RustProxy/docker-agent/main.go

package main

import (
	"context"
	"crypto/ecdsa"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/sha256"
	"crypto/subtle"
	"crypto/tls"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/hex"
	"encoding/json"
	"encoding/pem"
	"errors"
	"flag"
	"fmt"
	"io"
	"log"
	"math/big"
	"net"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"time"
)

const version = "0.24.7"

type config struct {
	Listen      string
	Token       string
	DockerSock  string
	AdvertiseIP string
	PublicIPURL string
	Hostname    string
	TLS         bool
	CertFile    string
	KeyFile     string
	Fingerprint string
}

type dockerPort struct {
	IP          string `json:"IP"`
	PrivatePort uint16 `json:"PrivatePort"`
	PublicPort  uint16 `json:"PublicPort"`
	Type        string `json:"Type"`
}

type dockerContainer struct {
	ID     string            `json:"Id"`
	Names  []string          `json:"Names"`
	Image  string            `json:"Image"`
	Labels map[string]string `json:"Labels"`
	Ports  []dockerPort      `json:"Ports"`
}

type binding struct {
	BindIP     string `json:"bind_ip"`
	PublicPort uint16 `json:"public_port"`
}

type service struct {
	Key           string    `json:"key"`
	TechnicalName string    `json:"technical_name"`
	ContainerID   string    `json:"container_id"`
	ContainerName string    `json:"container_name"`
	Image         string    `json:"image"`
	PrivatePort   uint16    `json:"private_port"`
	Protocol      string    `json:"protocol"`
	Bindings      []binding `json:"bindings"`
}

type hostAddress struct {
	IP        string `json:"ip"`
	Source    string `json:"source"`
	Interface string `json:"interface,omitempty"`
	Scope     string `json:"scope"`
}

type inventory struct {
	AgentVersion      string        `json:"agent_version"`
	Hostname          string        `json:"hostname"`
	PublicIP          string        `json:"public_ip"`
	PublicIPSource    string        `json:"public_ip_source"`
	CertificateSHA256 string        `json:"certificate_sha256"`
	Addresses         []hostAddress `json:"addresses"`
	ObservedAt        string        `json:"observed_at"`
	Services          []service     `json:"services"`
}

type unixRoundTripper struct{ sock string }

func (u unixRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
	transport := &http.Transport{
		DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
			var d net.Dialer
			return d.DialContext(ctx, "unix", u.sock)
		},
		DisableKeepAlives: false,
	}
	clone := req.Clone(req.Context())
	clone.URL.Scheme = "http"
	clone.URL.Host = "docker"
	return transport.RoundTrip(clone)
}

func dockerContainers(ctx context.Context, sock string) ([]dockerContainer, error) {
	client := &http.Client{Transport: unixRoundTripper{sock: sock}, Timeout: 4 * time.Second}
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://docker/containers/json?all=0", nil)
	if err != nil {
		return nil, err
	}
	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("docker API: %w", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return nil, fmt.Errorf("docker API returned %s: %s", resp.Status, strings.TrimSpace(string(body)))
	}
	var items []dockerContainer
	dec := json.NewDecoder(io.LimitReader(resp.Body, 4<<20))
	if err := dec.Decode(&items); err != nil {
		return nil, fmt.Errorf("decode Docker response: %w", err)
	}
	return items, nil
}

func cleanName(names []string) string {
	if len(names) == 0 {
		return "container"
	}
	name := strings.TrimPrefix(names[0], "/")
	if name == "" {
		return "container"
	}
	return name
}

func dnsLabel(value string) string {
	value = strings.ToLower(value)
	var b strings.Builder
	dash := false
	for _, r := range value {
		ok := (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9')
		if ok {
			b.WriteRune(r)
			dash = false
		} else if b.Len() > 0 && !dash {
			b.WriteByte('-')
			dash = true
		}
	}
	out := strings.Trim(b.String(), "-")
	if out == "" {
		out = "app"
	}
	if len(out) > 48 {
		out = strings.Trim(out[:48], "-")
	}
	return out
}

