wip

internal/firewall/nftables/conntrack.go

@@ -0,0 +1,61 @@
+package nftables
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/google/nftables"
+	"github.com/google/nftables/expr"
+)
+
+func (f *Firewall) AcceptEstablishedRelatedTraffic(_ context.Context) error {
+	f.mutex.Lock()
+	defer f.mutex.Unlock()
+
+	conn, err := nftables.New()
+	if err != nil {
+		return fmt.Errorf("creating nftables connection: %w", err)
+	}
+
+	table, inputChain, _, outputChain := setupFilterWithBaseChains(conn)
+
+	ctStateExprs := []expr.Any{
+		&expr.Ct{
+			Key:      expr.CtKeySTATE,
+			Register: 1,
+		},
+		&expr.Bitwise{
+			SourceRegister: 1,
+			DestRegister:   1,
+			Len:            4, //nolint:mnd
+			Mask:           []byte{byte(expr.CtStateBitESTABLISHED | expr.CtStateBitRELATED), 0x00, 0x00, 0x00},
+			Xor:            []byte{0x00, 0x00, 0x00, 0x00},
+		},
+		&expr.Cmp{
+			Op:       expr.CmpOpNeq,
+			Register: 1,
+			Data:     []byte{0x00, 0x00, 0x00, 0x00},
+		},
+		&expr.Verdict{
+			Kind: expr.VerdictAccept,
+		},
+	}
+
+	conn.AddRule(&nftables.Rule{
+		Table: table,
+		Chain: inputChain,
+		Exprs: ctStateExprs,
+	})
+
+	conn.AddRule(&nftables.Rule{
+		Table: table,
+		Chain: outputChain,
+		Exprs: ctStateExprs,
+	})
+
+	if err := conn.Flush(); err != nil {
+		return fmt.Errorf("flushing: %w", err)
+	}
+
+	return nil
+}