DNS collisions detection with F# Async Workflows

There is one more useful application of script from the “Explore local network with F# Async Workflows” post. During the check of the machine availability we can collect IP addresses of all machines. After that we can compare IPs of different host names for collision. It is a good way to understand what is going on in your network.

#r "System.DirectoryServices.dll"
open System
open System.Collections
open System.DirectoryServices
open System.Net.NetworkInformation
open System.Threading.Tasks

let hosts =
    use searcher =
        new DirectorySearcher(new DirectoryEntry(),
            Filter="(objectClass=computer)", PageSize=10000)
    (searcher.FindAll() :> IEnumerable)
    |> Seq.cast<SearchResult>
    |> Seq.map (fun x -> x.GetDirectoryEntry().Name)
    |> Seq.map (fun n -> n.Substring(n.IndexOf("=")+1))
    |> Seq.toList

let checkHosts hosts =
    let rec ping attempts (host:string) =
        async {
            let! pingResult =
                (new Ping()).SendPingAsync(host)
                |> Async.AwaitTask |> Async.Catch
            match pingResult with
            | Choice2Of2 e -> return None
            | Choice1Of2 reply when reply.Status = IPStatus.Success ->
                return Some(reply.Address.MapToIPv4().ToString())
            | _ when attempts > 0 -> return! ping (attempts-1) host
            | _ -> return None
    let results =
        |> Seq.map (ping 4)
        |> Async.Parallel
        |> Async.RunSynchronously
        |> Seq.toList
    List.zip results hosts

let dnsConflicts =
    |> checkHosts
    |> List.filter (fst >> Option.isSome)
    |> Seq.groupBy fst
    |> Seq.filter (fun (_, seq) -> Seq.length seq > 1)
    |> Seq.map (fun (k, seq) ->
        (Option.get k, seq |> Seq.map snd |> Seq.toList) )
    |> Seq.toList

One thought on “DNS collisions detection with F# Async Workflows

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s