func serviceIdentity(c dockerContainer, p dockerPort) (key, technical string) {
	name := cleanName(c.Names)
	project := c.Labels["com.docker.compose.project"]
	composeService := c.Labels["com.docker.compose.service"]
	replica := c.Labels["com.docker.compose.container-number"]
	suffix := strconv.Itoa(int(p.PrivatePort))
	if project != "" && composeService != "" {
		if replica == "" {
			replica = name
		}
		key = fmt.Sprintf("compose:%s/%s/%s:%d/%s", project, composeService, replica, p.PrivatePort, p.Type)
		technicalBase := project + "-" + composeService
		if replica != "1" {
			technicalBase += "-" + replica
		}
		technical = dnsLabel(technicalBase + "-" + suffix)
	} else {
		key = fmt.Sprintf("container:%s:%d/%s", name, p.PrivatePort, p.Type)
		technical = dnsLabel(name + "-" + suffix)
	}
	return key, technical
}

func validIP(raw string) string {
	ip := net.ParseIP(strings.TrimSpace(raw))
	if ip == nil || ip.IsUnspecified() || ip.IsLoopback() || ip.IsMulticast() || ip.IsLinkLocalUnicast() {
		return ""
	}
	return ip.String()
}

func servicesFrom(containers []dockerContainer) []service {
	byKey := make(map[string]*service)
	bindingSeen := make(map[string]map[string]struct{})
	for _, c := range containers {
		name := cleanName(c.Names)
		for _, p := range c.Ports {
			if p.PublicPort == 0 || p.Type != "tcp" {
				continue
			}
			if bind := net.ParseIP(strings.TrimSpace(p.IP)); bind != nil && bind.IsLoopback() {
				continue
			}
			key, technical := serviceIdentity(c, p)
			item := byKey[key]
			if item == nil {
				id := c.ID
				if len(id) > 12 {
					id = id[:12]
				}
				item = &service{
					Key: key, TechnicalName: technical, ContainerID: id, ContainerName: name,
					Image: c.Image, PrivatePort: p.PrivatePort, Protocol: p.Type,
				}
				byKey[key] = item
				bindingSeen[key] = make(map[string]struct{})
			}
			bindIP := strings.TrimSpace(p.IP)
			dedupe := bindIP + "|" + strconv.Itoa(int(p.PublicPort))
			if _, ok := bindingSeen[key][dedupe]; ok {
				continue
			}
			bindingSeen[key][dedupe] = struct{}{}
			item.Bindings = append(item.Bindings, binding{BindIP: bindIP, PublicPort: p.PublicPort})
		}
	}
	out := make([]service, 0, len(byKey))
	for _, item := range byKey {
		sort.Slice(item.Bindings, func(i, j int) bool {
			left := net.ParseIP(strings.TrimSpace(item.Bindings[i].BindIP))
			right := net.ParseIP(strings.TrimSpace(item.Bindings[j].BindIP))
			leftWildcard := left == nil || left.IsUnspecified()
			rightWildcard := right == nil || right.IsUnspecified()
			if leftWildcard != rightWildcard {
				return !leftWildcard
			}
			if item.Bindings[i].BindIP != item.Bindings[j].BindIP {
				return item.Bindings[i].BindIP < item.Bindings[j].BindIP
			}
			return item.Bindings[i].PublicPort < item.Bindings[j].PublicPort
		})
		out = append(out, *item)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].Key < out[j].Key })
	return out
}

func publicIPFromURL(ctx context.Context, rawURL string) string {
	if rawURL == "" {
		return ""
	}
	client := &http.Client{Timeout: 2 * time.Second}
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, rawURL, nil)
	if err != nil {
		return ""
	}
	resp, err := client.Do(req)
	if err != nil {
		return ""
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return ""
	}
	body, err := io.ReadAll(io.LimitReader(resp.Body, 128))
	if err != nil {
		return ""
	}
	return validIP(string(body))
}

