feat: add Eduroam Analyzer service

2026-01-19 18:50:51 +01:00
commit 5171dc7d99
16 changed files with 760 additions and 0 deletions
--- a/main.go
+++ b/main.go
@@ -0,0 +1,158 @@
+package main
+
+import (
+	"bufio"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+	"sync/atomic"
+	"time"
+
+	"github.com/oschwald/maxminddb-golang"
+)
+
+type asnRecord struct {
+	ASN uint   `maxminddb:"autonomous_system_number"`
+	Org string `maxminddb:"autonomous_system_organization"`
+}
+
+type server struct {
+	db         *maxminddb.Reader
+	nrenASNs   map[uint]struct{}
+	ready      atomic.Bool
+	versionTag string
+}
+
+func loadASNSet(path string) (map[uint]struct{}, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	set := make(map[uint]struct{}, 4096)
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		line := strings.TrimSpace(sc.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		v, err := strconv.ParseUint(line, 10, 32)
+		if err != nil {
+			continue
+		}
+		set[uint(v)] = struct{}{}
+	}
+	return set, sc.Err()
+}
+
+func firstForwardedFor(r *http.Request) string {
+	xff := r.Header.Get("X-Forwarded-For")
+	if xff == "" {
+		return ""
+	}
+	parts := strings.Split(xff, ",")
+	if len(parts) == 0 {
+		return ""
+	}
+	return strings.TrimSpace(parts[0])
+}
+
+func remoteIP(r *http.Request) string {
+	// Prefer XFF (because Traefik is proxy)
+	ip := firstForwardedFor(r)
+	if ip != "" {
+		return ip
+	}
+	host, _, err := net.SplitHostPort(r.RemoteAddr)
+	if err == nil {
+		return host
+	}
+	return r.RemoteAddr
+}
+
+func (s *server) authHandler(w http.ResponseWriter, r *http.Request) {
+	if !s.ready.Load() {
+		w.WriteHeader(http.StatusServiceUnavailable)
+		return
+	}
+
+	ipStr := remoteIP(r)
+	parsed := net.ParseIP(ipStr)
+	if parsed == nil {
+		// Always 200: we enrich, not block
+		w.Header().Set("X-NREN", "0")
+		w.WriteHeader(http.StatusOK)
+		return
+	}
+
+	var rec asnRecord
+	if err := s.db.Lookup(parsed, &rec); err != nil || rec.ASN == 0 {
+		w.Header().Set("X-NREN", "0")
+		w.WriteHeader(http.StatusOK)
+		return
+	}
+
+	w.Header().Set("X-ASN", strconv.FormatUint(uint64(rec.ASN), 10))
+	if rec.Org != "" {
+		// optional: keep it short; some org strings can be long
+		w.Header().Set("X-ASN-ORG", rec.Org)
+	}
+
+	_, ok := s.nrenASNs[rec.ASN]
+	if ok {
+		w.Header().Set("X-NREN", "1")
+	} else {
+		w.Header().Set("X-NREN", "0")
+	}
+
+	w.Header().Set("Cache-Control", "no-store")
+	w.Header().Set("X-Service", s.versionTag)
+	w.WriteHeader(http.StatusOK)
+}
+
+func main() {
+	mmdbPath := getenv("MMDB_PATH", "/data/GeoLite2-ASN.mmdb")
+	asnListPath := getenv("ASN_LIST_PATH", "/data/nren_asns.txt")
+	addr := getenv("ADDR", ":8080")
+	version := getenv("VERSION_TAG", "asn-header-service")
+
+	db, err := maxminddb.Open(mmdbPath)
+	if err != nil {
+		log.Fatalf("failed to open mmdb: %v", err)
+	}
+	defer db.Close()
+
+	set, err := loadASNSet(asnListPath)
+	if err != nil {
+		log.Fatalf("failed to load asn list: %v", err)
+	}
+
+	s := &server{db: db, nrenASNs: set, versionTag: version}
+	s.ready.Store(true)
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/auth", s.authHandler)
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, _ *http.Request) { w.WriteHeader(http.StatusOK) })
+
+	srv := &http.Server{
+		Addr:              addr,
+		Handler:           mux,
+		ReadHeaderTimeout: 2 * time.Second,
+	}
+
+	log.Printf("listening on %s (asn_count=%d)", addr, len(set))
+	log.Fatal(srv.ListenAndServe())
+}
+
+func getenv(k, def string) string {
+	v := strings.TrimSpace(os.Getenv(k))
+	if v == "" {
+		return def
+	}
+	return v
+}
+