Investigate interop multiplexing test failed for server

[nhorman]

The quic-interop-runner multiplexing test failed. The logs indicate that, while all files were served by the server and downloaded by the client, there was a file size mismatch (32 bytes on the server vs 0 bytes on the client) on one of the sent files.

Checking the logs it appears the short file (which is randomly generated by the test harness) was named bsyynqphdv, and the request was sent, but the server interpreted the name as bsyynqp (i.e. truncated), and as such could not find the file.

Investigation needed to determine why the file was truncated and fix it. Likely a server application issue

[Sashan]

failure in interop, I think we should fix the code to pass this test.

[nhorman]

problem appears to be a server side issue. Based on captured log data:

client  | Client creates stream id 2416 for request /downloads/sjmfldilrd   <= client sends full file name
...
server  | Server queues new stream 2416
...
server  | Reading from stream id 2416
...
server  | Request is GET /sjmfldi   <= Server reads truncated file name

it appears that the server is only reading part of the request here. That appears to occur when, according to the related tcpdump:

That the server assume such short http requests will always be satisfied in a single read, but when the data is split across stream packets, thats not the case. We need to handle short reads and ensure that we get all the data in the request