func routeIP() string {
	conn, err := net.DialTimeout("udp", "1.1.1.1:53", time.Second)
	if err != nil {
		return ""
	}
	defer conn.Close()
	if addr, ok := conn.LocalAddr().(*net.UDPAddr); ok {
		return validIP(addr.IP.String())
	}
	return ""
}

func ipScope(ip net.IP) string {
	switch {
	case ip.IsPrivate():
		return "private"
	case ip.IsLinkLocalUnicast():
		return "link_local"
	default:
		return "public"
	}
}

func skipInterface(name string) bool {
	name = strings.ToLower(strings.TrimSpace(name))
	return name == "docker0" || strings.HasPrefix(name, "docker") || strings.HasPrefix(name, "veth") || strings.HasPrefix(name, "br-") || strings.HasPrefix(name, "virbr")
}

func localHostAddresses() []hostAddress {
	interfaces, err := net.Interfaces()
	if err != nil {
		return nil
	}
	out := make([]hostAddress, 0)
	for _, iface := range interfaces {
		if iface.Flags&net.FlagUp == 0 || iface.Flags&net.FlagLoopback != 0 || skipInterface(iface.Name) {
			continue
		}
		addrs, err := iface.Addrs()
		if err != nil {
			continue
		}
		for _, addr := range addrs {
			raw := addr.String()
			if host, _, err := net.ParseCIDR(raw); err == nil {
				raw = host.String()
			} else if host, _, err := net.SplitHostPort(raw); err == nil {
				raw = host
			}
			clean := validIP(raw)
			if clean == "" {
				continue
			}
			ip := net.ParseIP(clean)
			out = append(out, hostAddress{IP: clean, Source: "interface", Interface: iface.Name, Scope: ipScope(ip)})
		}
	}
	sort.Slice(out, func(i, j int) bool {
		if out[i].Interface != out[j].Interface {
			return out[i].Interface < out[j].Interface
		}
		return out[i].IP < out[j].IP
	})
	return out
}

type ipDetector struct {
	mu       sync.Mutex
	publicIP string
	expires  time.Time
}

func (d *ipDetector) public(ctx context.Context, rawURL string) string {
	if rawURL == "" {
		return ""
	}
	d.mu.Lock()
	defer d.mu.Unlock()
	if time.Now().Before(d.expires) {
		return d.publicIP
	}
	d.publicIP = publicIPFromURL(ctx, rawURL)
	d.expires = time.Now().Add(5 * time.Minute)
	if d.publicIP == "" {
		d.expires = time.Now().Add(30 * time.Second)
	}
	return d.publicIP
}

func mergeHostAddress(out *[]hostAddress, index map[string]int, candidate hostAddress) {
	candidate.IP = validIP(candidate.IP)
	if candidate.IP == "" {
		return
	}
	if candidate.Scope == "" {
		candidate.Scope = ipScope(net.ParseIP(candidate.IP))
	}
	if pos, ok := index[candidate.IP]; ok {
		existing := &(*out)[pos]
		if candidate.Interface != "" && existing.Interface == "" {
			existing.Interface = candidate.Interface
		}
		if candidate.Source != "" && !strings.Contains(existing.Source, candidate.Source) {
			if existing.Source == "" {
				existing.Source = candidate.Source
			} else {
				existing.Source += "," + candidate.Source
			}
		}
		return
	}
	index[candidate.IP] = len(*out)
	*out = append(*out, candidate)
}

