[lwip-devel] [bug #38219] Assert on TCP netconn_write with sndtimeout set

[Marco Jakobs]

URL:
  <http://savannah.nongnu.org/bugs/?38219>

                 Summary: Assert on TCP netconn_write with sndtimeout set
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: marcoj
            Submitted on: Fr 01 Feb 2013 12:13:29 GMT
                Category: sockets/netconn
                Severity: 3 - Normal
              Item Group: Crash Error
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: 
            lwIP version: 1.4.1

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Details:

The sndtimeout of a nonblocking TCP connection (incoming) is set to 10ms.

An application sends a large number of packets on this TCP connection which is
using the internet, so ACK packets will need some time to return. So the
outgoing TCP packets will fill up the buffer until no space is left.

At this point the next netconn_write will not be able to write its data within
the set timeout of 10ms.

Expecting the netconn_write returning with an error (ERR_INPROGRESS),
unfortunately i'll get an LWIP-assert in this scenario:

ASSERT: C:/Projekte/HCS-CPU2/Libraries/lwIP/src/api/api_msg.c:1357:already
writing or closing

which points into the "do_write" function in api_msg.c

Additional info: Setting the timeout to 5000ms will make a short pause
(blocking) at the same place where 10ms produces the assert, and then continue
as soon as a buffer gets freed. This is just to prove that the assert is a
result of the sndtimeout running off.




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