basic UDP server bound to an interface

cmd/kdhcpd/BUILD.bazel

@@ -6,8 +6,10 @@ go_library(
     importpath = "git.wntrmute.dev/kyle/kdhcp/cmd/kdhcpd",
     visibility = ["//visibility:private"],
     deps = [
+        "//config",
         "//log",
         "//server",
+        "@com_github_peterbourgon_ff_v3//ffcli",
     ],
 )
 

cmd/kdhcpd/main.go

@@ -4,19 +4,25 @@ import (
 	"context"
 	"flag"
 	"os"
+	"strings"
 
-	"git.wntrmute.dev/kyle/kdhcp/bazel-kdhcp/external/com_github_davecgh_go_spew/spew"
 	"git.wntrmute.dev/kyle/kdhcp/config"
 	"git.wntrmute.dev/kyle/kdhcp/log"
+	"git.wntrmute.dev/kyle/kdhcp/server"
 	"github.com/peterbourgon/ff/v3/ffcli"
 )
 
 func main() {
 	var configPath string
+	logLevel := "DEBUG"
 
-	flag.StringVar(&configPath, "f", "kdhcpd.yaml", "path to `config file`")
+	flag.StringVar(&configPath, "f", "", "path to `config file`")
+	flag.StringVar(&logLevel, "l", logLevel, "log level")
 	flag.Parse()
 
+	logLevel = strings.ToUpper(logLevel)
+	log.Setup(logLevel, "kdhcpd")
+
 	root := &ffcli.Command{
 		Exec: func(ctx context.Context, args []string) error {
 			cfg, err := config.Load(configPath)
@@ -24,8 +30,15 @@ func main() {
 				log.Fatal(err)
 			}
 
-			log.Debugf("read configuration file with version=%d", cfg.Version)
+			srv, err := server.New(cfg)
-			spew.Dump(*cfg)
+			if err != nil {
+				log.Fatal(err)
+			}
+
+			defer srv.Close()
+
+			srv.Listen()
+
 			return nil
 		},
 	}

config/BUILD.bazel

@@ -0,0 +1,15 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "config",
+    srcs = [
+        "config.go",
+        "path.go",
+    ],
+    importpath = "git.wntrmute.dev/kyle/kdhcp/config",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//log",
+        "@in_gopkg_yaml_v2//:yaml_v2",
+    ],
+)

config/config.go

@@ -1,9 +1,11 @@
 package config
 
 import (
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"net"
+	"strconv"
 
 	"git.wntrmute.dev/kyle/kdhcp/log"
 	"gopkg.in/yaml.v2"
@@ -78,13 +80,15 @@ type ConfigFile struct {
 }
 
 type Config struct {
-	Version   int                 `yaml:"version"`
+	Version   int    `yaml:"version"`
-	Interface string              `yaml:"interface"`
+	Interface string `yaml:"interface"`
+	Address   string `yaml:"address"`
+	IP        net.IP
+	Port      int
 	LeaseFile string              `yaml:"lease_file"`
 	Network   *Network            `yaml:"network"`
 	Pools     map[string]*IPRange `yaml:"pools"`
 	Statics   map[string]net.IP   `yaml:"statics"`
-	Device    *net.Interface
 }
 
 func (cfg *Config) process() (err error) {
@@ -95,11 +99,31 @@ func (cfg *Config) process() (err error) {
 		log.Warningf("config: Version is greater than the current version %d. The config may not behave as expected.", CurrentVersion)
 	}
 
-	cfg.Device, err = net.InterfaceByName(cfg.Interface)
+	_, err = net.InterfaceByName(cfg.Interface)
 	if err != nil {
 		return fmt.Errorf("config: while looking up interface %s: %w", cfg.Interface, err)
 	}
 
+	ip, port, err := net.SplitHostPort(cfg.Address)
+	if err != nil {
+		return err
+	}
+
+	cfg.IP = net.ParseIP(ip)
+	if cfg.IP == nil {
+		return fmt.Errorf("config: parsing IP from address %s: %w", cfg.Address, err)
+	}
+
+	cfg.IP, err = ensureV4(cfg.IP)
+	if err != nil {
+		return fmt.Errorf("config: address %w", err)
+	}
+
+	cfg.Port, err = strconv.Atoi(port)
+	if err != nil {
+		return fmt.Errorf("config: invalid port %s: %w", port, err)
+	}
+
 	err = cfg.Network.ensureV4()
 	if err != nil {
 		return err
@@ -124,6 +148,14 @@ func (cfg *Config) process() (err error) {
 }
 
 func Load(path string) (*Config, error) {
+	if path == "" {
+		path = FindConfigPath()
+	}
+
+	if path == "" {
+		return nil, errors.New("config: no config file path specified and couldn't find a valid config file path")
+	}
+
 	data, err := ioutil.ReadFile(path)
 	if err != nil {
 		return nil, fmt.Errorf("config: loading %s: %w", path, err)
@@ -143,5 +175,6 @@ func Load(path string) (*Config, error) {
 		return nil, err
 	}
 
