network: fix ProxySocket receive edge cases

Routing recv() through RecvFrom made several old RecvFrom problems
reachable from the normal read path:

- A partial TCP read kept zero bytes in front of the unread data.
- A blocking read busy-waited with yield() and reported ETIMEDOUT.
- MSG_PEEK hit the flags == 0 assert.
- A UDP datagram larger than the buffer was dropped with EMSGSIZE.

Wait on a condition variable signalled when a packet arrives, and report
an expired wait as EAGAIN like an SO_RCVTIMEO timeout. Keep the existing
5s cap for sockets without a receive timeout. Allow MSG_PEEK. Truncate
oversized datagrams as BSD recv() does, and keep the unread tail of a
TCP packet for the next read.

Assisted-by: Claude Opus 5.5 (investigation and implementation)

1 files changed, 3 insertions, 1 deletions

diff --git a/src/core/internal_network/socket_proxy.h b/src/core/internal_network/socket_proxy.h
index caf5d1ee23..8343fcbae1 100644
--- a/src/core/internal_network/socket_proxy.h
+++ b/src/core/internal_network/socket_proxy.h
@@ -1,10 +1,11 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 // SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #pragma once
 
+#include <condition_variable>
 #include <mutex>
 #include <span>
 #include <vector>
@@ -92,6 +93,7 @@ private:
     Protocol protocol;
 
     std::mutex packets_mutex;
+    std::condition_variable packets_cv;
 };
 
 } // namespace Network