From 7acbbbee947626d9d411f8b3398400413d0fd0ce Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Thu, 30 Jun 2022 22:06:26 -0700
Subject: [PATCH] net: ignore edns0 option in resolv.conf

We use EDNS(0) by default. No need to fall back to netdns=cgo if we
see a explicit request for EDNS(0) in resolv.conf.

For #51153

Change-Id: I135363112e3de43ce877aad45aba71d1448068b7
Reviewed-on: https://go-review.googlesource.com/c/go/+/415579
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
---
 src/net/dnsconfig_unix.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/net/dnsconfig_unix.go b/src/net/dnsconfig_unix.go
index 94cd09ec710..3ba6d44fc3a 100644
--- a/src/net/dnsconfig_unix.go
+++ b/src/net/dnsconfig_unix.go
@@ -109,6 +109,9 @@ func dnsReadConfig(filename string) *dnsConfig {
 					// https://www.freebsd.org/cgi/man.cgi?query=resolv.conf&sektion=5&manpath=freebsd-release-ports
 					// https://man.openbsd.org/resolv.conf.5
 					conf.useTCP = true
+				case s == "edns0":
+					// We use EDNS by default.
+					// Ignore this option.
 				default:
 					conf.unknownOpt = true
 				}