Hi everyone,
I'm using MCUXpresso 10.2.1 and a custom board based on MK65F2M0 chip.
I have a problem on using LwIP: it sometimes crash generating an assert,
because of some invalid parameter.
The workflow is:
* The board is configured with a main connection using a GPRS modem
and an optional second LAN connection
* Every about 15 seconds the board connects to a server and sends two
types of packets, one smaller and one a little bigger. The bigger one is
sended once every 3/4 times typically
* Most of the time the server closes the connection (if no operation
on the device is requested), but sometimes it can go ahead in the
session, exchanging some data (if an operation on the device is
requested). In this debug session the server closes the connection every
time
* The problem is that after a while (5 minutes mean, but sometimes
after 20 minutes), the board generates an assertion on releasing a
network buffer, because it seems that is trying to free a buffer already
freed
Here is a snippet of code:
int sock;
int opt;
struct sockaddr_in outerdata;
int rn;
outerdata.sin_addr.s_addr = htonl( address );
outerdata.sin_family = AF_INET;
outerdata.sin_port = htons( port );
sock = socket( AF_INET, SOCK_STREAM, 0 );
//set non blocking
opt = 1;
ioctl( sock, FIONBIO, &opt );
connect( sock, ( struct sockaddr * )&outerdata, sizeof( outerdata )))
//set blocking
opt = 0;
ioctl( sock, FIONBIO, &opt );
send( sock, &data, sizeof( data ), 0 );
struct timeval tv;
tv.tv_sec = 2; /* 2 Secs Timeout */
tv.tv_usec = 0;
setsockopt( sock, SOL_SOCKET, SO_RCVTIMEO, ( const void * )&tv,
sizeof( struct timeval ));
//total timeout: 10 s
for( i = 0; i < 5; i++ )
{
rn = recv( sock, ( void * )&rxdata, sizeof( rxdata ), 0 );
if(( errno == EAGAIN ) && ( rn < 0 ))
{
PRINTF( "WAIT SERVER\n" );
continue;
}
if( rn < 0 )
{
PRINTF( "ERRORE %d ON RECV\n", errno );
break;
}
if( rn == 0 )
{
PRINTF( "CONNECTION CLOSED\n" );
break;
}
goto rx_ok;
}
closesocket( sock );
return( rn );
rx_ok:;
//exchange data
...
The problem occurs only when the bigger packet is sent and the first
timeout occurred on the recv function (I can see the "WAIT SERVER"
message on the debug monitor only once), but it doesn't occurs all the
times these conditions are present.
The assertion occurs on the pbuf_free() function at the instruction
LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
The image below shows the Wireshark captured session of the smaller
packet:
[1]
The image below shows the Wireshark captured session of the bigger
packet:
[2]
The image below shows the Wireshark captured session of the error
condition; note that the TCP Retransmission packets are present because
the device is stopped on the breakpoint:
[3]
I enabled statistics on LwIP and all used resources are below the
limits.
How can I debug this situation?
This is another situation maybe caused by the same issue:
[4]
Something to notice in the memp_TCP_SEG variable: the stats struct shows
that no element is now used and the maximum number of elements ever used
from the application start is 3. The tab variable points to the linked
list of all free elements: having now no used elements, the linked list
should link all the elements (26), but as it can be seen, there is only
one element in the list.
How can it be generated?
Many thanks
Biafra
Links:
------
[1]
https://community.nxp.com/servlet/JiveServlet/showImage/2-1081486-244804/pastedImage_1.png
[2]
https://community.nxp.com/servlet/JiveServlet/showImage/2-1081486-244826/pastedImage_2.png
[3]
https://community.nxp.com/servlet/JiveServlet/showImage/2-1081486-244827/pastedImage_3.png
[4]
https://community.nxp.com/servlet/JiveServlet/showImage/2-1081862-244937/pastedImage_1.png_______________________________________________
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