CNA-BUG-174: LocalNetworkGamer::ReceiveData(PacketReader&, NetworkGamer*&) always returns 0 instead of the packet size

CNA snapshot 009d40f5  ·  Known Issues › Current bugs  ·  source links pinned to 009d40f5

The PacketReader overload keeps FNA's never-updated length variable and returns 0 whether or not a packet was received, where XNA returns the number of bytes read.

Identifier

CNA-BUG-174

Category

Bug

Subsystem

Networking & gamer services

Status

Open

Verified against

CNA 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)

Severity

Low (a triage suggestion, not a project priority)

Evidence basis

Source-verified: read at TARGET, not executed

Tests touching this area

Yes: see Current tests

Affected contract

LocalNetworkGamer::ReceiveData(PacketReader&, NetworkGamer*&)

Expected behaviour

XNA 4.0's ReceiveData(PacketReader, out NetworkGamer) (decompiled) resizes the reader to the next packet and returns ReceiveData(data.ByteArray, 0, out sender), the received byte count; the byte-array overloads in CNA also return the count.

Actual behaviour at TARGET

LocalNetworkGamer.cpp declares uint32_t len = 0, never updates it and returns it. LocalNetworkGamer.hpp documents 'Always 0 when a packet was available; 0 when none was, too' as a preserved FNA quirk. LocalNetworkGamerTests.cpp's ReceiveDataIntoPacketReaderReturnsZero exercises only an empty queue (where 0 is also XNA's result), so no test pins the always-zero return for a received packet. Code that loops while (gamer.ReceiveData(reader, sender) > 0) never reads a packet. The reader-resize half of the same overload is CNA-BUG-171.

Source locations

• modules/net/src/Xna/LocalNetworkGamer.cpp — ReceiveData(PacketReader&, NetworkGamer*&): uint32_t len = 0 returned
• modules/net/include/Microsoft/Xna/Framework/Net/LocalNetworkGamer.hpp — documents the preserved zero return
• modules/net/tests/Microsoft/Xna/Framework/Net/LocalNetworkGamerTests.cpp — ReceiveDataIntoPacketReaderReturnsZero pins it

Evidence

Checked by reading at 009d40f5 against the decompiled XNA 4.0 LocalNetworkGamer.ReceiveData; not executed. CNA keeps the value deliberately for FNA parity; this entry applies CNA's rule that XNA wins where the two disagree.

Independent re-verification: Checked by reading at 009d40f5 against the decompiled XNA 4.0 LocalNetworkGamer.ReceiveData and CNA's own CLAUDE.md rule that XNA wins where FNA and XNA disagree; not executed. The named test calls the overload with nothing queued, so it never reaches the packet path.

Focused reproduction

No focused reproduction is known. Nothing has been invented here; the evidence above is what exists.

Current tests

LocalNetworkGamerTests.cpp asserts the zero return.

Regression test

Change the test to expect the packet size, and return it (together with the reader resize of CNA-BUG-171).

Blast radius

Games that use the return value of the PacketReader overload; most XNA samples test IsDataAvailable instead and are unaffected.

Workaround

Use IsDataAvailable and the reader's contents, or the byte-array overload.