From 464fbf0b543e6bc52eba0d5fdb305658e5669b68 Mon Sep 17 00:00:00 2001
From: Ainar Garipov <a.garipov@adguard.com>
Date: Mon, 7 Nov 2022 16:51:07 +0300
Subject: [PATCH] Pull request: 5089-windows-hosts-crash

Updates #5089.

Squashed commit of the following:

commit dd3ce763326ad3207de111bb911e0a2665bcebba
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Nov 7 16:21:43 2022 +0300

    aghnet: fix comparison

commit 0d736fb7fc5cb2e77fd533cd95fdf3fbc6dc86d1
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Nov 7 14:13:05 2022 +0300

    aghnet: fix crash
---
 CHANGELOG.md                      | 10 +++++++++-
 internal/aghnet/hostscontainer.go |  8 +++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7a0f1639..c1de040f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,14 @@ and this project adheres to
 
 
 
+### Fixed
+
+- Crash on Windows when system hosts files are read ([#5089]).
+
+[#5089]: https://github.com/AdguardTeam/AdGuardHome/issues/5089
+
+
+
 <!--
 ## [v0.107.18] - 2022-11-16 (APPROX.)
 
@@ -1088,7 +1096,7 @@ See also the [v0.106.0 GitHub milestone][ms-v0.106.0].
 - Hostname uniqueness validation in the DHCP server ([#2952]).
 - Hostname generating for DHCP clients which don't provide their own ([#2723]).
 - New flag `--no-etc-hosts` to disable client domain name lookups in the
-  operating system's /etc/hosts files ([#1947]).
+  operating system's `/etc/hosts` files ([#1947]).
 - The ability to set up custom upstreams to resolve PTR queries for local
   addresses and to disable the automatic resolving of clients' addresses
   ([#2704]).
diff --git a/internal/aghnet/hostscontainer.go b/internal/aghnet/hostscontainer.go
index f74ce1f9..a8170447 100644
--- a/internal/aghnet/hostscontainer.go
+++ b/internal/aghnet/hostscontainer.go
@@ -139,6 +139,8 @@ type HostsRecord struct {
 func (rec *HostsRecord) equal(other *HostsRecord) (ok bool) {
 	if rec == nil {
 		return other == nil
+	} else if other == nil {
+		return false
 	}
 
 	return rec.Canonical == other.Canonical && rec.Aliases.Equal(other.Aliases)
@@ -478,7 +480,11 @@ func (hc *HostsContainer) refresh() (err error) {
 		return fmt.Errorf("refreshing : %w", err)
 	}
 
-	if maps.EqualFunc(hp.table, hc.last, (*HostsRecord).equal) {
+	// hc.last is nil on the first refresh, so let that one through.
+	//
+	// TODO(a.garipov): Once https://github.com/golang/go/issues/56621 is
+	// resolved, remove the first condition.
+	if hc.last != nil && maps.EqualFunc(hp.table, hc.last, (*HostsRecord).equal) {
 		log.Debug("%s: no changes detected", hostsContainerPref)
 
 		return nil