func detectedAddresses(ctx context.Context, cfg config, detector *ipDetector) ([]hostAddress, string, string) {
	out := make([]hostAddress, 0, 8)
	index := make(map[string]int)
	for _, item := range localHostAddresses() {
		mergeHostAddress(&out, index, item)
	}
	routed := routeIP()
	if routed != "" {
		mergeHostAddress(&out, index, hostAddress{IP: routed, Source: "route"})
	}
	public := detector.public(ctx, cfg.PublicIPURL)
	if public != "" {
		mergeHostAddress(&out, index, hostAddress{IP: public, Source: "public_api"})
	}
	advertised := validIP(cfg.AdvertiseIP)
	if advertised != "" {
		mergeHostAddress(&out, index, hostAddress{IP: advertised, Source: "override"})
	}

	switch {
	case advertised != "":
		return out, advertised, "override"
	case routed != "":
		return out, routed, "route"
	case public != "":
		return out, public, "public_api"
	case len(out) > 0:
		return out, out[0].IP, out[0].Source
	default:
		return out, "", "unavailable"
	}
}

func certificateFingerprintDER(der []byte) string {
	sum := sha256.Sum256(der)
	return hex.EncodeToString(sum[:])
}

func certificateFingerprint(certFile string) (string, error) {
	raw, err := os.ReadFile(certFile)
	if err != nil {
		return "", err
	}
	block, _ := pem.Decode(raw)
	if block == nil || block.Type != "CERTIFICATE" {
		return "", fmt.Errorf("%s does not contain a PEM certificate", certFile)
	}
	cert, err := x509.ParseCertificate(block.Bytes)
	if err != nil {
		return "", fmt.Errorf("parse certificate: %w", err)
	}
	return certificateFingerprintDER(cert.Raw), nil
}

func atomicWrite(path string, data []byte, mode os.FileMode) error {
	dir := filepath.Dir(path)
	if err := os.MkdirAll(dir, 0750); err != nil {
		return err
	}
	tmp, err := os.CreateTemp(dir, ".rustproxy-agent-*")
	if err != nil {
		return err
	}
	tmpName := tmp.Name()
	defer os.Remove(tmpName)
	if err := tmp.Chmod(mode); err != nil {
		tmp.Close()
		return err
	}
	if _, err := tmp.Write(data); err != nil {
		tmp.Close()
		return err
	}
	if err := tmp.Sync(); err != nil {
		tmp.Close()
		return err
	}
	if err := tmp.Close(); err != nil {
		return err
	}
	return os.Rename(tmpName, path)
}

func ensureSelfSignedCertificate(certFile, keyFile, hostname string) (string, bool, error) {
	certInfo, certErr := os.Stat(certFile)
	keyInfo, keyErr := os.Stat(keyFile)
	if certErr == nil && keyErr == nil {
		if certInfo.IsDir() || keyInfo.IsDir() {
			return "", false, errors.New("TLS certificate/key path points to a directory")
		}
		if _, err := tls.LoadX509KeyPair(certFile, keyFile); err != nil {
			return "", false, fmt.Errorf("load TLS certificate/key: %w", err)
		}
		fp, err := certificateFingerprint(certFile)
		return fp, false, err
	}
	if (certErr == nil) != (keyErr == nil) {
		return "", false, errors.New("only one TLS certificate/key file exists; refusing to replace the other")
	}
	if certErr != nil && !os.IsNotExist(certErr) {
		return "", false, certErr
	}
	if keyErr != nil && !os.IsNotExist(keyErr) {
		return "", false, keyErr
	}
	privateKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		return "", false, fmt.Errorf("generate TLS key: %w", err)
	}
	serialLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serial, err := rand.Int(rand.Reader, serialLimit)
	if err != nil {
		return "", false, fmt.Errorf("generate TLS serial: %w", err)
	}
	now := time.Now().UTC()
	template := &x509.Certificate{
		SerialNumber:          serial,
		Subject:               pkix.Name{CommonName: hostname, Organization: []string{"RustProxy Docker Agent"}},
		NotBefore:             now.Add(-5 * time.Minute),
		NotAfter:              now.AddDate(10, 0, 0),
		KeyUsage:              x509.KeyUsageDigitalSignature,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
	}
	if hostname != "" {
		if ip := net.ParseIP(hostname); ip != nil {
			template.IPAddresses = append(template.IPAddresses, ip)
		} else {
			template.DNSNames = append(template.DNSNames, hostname)
		}
	}
	der, err := x509.CreateCertificate(rand.Reader, template, template, &privateKey.PublicKey, privateKey)
	if err != nil {
		return "", false, fmt.Errorf("create TLS certificate: %w", err)
	}
	keyDER, err := x509.MarshalPKCS8PrivateKey(privateKey)
	if err != nil {
		return "", false, fmt.Errorf("marshal TLS key: %w", err)
	}
	if err := atomicWrite(keyFile, pem.EncodeToMemory(&pem.Block{Type: "PRIVATE KEY", Bytes: keyDER}), 0600); err != nil {
		return "", false, fmt.Errorf("write TLS key: %w", err)
	}
	if err := atomicWrite(certFile, pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: der}), 0644); err != nil {
		_ = os.Remove(keyFile)
		return "", false, fmt.Errorf("write TLS certificate: %w", err)
	}
	return certificateFingerprintDER(der), true, nil
}

