jbergner
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215 lines
6.5 KiB
Go
215 lines
6.5 KiB
Go
// A small Go web‑server that converts an IPv4 address into an IPv6 address
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// inside a user‑defined /96 ULA prefix and outputs Windows 11‑ready fields.
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//
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// Environment variables (all optional):
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//
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// ULA_PREFIX – /96 prefix to embed into, default "fdcb:7de3:a12a:0::"
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// FORM_DEFAULT_IP - legt das Form Placeholder IP Feld fest (default: 172.16.0.0)
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// DNS1 – preferred DNS IPv6 address (default: <prefix with 1::53>)
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// DNS2 – alternate DNS IPv6 address (default: <prefix with 1::54>)
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//
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// Build & run:
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//
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// export ULA_PREFIX="fde5:1234:abcd:0::"
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// export DNS1="fde5:1234:abcd:1::53" # optional
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// export DNS2="fde5:1234:abcd:1::54" # optional
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// go run main.go
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//
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// Open http://localhost:8080 in a browser.
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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"
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defaultPrefix = "fd09:cafe:affe:4010::" // fallback /96
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prefixLen = 96 // fixed /96 mapping
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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 ends with ::)
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dns1 string // preferred DNS
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dns2 string // alternate DNS
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pageIP string
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pageTemplate *template.Template // compiled HTML template
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)
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// viewData is passed into the template.
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type viewData struct {
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IPv4 string
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IPv6 string
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Gateway string
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DNS1 string
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DNS2 string
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Error string
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HaveResult bool
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}
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func main() {
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initConfigAndTemplate()
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http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
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renderPage(w, viewData{})
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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.HaveResult = true
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data.IPv6 = ipv6
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data.Gateway = ulaPrefix + "1" // router IP = <prefix>::1
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data.DNS1 = dns1
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data.DNS2 = dns2
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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, DNS1 %s, DNS2 %s)", listenAddr, ulaPrefix, dns1, dns2)
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log.Fatal(http.ListenAndServe(listenAddr, nil))
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}
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// initConfigAndTemplate reads env vars and prepares HTML template.
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func initConfigAndTemplate() {
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// ---- ULA prefix -------------------------------------------------------
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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("FORM_DEFAULT_IP")
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if pageIP == "" {
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pageIP = defaultIP
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}
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// ensure trailing :: so we can simply 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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// ---- DNS addresses ----------------------------------------------------
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dns1 = os.Getenv("DNS1")
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dns2 = os.Getenv("DNS2")
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// default DNS: change subnet 0 → 1 and append ::53 / ::54
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if dns1 == "" {
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dns1 = strings.Replace(ulaPrefix, "::", "::53", 1)
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}
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if dns2 == "" {
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dns2 = strings.Replace(ulaPrefix, "::", "::54", 1)
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}
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// ---- HTML template ----------------------------------------------------
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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;max-width:46rem}
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form{display:flex;gap:.5rem;flex-wrap:wrap}
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input[type=text],input[readonly]{padding:.4rem;font-size:1rem;border:1px solid #ccc;border-radius:4px;flex:1}
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button{padding:.5rem 1rem;font-size:1rem;cursor:pointer;border-radius:4px;border:1px solid #666;background:#eee}
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button.copy{padding:.3rem .6rem;font-size:.9rem;margin-left:.3rem;background:#def}
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#result{margin-top:1.5rem}
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.row{display:flex;align-items:center;margin-bottom:.4rem}
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.row label{width:14rem}
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</style>
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<script>
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async function copy(id){
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const val=document.getElementById(id).value;
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await navigator.clipboard.writeText(val);
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const btn=document.getElementById(id+"Btn");
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const old=btn.textContent;
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btn.textContent="✔ kopiert";
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setTimeout(()=>btn.textContent=old,1200);
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}
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</script>
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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 .HaveResult}}
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<div id="result">
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<h2>Windows 11‑Eingaben</h2>
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<div class="row">
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<label for="ip">IP‑Adresse</label>
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<input readonly id="ip" value="{{.IPv6}}" />
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<button type="button" class="copy" id="ipBtn" onclick="copy('ip')">Kopieren</button>
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</div>
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<div class="row">
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<label for="pl">Subnetzpräfixlänge</label>
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<input readonly id="pl" value="96" />
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<button type="button" class="copy" id="plBtn" onclick="copy('pl')">Kopieren</button>
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</div>
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<div class="row">
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<label for="gw">Gateway (Bleibt vorerst leer!)</label>
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<input readonly id="gw" value="{{.Gateway}}" />
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<button type="button" class="copy" id="gwBtn" onclick="copy('gw')">Kopieren</button>
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</div>
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<div class="row">
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<label for="dns1">Bevorzugter DNS</label>
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<input readonly id="dns1" value="{{.DNS1}}" />
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<button type="button" class="copy" id="dns1Btn" onclick="copy('dns1')">Kopieren</button>
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</div>
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<div class="row">
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<label for="dns2">Alternativer DNS</label>
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<input readonly id="dns2" value="{{.DNS2}}" />
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<button type="button" class="copy" id="dns2Btn" onclick="copy('dns2')">Kopieren</button>
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</div>
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</div>
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{{end}}
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{{if .Error}}
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<p style="color:#b00">Fehler: {{.Error}}</p>
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{{end}}
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<p style="margin-top:1.5rem">Aktives Präfix: <code>%s</code> (/96)</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 an IPv6 address within ulaPrefix/96.
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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])
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lo := uint16(ip[2])<<8 | uint16(ip[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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