ip2hostname.go

/*
    >> Sinden's HTTP IP to Hostname Filter
    Credits to Google and the mind of Sinden.
    Info: Reads a list of ips and resolves them and
    checks the status to see if there online and outputs the online results.
*/

package main

import (
    "bufio"
    "fmt"
    "log"
    "net"
    "net/http"
    "os"
    "strings"
    "time"
)

func dnshure_online(host string) bool {
    timeout := time.Duration(3 * time.Second)
    client := http.Client{
        Timeout: timeout,
    }

    rs, err := client.Get("http://" + host)
    if err != nil {
        return false
    }

    defer rs.Body.Close()

    return rs.StatusCode == 200
}

func dnshure_handle_host(current_host string, file *os.File) {
    rev_dns, err := net.LookupAddr(current_host)
    if err != nil {
        return
    }

    if !dnshure_online(rev_dns[0]) {
        fmt.Printf("[OFFLINE] -> %s | %s\r\n", current_host, rev_dns[0])
        return
    }

    fmt.Printf("[ONLINE] -> %s | %s\r\n", current_host, rev_dns[0])

    if len(rev_dns) > 0 && rev_dns[0] != current_host {
        hostname := strings.TrimSuffix(rev_dns[0], ".")
        fmt.Fprintf(file, hostname+"\r\n")
    } else {
        fmt.Fprintf(file, current_host+"\r\n")
    }
}

func main() {
    if len(os.Args) != 3 {
        log.Fatal("Arguments: <ip_list> <out>")
    }

    in_file, err := os.Open(os.Args[1])
    if err != nil {
        log.Fatal(err)
    }
    defer in_file.Close()

    file, err := os.Create(os.Args[2])
    if err != nil {
        log.Fatal(err)
    }
    defer file.Close()

    scanner := bufio.NewScanner(in_file)
    for scanner.Scan() {
        current_host := scanner.Text()

        go dnshure_handle_host(current_host, file)
    }

    input, _ := bufio.NewReader(os.Stdin).ReadString('\n')
    fmt.Printf("You just entered this..%s - terminating!\n", input)
}