OVERVIEW
================================================================================

This folder contains the "vector boost" program source code.

"Vector boost" is a feature of G.hn that allows point-to-point channels to
reach its maximum capacity even when interferences from other point-to-point
channels are present.

"Vector boost" is made up of two software components:

  1. The "driver". This is executed in a PC directly connected to all "Domain
     Masters" (by means of an ethernet cable).
     The CPU load produced by the "driver" is quite low, and thus this PC does
     not need to be top-notch.

  2. The "engine". This is *typically* executed in a *different* PC (but it
     can be the same, if desired). The amount of CPU computation required by the
     "engine" is quite high and thus the PC should be as fast as possible.


TYPICAL SCENARIO
================================================================================

                  -----------
  User #1's house |EndPoint |--------------------------------------------
                  -----------                    -----------------------|
                                                 |   ------------------||
                  -----------                    |   |                |||
  User #2's house |EndPoint |---------------------   |                |||
                  -----------                        |                |||
                                                     |                |||
                                    -----------      |                |||
                    User #N's house |EndPoint |-------                |||
                                    -----------                       ||| G.hn
                                                                      |||
                                                                      |||
                                                                      |||
                                                                      |||
        "driver"                        Operator equipment            |||
         ------       -------   eth    --------------------           |||
         | PC |  eth  |     |~~~~~~~~~~| Domain master #N |------------||
         | #1 |~~~~~~~| HUB |~~~~~~~~~~| Domain master #2 |------------||
         |    |       |     |~~~~~~~~~~| Domain master #1 |-------------|
         ------       -------          --------------------
           .
           .
           .
           .
         ------
         | PC |
         | #2 |
         ------
        "engine"
         
NOTES:

  * PC #2 and #1 can be the same computer, but they typically aren't. In fact,
    PC #2 (where the "engine" runs) does not even need to be in the same
    operator facilities where PC #1 is located: it could be some remote "cloud"
    server at the other side of the planet.

  * The G.hn interferences come from the fact that client connections typically
    travel together, inside one same "big" plastic tube, as soon as they leave
    the user's own house, until the operator station.


HOW IT WORKS
================================================================================

The "driver" talks to the Domain Masters and receives data regarding the G.hn
network status (interferences, throughput requirements for each domain,
etc...).

All this data is sent to the "engine" which then processes it and comes up with
an "optimal" transmission strategy for each instant. This strategy is finally
sent back to the "driver" which, in turn, distrubutes it among all Domain
Masters.


BUILDING THE SOFTWARE
================================================================================

Just type "make" and both the "driver" and "engine" binaries will be generated.

  NOTE: You can set the "COMPILER" environment variable before calling "make"
        in order to cross-compile the binaries for different target
        architectures (check inside the "Makefile" file for more info.

Then execute this:

  # INSTALL_PATH=<some_folder> make install

... and <some_folder> will be filled with the final binaries and configuration
files needed to run them


EXECUTING THE SOFTWARE
================================================================================

"driver":

  1. Copy the "vector_boost_driver" binary and its configuration file to PC #1.
  2. Open its configuration file and customize it according to your needs.
  3. Run it like this: ./vector_boost_driver

"engine":

  1. Copy the "vector_boost_engine" binary and its configuration file to PC #2.
  2. Open its configuration file and customize it according to your needs.
  3. Run it like this: ./vector_boost_engine

Note that both binaries can be controlled by means of a "console" accessible on
ports 50000 and 60000 respectively.

You can, for instance, to keep an eye on what's going on, execute these two
commands from two different terminals:

  # watch -n1 "echo report | wc -C <PC_1_ip> 50000"
  # watch -n1 "echo report | wc -C <PC_2_ip> 60000"

TIP: There is a "nice" way to execute the "engine" binary and be able to
     display all log information *and* status on the same screen at the same
     time is this:

       # multitail -l ./vector_boost_engine -r 1 -wh 15 -l "echo -ne '\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n'; echo report | nc -C localhost 60000"


CONFIGURATION PARAMETERS
================================================================================

The "driver", when executed, reads configuration parameters from
"vb_driver.ini".

