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subnet.go
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/*
Copyright © 2025 Seednode <seednode@seedno.de>
*/
package main
import (
"errors"
"fmt"
"math/big"
"net"
"net/http"
"strings"
"sync"
"text/template"
"time"
"github.com/julienschmidt/httprouter"
)
const (
tpl4 = `
<!DOCTYPE html>
<html lang="en">
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="Description" content="Serves a variety of web-based utilities." />
<meta charset="utf-8" />
<title>Query v{{.Version}}</title>
<link rel="stylesheet" href="/css/subnet.css" />
<meta property="og:site_name" content="https://github.com/Seednode/trivia"/>
<meta property="og:title" content="Query v{{.Version}}"/>
<meta property="og:description" content="Serves a variety of web-based utilities."/>
<meta property="og:url" content="https://github.com/Seednode/query"/>
<meta property="og:type" content="website"/>
</head>
<body>
<p id="table">
<table>
<tr>
<th></th>
<th>Binary</th>
<th>Decimal</th>
</tr>
<tr>
<th>Address</th>
<td>{{.Address_Binary}}</td>
<td>{{.Address_Decimal}}</td>
</tr>
<tr>
<th>Mask</th>
<td>{{.Mask_Binary}}</td>
<td>{{.Mask_Decimal}}</td>
</tr>
<tr>
<th>First</th>
<td>{{.First_Binary}}</td>
<td>{{.First_Decimal}}</td>
</tr>
<tr>
<th>Last</th>
<td>{{.Last_Binary}}</td>
<td>{{.Last_Decimal}}</td>
</tr>
<tr>
<th>Total</th>
<td colspan="2">{{.Total}}</td>
</tr>
</table>
</p>
</body>
</html>
`
tpl6 = `
<!DOCTYPE html>
<html lang="en">
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="Description" content="Serves a variety of web-based utilities." />
<meta charset="utf-8" />
<title>Query v{{.Version}}</title>
<link rel="stylesheet" href="/css/subnet.css" />
<meta property="og:site_name" content="https://github.com/Seednode/trivia"/>
<meta property="og:title" content="Query v{{.Version}}"/>
<meta property="og:description" content="Serves a variety of web-based utilities."/>
<meta property="og:url" content="https://github.com/Seednode/query"/>
<meta property="og:type" content="website"/>
</head>
<body>
<p id="table">
<table>
<tr>
<th></th>
<th>Binary</th>
<th>Hex (Full)</th>
<th>Hex (Shortened)</th>
</tr>
<tr>
<th>Address</th>
<td>{{.Address_Binary}}</td>
<td>{{.Address_Hex}}</td>
<td>{{.Address_Short}}</td>
</tr>
<tr>
<th>Mask</th>
<td>{{.Mask_Binary}}</td>
<td>{{.Mask_Hex}}</td>
<td>{{.Mask_Short}}</td>
</tr>
<tr>
<th>First</th>
<td>{{.First_Binary}}</td>
<td>{{.First_Hex}}</td>
<td>{{.First_Short}}</td>
</tr>
<tr>
<th>Last</th>
<td>{{.Last_Binary}}</td>
<td>{{.Last_Hex}}</td>
<td>{{.Last_Short}}</td>
</tr>
<tr>
<th>Total</th>
<td colspan="3">{{.Total}}</td>
</tr>
</table>
</p>
</body>
</html>
`
)
type Template4 struct {
Version string
Address_Binary string
Address_Decimal string
Mask_Binary string
Mask_Decimal string
First_Binary string
First_Decimal string
Last_Binary string
Last_Decimal string
Total string
}
type Template6 struct {
Version string
Address_Binary string
Address_Hex string
Address_Short string
Mask_Binary string
Mask_Hex string
Mask_Short string
First_Binary string
First_Hex string
First_Short string
Last_Binary string
Last_Hex string
Last_Short string
Total string
}
func toBinary(b []byte) string {
var s strings.Builder
for i := 0; i < len(b); i++ {
s.WriteString(fmt.Sprintf("%08b", b[i]))
if i < (len(b) - 1) {
s.WriteString(" ")
}
}
return s.String()
}
func subtract(a, b []byte) string {
var c, d, e big.Int
c.SetBytes(a)
d.SetBytes(b)
comp := c.Cmp(&d)
switch comp {
case -1:
e.Sub(&d, &c)
case 0:
e = *big.NewInt(0)
case 1:
e.Sub(&c, &d)
}
return e.Add(&e, big.NewInt(1)).String()
}
func and(a, b []byte) (net.IP, error) {
if len(a) != len(b) {
return nil, fmt.Errorf("length %d does not equal length %d", len(a), len(b))
}
result := make([]byte, len(a))
for i := 0; i < len(a); i++ {
result[i] = a[i] & b[i]
}
return result, nil
}
func or(a, b []byte) (net.IP, error) {
if len(a) != len(b) {
return nil, fmt.Errorf("length %d does not equal length %d", len(a), len(b))
}
result := make([]byte, len(a))
for i := 0; i < len(a); i++ {
result[i] = a[i] | b[i]
}
return result, nil
}
func invert(b []byte) net.IP {
inverted := make([]byte, len(b))
for i := 0; i < len(b); i++ {
inverted[i] = b[i] ^ ((2 << 7) - 1)
}
return inverted
}
func toHex(b []byte) string {
if len(b) != 16 {
return ""
}
return fmt.Sprintf("%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x",
b[0], b[1], b[2], b[3],
b[4], b[5], b[6], b[7],
b[8], b[9], b[10], b[11],
b[12], b[13], b[14], b[15])
}
func toDecimal(b []byte) string {
var s strings.Builder
for i := 0; i < len(b); i++ {
s.WriteString(fmt.Sprintf("%d", b[i]))
if i != len(b)-1 {
s.WriteString(".")
