Pull request 2720: AGDNS-4254-support-bootstrap-comments

Squashed commit of the following:

commit 91c992eb126dc2f447d60801895c35bc51634b3f
Merge: 83c721762 48b98bb5a
Author: Maksim Kazantsev <m.kazantsev@adguard.com>
Date:   Mon Jul 20 14:21:06 2026 +0300

    Merge branch 'master' into AGDNS-4254-support-bootstrap-comments

commit 83c7217629
Author: Maksim Kazantsev <m.kazantsev@adguard.com>
Date:   Fri Jul 17 12:34:48 2026 +0300

    all: imp ui text;

commit d15d6d19c6
Author: Maksim Kazantsev <m.kazantsev@adguard.com>
Date:   Fri Jul 17 12:30:23 2026 +0300

    all: imp chlog and ui text;

commit 9e1074fabe
Author: Maksim Kazantsev <m.kazantsev@adguard.com>
Date:   Thu Jul 16 18:57:24 2026 +0300

    all: imp chlog;

commit 25a864b343
Author: Maksim Kazantsev <m.kazantsev@adguard.com>
Date:   Thu Jul 16 18:56:33 2026 +0300

    all: imp chlog and ui text;

commit bf6ad5108e
Author: Maksim Kazantsev <m.kazantsev@adguard.com>
Date:   Thu Jul 16 17:18:55 2026 +0300

    all: upd chlog; openapi: upd openapi and api chlog; client_V2: upd ui text;

commit 13b595c36e
Author: Maksim Kazantsev <m.kazantsev@adguard.com>
Date:   Thu Jul 16 12:50:53 2026 +0300

    dnsforward: add support of comments in bootstraps;

CHANGELOG.md

@@ -20,6 +20,8 @@ NOTE: Add new changes BELOW THIS COMMENT.
 
 ### Added
 
+- Bootstrap servers configuration now supports comments.
+
 - New property `"language"` in `POST /control/install/check_config` and `POST /control/install/configure` HTTP APIs.
 
 - The user is able to remove the static lease's hostname via the HTTP API.

client/src/__locales/en.json

@@ -63,7 +63,7 @@
   "blocking_mode_refused": "REFUSED: Respond with REFUSED code",
   "blocklist": "Blocklist",
   "bootstrap_dns": "Bootstrap DNS servers",
-  "bootstrap_dns_desc": "IP addresses of DNS servers used to resolve IP addresses of the DoH/DoT resolvers you specify as upstreams. Comments are not permitted.",
+  "bootstrap_dns_desc": "IP addresses of DNS servers used to resolve IP addresses of the DoH/DoT resolvers you specify as upstreams. Empty lines and comments, starting with '#', are ignored.",
   "cache_cleared": "DNS cache successfully cleared",
   "cache_enabled": "Enable cache",
   "cache_enabled_desc": "Store DNS responses locally.",

client_v2/src/__locales/en.json

@@ -329,7 +329,7 @@
   "dns_blocking_mode_ttl_label": "Blocked response TTL, in seconds",
   "dns_blocking_mode_ttl_placeholder": "Enter TTL",
   "dns_bootstrap_dns_desc": "Sets the DNS servers used to resolve DoH/DoT upstream resolver hostnames",
-  "dns_bootstrap_dns_desc_2": "Enter IP addresses only. Comments are not allowed",
+  "dns_bootstrap_dns_desc_2": "Enter IP addresses and, optionally, comments. Comments must start with a hash (#) and be on exclusive lines",
   "dns_bootstrap_dns_label": "Bootstrap DNS servers, one per line",
   "dns_bootstrap_dns_placeholder": "IP addresses",
   "dns_bootstrap_dns_title": "Bootstrap DNS servers",
@@ -466,7 +466,7 @@
   "upstream_fallback_title_faq": "Fallback DNS servers to use when upstream DNS servers are unavailable. Use the same syntax as for the upstream DNS servers",
   "ip_addresses_placeholder": "Enter IP addresses, one per line",
   "upstream_bootstrap_dns_title": "Bootstrap DNS servers, one per line",
-  "upstream_bootstrap_dns_faq": "IP addresses of DNS servers used to resolve the IP addresses of DoH/DoT upstream resolvers. Comments are not allowed",
+  "upstream_bootstrap_dns_faq": "IP addresses of DNS servers used to resolve the IP addresses of DoH/DoT upstream resolvers. Empty lines and comments, starting with '#', are ignored.",
   "upstream_ptr": "Private reverse DNS servers, one per line",
   "upstream_ptr_faq_1": "AdGuard Home uses these DNS servers for private PTR, SOA, and NS requests. Private requests come from clients with a private IP address and ask for an ARPA domain that contains a subnet from a private IP address range, such as %value%",
   "upstream_ptr_faq_2": "If this field is empty, the default DNS resolvers of your OS will be used, except for the AdGuard Home IP addresses",

