basic UDP server bound to an interface

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"`
-	Interface string              `yaml:"interface"`
+	Version   int    `yaml:"version"`
+	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 ""
+}