kube-proxy: make iptables buffer-writing cleaner

pkg/proxy/util/utils.go

@@ -468,23 +468,35 @@ func GetClusterIPByFamily(ipFamily v1.IPFamily, service *v1.Service) string {
 	return ""
 }
 
-// WriteLine join all words with spaces, terminate with newline and write to buff.
-func WriteLine(buf *bytes.Buffer, words ...string) {
+type LineBuffer struct {
+	b bytes.Buffer
+}
+
+// Write joins all words with spaces, terminates with newline and writes to buf.
+func (buf *LineBuffer) Write(words ...string) {
 	// We avoid strings.Join for performance reasons.
 	for i := range words {
-		buf.WriteString(words[i])
+		buf.b.WriteString(words[i])
 		if i < len(words)-1 {
-			buf.WriteByte(' ')
+			buf.b.WriteByte(' ')
 		} else {
-			buf.WriteByte('\n')
+			buf.b.WriteByte('\n')
 		}
 	}
 }
 
-// WriteBytesLine write bytes to buffer, terminate with newline
-func WriteBytesLine(buf *bytes.Buffer, bytes []byte) {
-	buf.Write(bytes)
-	buf.WriteByte('\n')
+// WriteBytes writes bytes to buffer, and terminates with newline.
+func (buf *LineBuffer) WriteBytes(bytes []byte) {
+	buf.b.Write(bytes)
+	buf.b.WriteByte('\n')
+}
+
+func (buf *LineBuffer) Reset() {
+	buf.b.Reset()
+}
+
+func (buf *LineBuffer) Bytes() []byte {
+	return buf.b.Bytes()
 }
 
 // RevertPorts is closing ports in replacementPortsMap but not in originalPortsMap. In other words, it only

pkg/proxy/util/utils_test.go

@@ -17,7 +17,6 @@ limitations under the License.
 package util
 
 import (
-	"bytes"
 	"context"
 	"fmt"
 	"math/rand"
@@ -1171,13 +1170,13 @@ func TestWriteLine(t *testing.T) {
 			expected: "test1 test2 test3\n",
 		},
 	}
-	testBuffer := bytes.NewBuffer(nil)
+	testBuffer := LineBuffer{}
 	for _, testCase := range testCases {
 		t.Run(testCase.name, func(t *testing.T) {
 			testBuffer.Reset()
-			WriteLine(testBuffer, testCase.words...)
-			if !strings.EqualFold(testBuffer.String(), testCase.expected) {
-				t.Fatalf("write word is %v\n expected: %s, got: %s", testCase.words, testCase.expected, testBuffer.String())
+			testBuffer.Write(testCase.words...)
+			if want, got := testCase.expected, string(testBuffer.Bytes()); !strings.EqualFold(want, got) {
+				t.Fatalf("write word is %v\n expected: %s, got: %s", testCase.words, want, got)
 			}
 		})
 	}
@@ -1201,13 +1200,13 @@ func TestWriteBytesLine(t *testing.T) {
 		},
 	}
 
-	testBuffer := bytes.NewBuffer(nil)
+	testBuffer := LineBuffer{}
 	for _, testCase := range testCases {
 		t.Run(testCase.name, func(t *testing.T) {
 			testBuffer.Reset()
-			WriteBytesLine(testBuffer, testCase.bytes)
-			if !strings.EqualFold(testBuffer.String(), testCase.expected) {
-				t.Fatalf("write word is %v\n expected: %s, got: %s", testCase.bytes, testCase.expected, testBuffer.String())
+			testBuffer.WriteBytes(testCase.bytes)
+			if want, got := testCase.expected, string(testBuffer.Bytes()); !strings.EqualFold(want, got) {
+				t.Fatalf("write bytes is %v\n expected: %s, got: %s", testCase.bytes, want, got)
 			}
 		})
 	}
@@ -1244,12 +1243,12 @@ func TestWriteCountLines(t *testing.T) {
 			expected: 100000,
 		},
 	}
-	testBuffer := bytes.NewBuffer(nil)
+	testBuffer := LineBuffer{}
 	for _, testCase := range testCases {
 		t.Run(testCase.name, func(t *testing.T) {
 			testBuffer.Reset()
 			for i := 0; i < testCase.expected; i++ {
-				WriteLine(testBuffer, randSeq())
+				testBuffer.Write(randSeq())
 			}
 			n := CountBytesLines(testBuffer.Bytes())
 			if n != testCase.expected {