freebsd-skq/share/man/man4/ng_pipe.4

.\" Copyright (c) 2019 Lutz Donnerhacke
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.Dd October 17, 2019
.Dt NG_PIPE 4
.Os
.Sh NAME
.Nm ng_pipe
.Nd Traffic manipulating netgraph node type
.Sh SYNOPSIS
.In netgraph/ng_pipe.h
.Sh DESCRIPTION
The
.Nm pipe
node type manipulates traffic by emulating bandwidth and delay, as well as
random packet losses.
.Sh HOOKS
This node type supports the following hooks:
.Bl -tag -width ".Va upper"
.It Va upper
Hook leading to upper layer protocols.
.It Va lower
Hook leading to lower layer protocols.
.El
.Pp
Traffic flowing from
.Va upper
to
.Va lower
is considered
.Sy downstream
traffic.
Traffic flowing from
.Va lower
to
.Va upper
is considered
.Sy upstream
traffic.
.Sh MODE OF OPERATION
Data received on a hook - both in upstream and downstream direction -
is put into an inbound queue.
If inbound queue is full, discard one frame
depending on dropping policy (from the head or from the tail of the
queue).
.Pp
There are three mutually exclusive modes for the input queue:
.Bl -tag -width foo
.It Dv "First In First Out (FIFO)"
A single queue holds packets in chronological order.
.It Dv Weighted fair queuing (WFQ)
There are multiple queues for different traffic flows (based on IPv4
IPs).
The longest queue is truncated if necessary.
This approach
assumes that the stalling flow is the flow with the most packets currently
on hold.
.It Dv Deficit Round Robin (DRR)
This mode is similar to WFQ, but packets are not taken out in
strict chronological order.
In principle oldest packets come first,
but not too many packets from the same flow.
.El
.Pp
It is possible to configure a duplication probability.
As the dice
decides, the currently active packet stays in the queue while a copy
of the packet is sent out.
Nothing prevents a packet from being
duplicated multiple times.
.Pp
Packets are dropped with an increasing probability depending on the
size of the packet, if a
.Va ber
(bit error rate) is configured.
.Pp
Surviving packets are delayed by the time the packet would need to
travel through a link of the configured bandwidth.
If this outbound
queue is full, the packet is dropped.
.Sh CONTROL MESSAGES
This node type supports the generic control messages and the following
specific messages.
.Bl -tag -width foo
.It Dv NGM_PIPE_SET_CFG Pq Ic setcfg
Set node configuration to the one specified in
.Vt "struct ng_pipe_cfg"
.Pp
Note: To set a value to zero, specify -1 instead.
This allows omitting configuration values, which should not be
modified.
.It Dv NGM_PIPE_GET_CFG Pq Ic getcfg
Return current node configuration as
.Vt "struct ng_pipe_cfg"
.Bd -literal
struct ng_pipe_cfg {
  u_int64_t  bandwidth;     /* bits per second */
  u_int64_t  delay;         /* additional delay, usec */
  u_int32_t  header_offset; /* offset of IP header in bytes */
  u_int32_t  overhead;      /* assumed L2 overhead in bytes */
  struct ng_pipe_hookcfg  downstream;
  struct ng_pipe_hookcfg  upstream;
};

/* Config structure for one hook */
struct ng_pipe_hookcfg {
  u_int64_t  bandwidth;       /* bits per second */
  u_int64_t  ber;             /* avg. interval between bit errors (1 / BER) */
  u_int32_t  qin_size_limit;  /* number of queue items */
  u_int32_t  qout_size_limit; /* number of queue items */
  u_int32_t  duplicate;       /* probability in % */
  u_int32_t  fifo;            /* 0 = off, 1 = on */
  u_int32_t  drr;             /* 0 = off, 1 = 2048 bytes, or x bytes */
  u_int32_t  wfq;             /* 0 = off, 1 = on */
  u_int32_t  droptail;        /* 0 = off, 1 = on */
  u_int32_t  drophead;        /* 0 = off, 1 = on */
};
.Ed
.It Dv NGM_PIPE_GET_STATS Pq Ic getstats
Return node statistics as
.Vt "struct ng_pipe_stats"
.Bd -literal
/* Statistics structure for one hook */
struct ng_pipe_hookstat {
  u_int64_t  fwd_octets;
  u_int64_t  fwd_frames;
  u_int64_t  in_disc_octets;
  u_int64_t  in_disc_frames;
  u_int64_t  out_disc_octets;
  u_int64_t  out_disc_frames;
};

/* Statistics structure returned by NGM_PIPE_GET_STATS */
struct ng_pipe_stats {
  struct ng_pipe_hookstat  downstream;
  struct ng_pipe_hookstat  upstream;
};
.Ed
.It Dv NGM_PIPE_CLR_STATS Pq Ic clrstats
Clear node statistics.
.It Dv NGM_PIPE_GETCLR_STATS Pq Ic getclrstats
Atomically return and clear node statistics.
.It Dv NGM_PIPE_GET_RUN Pq Ic getrun
Return node statistics as
.Vt "struct ng_pipe_run"
.Bd -literal
/* Runtime structure for one hook */
struct ng_pipe_hookrun {
  u_int32_t  fifo_queues;
  u_int32_t  qin_octets;
  u_int32_t  qin_frames;
  u_int32_t  qout_octets;
  u_int32_t  qout_frames;
};

/* Runtime structure returned by NGM_PIPE_GET_RUN */
struct ng_pipe_run {
  struct ng_pipe_hookrun  downstream;
  struct ng_pipe_hookrun  upstream;
};
.Ed
.El
.Sh SHUTDOWN
This node shuts down upon receipt of a
.Dv NGM_SHUTDOWN
control message, or when all hooks have been disconnected.
.Sh EXAMPLES
Limit outgoing data rate over fxp0 Ethernet interface to 20Mbps in
fifo mode and incoming to 50kbps in drr mode and 2% duplicate
probability.
.Bd -literal -offset indent
/usr/sbin/ngctl -f- <<-SEQ
  mkpeer fxp0: pipe lower lower
  name fxp0:lower fxp0_pipe
  connect fxp0: fxp0_pipe: upper upper
  msg fxp0_pipe: setcfg { downstream={ bandwidth=20000000 fifo=1 } }
  msg fxp0_pipe: setcfg { upstream={ bandwidth=500000 drr=1 duplicate=2 } }
SEQ
.Ed
.Sh SEE ALSO
.Xr netgraph 4 ,
.Xr ngctl 8
.Sh AUTHORS
.An Lutz Donnerhacke Aq Mt lutz@donnerhacke.de
.Pq man page
.Sh BUGS
Error handling for memory issues is missing.
If kernel memory cannot be allocated immediately, a kernel panic will
be triggered.
Same happens if an mbuf is fragmented within the transport headers.