diff --git a/go.mod b/go.mod index 1f0c71e..2b19e2e 100644 --- a/go.mod +++ b/go.mod @@ -1,3 +1,3 @@ -module git.send.nrw/StadtHilden/ipv6calculator +module git.send.nrw/sendnrw/ipv6calculator go 1.23.1 diff --git a/main.go b/main.go index 935c74c..8de3e1f 100644 --- a/main.go +++ b/main.go @@ -6,45 +6,23 @@ import ( "log" "net" "net/http" + "os" + "strings" ) const ( - listenAddr = ":8080" // server port - ulaPrefix = "fdcb:7de3:a12a:0::" // fixed ULA /96 prefix + listenAddr = ":8080" // TCP port for the web UI + defaultPrefix = "fdcb:7de3:a12a:0::" // fallback when ULA_PREFIX is unset + defaultIP = "172.16.0.0" ) -// pageTemplate is served for both GET (empty result) and POST (with result). -var pageTemplate = template.Must(template.New("page").Parse(` - - - -IPv4 → IPv6‑Mapper - - - -

IPv4 → IPv6‑Mapper

-
- - -
- {{if .IPv6}} -
IPv6‑Adresse: {{.IPv6}}
- {{end}} - {{if .Error}} -
Fehler: {{.Error}}
- {{end}} -

Präfix: ` + ulaPrefix + `   (feste /96‑Zuordnung)

- -`)) +var ( + ulaPrefix string // effective /96 prefix (always ending in "::") + pageTemplate *template.Template // populated in init() + pageIP string +) -// viewData transports data into the page template. +// viewData feeds data into the HTML template. type viewData struct { IPv4 string IPv6 string @@ -52,9 +30,10 @@ type viewData struct { } func main() { + initPrefixAndTemplate() + http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { - // Empty page on root - renderPage(w, viewData{}) + renderPage(w, viewData{}) // empty form }) http.HandleFunc("/convert", func(w http.ResponseWriter, r *http.Request) { @@ -73,19 +52,73 @@ func main() { renderPage(w, data) }) - log.Printf("Server läuft auf http://localhost%s …", listenAddr) + log.Printf("Server läuft auf http://localhost%s (Präfix: %s)", listenAddr, ulaPrefix) log.Fatal(http.ListenAndServe(listenAddr, nil)) } -// embedIPv4 converts an IPv4 dotted string into the ulaPrefix‑based IPv6 address. +// initPrefixAndTemplate reads the environment variable and prepares the HTML template. +func initPrefixAndTemplate() { + ulaPrefix = os.Getenv("ULA_PREFIX") + if ulaPrefix == "" { + ulaPrefix = defaultPrefix + } + + pageIP = os.Getenv("IPv4") + if pageIP == "" { + pageIP = defaultIP + } + + // Ensure the prefix ends with exactly two colons (::) so that we can append hex words. + if !strings.HasSuffix(ulaPrefix, "::") { + if strings.HasSuffix(ulaPrefix, ":") { + ulaPrefix += ":" + } else { + ulaPrefix += "::" + } + } + + html := fmt.Sprintf(` + + + +IPv4 → IPv6‑Mapper + + + +

IPv4 → IPv6-Mapper

+
+ + +
+ {{if .IPv6}} +
IPv6-Adresse: {{.IPv6}}
+ {{end}} + {{if .Error}} +
Fehler: {{.Error}}
+ {{end}} +

Präfix: %s   (/96‑Zuordnung)

+ +`, pageIP, ulaPrefix) + + pageTemplate = template.Must(template.New("page").Parse(html)) +} + +// embedIPv4 converts a dotted IPv4 string into the chosen ULA /96 IPv6 address. func embedIPv4(ipv4 string) (string, error) { ip := net.ParseIP(ipv4).To4() if ip == nil { - return "", fmt.Errorf("'%s' ist keine gültige IPv4‑Adresse", ipv4) + return "", fmt.Errorf("'%s' ist keine gültige IPv4-Adresse", ipv4) } - first := uint16(ip[0])<<8 | uint16(ip[1]) // High 16 bits - second := uint16(ip[2])<<8 | uint16(ip[3]) // Low 16 bits - return fmt.Sprintf("%s%x:%x", ulaPrefix, first, second), nil + hi := uint16(ip[0])<<8 | uint16(ip[1]) // high 16 bits (octets 0–1) + lo := uint16(ip[2])<<8 | uint16(ip[3]) // low 16 bits (octets 2–3) + return fmt.Sprintf("%s%x:%x", ulaPrefix, hi, lo), nil } func renderPage(w http.ResponseWriter, d viewData) {