RE: [lwip-users] tcp_enqueue problem, using socket:

[Bill Auerbach]

Piero,

 

This occurs with a lot of calls to tcp_write with small pieces of data. If you called it with 15 bytes per call, you could have over 100 elements in the queue.  I think there are 2 possibilities.  Increase TCP_SND_QUEUELEN or before you call tcp_write, check pcb->snd_queuelen and call tcp_output if it’s at TCP_SND_QUEUELEN – 1.  This makes me wonder why tcp_enqueue doesn’t do this test and call tcp_output instead of exceeding the queue len causing an error.  Can’t tcp_enqueue prevent this?

 

Bill

 

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From: address@hidden [mailto:address@hidden On Behalf Of Piero 74
Sent: Tuesday, March 18, 2008 1:11 PM
To: Mailing list for lwIP users
Subject: [lwip-users] tcp_enqueue problem, using socket:

 

Hi.

i'm using socket on lwip 130rc1.

i have this problem:

after some send operation, in tcp_enqueue, here:

  /* If total number of pbufs on the unsent/unacked queues exceeds the
   * configured maximum, return an error */
  queuelen = pcb->snd_queuelen;
  /* check for configured max queuelen and possible overflow */
  if ((queuelen >= TCP_SND_QUEUELEN) || (queuelen > TCP_SNDQUEUELEN_OVERFLOW)) {
    LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 3, ("tcp_enqueue: too long queue %"U16_F" (max %"U16_F")\n", queuelen, TCP_SND_QUEUELEN));
    TCP_STATS_INC(tcp.memerr);                           
    pcb->flags |= TF_NAGLEMEMERR;
    return ERR_MEM;
  }

my code loop forever, in this piece of code, with queuelen = TCP_SND_QUEUELEN, without send any packet, incremeting err in tcp.memerr

i cannot recovery this situation?
my thread is blocked on send operation i suppose....


bye,
Piero