From ce5baa125b2334195e995099fe6c8274a603efdf Mon Sep 17 00:00:00 2001
From: Parham Alvani <1995parham@tuta.io>
Date: Sat, 4 Sep 2021 18:24:41 +0430
Subject: feat: add localhost into hosts if the networking mode is not host

Signed-off-by: Parham Alvani <1995parham@tuta.io>
---
 libpod/container_internal_linux.go      | 16 ++++++++++++++++
 libpod/container_internal_linux_test.go | 29 +++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go
index 847122929..cafa3c642 100644
--- a/libpod/container_internal_linux.go
+++ b/libpod/container_internal_linux.go
@@ -1,3 +1,4 @@
+//go:build linux
 // +build linux
 
 package libpod
@@ -1942,9 +1943,24 @@ func (c *Container) generateHosts(path string) (string, error) {
 	}
 	hosts := string(orig)
 	hosts += c.getHosts()
+
+	hosts = c.appendLocalhost(hosts)
+
 	return c.writeStringToRundir("hosts", hosts)
 }
 
+// based on networking mode we may want to append the localhost
+// if there isn't any record for it and also this shoud happen
+// in slirp4netns and similar network modes.
+func (c *Container) appendLocalhost(hosts string) string {
+	if !strings.Contains(hosts, "localhost") &&
+		!c.config.NetMode.IsHost() {
+		hosts += "127.0.0.1\tlocalhost\n::1\tlocalhost\n"
+	}
+
+	return hosts
+}
+
 // appendHosts appends a container's config and state pertaining to hosts to a container's
 // local hosts file. netCtr is the container from which the netNS information is
 // taken.
diff --git a/libpod/container_internal_linux_test.go b/libpod/container_internal_linux_test.go
index 1465ffbea..899f9bffd 100644
--- a/libpod/container_internal_linux_test.go
+++ b/libpod/container_internal_linux_test.go
@@ -1,3 +1,4 @@
+//go:build linux
 // +build linux
 
 package libpod
@@ -7,6 +8,7 @@ import (
 	"os"
 	"testing"
 
+	"github.com/containers/podman/v3/pkg/namespaces"
 	spec "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/stretchr/testify/assert"
 )
@@ -68,3 +70,30 @@ func TestGenerateUserGroupEntry(t *testing.T) {
 	}
 	assert.Equal(t, group, "567:x:567:567\n")
 }
+
+func TestAppendLocalhost(t *testing.T) {
+	{
+		c := Container{
+			config: &ContainerConfig{
+				ContainerNetworkConfig: ContainerNetworkConfig{
+					NetMode: namespaces.NetworkMode("slirp4netns"),
+				},
+			},
+		}
+
+		assert.Equal(t, "127.0.0.1\tlocalhost\n::1\tlocalhost\n", c.appendLocalhost(""))
+		assert.Equal(t, "127.0.0.1\tlocalhost", c.appendLocalhost("127.0.0.1\tlocalhost"))
+	}
+	{
+		c := Container{
+			config: &ContainerConfig{
+				ContainerNetworkConfig: ContainerNetworkConfig{
+					NetMode: namespaces.NetworkMode("host"),
+				},
+			},
+		}
+
+		assert.Equal(t, "", c.appendLocalhost(""))
+		assert.Equal(t, "127.0.0.1\tlocalhost", c.appendLocalhost("127.0.0.1\tlocalhost"))
+	}
+}
-- 
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