From 2a6c237d4cdf50d245ed38a371c3d6b11c981762 Mon Sep 17 00:00:00 2001
From: Michael Stapelberg <michael@stapelberg.de>
Date: Sun, 23 Jul 2023 17:49:20 +0200
Subject: [PATCH] net/dns: overwrite /tmp/resolv.conf on gokrazy
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Appliances built using https://gokrazy.org/ have a read-only root file system,
including /etc/resolv.conf, which is a symlink to /tmp/resolv.conf.

The system’s dhcp client overwrites /tmp/resolv.conf instead,
so we need to use this path in Tailscale, too.

related to https://github.com/gokrazy/gokrazy/issues/209

fixes https://github.com/tailscale/tailscale/issues/8689

Signed-off-by: Michael Stapelberg <michael@stapelberg.de>
---
 net/dns/direct.go                 |  5 -----
 net/dns/resolvconfpath_default.go | 11 +++++++++++
 net/dns/resolvconfpath_gokrazy.go | 11 +++++++++++
 3 files changed, 22 insertions(+), 5 deletions(-)
 create mode 100644 net/dns/resolvconfpath_default.go
 create mode 100644 net/dns/resolvconfpath_gokrazy.go

diff --git a/net/dns/direct.go b/net/dns/direct.go
index 0cae70d0e..e9279d13a 100644
--- a/net/dns/direct.go
+++ b/net/dns/direct.go
@@ -27,11 +27,6 @@ import (
 	"tailscale.com/version/distro"
 )
 
-const (
-	backupConf = "/etc/resolv.pre-tailscale-backup.conf"
-	resolvConf = "/etc/resolv.conf"
-)
-
 // writeResolvConf writes DNS configuration in resolv.conf format to the given writer.
 func writeResolvConf(w io.Writer, servers []netip.Addr, domains []dnsname.FQDN) error {
 	c := &resolvconffile.Config{
diff --git a/net/dns/resolvconfpath_default.go b/net/dns/resolvconfpath_default.go
new file mode 100644
index 000000000..57e82c4c7
--- /dev/null
+++ b/net/dns/resolvconfpath_default.go
@@ -0,0 +1,11 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !gokrazy
+
+package dns
+
+const (
+	resolvConf = "/etc/resolv.conf"
+	backupConf = "/etc/resolv.pre-tailscale-backup.conf"
+)
diff --git a/net/dns/resolvconfpath_gokrazy.go b/net/dns/resolvconfpath_gokrazy.go
new file mode 100644
index 000000000..f0759b0e3
--- /dev/null
+++ b/net/dns/resolvconfpath_gokrazy.go
@@ -0,0 +1,11 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build gokrazy
+
+package dns
+
+const (
+	resolvConf = "/tmp/resolv.conf"
+	backupConf = "/tmp/resolv.pre-tailscale-backup.conf"
+)