. The authors demonstrate through code examples and output that disabling IPv6 alters the IP address sorting order for Cgo and C resolvers, while having no effect on Go's native resolver. The core issue identified is Go's native resolver's partial implementation of RFC 6724, specifically its lack of source address selection, which differs from the glibc implementation used by Cgo/C.