Files
routewatch/cmd/asinfo-gen/main.go
T
clawbot 023c3f9b41
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Keep the AS list when the asupdate generator fails (closes #173)
make asupdate piped the generator into gzip, so the target saw gzip's
exit status. A failed download replaced pkg/asinfo/asdata.json.gz with
an empty file and the target still exited 0.

The target now runs the new script/asupdate. It writes the output of
cmd/asinfo-gen to a temporary file. Only when the generator succeeds
does it compress the list and move it into place. Otherwise it leaves
the file alone and exits non-zero. The generator now fails when as.csv
holds no AS.

The generator reads as.csv from ipverse/as-metadata, the source's new
name. The list it builds there is unchanged, so no new list is
committed.

Model: opus-5-5
2026-10-27 02:43:35 +01:00

138 lines
3.1 KiB
Go

// Package main generates the embedded AS info data for the asinfo package
package main
import (
"context"
"encoding/csv"
"encoding/json"
"errors"
"fmt"
"io"
"log"
"net/http"
"os"
"strconv"
"strings"
)
const asCsvURL = "https://github.com/ipverse/as-metadata/raw/refs/heads/master/as.csv"
// The first columns of as.csv, the ones the generator reads. It reads past
// the columns after them, such as the country code.
const (
asnColumn = "asn"
handleColumn = "handle"
descriptionColumn = "description"
columnsRead = 3
)
var (
errUnexpectedHeader = errors.New("unexpected CSV header")
errNoASes = errors.New("no AS in the 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...")
req, err := http.NewRequestWithContext(
context.Background(), http.MethodGet, asCsvURL, nil)
if err != nil {
log.Fatalf("Failed to fetch CSV: %v", err)
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
log.Fatalf("Failed to fetch CSV: %v", err)
}
if resp.StatusCode != http.StatusOK {
log.Fatalf("Failed to fetch CSV: HTTP %d", resp.StatusCode)
}
asInfos, err := parseCSV(resp.Body)
// Closed here rather than deferred: log.Fatalf exits without running
// deferred calls.
_ = resp.Body.Close()
if err != nil {
log.Fatalf("Failed to parse CSV: %v", err)
}
log.Printf("Parsed %d AS records", len(asInfos))
// Convert to JSON and output to stdout
encoder := json.NewEncoder(os.Stdout)
encoder.SetIndent("", "\t")
err = encoder.Encode(asInfos)
if err != nil {
log.Fatalf("Failed to encode JSON: %v", err)
}
}
// parseCSV reads as.csv from r and returns its ASes, with the handle and the
// description as the file spells them. A header whose first columns are not
// the AS number, the handle and the description is an error. A record that
// does not parse is logged and skipped. A file left with no AS is an error.
func parseCSV(r io.Reader) ([]ASInfo, error) {
reader := csv.NewReader(r)
header, err := reader.Read()
if err != nil {
return nil, fmt.Errorf("read CSV header: %w", err)
}
if len(header) < columnsRead || header[0] != asnColumn ||
header[1] != handleColumn || header[2] != descriptionColumn {
return nil, fmt.Errorf("%w: %v", errUnexpectedHeader, header)
}
var asInfos []ASInfo
for {
// The reader returns an error for a record with a different number
// of fields than the header.
record, err := reader.Read()
if errors.Is(err, io.EOF) {
break
}
if err != nil {
log.Printf("Error reading CSV record: %v", err)
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]),
})
}
if len(asInfos) == 0 {
return nil, errNoASes
}
return asInfos, nil
}