Unhandled exception in FtpWebRequest.CreateConnectionAsync crashes process #56376
Description
Description
When System.Net.FtpWebRequest.CreateConnectionAsync throws an exception in creating a TcpClient the exception is unhandled, because it happens on a thread-pool thread, so this crashes the whole process. This happens when the open file handle limit is reached (and possibly in other scenarios).
Console EXE code to reproduce:
using System;
using System.Diagnostics;
using System.Net;
using System.Threading.Tasks;
namespace FtpWebRequestCrash
{
class Program
{
static void Main(string[] args)
{
TryGetFileList(); // Do this before setting ulimit to load all assemblies, etc., otherwise that fails
Console.WriteLine("Ready to try FTP request again. Run\n\tprlimit --nofile=10:10 --pid {0}\nand press Enter to continue.", Process.GetCurrentProcess().Id);
Console.ReadLine();
TryGetFileList(); // If ulimit was lowered this will now crash the process
Console.WriteLine("Exiting normally");
}
private static void TryGetFileList()
{
try
{
var request = (FtpWebRequest)WebRequest.Create("ftp://www.example.com/test");
request.Method = WebRequestMethods.Ftp.ListDirectoryDetails;
var task = request.GetResponseAsync();
if (!Task.WaitAll(new Task[] {task}, 1000)) // Work around .NET Core ignoring Timeout property: https://github.com/dotnet/corefx/issues/35888
throw new TimeoutException($"FTP request to {request.RequestUri} timed out after 1000 ms");
Console.WriteLine("Connected successfully - this should not happen");
}
catch (Exception ex)
{
Console.WriteLine("Exception in getting file list: " + ex);
}
}
}
}Project file:
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>net5.0</TargetFramework>
</PropertyGroup>
</Project>Run the above with dotnet run and it should output:
Exception in getting file list: System.TimeoutException: FTP request to ftp://www.example.com/test timed out after 1000 ms
at FtpWebRequestCrash.Program.TryGetFileList() in /media/sf_work/Play/FtpWebRequestCrash/Program.cs:line 31
Ready to try FTP request again. Run
prlimit --nofile=10:10 --pid 58520
and press Enter to continue.
Run the command above (prlimit --nofile=10:10 --pid 58520 or alternatively prlimit --nofile=10:10 --pid $(pgrep -f FtpWebRequestCrash)) in another terminal, then press Enter in the running program and it crashes with an unhandled exception:
Unhandled exception. System.Net.Sockets.SocketException (23): Too many open files in system
at System.Net.Sockets.Socket..ctor(AddressFamily addressFamily, SocketType socketType, ProtocolType protocolType)
at System.Net.Sockets.Socket..ctor(SocketType socketType, ProtocolType protocolType)
at System.Net.Sockets.TcpClient.InitializeClientSocket()
at System.Net.Sockets.TcpClient..ctor(AddressFamily family)
at System.Net.Sockets.TcpClient..ctor()
at System.Net.FtpWebRequest.CreateConnectionAsync()
at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__140_1(Object state)
at System.Threading.QueueUserWorkItemCallbackDefaultContext.Execute()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
Expected result: exception is handled, i.e.
Exception in getting file list: System.TimeoutException: FTP request to ftp://www.example.com/test timed out after 1000 ms
at FtpWebRequestCrash.Program.TryGetFileList() in /media/sf_work/Play/FtpWebRequestCrash/Program.cs:line 31
Ready to try FTP request again. Run
prlimit --nofile=10:10 --pid 58615
and press Enter to continue.
Exception in getting file list: System.Net.Sockets.SocketException (23): Too many open files in system
at System.Net.Sockets.Socket..ctor(AddressFamily addressFamily, SocketType socketType, ProtocolType protocolType)
...
Exiting normally
Configuration
$ dotnet --info
.NET SDK (reflecting any global.json):
Version: 5.0.302
Commit: c005824e35
Runtime Environment:
OS Name: linuxmint
OS Version: 20
OS Platform: Linux
RID: linux-x64
Base Path: /usr/share/dotnet/sdk/5.0.302/
Host (useful for support):
Version: 5.0.8
Commit: 35964c9215
.NET SDKs installed:
5.0.302 [/usr/share/dotnet/sdk]
.NET runtimes installed:
Microsoft.AspNetCore.App 3.1.17 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.8 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.17 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.8 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
Other information
I believe the problem is that FtpWebRequest.CreateConnectionAsync() runs new TcpClient() outside of its try/catch. The entire method body should probably be inside a try/catch. Please handle AsyncRequestCallback throwing, too.