internal/dnsforward/http.go

@@ -342,8 +342,8 @@ func (req *jsonDNSConfig) checkBootstrap() (err error) {
 	defer func() { err = errors.Annotate(err, "checking bootstrap %s: %w", b) }()
 
 	for _, b = range *req.Bootstraps {
-		if b == "" {
-			return errors.Error("empty")
+		if aghnet.IsCommentOrEmpty(b) {
+			continue
 		}
 
 		var resolver *upstream.UpstreamResolver
@@ -730,8 +730,6 @@ func (s *Server) handleTestUpstreamDNS(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	req.BootstrapDNS = stringutil.FilterOut(req.BootstrapDNS, aghnet.IsCommentOrEmpty)
-
 	opts := &upstream.Options{
 		Logger:     aghslog.NewForUpstream(s.baseLogger, aghslog.UpstreamTypeTest),
 		Timeout:    s.conf.UpstreamTimeout,

internal/dnsforward/upstreams.go

@@ -29,6 +29,8 @@ func newBootstrap(
 	etcHosts upstream.Resolver,
 	opts *upstream.Options,
 ) (r upstream.Resolver, boots []*upstream.UpstreamResolver, err error) {
+	addrs = stringutil.FilterOut(addrs, aghnet.IsCommentOrEmpty)
+
 	if len(addrs) == 0 {
 		addrs = defaultBootstrap
 	}

openapi/CHANGELOG.md

@@ -4,6 +4,8 @@
 
 ## v0.107.79: API changes
 
+- Field `bootstrap_dns` in `POST /control/dns_config` now accepts comments.  A comment must start with the `#` symbol.
+
 ### Setting the UI language through the install API
 
 - New property `"language"` in `POST /control/install/check_config` and `POST /control/install/configure` HTTP APIs defines the language to use once AdGuard Home is installed.

openapi/openapi.yaml

@@ -1557,7 +1557,8 @@
           'type': 'array'
           'description': >
             Bootstrap servers, port is optional after colon.  Empty value will
-            reset it to default values.
+            reset it to default values.  Comments are allowed, a comment line
+            starts with a `#` symbol.
           'items':
             'type': 'string'
           'example':
@@ -1567,7 +1568,8 @@
           'type': 'array'
           'description': >
             Upstream servers, port is optional after colon.  Empty value will
-            reset it to default values.
+            reset it to default values.  Comments are allowed, a comment line
+            starts with a `#` symbol.
           'items':
             'type': 'string'
           'example':
@@ -1577,7 +1579,8 @@
           'type': 'array'
           'description': >
             List of fallback DNS servers used when upstream DNS servers are not
-            responding.  Empty value will clear the list.
+            responding.  Empty value will clear the list.  Comments are allowed,
+            a comment line starts with a `#` symbol.
           'items':
             'type': 'string'
           'example':
@@ -1670,7 +1673,8 @@
           'type': 'array'
           'description': >
             Upstream servers, port is optional after colon.  Empty value will
-            reset it to default values.
+            reset it to default values.  Comments are allowed, a comment line
+            starts with a `#` symbol.
           'items':
             'type': 'string'
           'example':