libnetwork: TestUserChain: re-use IPTables instances

The test already creates instances for each ip-version, so let's
re-use them. While changing, also use assert.Check to not fail early.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libnetwork/firewall_linux_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/docker/docker/libnetwork/options"
 	"github.com/docker/docker/libnetwork/testutils"
 	"gotest.tools/v3/assert"
+	is "gotest.tools/v3/assert/cmp"
 )
 
 const (
@@ -63,8 +64,8 @@ func TestUserChain(t *testing.T) {
 			defer c.Stop()
 
 			// init. condition, FORWARD chain empty DOCKER-USER not exist
-			assert.DeepEqual(t, getRules(t, iptables.IPv4, fwdChainName), []string{"-P FORWARD ACCEPT"})
-			assert.DeepEqual(t, getRules(t, iptables.IPv6, fwdChainName), []string{"-P FORWARD ACCEPT"})
+			assert.Check(t, is.DeepEqual(getRules(t, iptable4, fwdChainName), []string{"-P FORWARD ACCEPT"}))
+			assert.Check(t, is.DeepEqual(getRules(t, iptable6, fwdChainName), []string{"-P FORWARD ACCEPT"}))
 
 			if tc.insert {
 				_, err = iptable4.Raw("-A", fwdChainName, "-j", "DROP")
@@ -74,11 +75,11 @@ func TestUserChain(t *testing.T) {
 			}
 			arrangeUserFilterRule()
 
-			assert.DeepEqual(t, getRules(t, iptables.IPv4, fwdChainName), tc.fwdChain)
-			assert.DeepEqual(t, getRules(t, iptables.IPv6, fwdChainName), tc.fwdChain)
+			assert.Check(t, is.DeepEqual(getRules(t, iptable4, fwdChainName), tc.fwdChain))
+			assert.Check(t, is.DeepEqual(getRules(t, iptable6, fwdChainName), tc.fwdChain))
 			if tc.userChain != nil {
-				assert.DeepEqual(t, getRules(t, iptables.IPv4, usrChainName), tc.userChain)
-				assert.DeepEqual(t, getRules(t, iptables.IPv6, usrChainName), tc.userChain)
+				assert.Check(t, is.DeepEqual(getRules(t, iptable4, usrChainName), tc.userChain))
+				assert.Check(t, is.DeepEqual(getRules(t, iptable6, usrChainName), tc.userChain))
 			} else {
 				_, err := iptable4.Raw("-S", usrChainName)
 				assert.Assert(t, err != nil, "ipv4 chain %v: created unexpectedly", usrChainName)
@@ -89,9 +90,7 @@ func TestUserChain(t *testing.T) {
 	}
 }
 
-func getRules(t *testing.T, ipVer iptables.IPVersion, chain string) []string {
-	iptable := iptables.GetIptable(ipVer)
-
+func getRules(t *testing.T, iptable *iptables.IPTable, chain string) []string {
 	t.Helper()
 	output, err := iptable.Raw("-S", chain)
 	assert.NilError(t, err, "chain %s: failed to get rules", chain)