[lwip-devel] [bug #23726] pbuf pool exhaustion on slow recv()

[Simon Goldschmidt]

Follow-up Comment #4, bug #23726 (project lwip):

re comment #3:
Jim, your ideas are interesting, but seem a little off-topic here, I'm
afraid.


re original post:

First, which kind of connection are you talking about, RAW/UDP (which are
handled the same way) or TCP?

I think this is already covered but must (of course) be achieved by the
programmer through lwipopts.h:

- For TCP, of course limit the receive window: you have to tweak the window
and the PBUF_POOL count to never run out of pbufs!
- For UDP/RAW: use SO_RCVBUF (it is already implemented!) and change the
default from INT_MAX (as it is now) to a reasonable, configurable default
(again, PBUF_POOL must be configured accordingly, keeping the number of
connections in mind)

Of course, this configuration (buf-size per connection * connection count vs.
PBUF_POOL size) is not easy and it would be better to have some kind of
handling here, but like Kieran, I think the current situation is acceptable.

The only reasonable change would be to introduce a second limitation (number
of pbufs) in addition to the already introduced TCP window size and
conn->recv_bufsize (which is used by SO_RCVBUF) and to change the default of
conn->recv_bufsize.

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