func tokenOK(got, expected string) bool {
	if expected == "" || len(got) != len(expected) {
		return false
	}
	return subtle.ConstantTimeCompare([]byte(got), []byte(expected)) == 1
}

func handler(cfg config) http.Handler {
	mux := http.NewServeMux()
	detector := &ipDetector{}
	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		w.Header().Set("Cache-Control", "no-store")
		if cfg.Fingerprint != "" {
			w.Header().Set("X-RustProxy-Agent-Certificate-SHA256", cfg.Fingerprint)
		}
		_, _ = io.WriteString(w, `{"status":"ok"}`)
	})
	mux.HandleFunc("/v1/inventory", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}
		auth := strings.TrimSpace(r.Header.Get("Authorization"))
		const prefix = "Bearer "
		if !strings.HasPrefix(auth, prefix) || !tokenOK(strings.TrimSpace(strings.TrimPrefix(auth, prefix)), cfg.Token) {
			w.Header().Set("WWW-Authenticate", "Bearer")
			http.Error(w, "unauthorized", http.StatusUnauthorized)
			return
		}
		containers, err := dockerContainers(r.Context(), cfg.DockerSock)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadGateway)
			return
		}
		addresses, primaryIP, primarySource := detectedAddresses(r.Context(), cfg, detector)
		w.Header().Set("Content-Type", "application/json")
		w.Header().Set("Cache-Control", "no-store")
		if cfg.Fingerprint != "" {
			w.Header().Set("X-RustProxy-Agent-Certificate-SHA256", cfg.Fingerprint)
		}
		_ = json.NewEncoder(w).Encode(inventory{
			AgentVersion: version, Hostname: cfg.Hostname, PublicIP: primaryIP, PublicIPSource: primarySource, CertificateSHA256: cfg.Fingerprint,
			Addresses: addresses, ObservedAt: time.Now().UTC().Format(time.RFC3339), Services: servicesFrom(containers),
		})
	})
	return mux
}

func envOr(name, fallback string) string {
	if value := strings.TrimSpace(os.Getenv(name)); value != "" {
		return value
	}
	return fallback
}

func envBool(name string, fallback bool) bool {
	raw := strings.TrimSpace(os.Getenv(name))
	if raw == "" {
		return fallback
	}
	value, err := strconv.ParseBool(raw)
	if err != nil {
		return fallback
	}
	return value
}

