From: 'Marcelo Ricardo Leitner' > Sent: 21 August 2020 21:47 ... > > 3) Defer the allocation until the stream is used. > > for outbound streams this could remove the extra buffer. > > This can be tricky. What should happen if it gets a packet on a stream > that it couldn't allocate, and then another on a stream that was > already allocated? Just a drop, it will retransmit and recover, and > then again.. While, OTOH, if the application requested such amount of > streams, it is likely going to use it. If not, that's an application > bug. You'd probably need to (effectively) drop the ethernet frame that contained the chunk. But the problem I see is that GFP flags are passed in. So there must me a path where the allocation can't sleep. Now allocating a couple of pages is fine but if the maximum is just over 300 for each of 'in' and 'out'. I can well imagine that is likely to fail. I suspect this happens because the remote system can (if my quick scan of the code is right) negotiate a much larger number on an active connection. I don't know what applications might be doing such things. But I can imagine someone will try to negotiate 64k-1 streams just because that is the maximum. And/or deciding to use stream 65535 for 'special' traffic. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
