Initial commit

Gopkg.toml

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+
+# Gopkg.toml example
+#
+# Refer to https://github.com/golang/dep/blob/master/docs/Gopkg.toml.md
+# for detailed Gopkg.toml documentation.
+#
+# required = ["github.com/user/thing/cmd/thing"]
+# ignored = ["github.com/user/project/pkgX", "bitbucket.org/user/project/pkgA/pkgY"]
+#
+# [[constraint]]
+#   name = "github.com/user/project"
+#   version = "1.0.0"
+#
+# [[constraint]]
+#   name = "github.com/user/project2"
+#   branch = "dev"
+#   source = "github.com/myfork/project2"
+#
+# [[override]]
+#  name = "github.com/x/y"
+#  version = "2.4.0"
+
+
+[[constraint]]
+  name = "github.com/coreos/go-iptables"
+  version = "0.2.0"

Makefile

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+default:
+	go build -o bin/lsrv cmd/lsrv.go

cmd/lsrv.go

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+package main
+
+import (
+	"flag"
+	"fmt"
+
+	lsrv "github.com/jaym/lsrv"
+)
+
+var (
+	VERSION string = "0.0.1"
+	socket         = flag.String("socket", "/tmp/lsrv.sock", "UNIX domain socket")
+	daemon         = flag.Bool("daemon", false, "Run the lsrv daemon if true")
+)
+
+func main() {
+	flag.Parse()
+
+	if *daemon {
+		fmt.Println("Starting lsrv daemon")
+		lsrv.Spawn(*socket)
+	} else {
+		fmt.Println("Client mode")
+	}
+}

server.go

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+package lsrv
+
+import (
+	"bufio"
+	"encoding/binary"
+	"log"
+	"net"
+	"strconv"
+	"strings"
+
+	"github.com/coreos/go-iptables/iptables"
+)
+
+type ServiceEntry struct {
+	service_name    string
+	service_address string
+	service_port    uint16
+
+	// The service will respond to the address/port below
+	dest_address string
+	dest_port    uint16
+}
+
+func Spawn(socket_path string) error {
+	ipt, iperr := initializeIpTables()
+
+	if iperr != nil {
+		log.Fatal("Could not initialize IPTables: ", iperr)
+	}
+
+	ln, err := net.Listen("unix", socket_path)
+
+	if err != nil {
+		log.Fatal("Listen error: ", err)
+		return err
+	}
+
+	services := []ServiceEntry{}
+	start_ip := net.IPv4(172, 22, 0, 1)
+
+	for {
+		//TODO: err check
+		fd, _ := ln.Accept()
+		input := bufio.NewScanner(fd)
+
+		success := input.Scan()
+		if !success {
+			log.Println(input.Err())
+			fd.Close()
+		}
+
+		command := input.Text()
+		command_split := strings.Fields(command)
+
+		if len(command_split) == 0 {
+			log.Println("Could not parse command")
+			fd.Close()
+		}
+
+		switch command_split[0] {
+		case "ADD":
+			// ADD service_name service_ip service_port dest_port
+			// Returns:
+			//   OK
+			if len(command_split) != 5 {
+				log.Println("Could not parse command")
+				fd.Close()
+			} else {
+				service_port, serr := strconv.ParseUint(command_split[3], 10, 16)
+				dest_port, derr := strconv.ParseUint(command_split[4], 10, 16)
+
+				if serr != nil || derr != nil {
+					log.Println("Could not parse port")
+					fd.Close()
+					break
+				}
+
+				entry := ServiceEntry{
+					service_name:    command_split[1],
+					service_address: command_split[2],
+					service_port:    uint16(service_port),
+					dest_address:    ipAdd(start_ip, len(services)).String(),
+					dest_port:       uint16(dest_port),
+				}
+
+				services = append(services, entry)
+				err = materialize(ipt, &services)
+
+				if err != nil {
+					log.Println(err)
+					break
+				}
+
+				log.Println("Added ", entry)
+			}
+		default:
+			log.Println("Unknown command: ", command_split[0])
+		}
+		fd.Close()
+	}
+
+	return nil
+}
+
+func materialize(ipt *iptables.IPTables, services *[]ServiceEntry) error {
+	// Recreate the chain. This is wasteful and not zero downtime, but
+	// it's easy
+	err := createChain(ipt)
+	if err != nil {
+		return err
+	}
+
+	for _, entry := range *services {
+		rulespec := []string{"-p", "tcp", "-d", entry.dest_address, "--dport",
+			strconv.FormatUint(uint64(entry.dest_port), 10), "-j", "DNAT",
+			"--to", entry.service_address + ":" + strconv.FormatUint(uint64(entry.service_port), 10)}
+		err = ipt.Append("nat", "LSRV", rulespec...)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+
+	return nil
+}
+
+func ipAdd(start net.IP, add int) net.IP { // IPv4 only
+	start = start.To4()
+	result := make(net.IP, 4)
+	binary.BigEndian.PutUint32(result, binary.BigEndian.Uint32(start)+uint32(add))
+	return result
+}
+
+func initializeIpTables() (*iptables.IPTables, error) {
+	ipt, err := iptables.New()
+
+	if err != nil {
+		return nil, err
+	}
+
+	err = createChain(ipt)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return ipt, nil
+}
+
+func createChain(ipt *iptables.IPTables) error {
+	cleanup(ipt)
+
+	ipt.NewChain("nat", "LSRV")
+	ipt.AppendUnique("nat", "OUTPUT", "-jLSRV")
+
+	return nil
+}
+
+func cleanup(ipt *iptables.IPTables) error {
+	chains, err := ipt.ListChains("nat")
+	if err != nil {
+		return err
+	}
+
+	containsChain := false
+	for _, elem := range chains {
+		if elem == "LSRV" {
+			containsChain = true
+		}
+	}
+
+	if containsChain {
+		log.Println("Deleting chain LSRV")
+		ipt.Delete("nat", "OUTPUT", "-jLSRV")
+		ipt.ClearChain("nat", "LSRV")
+		ipt.DeleteChain("nat", "LSRV")
+	}
+	return nil
+}