Fxes /etc/hosts duplicated every time after container restarted in a pod

Signed-off-by: zhangguanzhang <zhangguanzhang@qq.com>

libpod/container_internal.go

@@ -1,6 +1,7 @@
 package libpod
 
 import (
+	"bufio"
 	"bytes"
 	"context"
 	"fmt"
@@ -1865,16 +1866,26 @@ func (c *Container) writeStringToStaticDir(filename, contents string) (string, e
 	return destFileName, nil
 }
 
-// appendStringToRundir appends the provided string to the runtimedir file
-func (c *Container) appendStringToRundir(destFile, output string) (string, error) {
+// appendStringToRunDir appends the provided string to the runtimedir file
+func (c *Container) appendStringToRunDir(destFile, output string) (string, error) {
 	destFileName := filepath.Join(c.state.RunDir, destFile)
 
-	f, err := os.OpenFile(destFileName, os.O_APPEND|os.O_WRONLY, 0600)
+	f, err := os.OpenFile(destFileName, os.O_APPEND|os.O_RDWR, 0600)
 	if err != nil {
 		return "", err
 	}
 	defer f.Close()
 
+	compareStr := strings.TrimRight(output, "\n")
+	scanner := bufio.NewScanner(f)
+	scanner.Split(bufio.ScanLines)
+
+	for scanner.Scan() {
+		if strings.Compare(scanner.Text(), compareStr) == 0 {
+			return filepath.Join(c.state.RunDir, destFile), nil
+		}
+	}
+
 	if _, err := f.WriteString(output); err != nil {
 		return "", errors.Wrapf(err, "unable to write %s", destFileName)
 	}

libpod/container_internal_linux.go

@@ -1742,7 +1742,7 @@ func (c *Container) generateHosts(path string) (string, error) {
 // FIXME.  Path should be used by this function,but I am not sure what is correct; remove //lint
 // once this is fixed
 func (c *Container) appendHosts(path string, netCtr *Container) (string, error) { //nolint
-	return c.appendStringToRundir("hosts", netCtr.getHosts())
+	return c.appendStringToRunDir("hosts", netCtr.getHosts())
 }
 
 // getHosts finds the pertinent information for a container's host file in its config and state

test/e2e/restart_test.go

@@ -196,4 +196,33 @@ var _ = Describe("Podman restart", func() {
 		Expect(restartTime.OutputToStringArray()[0]).To(Equal(startTime.OutputToStringArray()[0]))
 		Expect(restartTime.OutputToStringArray()[1]).To(Not(Equal(startTime.OutputToStringArray()[1])))
 	})
+
+	It("Podman restart a container in a pod and hosts shouln't duplicated", func() {
+		// Fixes: https://github.com/containers/podman/issues/8921
+
+		_, ec, _ := podmanTest.CreatePod("foobar99")
+		Expect(ec).To(Equal(0))
+
+		session := podmanTest.RunTopContainerInPod("host-restart-test", "foobar99")
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+
+		testCmd := []string{"exec", "host-restart-test", "sh", "-c", "wc -l < /etc/hosts"}
+
+		// before restart
+		beforeRestart := podmanTest.Podman(testCmd)
+		beforeRestart.WaitWithDefaultTimeout()
+		Expect(beforeRestart.ExitCode()).To(Equal(0))
+
+		session = podmanTest.Podman([]string{"restart", "host-restart-test"})
+		session.WaitWithDefaultTimeout()
+		Expect(session.ExitCode()).To(Equal(0))
+
+		afterRestart := podmanTest.Podman(testCmd)
+		afterRestart.WaitWithDefaultTimeout()
+		Expect(afterRestart.ExitCode()).To(Equal(0))
+
+		// line count should be equal
+		Expect(beforeRestart.OutputToString()).To(Equal(afterRestart.OutputToString()))
+	})
 })