func main() {
	hostname, _ := os.Hostname()
	cfg := config{}
	flag.StringVar(&cfg.Listen, "listen", envOr("RUSTPROXY_DOCKER_AGENT_LISTEN", "127.0.0.1:9876"), "listen address")
	flag.StringVar(&cfg.Token, "token", envOr("RUSTPROXY_DOCKER_AGENT_TOKEN", ""), "Bearer token (prefer environment variable)")
	flag.StringVar(&cfg.DockerSock, "docker-socket", envOr("RUSTPROXY_DOCKER_SOCKET", "/var/run/docker.sock"), "Docker Engine unix socket")
	flag.StringVar(&cfg.AdvertiseIP, "advertise-ip", envOr("RUSTPROXY_DOCKER_ADVERTISE_IP", ""), "optional preferred host IP; all usable host addresses are still reported")
	flag.StringVar(&cfg.PublicIPURL, "public-ip-url", envOr("RUSTPROXY_DOCKER_PUBLIC_IP_URL", "https://api.ipify.org"), "public IP lookup URL; empty disables")
	flag.StringVar(&cfg.Hostname, "hostname", envOr("RUSTPROXY_DOCKER_HOSTNAME", hostname), "reported host name")
	flag.BoolVar(&cfg.TLS, "tls", envBool("RUSTPROXY_DOCKER_AGENT_TLS", true), "serve HTTPS; enabled by default")
	flag.StringVar(&cfg.CertFile, "cert-file", envOr("RUSTPROXY_DOCKER_AGENT_CERT_FILE", "/var/lib/rustproxy-docker-agent/agent.crt"), "TLS certificate file")
	flag.StringVar(&cfg.KeyFile, "key-file", envOr("RUSTPROXY_DOCKER_AGENT_KEY_FILE", "/var/lib/rustproxy-docker-agent/agent.key"), "TLS private key file")
	initCert := flag.Bool("init-cert", false, "create the self-signed TLS certificate if missing and exit")
	printFingerprint := flag.Bool("print-fingerprint", false, "print SHA-256 certificate fingerprint and exit")
	flag.Parse()

	if *initCert {
		fingerprint, created, err := ensureSelfSignedCertificate(cfg.CertFile, cfg.KeyFile, cfg.Hostname)
		if err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%s\n", fingerprint)
		if created {
			log.Printf("created self-signed certificate %s", cfg.CertFile)
		}
		return
	}
	if *printFingerprint {
		fingerprint, err := certificateFingerprint(cfg.CertFile)
		if err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%s\n", fingerprint)
		return
	}
	if len(cfg.Token) < 24 {
		log.Fatal("RUSTPROXY_DOCKER_AGENT_TOKEN must contain at least 24 characters")
	}
	if _, err := os.Stat(cfg.DockerSock); err != nil {
		log.Fatalf("Docker socket unavailable: %v", err)
	}
	if _, _, err := net.SplitHostPort(cfg.Listen); err != nil {
		log.Fatalf("invalid listen address: %v", err)
	}
	if cfg.TLS {
		fingerprint, created, err := ensureSelfSignedCertificate(cfg.CertFile, cfg.KeyFile, cfg.Hostname)
		if err != nil {
			log.Fatalf("TLS certificate: %v", err)
		}
		cfg.Fingerprint = fingerprint
		if created {
			log.Printf("generated self-signed TLS certificate; SHA-256 %s", fingerprint)
		}
	}

	server := &http.Server{Addr: cfg.Listen, Handler: handler(cfg), ReadHeaderTimeout: 3 * time.Second, IdleTimeout: 30 * time.Second, MaxHeaderBytes: 16 << 10}
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	go func() {
		<-ctx.Done()
		shutdown, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()
		_ = server.Shutdown(shutdown)
	}()
	scheme := "http"
	if cfg.TLS {
		scheme = "https"
	}
	log.Printf("RustProxy Docker Agent %s listening on %s://%s", version, scheme, cfg.Listen)
	if cfg.Fingerprint != "" {
		log.Printf("TLS certificate SHA-256: %s", cfg.Fingerprint)
	}
	var err error
	if cfg.TLS {
		err = server.ListenAndServeTLS(cfg.CertFile, cfg.KeyFile)
	} else {
		err = server.ListenAndServe()
	}
	if err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Fatal(err)
	}
}