sendnrw/ipv6calculator
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jbergner
2025-05-09 08:29:11 +02:00
parent c63c141543
commit b4e90b1e92
2 changed files with 75 additions and 42 deletions
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2
go.mod
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@@ -1,3 +1,3 @@
module git.send.nrw/StadtHilden/ipv6calculator module git.send.nrw/sendnrw/ipv6calculator
go 1.23.1 go 1.23.1

115
main.go
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@@ -6,45 +6,23 @@ import (
"log" "log"
"net" "net"
"net/http" "net/http"
"os"
"strings"
) )
const ( const (
listenAddr = ":8080" // server port listenAddr = ":8080" // TCP port for the web UI
ulaPrefix = "fdcb:7de3:a12a:0::" // fixed ULA /96 prefix 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 (
var pageTemplate = template.Must(template.New("page").Parse(`<!DOCTYPE html> ulaPrefix string // effective /96 prefix (always ending in "::")
<html lang="de"> pageTemplate *template.Template // populated in init()
<head> pageIP string
<meta charset="utf-8"/> )
<title>IPv4 → IPv6‑Mapper</title>
<style>
body { font-family: system-ui, sans-serif; margin: 2rem; }
form { display:flex; gap:.5rem; }
input[type=text] { flex:1; padding:.4rem; font-size:1rem; }
button { padding:.5rem 1rem; font-size:1rem; cursor:pointer; }
#result { margin-top:1.5rem; font-weight:bold; }
.error { color:#b00; }
</style>
</head>
<body>
<h1>IPv4 → IPv6‑Mapper</h1>
<form action="/convert" method="post">
<input type="text" name="ipv4" placeholder="172.29.0.0" value="{{.IPv4}}" required />
<button type="submit">Umrechnen</button>
</form>
{{if .IPv6}}
<div id="result">IPv6‑Adresse: <code>{{.IPv6}}</code></div>
{{end}}
{{if .Error}}
<div class="error">Fehler: {{.Error}}</div>
{{end}}
<p>Präfix: <code>` + ulaPrefix + `</code> &nbsp; (feste /96‑Zuordnung)</p>
</body>
</html>`))
// viewData transports data into the page template. // viewData feeds data into the HTML template.
type viewData struct { type viewData struct {
IPv4 string IPv4 string
IPv6 string IPv6 string
@@ -52,9 +30,10 @@ type viewData struct {
} }
func main() { func main() {
initPrefixAndTemplate()
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
// Empty page on root renderPage(w, viewData{}) // empty form
renderPage(w, viewData{})
}) })
http.HandleFunc("/convert", func(w http.ResponseWriter, r *http.Request) { http.HandleFunc("/convert", func(w http.ResponseWriter, r *http.Request) {
@@ -73,19 +52,73 @@ func main() {
renderPage(w, data) 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)) 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(`<!DOCTYPE html>
<html lang="de">
<head>
<meta charset="utf-8" />
<title>IPv4 → IPv6‑Mapper</title>
<style>
body { font-family: system-ui, sans-serif; margin: 2rem; }
form { display: flex; gap: .5rem; }
input[type=text] { flex: 1; padding: .4rem; font-size: 1rem; }
button { padding: .5rem 1rem; font-size: 1rem; cursor: pointer; }
#result { margin-top: 1.5rem; font-weight: bold; }
.error { color: #b00; }
</style>
</head>
<body>
<h1>IPv4 → IPv6-Mapper</h1>
<form action="/convert" method="post">
<input type="text" name="ipv4" placeholder="%s" value="{{.IPv4}}" required />
<button type="submit">Umrechnen</button>
</form>
{{if .IPv6}}
<div id="result">IPv6-Adresse: <code>{{.IPv6}}</code></div>
{{end}}
{{if .Error}}
<div class="error">Fehler: {{.Error}}</div>
{{end}}
<p>Präfix: <code>%s</code> &nbsp; (/96‑Zuordnung)</p>
</body>
</html>`, 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) { func embedIPv4(ipv4 string) (string, error) {
ip := net.ParseIP(ipv4).To4() ip := net.ParseIP(ipv4).To4()
if ip == nil { 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 hi := uint16(ip[0])<<8 | uint16(ip[1]) // high 16 bits (octets 0–1)
second := uint16(ip[2])<<8 | uint16(ip[3]) // Low 16 bits lo := uint16(ip[2])<<8 | uint16(ip[3]) // low 16 bits (octets 2–3)
return fmt.Sprintf("%s%x:%x", ulaPrefix, first, second), nil return fmt.Sprintf("%s%x:%x", ulaPrefix, hi, lo), nil
} }
func renderPage(w http.ResponseWriter, d viewData) { func renderPage(w http.ResponseWriter, d viewData) {