From 9266d45b5606731767359d44be0cabc4b65e5ada Mon Sep 17 00:00:00 2001
From: Shadowghost <Shadowghost@users.noreply.github.com>
Date: Tue, 15 Sep 2026 11:16:12 -0400
Subject: Backport pull request #17958 from jellyfin/release-12.z

Don't let a torn-down WebSocket take down the request handler

Original-merge: f4c76aabad7523d263a8a1f1a1232b27187e7584

Merged-by: crobibero <cody@robibe.ro>

Backported-by: Cody Robibero <cody@robibe.ro>
---
 .../HttpServer/WebSocketConnectionTests.cs         | 90 ++++++++++++++++++++++
 1 file changed, 90 insertions(+)

(limited to 'tests/Jellyfin.Server.Implementations.Tests/HttpServer/WebSocketConnectionTests.cs')

diff --git a/tests/Jellyfin.Server.Implementations.Tests/HttpServer/WebSocketConnectionTests.cs b/tests/Jellyfin.Server.Implementations.Tests/HttpServer/WebSocketConnectionTests.cs
index 22667ee82d..b9ae16255e 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/HttpServer/WebSocketConnectionTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/HttpServer/WebSocketConnectionTests.cs
@@ -1,7 +1,11 @@
 using System;
 using System.Buffers;
 using System.IO;
+using System.Net.WebSockets;
+using System.Text;
 using System.Text.Json;
+using System.Threading;
+using System.Threading.Tasks;
 using Emby.Server.Implementations.HttpServer;
 using Microsoft.Extensions.Logging.Abstractions;
 using Xunit;
@@ -48,6 +52,92 @@ namespace Jellyfin.Server.Implementations.Tests.HttpServer
             Assert.Throws<JsonException>(() => con.DeserializeWebSocketMessage(new ReadOnlySequence<byte>(bytes), out var bytesConsumed));
         }
 
+        [Fact]
+        public async Task ReceiveAsync_SocketTornDownWhileAnswering_RaisesClosedWithoutThrowing()
+        {
+            // The keep-alive watchdog can dispose a connection while the receive loop is
+            // answering a message on it. The failing answer must not escape into the request
+            // handler, as that would skip the Closed event the session needs to release it.
+            var socket = new DisposedOnSendWebSocket(Encoding.UTF8.GetBytes("{\"MessageType\":\"KeepAlive\"}"));
+            var con = new WebSocketConnection(new NullLogger<WebSocketConnection>(), socket, null!, null!)
+            {
+                OnReceive = _ => Task.CompletedTask
+            };
+
+            var closed = false;
+            con.Closed += (_, _) => closed = true;
+
+            await con.ReceiveAsync(TestContext.Current.CancellationToken);
+
+            Assert.True(closed);
+            Assert.Equal(1, socket.SendAttempts);
+        }
+
+        /// <summary>
+        /// A socket that hands out a single message and then behaves like a socket that was
+        /// disposed underneath the receive loop.
+        /// </summary>
+        internal sealed class DisposedOnSendWebSocket : WebSocket
+        {
+            private readonly byte[] _message;
+            private bool _received;
+
+            public DisposedOnSendWebSocket(byte[] message)
+            {
+                _message = message;
+            }
+
+            public int SendAttempts { get; private set; }
+
+            public override WebSocketCloseStatus? CloseStatus => null;
+
+            public override string? CloseStatusDescription => null;
+
+            public override string? SubProtocol => null;
+
+            public override WebSocketState State => SendAttempts == 0 ? WebSocketState.Open : WebSocketState.Closed;
+
+            public override void Abort()
+            {
+            }
+
+            public override Task CloseAsync(WebSocketCloseStatus closeStatus, string? statusDescription, CancellationToken cancellationToken)
+                => Task.CompletedTask;
+
+            public override Task CloseOutputAsync(WebSocketCloseStatus closeStatus, string? statusDescription, CancellationToken cancellationToken)
+                => Task.CompletedTask;
+
+            public override void Dispose()
+            {
+            }
+
+            public override ValueTask<ValueWebSocketReceiveResult> ReceiveAsync(Memory<byte> buffer, CancellationToken cancellationToken)
+            {
+                ObjectDisposedException.ThrowIf(_received, this);
+
+                _received = true;
+                _message.CopyTo(buffer);
+                return ValueTask.FromResult(new ValueWebSocketReceiveResult(_message.Length, WebSocketMessageType.Text, true));
+            }
+
+            public override Task<WebSocketReceiveResult> ReceiveAsync(ArraySegment<byte> buffer, CancellationToken cancellationToken)
+                => throw new NotImplementedException();
+
+            public override ValueTask SendAsync(ReadOnlyMemory<byte> buffer, WebSocketMessageType messageType, bool endOfMessage, CancellationToken cancellationToken)
+                => throw FailSend();
+
+            public override Task SendAsync(ArraySegment<byte> buffer, WebSocketMessageType messageType, bool endOfMessage, CancellationToken cancellationToken)
+                => throw FailSend();
+
+            private WebSocketException FailSend()
+            {
+                SendAttempts++;
+                return new WebSocketException(
+                    WebSocketError.InvalidState,
+                    "The WebSocket is in an invalid state ('Closed') for this operation. Valid states are: 'Open, CloseReceived'");
+            }
+        }
+
         internal sealed class BufferSegment : ReadOnlySequenceSegment<byte>
         {
             public BufferSegment(Memory<byte> memory)
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