The "engine" does the same with "vb_engine.ini".

This is what each of the parameters on each of those files does:

  <<TODO!!>>


DEBUGGING
================================================================================

"driver":

  1. On PC #1, run "vector_boost_engine" like this:

       # gdbserver host:20000 ./vector_boost_driver

  2. On the PC where the source code is located, run this:

       # gdb -tui vectorBoost/driver/bin/vector_boost_driver

  3. Inside the gdb console, type this:

       > tar rem <PC_1_ip>:20000
       
  4. You can now set your breakpoints and start executing the binary:

       > break main
       > continue

  NOTES:

    * If the PC where you compile the source code does not have direct
      connectivity to PC #1, you can always use an SSH tunnel. It works like
      this:

        1. Imagine the PC where you compile cannot access PC #1, but it can
           access "PC #X", and "PC #X" can access PC #1.

        2. From the PC where you compile type this:

             # ssh root@<PC_X_ip> -L6969:<PC_1_ip>:20000

        3. Now, from the PC where you compile, open a new terminal and run
           gdb. Then connect to localhost:6969:

             > tar rem localhost:6969

    * In orther to avoid having to type "tar rem ..." on the gdb console each
      time, you can do this:

        1. Create a connect_driver.txt file containing this line:

             tar rem <ip>:<port>

           NOTE: Remember that <ip>:<port> can be either <PC_1_ip>:20000 or
                 localhost:6969, depending on whether you are using and ssh
                 tunnel or not.

        2. Execute gdb like this:

             # gdb -tui vectorBoost/driver/bin/vector_boost_driver -x connect_driver.txt

    * If you are compiling the binary with SHARED LIBRARIES (ie. you are not
      using "-static"), you need to tell gdb *where* (on the remote system)
      shared libraries are located.
      If the path is the same as the one in the system where you compiled the
      binaries (ex: "/usr/lib"), you don't need to do anything. However, if it
      is different (ex: "/lib") you need to tell this to gdb using this command:

        > set solib-search-path /lib/

    * The driver makes use of signals (in particular, there is a function
      that calls "pthread_kill(...,SIGCONT)" to stop a particular process).
      By default, gdb will *capture* this signal and stop the program execution
      every time.
      In order to avoid this, you have to tell gdb to "ignore" this signal and
      send it to the program in the same way it happens when gdb is not running.
      In order to do this, you need to execute these two commands in the gdb
      console, before anything else:

        > handle SIGCONT pass
        > handle SIGCONT nostop

    * In addition to what we have just said regarding SIGCONT, the driver also
      blocks other signals.
      Because of the way this blocking is implemented, pressing "CTRL+c" while
      in gdb will not stop the program execution. You need to manually send
      the "TERM" signal from another console the program:

        # kill -TERM <pid>

      For more info red the *.h documentation of function "VbBlockSignals()"
         
"engine":

  1. Follow the same steps as with "engine", only remember that this time:

     a) You are executing the "vector_boost_engine" binary

     b) You are connecting to PC #2

     c) In case you want to debug the "driver" and the "engine" at the same
        time, use different ports for gdbservers (ex: 20000 and 20001) and/or
        the ssh tunnels (ex: 6969 and 7070)


STATIC ANALYSIS
================================================================================

Static analysis of the source code can be performed by executing this:

  # make static-analysis

This command will use "clang"'s built in static analysis tool ("scan-build") to
generate an HTML report with a fabulous level of detail.

In order for this to work you need to have the latest "clang" compiler and
additional tools installed.


RUNTIME ANALYSIS (VALGRIND)
================================================================================

This software has also been analyzed in runtine with "valgrind".

