From 7f69142aa01260bca812250c96a6a566a80e557a Mon Sep 17 00:00:00 2001
From: Rob Murray <rob.murray@docker.com>
Date: Fri, 1 Mar 2024 16:52:29 +0000
Subject: [PATCH] resolv.conf comments have '#' or ';' in the first column

When a '#' or ';' appears anywhere else, it's not a comment marker.

Signed-off-by: Rob Murray <rob.murray@docker.com>
---
 libnetwork/internal/resolvconf/resolvconf.go  | 14 ++------
 libnetwork/resolvconf/resolvconf_unix_test.go | 35 +++++++++++--------
 2 files changed, 23 insertions(+), 26 deletions(-)

diff --git a/libnetwork/internal/resolvconf/resolvconf.go b/libnetwork/internal/resolvconf/resolvconf.go
index 6e49c37927..5e9278c48a 100644
--- a/libnetwork/internal/resolvconf/resolvconf.go
+++ b/libnetwork/internal/resolvconf/resolvconf.go
@@ -452,18 +452,8 @@ func UserModified(rcPath, rcHashPath string) (bool, error) {
 func (rc *ResolvConf) processLine(line string) {
 	fields := strings.Fields(line)
 
-	// Strip comments.
-	// TODO(robmry) - ignore comment chars except in column 0.
-	//   This preserves old behaviour, but it's wrong. For example, resolvers
-	//   will honour the option in line "options # ndots:0" (and ignore the
-	//   "#" as an unknown option).
-	for i, s := range fields {
-		if s[0] == '#' || s[0] == ';' {
-			fields = fields[:i]
-			break
-		}
-	}
-	if len(fields) == 0 {
+	// Strip blank lines and comments.
+	if len(fields) == 0 || fields[0][0] == '#' || fields[0][0] == ';' {
 		return
 	}
 
diff --git a/libnetwork/resolvconf/resolvconf_unix_test.go b/libnetwork/resolvconf/resolvconf_unix_test.go
index 6fcbe34381..86ccbf4106 100644
--- a/libnetwork/resolvconf/resolvconf_unix_test.go
+++ b/libnetwork/resolvconf/resolvconf_unix_test.go
@@ -149,16 +149,16 @@ func TestGetSearchDomains(t *testing.T) {
 			result: []string{"example.com"},
 		},
 		{
-			input:  `search example.com # ignored`,
-			result: []string{"example.com"},
+			input:  `search example.com # notignored`,
+			result: []string{"example.com", "#", "notignored"},
 		},
 		{
 			input:  `	  search	 example.com	  `,
 			result: []string{"example.com"},
 		},
 		{
-			input:  `	  search	 example.com	  # ignored`,
-			result: []string{"example.com"},
+			input:  `	  search	 example.com	  # notignored`,
+			result: []string{"example.com", "#", "notignored"},
 		},
 		{
 			input:  `search foo.example.com example.com`,
@@ -169,8 +169,8 @@ func TestGetSearchDomains(t *testing.T) {
 			result: []string{"foo.example.com", "example.com"},
 		},
 		{
-			input:  `	   search	   foo.example.com	 example.com	# ignored`,
-			result: []string{"foo.example.com", "example.com"},
+			input:  `	   search	   foo.example.com	 example.com	# notignored`,
+			result: []string{"foo.example.com", "example.com", "#", "notignored"},
 		},
 		{
 			input: `nameserver 1.2.3.4
@@ -212,6 +212,9 @@ func TestGetOptions(t *testing.T) {
 		{
 			input: `# ignored`,
 		},
+		{
+			input: `; ignored`,
+		},
 		{
 			input: `nameserver 1.2.3.4`,
 		},
@@ -220,32 +223,36 @@ func TestGetOptions(t *testing.T) {
 			result: []string{"opt1"},
 		},
 		{
-			input:  `options opt1 # ignored`,
-			result: []string{"opt1"},
+			input:  `options opt1 # notignored`,
+			result: []string{"opt1", "#", "notignored"},
+		},
+		{
+			input:  `options opt1 ; notignored`,
+			result: []string{"opt1", ";", "notignored"},
 		},
 		{
 			input:  `	  options	 opt1	  `,
 			result: []string{"opt1"},
 		},
 		{
-			input:  `	  options	 opt1	  # ignored`,
-			result: []string{"opt1"},
+			input:  `	  options	 opt1	  # notignored`,
+			result: []string{"opt1", "#", "notignored"},
 		},
 		{
 			input:  `options opt1 opt2 opt3`,
 			result: []string{"opt1", "opt2", "opt3"},
 		},
 		{
-			input:  `options opt1 opt2 opt3 # ignored`,
-			result: []string{"opt1", "opt2", "opt3"},
+			input:  `options opt1 opt2 opt3 # notignored`,
+			result: []string{"opt1", "opt2", "opt3", "#", "notignored"},
 		},
 		{
 			input:  `	   options	 opt1	 opt2	 opt3	`,
 			result: []string{"opt1", "opt2", "opt3"},
 		},
 		{
-			input:  `	   options	 opt1	 opt2	 opt3	# ignored`,
-			result: []string{"opt1", "opt2", "opt3"},
+			input:  `	   options	 opt1	 opt2	 opt3	# notignored`,
+			result: []string{"opt1", "opt2", "opt3", "#", "notignored"},
 		},
 		{
 			input: `nameserver 1.2.3.4