feat: add nftables object monitor functions and unit tests

monitor_test.go

@@ -0,0 +1,117 @@
+package nftables_test
+
+import (
+	"fmt"
+	"net"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/google/nftables"
+	"github.com/google/nftables/expr"
+	"github.com/google/nftables/internal/nftest"
+)
+
+func TestMonitor(t *testing.T) {
+
+	// Create a new network namespace to test these operations,
+	// and tear down the namespace at test completion.
+	c, newNS := nftest.OpenSystemConn(t, *enableSysTests)
+	defer nftest.CleanupSystemConn(t, newNS)
+	// Clear all rules at the beginning + end of the test.
+	c.FlushRuleset()
+	defer c.FlushRuleset()
+
+	// default to monitor all
+	monitor := nftables.NewMonitor()
+	events, err := c.AddMonitor(monitor)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var gotTable *nftables.Table
+	var gotChain *nftables.Chain
+	var gotRule *nftables.Rule
+	wg := sync.WaitGroup{}
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for {
+			select {
+			case event, ok := <-events:
+				if !ok {
+					return
+				}
+				if event.Error != nil {
+					err = fmt.Errorf("monitor err: %s", event.Error)
+					return
+				}
+				switch event.Type {
+				case nftables.EventTypeNewTable:
+					gotTable = event.Data.(*nftables.Table)
+				case nftables.EventTypeNewChain:
+					gotChain = event.Data.(*nftables.Chain)
+				case nftables.EventTypeNewRule:
+					gotRule = event.Data.(*nftables.Rule)
+				}
+			}
+		}
+	}()
+
+	nat := c.AddTable(&nftables.Table{
+		Family: nftables.TableFamilyIPv4,
+		Name:   "nat",
+	})
+
+	postrouting := c.AddChain(&nftables.Chain{
+		Name:     "postrouting",
+		Hooknum:  nftables.ChainHookPostrouting,
+		Priority: nftables.ChainPriorityNATSource,
+		Table:    nat,
+		Type:     nftables.ChainTypeNAT,
+	})
+
+	rule := c.AddRule(&nftables.Rule{
+		Table: nat,
+		Chain: postrouting,
+		Exprs: []expr.Any{
+			// payload load 4b @ network header + 12 => reg 1
+			&expr.Payload{
+				DestRegister: 1,
+				Base:         expr.PayloadBaseNetworkHeader,
+				Offset:       12,
+				Len:          4,
+			},
+			// cmp eq reg 1 0x0245a8c0
+			&expr.Cmp{
+				Op:       expr.CmpOpEq,
+				Register: 1,
+				Data:     net.ParseIP("192.168.69.2").To4(),
+			},
+
+			// masq
+			&expr.Masq{},
+		},
+	})
+
+	if err := c.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	// It takes time for the kernel to take effect
+	time.Sleep(time.Second)
+	monitor.Close()
+	wg.Wait()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if gotTable.Family != nat.Family || gotTable.Name != nat.Name {
+		t.Fatal("no want table", gotTable.Family, gotTable.Name)
+	}
+	if gotChain.Type != postrouting.Type || gotChain.Name != postrouting.Name ||
+		*gotChain.Hooknum != *postrouting.Hooknum {
+		t.Fatal("no want chain", gotChain.Type, gotChain.Name, gotChain.Hooknum)
+	}
+	if len(gotRule.Exprs) != len(rule.Exprs) {
+		t.Fatal("no want rule")
+	}
+}