In order to run the vector boost tools with valgrind, the version 
of the libc in the compiling machine has to be the same as in the
machine you execute the programs. They have to be compiled without the
-static flag and is recomended to use -O0 and -g flags. To compile, use:

 # make COMPILER="x86" VECTORBOOST_VALGRIND=yes all

This is how you run valgrind:

  1. Memory analysis:
  
     1.1 Instead of directly running "vector_boost_driver" or
         "vector_boost_driver", use the valgring wrapper, like this:

           # valgrind --time-stamp=yes --gen-suppressions=yes --tool=memcheck --read-var-info=yes --track-origins=yes ./vector_boost_driver
           # valgrind --time-stamp=yes --gen-suppressions=yes --tool=memcheck --read-var-info=yes --track-origins=yes ./vector_boost_engine

     1.2 Then let them run for a while and check the errors shown. After each
         error you can print the suppression block or ignore it, pressing 'y'
         or 'n'. You can dump the output logs to a log file and analyze it after
         finishing the execution by adding the option --log-file=<filename>. If 
         you use a log file, set gen-suppressions=all

     1.3 If you want to ignore a specific type of error, do this:

         1.3.1 Copy the "supression block" information (from the particular
               error you want to ignore) from the "val_xxxx.txt" output file.

         1.3.2 Place that "block" inside a file called "ignore.txt"

         1.3.3 Re-run "valgrind" adding the following option:

                 --suppressions=ignore.txt

         1.3.4 More info, here:
         
                 http://valgrind.org/docs/manual/manual-core.html#manual-core.suppress

  2. Thread analysis:
  
     2.1. Before executing the thread analysys you should have cleaned as many
          "memory" problems (from the previous step) as possible.

     2.2 Once again, use the valgrind wrapper, but this time with the following
         options:

           # valgrind --time-stamp=yes --gen-suppressions=yes --read-var-info=yes --tool=helgrind ./vector_boost_driver
           # valgrind --time-stamp=yes --gen-suppressions=yes --read-var-info=yes --tool=helgrind ./vector_boost_engine

     2.3 In addition, after you have also cleaned all these thread errors, try
         re-running the tool like this (it will detect even more thread
         problems):

           # valgrind --time-stamp=yes --gen-suppressions=yes --tool=drd ./vector_boost_driver
           # valgrind --time-stamp=yes --gen-suppressions=yes --tool=drd ./vector_boost_engine

     2.4 In both cases, you can (once again) use the "--suppressions=" option
         to ignore repetitive (and unsolvable) problems.

     Note: All registered suppressions are stored inside driver or engine/debug/helgrind.txt.
     Most of them correspond to a read-write possible data race condition caused when one thread
     reads one varible and other thread writes it without a mutex. The use of a mutex here will
     not have any effect, since the access to this variable is atomic. 
     
RUNTIME ANALYSIS (ELECTRIC FENCE)
================================================================================

As extracted from manpage: Electric Fence is a tool which helps you detect
two common programming bugs: software that overruns the boundaries  of  a  malloc()  
memory  allocation,  and software  that  touches  a  memory allocation that has been 
released by free(). Unlike other malloc() debuggers,  Electric  Fence  will  detect
read  accesses  as  well  as  writes,  and  it  will pinpoint the exact instruction 
that causes an error.

To debug VectorBoost with Electric Fence tool, follow this steps:
  1. Compile VectorBoost using dynamic linking, as in valgrind section:
        # make COMPILER="x86" VECTORBOOST_VALGRIND=yes all
        
  2. Install Electric Fence tool in the same PC running VectorBoost, for instance, in Ubuntu:
        # aptitude install electric-fence
        
  3. Run VectorBoost using  Electric Fence library and GDB:
        # LD_PRELOAD=/usr/lib/libefence.so gdb ./vector_boost_engine
        or
        # LD_PRELOAD=/usr/lib/libefence.so gdb ./vector_boost_driver
        
  4. Insert a breakpoint in EF_Abort function to capture also "malloc's" with a size of 0:
        (gdb) b EF_Abort
        
  5. Run the program: 
        (gdb) r
  
  6. The debugger will stop in each memory overrun or malloc with a 0-size. 
        
  7. By default Electric Fence will detect memory overruns or accesses to free memory.   
  Once all memory overruns have been fixed, it is advisable to repeat this process setting
  EF_PROTECT_BELOW environment variable to 1. This allows Electric Fence to detect 
  underruns (if they occur).
        
        
ISSUE TRACKING
================================================================================

Please use the issues mechanism to track todos, bugs, feature requests