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       wirefilter - Wire packet filter for Virtual Distributed Ethernet



       [-f rcfile] [-l loss] [-l lostburst] [-d delay] [-D dup] [-b bandwidth]
       [-s  interface_speed]  [-c  channel_bufsize]  [-n   noise_factor]   [-m
       mtu_size]   [-M   mgmt   socket]  [-v  vde_plug1:vde_plug2]  [--daemon]
       [--pidfile pidfile_path] [--blink blink]  [--blinkid  blink_identifier]


       A  wirefilter  is  able  to  emulate  delays and packet loss on virtual
       wires.  e.g.:

       dpipe vde_plug /tmp/s1 = wirefilter -l 10 = vde_plug /tmp/s2

       creates a wire between  two  vde_switches  (with  sockets  /tmp/s1  and
       /tmp/s2  respectively).  This  cable  looses 10% of the packets in each

       The same cable can be created using:

       wirefilter -v /tmp/s1:/tmp/s2 -l 10


       -f rcfile
              use a startup configuration  file.  It  is  useful  for  complex
              defitions  such  as  those for the Markov mode (see below).  The
              startup configuration file has the same syntax of the management
              interface,  in  other word it is a script of management commands
              executed before the first packet is forwarded.

       -l loss
              percentage of loss as a floating point number. It is possible to
              specify  different  loss percentage for the two channels: LR20.5
              means 20.5% of packet flowing left to right are lost, RL10 means
              10% from right to left.

       -L lostburst
              when  this  is  not  zero, wirefilter uses the Gilbert model for
              bursty errors.  This is the mean length of lost  packet  bursts.
              (it  is  a  two state Markov chain: the probability to exit from
              the faulty state is 1/lostburst, the probability  to  enter  the
              faulty   state   is  loss/(lostburst-(1-loss)).  The  loss  rate
              converges to the value loss.

       -d delay
              Extra delay (in milliseconds). This delay is added to  the  real
              communication  delay.  Packets are temporarily stored and resent
              after the delay.  It is possible to specify different values for
              LR  and  RL  like  in  the  previous  option.  When the delay is
              specified as two numbers with a + in between, the first  is  the
              standard  delay  and the second is a random variation.  1000+500
              means that the delay can be randomly chosen between half  second
              and  1.5  seconds.  It is possible to add 'U' or 'N' at the end.
              1000+500U means  that  the  dealys  are  uniformly  distributed,
              1000+500N  means  that  the  delays  follow  a  Gaussian  normal
              distribution (more  than  98%  of  the  values  are  inside  the

       -D dup percentage  of  dup packet. It has the same syntax of -l. Do not
              use dup factor 100% because it means that each  packet  is  sent
              infinite times.

       -b bandwidth
              Channel bandwidth in Bytes/sec. It has the same syntax of -d. It
              is also possible to use suffixes K,M,G to abbreviate 2^10, 2^20,
              2^30.    128K   means   128KBytes/sec.   128+64K  means  64i  to
              196KBytes/sec.  Sender is not prevented  from  sending  packets,
              delivery is delayed to limit the bandwidth to the desired value.
              (Like a bottleneck along the path) U  and  N  after  the  values
              (e.g.  128+64KN)  set the statistic distribution to use (uniform
              or normal).

       -s speed
              Interface speed in Bytes/sec. It has  the  same  syntax  of  -b.
              Input is blocked for the tramission time of the packet, thus the
              sender is prevented from sending too fast.

       -c channel_bufsize
              Channel buffer size (in  Bytes):  maximum  size  of  the  packet
              queue. Exceeding packets are discarded.

       -n noise factor
              Number of bits damaged/one megabyte.

       -m mtu size
              Packets longer than mtu_size are discarded.

       -N     nofifo. with -N packets can be reordered.

       -M mgmt socket
              the  unix  socket  where  the parameters (loss percentage, delay
              etc) can be checked and changed runtime. unixterm(1) can be used
              as a remote terminal for wirefilter.

       -v vde_plug1:vde_plug2
              If  this  option is used, the two local vde_plugs (vde_plug1 and
              vde_plug2) will be connected each other instead of stdin/stdout,
              using   the  libvdeplug  libraries.  This  option  activates  an
              interactive management session on console (stdin/stdout).

       --mgmtmode mode
              this option sets the  access  mode  of  the  mgmt  socket.   The
              command  syntax  is  quite  simple.  help  provides  the list of
              commands.  It is possible to load a script file using  the  load
              management command.

              wirefilter becomes a daemon

       --pidfile pathnamefP
              wirefilter saves its pid into the  file.

       --blinkid name
              This  option  defines  the  id sent for each packet to the blink
              server (see the --blink option below).  The stardard  identifier
              for a wirefilter is the process pid.

       --blink socket
              wirefilter sends a log message to the specified PF_UNIX/DATAGRAM
              socket for each packet sent. Each  packet  has  the  format:  id
              direction length.  e.g:

                  6768 LR 44
                  6768 LR 44
                  6768 RL 100
                  6768 LR 100
                  6768 LR 44

Markov mode

       wirefilter  provides  also  a  more  complex  set of parameters using a
       Markov  chain  to  emulate  different  states  of  the  link  and   the
       tranistions  between  states.  Each  state  is  represented  by a node.
       Markov chain parameters can be set with management commands or rc files
       only.   In fact, due to the large number of parameters the command line
       would have been unreadable.

       markov-numnodes n
              defines the number of different states. All  the  parameters  of
              the  connection  can be defined node by node. Nodes are numbered
              starting from zero (to n-1).  e.g.:

                                                      delay 100+10N[4]
                                                      loss 10[2]

              these command define a delay of 90-110 ms (normal  distribution)
              for  the  node  number  4  and  a 10 loss for the node 2.  It is
              possible to resize the Markov chain at run-time.  New nodes  are
              unreachable and do not have any edge to other states (i.e.  each
              new node has a loopback  edge  to  the  node  itself  with  100%
              probability).   When reducing the number of nodes, the weight of
              the edges towards deleted nodes is added to the  loopback  edge.
              When  the  current  node  of  the  emulation  is deleted, node 0
              becomes the current node.  (The  emulation  always  starts  from
              node 0).

       markov-time ms
              time  period  (ms)  for  the  markov  chain computation. Each ms
              microseconds a random number generator decides which is the next
              state (default value=100ms).

       markov-name n,name
              assign a name to a node of the markov chain.

       markov-setnode n
              manually set the current node to the node n.

       setedge n1,n2,w
              define  an  edge between n1 and n2; w is the weight (probability
              percentage) of the edge.  The loopback  edge  (from  a  node  to
              itself)  is always computed as 100% minus the sum of the weights
              of outgoing edges.

       showedges [ n ]
              list the edges from node n (or from the current  node  when  the
              command has no parameters). Null weight edges are omitted.

              show the current Markov state.

       showinfo [ n ]
              show  status  and  information  on  state  (node)   n.   If  the
              parameter is omitted it shows the status and information on  the
              current state.

       markov-debug [ n ]
              set  the  debug level for the current management connection.  In
              the actual implementation when  n  is  greater  than  zero  each
              change of markov node causes the output of a debug trace.  Debug
              tracing get disabled when n is zero or the parameter is missing.


       Virtual Distributed Ethernet is not related in any way with
       ("Verband  der Elektrotechnik, Elektronik und Informationstechnik" i.e.
       the  German  "Association  for  Electrical,  Electronic  &  Information


       vde_switch(1), vdeq(1).  dpipe(1).  unixterm(1).


       VDE is a project by Renzo Davoli <>

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