Add asinfo package for AS number information lookups

- Created pkg/asinfo with embedded AS data from ipverse/asn-info
- Provides fast lookups by ASN with GetDescription() and GetHandle()
- Includes Search() functionality for finding AS by name/handle
- Added asinfo-gen tool to fetch and convert CSV data to JSON
- Added 'make asupdate' target to refresh AS data
- Embedded JSON data contains 130k+ AS entries
- Added comprehensive tests and examples

cmd/asinfo-gen/main.go

@@ -0,0 +1,91 @@
+// Package main generates the embedded AS info data for the asinfo package
+package main
+
+import (
+	"encoding/csv"
+	"encoding/json"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+)
+
+const asCsvURL = "https://github.com/ipverse/asn-info/raw/refs/heads/master/as.csv"
+
+// ASInfo represents information about an Autonomous System
+type ASInfo struct {
+	ASN         int    `json:"asn"`
+	Handle      string `json:"handle"`
+	Description string `json:"description"`
+}
+
+func main() {
+	// Configure logger to write to stderr
+	log.SetOutput(os.Stderr)
+	
+	// Fetch the CSV data
+	log.Println("Fetching AS CSV data...")
+	resp, err := http.Get(asCsvURL)
+	if err != nil {
+		log.Fatalf("Failed to fetch CSV: %v", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		log.Fatalf("Failed to fetch CSV: HTTP %d", resp.StatusCode)
+	}
+
+	// Parse CSV
+	reader := csv.NewReader(resp.Body)
+	
+	// Read header
+	header, err := reader.Read()
+	if err != nil {
+		log.Fatalf("Failed to read CSV header: %v", err)
+	}
+	
+	if len(header) != 3 || header[0] != "asn" || header[1] != "handle" || header[2] != "description" {
+		log.Fatalf("Unexpected CSV header: %v", header)
+	}
+
+	// Read all records
+	var asInfos []ASInfo
+	for {
+		record, err := reader.Read()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			log.Printf("Error reading CSV record: %v", err)
+			continue
+		}
+
+		if len(record) != 3 {
+			log.Printf("Skipping invalid record: %v", record)
+			continue
+		}
+
+		asn, err := strconv.Atoi(record[0])
+		if err != nil {
+			log.Printf("Invalid ASN %q: %v", record[0], err)
+			continue
+		}
+
+		asInfos = append(asInfos, ASInfo{
+			ASN:         asn,
+			Handle:      strings.TrimSpace(record[1]),
+			Description: strings.TrimSpace(record[2]),
+		})
+	}
+
+	log.Printf("Parsed %d AS records", len(asInfos))
+
+	// Convert to JSON and output to stdout
+	encoder := json.NewEncoder(os.Stdout)
+	encoder.SetIndent("", "\t")
+	if err := encoder.Encode(asInfos); err != nil {
+		log.Fatalf("Failed to encode JSON: %v", err)
+	}
+}