jbergner
b4e90b1e92
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130 lines
3.3 KiB
Go
130 lines
3.3 KiB
Go
package main
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import (
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"fmt"
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"html/template"
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"log"
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"net"
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"net/http"
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"os"
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"strings"
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)
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const (
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listenAddr = ":8080" // TCP port for the web UI
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defaultPrefix = "fdcb:7de3:a12a:0::" // fallback when ULA_PREFIX is unset
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defaultIP = "172.16.0.0"
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)
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var (
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ulaPrefix string // effective /96 prefix (always ending in "::")
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pageTemplate *template.Template // populated in init()
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pageIP string
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)
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// viewData feeds data into the HTML template.
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type viewData struct {
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IPv4 string
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IPv6 string
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Error string
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}
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func main() {
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initPrefixAndTemplate()
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http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
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renderPage(w, viewData{}) // empty form
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})
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http.HandleFunc("/convert", func(w http.ResponseWriter, r *http.Request) {
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if err := r.ParseForm(); err != nil {
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renderPage(w, viewData{Error: "Ungültiges Formular"})
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return
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}
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ipv4Str := r.FormValue("ipv4")
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ipv6, err := embedIPv4(ipv4Str)
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data := viewData{IPv4: ipv4Str}
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if err != nil {
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data.Error = err.Error()
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} else {
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data.IPv6 = ipv6
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}
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renderPage(w, data)
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})
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log.Printf("Server läuft auf http://localhost%s (Präfix: %s)", listenAddr, ulaPrefix)
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log.Fatal(http.ListenAndServe(listenAddr, nil))
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}
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// initPrefixAndTemplate reads the environment variable and prepares the HTML template.
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func initPrefixAndTemplate() {
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ulaPrefix = os.Getenv("ULA_PREFIX")
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if ulaPrefix == "" {
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ulaPrefix = defaultPrefix
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}
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pageIP = os.Getenv("IPv4")
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if pageIP == "" {
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pageIP = defaultIP
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}
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// Ensure the prefix ends with exactly two colons (::) so that we can append hex words.
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if !strings.HasSuffix(ulaPrefix, "::") {
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if strings.HasSuffix(ulaPrefix, ":") {
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ulaPrefix += ":"
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} else {
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ulaPrefix += "::"
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}
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}
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html := fmt.Sprintf(`<!DOCTYPE html>
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<html lang="de">
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<head>
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<meta charset="utf-8" />
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<title>IPv4 → IPv6‑Mapper</title>
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<style>
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body { font-family: system-ui, sans-serif; margin: 2rem; }
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form { display: flex; gap: .5rem; }
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input[type=text] { flex: 1; padding: .4rem; font-size: 1rem; }
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button { padding: .5rem 1rem; font-size: 1rem; cursor: pointer; }
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#result { margin-top: 1.5rem; font-weight: bold; }
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.error { color: #b00; }
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</style>
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</head>
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<body>
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<h1>IPv4 → IPv6-Mapper</h1>
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<form action="/convert" method="post">
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<input type="text" name="ipv4" placeholder="%s" value="{{.IPv4}}" required />
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<button type="submit">Umrechnen</button>
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</form>
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{{if .IPv6}}
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<div id="result">IPv6-Adresse: <code>{{.IPv6}}</code></div>
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{{end}}
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{{if .Error}}
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<div class="error">Fehler: {{.Error}}</div>
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{{end}}
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<p>Präfix: <code>%s</code> (/96‑Zuordnung)</p>
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</body>
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</html>`, pageIP, ulaPrefix)
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pageTemplate = template.Must(template.New("page").Parse(html))
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}
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// embedIPv4 converts a dotted IPv4 string into the chosen ULA /96 IPv6 address.
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func embedIPv4(ipv4 string) (string, error) {
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ip := net.ParseIP(ipv4).To4()
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if ip == nil {
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return "", fmt.Errorf("'%s' ist keine gültige IPv4-Adresse", ipv4)
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}
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hi := uint16(ip[0])<<8 | uint16(ip[1]) // high 16 bits (octets 0–1)
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lo := uint16(ip[2])<<8 | uint16(ip[3]) // low 16 bits (octets 2–3)
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return fmt.Sprintf("%s%x:%x", ulaPrefix, hi, lo), nil
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}
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func renderPage(w http.ResponseWriter, d viewData) {
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w.Header().Set("Content-Type", "text/html; charset=utf-8")
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if err := pageTemplate.Execute(w, d); err != nil {
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http.Error(w, err.Error(), http.StatusInternalServerError)
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}
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}
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