+	log.Debugf("config: read configuration from %s", path)
 	return config, nil
 }

config/path.go

@@ -0,0 +1,37 @@
+package config
+
+import (
+	"os"
+	"os/user"
+	"path/filepath"
+
+	"git.wntrmute.dev/kyle/kdhcp/log"
+)
+
+func FindConfigPath() string {
+	paths := []string{"/home/kyle/code/kdhcp/kdhcpd.yaml"}
+	user, err := user.Current()
+	if err == nil {
+		if homedir := user.HomeDir; homedir != "" {
+			paths = append(paths, filepath.Join(homedir, ".config", "kdhcp", "kdhcpd.yaml"))
+		}
+	}
+
+	paths = append(paths, "/etc/kdhcp/kdhcpd.yaml")
+
+	for _, path := range paths {
+		_, err = os.Stat(path)
+		if os.IsNotExist(err) {
+			continue
+		}
+
+		if err != nil {
+			log.Debugf("config: while trying to stat config file at '%s': %s", path, err)
+			continue
+		}
+
+		return path
+	}
+
+	return ""
+}

deps.bzl

@@ -13,3 +13,27 @@ def go_dependencies():
         sum = "h1:KaodqZuhUoZereWVIYmpUgZysurB1kBLX2j0MwMrUAE=",
         version = "v1.0.0",
     )
+    go_repository(
+        name = "com_github_pelletier_go_toml",
+        importpath = "github.com/pelletier/go-toml",
+        sum = "h1:4yBQzkHv+7BHq2PQUZF3Mx0IYxG7LsP222s7Agd3ve8=",
+        version = "v1.9.5",
+    )
+    go_repository(
+        name = "com_github_peterbourgon_ff_v3",
+        importpath = "github.com/peterbourgon/ff/v3",
+        sum = "h1:PaKe7GW8orVFh8Unb5jNHS+JZBwWUMa2se0HM6/BI24=",
+        version = "v3.3.0",
+    )
+    go_repository(
+        name = "in_gopkg_check_v1",
+        importpath = "gopkg.in/check.v1",
+        sum = "h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=",
+        version = "v0.0.0-20161208181325-20d25e280405",
+    )
+    go_repository(
+        name = "in_gopkg_yaml_v2",
+        importpath = "gopkg.in/yaml.v2",
+        sum = "h1:D8xgwECY7CYvx+Y2n4sBz93Jn9JRvxdiyyo8CTfuKaY=",
+        version = "v2.4.0",
+    )

kdhcpd.yaml

@@ -2,7 +2,8 @@ kdhcp:
   version: 1
   lease_file: /tmp/kdhcp_lease.yaml
     #  interface: enp89s0
-  interface: wlp166s0
+  interface: eth0 
+  address: 192.168.4.250:67
   network:
     gateway: 192.168.4.254
     mask: 255.255.255.0

server/BUILD.bazel

@@ -0,0 +1,15 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "server",
+    srcs = [
+        "ifi.go",
+        "server.go",
+    ],
+    importpath = "git.wntrmute.dev/kyle/kdhcp/server",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//config",
+        "//log",
+    ],
+)

server/ifi.go

@@ -0,0 +1,39 @@
+package server
+
+import (
+	"net"
+	"syscall"
+)
+
+func BindInterface(ip net.IP, port int, dev string) (net.PacketConn, error) {
+	if port == 0 {
+		port = 67
+	}
+
+	udpAddr := &net.UDPAddr{
+		IP:   ip,
+		Port: port,
+	}
+
+	conn, err := net.ListenUDP("udp4", udpAddr)
+	if err != nil {
+		return nil, err
+	}
+
+	sysconn, err := conn.SyscallConn()
+	if err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	sysconn.Control(func(fd uintptr) {
+		err = syscall.BindToDevice(int(fd), dev)
+	})
+
+	if err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	return conn, nil
+}

server/server.go

@@ -0,0 +1,76 @@
+package server
+
+import (
+	"errors"
+	"net"
+
+	"git.wntrmute.dev/kyle/kdhcp/config"
+	"git.wntrmute.dev/kyle/kdhcp/log"
+)
+
+const (
+	MaxPacketSize = 512
+)
+
+type Server struct {
+	Conn   net.PacketConn
+	Config *config.Config
+}
+
+func (s *Server) Close() error {
+	return s.Conn.Close()
+}
+
+func (s *Server) Bind() (err error) {
+	s.Conn, err = BindInterface(s.Config.IP, s.Config.Port, s.Config.Interface)
+	return err
+}
+
+func (s *Server) ReadFrom() ([]byte, net.Addr, error) {
+	b := make([]byte, MaxPacketSize)
+	n, addr, err := s.Conn.ReadFrom(b)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	b = b[:n]
+	return b, addr, nil
+}
+
+func (s *Server) WriteTo(b []byte, addr net.Addr) error {
+	return errors.New("server: not implemented")
+}
+
+func (s *Server) AcceptPacket() error {
+	packet, addr, err := s.ReadFrom()
+	if err != nil {
+		return err
+	}
+
+	log.Debugf("accepted %d byte packet from %s", len(packet), addr)
+	return nil
+}
+
+func (s *Server) Listen() {
+	for {
+		if err := s.AcceptPacket(); err != nil {
+			log.Errf("server: error reading packet: %s", err)
+			continue
+		}
+	}
+}
+
+func New(cfg *config.Config) (*Server, error) {
+	srv := &Server{
+		Config: cfg,
+	}
+
+	err := srv.Bind()
+	if err != nil {
+		return nil, err
+	}
+
+	log.Infof("server: bound to %s:%s", cfg.Interface, srv.Conn.LocalAddr())
+
+	return srv, nil
+}