Merge 5dae564e86 into 69f487d596

One of the biggest barriers to adopt the netlink format for nftables is
the complexity of writing bytecode.

This commits adds a tool that allows to take an nftables dump and
generate the corresponding golang code and validating that the generated
code produces the exact same output.

Change-Id: I491b35e0d8062de33c67091dd4126d843b231838
Signed-off-by: Antonio Ojea <aojea@google.com>

expr/expr.go

@@ -209,8 +209,6 @@ func exprFromName(name string) Any {
 		e = &CtTimeout{}
 	case "fib":
 		e = &Fib{}
-	case "numgen":
-		e = &Numgen{}
 	}
 	return e
 }

internal/nf2go/main.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"bytes"
-	"context"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -13,7 +12,6 @@ import (
 	"regexp"
 	"runtime"
 	"strings"
-	"time"
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/nftables"
@@ -71,7 +69,6 @@ func main() {
 	pf("\n")
 	pf("\tvar expressions []expr.Any\n")
 	pf("\tvar chain *nftables.Chain\n")
-	pf("\tvar table *nftables.Table\n")
 
 	tables, err := n.ListTables()
 	if err != nil {
@@ -84,9 +81,7 @@ func main() {
 	}
 
 	for _, table := range tables {
-		log.Printf("processing table: %s", table.Name)
+		pf("\ttable:= n.AddTable(&nftables.Table{Family: %s,Name: \"%s\"})\n", TableFamilyString(table.Family), table.Name)
-
-		pf("\ttable = n.AddTable(&nftables.Table{Family: %s,Name: \"%s\"})\n", TableFamilyString(table.Family), table.Name)
 		for _, chain := range chains {
 			if chain.Table.Name != table.Name {
 				continue
@@ -125,10 +120,9 @@ func main() {
 				pf("\t})\n")
 			}
 		}
-	}
 
 		pf("\n\tif err:= n.Flush(); err!= nil {\n")
-	pf("\t\tlog.Fatal(err)\n")
+		pf("\t\tlog.Fatalf(\"fail to flush rules: %v\", err)\n")
 		pf("\t}\n\n")
 		pf("\tfmt.Println(\"nft ruleset applied.\")\n")
 		pf("}\n")
@@ -154,11 +148,12 @@ func main() {
 		}
 		defer f.Close()
 
+		fmt.Println("Generated code:")
+
 		mw := io.MultiWriter(f, os.Stdout)
 		buf.WriteTo(mw)
 
 		// Format the generated code
-	log.Printf("formating file: %s", tempGoFile)
 		cmd := exec.Command("gofmt", "-w", "-s", tempGoFile)
 		output, err := cmd.CombinedOutput()
 		if err != nil {
@@ -166,18 +161,13 @@ func main() {
 		}
 
 		// Run the generated code
-	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		cmd = exec.Command("go", "run", tempGoFile)
-	defer cancel()
-
-	log.Printf("executing file: %s", tempGoFile)
-	cmd = exec.CommandContext(ctx, "go", "run", tempGoFile)
 		output, err = cmd.CombinedOutput()
 		if err != nil {
 			log.Fatalf("Execution error: %v\nOutput: %s", err, output)
 		}
 
 		// Retrieve nftables state using nft
-	log.Printf("obtain current ruleset: %s", tempGoFile)
 		actualOutput, err := listNFTRuleset()
 		if err != nil {
 			log.Fatalf("Failed to list nftables ruleset: %v\noutput:%s", err, actualOutput)
@@ -199,6 +189,7 @@ func main() {
 			log.Fatalf("Failed to flush nftables ruleset: %v", err)
 		}
 	}
+}
 
 func applyNFTRuleset(scriptPath string) (string, error) {
 	cmd := exec.Command("nft", "--debug=netlink", "-f", scriptPath)