}
}
return s.String()
}
func calculateV4Subnet(cidr string) (Template4, error) {
ip, net, err := net.ParseCIDR(cidr)
if err != nil {
return Template4{}, errors.New("not valid CIDR notation")
}
as4 := ip.To4()
if as4 == nil {
return Template4{}, errors.New("not a valid IPv6 address")
}
first, err := and(as4, net.Mask)
if err != nil {
return Template4{}, err
}
last, err := or(as4, invert(net.Mask))
if err != nil {
return Template4{}, err
}
return Template4{
Version: ReleaseVersion,
Address_Binary: toBinary(as4),
Address_Decimal: toDecimal(as4),
Mask_Binary: toBinary(net.Mask),
Mask_Decimal: toDecimal(net.Mask),
First_Binary: toBinary(first),
First_Decimal: toDecimal(first),
Last_Binary: toBinary(last),
Last_Decimal: toDecimal(last),
Total: subtract(first, last),
}, nil
}
func serveV4Subnet(template *template.Template, errorChannel chan<- Error) httprouter.Handle {
return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
startTime := time.Now()
w.Header().Set("Content-Type", "text/html;charset=UTF-8")
securityHeaders(w)
data, err := calculateV4Subnet(strings.TrimPrefix(p.ByName("v4"), "/"))
if err != nil {
errorChannel <- Error{err, realIP(r, true), r.URL.Path}
return
}
err = template.Execute(w, data)
if err != nil {
errorChannel <- Error{err, realIP(r, true), r.URL.Path}
return
}
if verbose {
fmt.Printf("%s | %s => %s\n",
startTime.Format(timeFormats["RFC3339"]),
realIP(r, true),
r.RequestURI)
}
}
}
func calculateV6Subnet(cidr string) (Template6, error) {
ip, net, err := net.ParseCIDR(cidr)
if err != nil {
return Template6{}, errors.New("not valid CIDR notation")
}
as4 := ip.To4()
if as4 != nil {
return Template6{}, errors.New("not a valid IPv6 address")
}
first, err := and(ip, net.Mask)
if err != nil {
return Template6{}, err
}
last, err := or(ip, invert(net.Mask))
if err != nil {
return Template6{}, err
}
return Template6{
Version: ReleaseVersion,
Address_Binary: toBinary(ip),
Address_Hex: toHex(ip),
Address_Short: ip.String(),
Mask_Binary: toBinary(net.Mask),
Mask_Hex: toHex(net.Mask),
Mask_Short: "n/a",
First_Binary: toBinary(first),
First_Hex: toHex(first),
First_Short: first.String(),
Last_Binary: toBinary(last),
Last_Hex: toHex(last),
Last_Short: last.String(),
Total: subtract(first, last),
}, nil
}
func serveV6Subnet(template *template.Template, errorChannel chan<- Error) httprouter.Handle {
return func(w http.ResponseWriter, r *http.Request, p httprouter.Params) {
startTime := time.Now()
w.Header().Set("Content-Type", "text/html;charset=UTF-8")
securityHeaders(w)
data, err := calculateV6Subnet(strings.TrimPrefix(p.ByName("v6"), "/"))
if err != nil {
errorChannel <- Error{err, realIP(r, true), r.URL.Path}
return
}
err = template.Execute(w, data)
if err != nil {
errorChannel <- Error{err, realIP(r, true), r.URL.Path}
return
}
if verbose {
fmt.Printf("%s | %s => %s\n",
startTime.Format(timeFormats["RFC3339"]),
realIP(r, true),
r.RequestURI)
}
}
}
func registerSubnetting(mux *httprouter.Router, usage *sync.Map, errorChannel chan<- Error) {
const module = "subnet"
template4, err := template.New("subnet").Parse(tpl4)
if err != nil {
errorChannel <- Error{err, "", ""}
return
}
template6, err := template.New("subnet").Parse(tpl6)
if err != nil {
errorChannel <- Error{err, "", ""}
return
}
mux.GET("/subnet/", serveUsage(module, usage, errorChannel))
mux.GET("/subnet/v4/*v4", serveV4Subnet(template4, errorChannel))
mux.GET("/subnet/v6/*v6", serveV6Subnet(template6, errorChannel))
usage.Store(module, []string{
"/subnet/v4/192.168.0.1/24",
"/subnet/v4/10.10.100.0/22",
"/subnet/v6/fdd8:0c61:bf60:590f::/64",
"/subnet/v6/2606:4700:a560::/48",
})
}