iptables: add idempotent functions

Add the following idempotent functions to iptables utils:

DeleteRule: idempotently delete an iptables rule
DeleteChain: idempotently delete an iptables chain
ClearChain: idempotently flush an iptables chain

Signed-off-by: Antonio Ojea <antonio.ojea.garcia@gmail.com>

pkg/utils/iptables.go

@@ -62,3 +62,60 @@ func ChainExists(ipt *iptables.IPTables, table, chain string) (bool, error) {
 	}
 	return false, nil
 }
+
+// DeleteRule idempotently delete the iptables rule in the specified table/chain.
+// It does not return an error if the referring chain doesn't exist
+func DeleteRule(ipt *iptables.IPTables, table, chain string, rulespec ...string) error {
+	if ipt == nil {
+		return errors.New("failed to ensure iptable chain: IPTables was nil")
+	}
+	if err := ipt.Delete(table, chain, rulespec...); err != nil {
+		eerr, eok := err.(*iptables.Error)
+		switch {
+		case eok && eerr.IsNotExist():
+			// swallow here, the chain was already deleted
+			return nil
+		case eok && eerr.ExitStatus() == 2:
+			// swallow here, invalid command line parameter because the referring rule is missing
+			return nil
+		default:
+			return fmt.Errorf("Failed to delete referring rule %s %s: %v", table, chain, err)
+		}
+	}
+	return nil
+}
+
+// DeleteChain idempotently deletes the specified table/chain.
+// It does not return an errors if the chain does not exist
+func DeleteChain(ipt *iptables.IPTables, table, chain string) error {
+	if ipt == nil {
+		return errors.New("failed to ensure iptable chain: IPTables was nil")
+	}
+
+	err := ipt.DeleteChain(table, chain)
+	eerr, eok := err.(*iptables.Error)
+	switch {
+	case eok && eerr.IsNotExist():
+		// swallow here, the chain was already deleted
+		return nil
+	default:
+		return err
+	}
+}
+
+// ClearChain idempotently clear the iptables rules in the specified table/chain.
+// If the chain does not exist, a new one will be created
+func ClearChain(ipt *iptables.IPTables, table, chain string) error {
+	if ipt == nil {
+		return errors.New("failed to ensure iptable chain: IPTables was nil")
+	}
+	err := ipt.ClearChain(table, chain)
+	eerr, eok := err.(*iptables.Error)
+	switch {
+	case eok && eerr.IsNotExist():
+		// swallow here, the chain was already deleted
+		return EnsureChain(ipt, table, chain)
+	default:
+		return err
+	}
+}

pkg/utils/iptables_test.go

@@ -67,12 +67,31 @@ var _ = Describe("chain tests", func() {
 		cleanup()
 	})
 
-	It("creates chains idempotently", func() {
-		err := EnsureChain(ipt, TABLE, testChain)
-		Expect(err).NotTo(HaveOccurred())
+	Describe("EnsureChain", func() {
+		It("creates chains idempotently", func() {
+			err := EnsureChain(ipt, TABLE, testChain)
+			Expect(err).NotTo(HaveOccurred())
 
-		// Create it again!
-		err = EnsureChain(ipt, TABLE, testChain)
-		Expect(err).NotTo(HaveOccurred())
+			// Create it again!
+			err = EnsureChain(ipt, TABLE, testChain)
+			Expect(err).NotTo(HaveOccurred())
+		})
 	})
+
+	Describe("DeleteChain", func() {
+		It("delete chains idempotently", func() {
+			// Create chain
+			err := EnsureChain(ipt, TABLE, testChain)
+			Expect(err).NotTo(HaveOccurred())
+
+			// Delete chain
+			err = DeleteChain(ipt, TABLE, testChain)
+			Expect(err).NotTo(HaveOccurred())
+
+			// Delete it again!
+			err = DeleteChain(ipt, TABLE, testChain)
+			Expect(err).NotTo(HaveOccurred())
+		})
+	})
+
 })

plugins/meta/portmap/chain.go

@@ -70,15 +70,8 @@ func (c *chain) teardown(ipt *iptables.IPTables) error {
 	// flush the chain
 	// This will succeed *and create the chain* if it does not exist.
 	// If the chain doesn't exist, the next checks will fail.
-	if err := ipt.ClearChain(c.table, c.name); err != nil {
-		eerr, eok := err.(*iptables.Error)
-		switch {
-		case eok && eerr.IsNotExist():
-			// swallow here, the chain was already deleted
-			return nil
-		default:
-			return err
-		}
+	if err := utils.ClearChain(ipt, c.table, c.name); err != nil {
+		return err
 	}
 
 	for _, entryChain := range c.entryChains {
@@ -97,32 +90,15 @@ func (c *chain) teardown(ipt *iptables.IPTables) error {
 				}
 				chainParts = chainParts[2:] // List results always include an -A CHAINNAME
 
-				if err := ipt.Delete(c.table, entryChain, chainParts...); err != nil {
-					eerr, eok := err.(*iptables.Error)
-					switch {
-					case eok && eerr.IsNotExist():
-						// swallow here, the chain was already deleted
-						continue
-					case eok && eerr.ExitStatus() == 2:
-						// swallow here, invalid command line parameter because the referring rule is missing
-						continue
-					default:
-						return fmt.Errorf("Failed to delete referring rule %s %s: %v", c.table, entryChainRule, err)
-					}
+				if err := utils.DeleteRule(ipt, c.table, entryChain, chainParts...); err != nil {
+					return err
 				}
+
 			}
 		}
 	}
 
-	err := ipt.DeleteChain(c.table, c.name)
-	eerr, eok := err.(*iptables.Error)
-	switch {
-	case eok && eerr.IsNotExist():
-		// swallow here, the chain was already deleted
-		return nil
-	default:
-		return err
-	}
+	return utils.DeleteChain(ipt, c.table, c.name)
 }
 
 // insertUnique will add a rule to a chain if it does not already exist.