bug-report: tcp-full.cc

[Li Fan <lfan@cisco.com>]

Hi, 

The bug is found when we worked on our own customized 
version of NS-2. I checked out the newest release (ns-2.1b6)
and found the bug is there too. 

It is in ReassemblyQueue::add function, around line 2201
The code was:
                              // insert in the middle or end
                                n->next_ = p->next_;
                                p->next_ = n;
                                n->prev_ = p;
                                if (p == tail_)
                                        tail_ = n;

It is obvious that the double link is broken here. Because the 
p->next_->prev_ is still pointing to p, not n.  To fix, only
need to add two lines:

                                // insert in the middle or end
                                n->next_ = p->next_;
				if(p->next_)
					p->next_->prev_= n;
                                p->next_ = n;
                                n->prev_ = p;
                                if (p == tail_)
                                        tail_ = n;


The bug messed up the assembly queue when the holes in sequence
number is more than one at a certain time, though not common, it
 happens as congestion is heavy.  

For those who used version of NS-2 at our ftp site:
 ftp://ftp-eng.cisco.com/ftp/kmn-group/ns-2/, we will
 put the fix there too. 

Thanks.

Li