executor: make sure hostname is resolvable

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

client/client_test.go

@@ -80,6 +80,7 @@ func TestClientIntegration(t *testing.T) {
 		testFrontendMetadataReturn,
 		testSSHMount,
 		testStdinClosed,
+		testHostnameLookup,
 	},
 		integration.WithMirroredImages(integration.OfficialImages("busybox:latest", "alpine:latest")),
 	)
@@ -89,6 +90,25 @@ func newContainerd(cdAddress string) (*containerd.Client, error) {
 	return containerd.New(cdAddress, containerd.WithTimeout(60*time.Second))
 }
 
+func testHostnameLookup(t *testing.T, sb integration.Sandbox) {
+	if sb.Rootless() {
+		t.SkipNow()
+	}
+	t.Parallel()
+
+	c, err := New(context.TODO(), sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	st := llb.Image("busybox:latest").Run(llb.Shlex(`sh -c "ping -c 1 $(hostname)"`))
+
+	def, err := st.Marshal()
+	require.NoError(t, err)
+
+	_, err = c.Solve(context.TODO(), def, SolveOpt{}, nil)
+	require.NoError(t, err)
+}
+
 // moby/buildkit#614
 func testStdinClosed(t *testing.T, sb integration.Sandbox) {
 	t.Parallel()

executor/oci/hosts.go

@@ -13,7 +13,7 @@ import (
 )
 
 const hostsContent = `
-127.0.0.1	localhost
+127.0.0.1	localhost buildkitsandbox
 ::1	localhost ip6-localhost ip6-loopback
 `
 

executor/oci/spec_unix.go

@@ -44,6 +44,7 @@ func GenerateSpec(ctx context.Context, meta executor.Meta, mounts []executor.Mou
 	s.Process.Args = meta.Args
 	s.Process.Env = meta.Env
 	s.Process.Cwd = meta.Cwd
+	s.Hostname = "buildkitsandbox"
 
 	s.Mounts = GetMounts(ctx,
 		withROBind(resolvConf, "/etc/resolv.conf"),