(1)    if (csk->lastack < ch->ack && ch->ack <= csk->nxtsnd){
      what if lastack = 254 and nxtsnd = 4 and ack = 2????

(2)  the call to drive_tx is commented out... hopefully you know that.

(3)  usable_win = csk->win - ((csk->nxtsnd - csk->lastack) % sequence_space(csk));
      are you real sure this works in the presence of sequence number wrap????


   737           case CPT_ACK:
   738               spin_lock_irqsave(&csk->cop_txlock, lock_flags);
   739               if (csk->lastack < ch->ack && ch->ack <= csk->nxtsnd){
   740                   csk->lastack = ch->ack;
   741                   csk->win = ch->win;
   742                   spin_unlock_irqrestore(&csk->cop_txlock, lock_flags);
   743                   //cop_drive_tx(sk);
   744                   #if COP_FCD_DEBUG
   745                   printk(KERN_ALERT "last ack received %x and RECEIVED WINDOW SIZE %x\n",
   746                   #endif
   747               }
   748               else
   749                   spin_unlock_irqrestore(&csk->cop_txlock, lock_flags);
   750               kfree_skb(skb)

(4)   This section here needs to be a single locked section!!   If your front
end gets preempted after testing qlen but before dequeuing evil beyond
belief can ensue

(5) If line 300 EVER executes,  it is PROOF that something has gone
HORRIBLY WRONG --- It is a SUPREMELY BAD idea to silently
ignore such situations.... Much better to printk then while (1);

   292     spin_lock_irqsave(&csk->cop_txlock,flags);
   293     usable_win = csk->win - ((csk->nxtsnd - csk->lastack) % sequence_space(csk));
   294     qlen = sk->sk_write_queue.qlen;
   295     spin_unlock_irqrestore(&csk->cop_txlock,flags);
   296
   297     while(usable_win && qlen){
   298         skb = skb_dequeue(&sk->sk_write_queue);
   299         if (!skb){
   300             err = -1;
   301             break;
   302         }
   303         ch = skb->h.raw;
   304
   305         spin_lock_irqsave(&csk->cop_txlock,flags);
   306         ch->seq = ++csk->nxtsnd;
   307         if(csk->state == CPS_UAD)
   308             csk->lastack++;
   309         spin_unlock_irqrestore(&csk->cop_txlock,flags);