[lwip-devel] [bug #35015] Lost segments over wireless access point

[Brad Benjamin]

Follow-up Comment #3, bug #35015 (project lwip):

Sorry this took so long but I got side tracked to other matters. Anyway, while
investigating further I've made some tests that may help reveal what may be
going on here. I'll explain my changes and observations and then I'll enable
logging as you advised below and report the results in a follow-on comment
later.

It seems that if the protocol stack can transport segments on the wire faster
than my web server can generate them everything works fine (files for web
content reside on a microSD card connected through an 18MHz SPI interface and
the network is running at 100Mb). However, as soon as I attempt to browse via
an access point hop over WiFi I see the lost segment issue which is shown in
the PCAP file attached to original post below. Once the segment is lost, the
stack never recovers and frequently crashes to a hardfault on Cortex-M3.
Analyzing the crash reveals that there are buffer overlaps (not having trace
this has proven very difficult to back track).

Now here's the really interesting part: if I insert a thread sleep (10ms) just
after each call to netconn_write, it works. Page loads are very slow,
obviously, but the overwrites and lost segments are not observed.

This is just a data point which seems relevant.

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