network: close each bsd fd once and drop unwanted or malformed room packets

Two threads closing the same fd both copied the descriptor and both called
Close(), so a host socket could be closed twice, and the second closesocket
could hit an unrelated socket that had reused the host fd. CloseImpl now
frees the slot under file_descriptors_mutex first and only that thread closes
the socket; the other gets EBADF.

OnProxyPacketReceived decompressed every room packet when any fd had a
socket, including native sockets and proxy sockets on other ports. Sockets
now report through AcceptsProxyPacket whether they want a packet, and only
those are collected, so an unwanted packet is not decompressed.

DecompressDataZSTD passed the frame's declared size straight to the vector
constructor, so a malformed or unsized frame from a room member threw on the
room thread. The new TryDecompressDataZSTD rejects invalid, unsized and
oversized frames, and bsd drops such packets with a warning.
DecompressDataZSTD now returns an empty vector for them instead of throwing.

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

1 files changed, 5 insertions, 0 deletions

diff --git a/src/core/internal_network/socket_proxy.h b/src/core/internal_network/socket_proxy.h
index 5d6e35693c..078baa7806 100644
--- a/src/core/internal_network/socket_proxy.h
+++ b/src/core/internal_network/socket_proxy.h
@@ -22,6 +22,8 @@ public:
     explicit ProxySocket() noexcept;
     ~ProxySocket() override;
 
+    bool AcceptsProxyPacket(const ProxyPacket& packet) override;
+
     void HandleProxyPacket(const ProxyPacket& packet) override;
 
     Errno Initialize(Domain domain, Type type, Protocol socket_protocol) override;
@@ -82,6 +84,9 @@ public:
     bool IsOpened() const override;
 
 private:
+    /// Expects packets_mutex to be held
+    bool MatchesPacket(const ProxyPacket& packet) const;
+
     bool broadcast = false;
     bool closed = false;
     u32 send_timeout = 0;