1.\" Copyright (c) 2008 George V. Neville-Neil
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25.\" $FreeBSD$
26.\"
27.Dd December 23, 2008
28.Dt ETHER_REFLECT 1
29.Os
30.Sh NAME
31.Nm ether_reflect
32.Nd "reflect ethernet packets"
33.Sh SYNOPSIS
34.Nm
35.Op Fl a Ar ethernet address
36.Op Fl e Ar ethertype
37.Op Fl i Ar interface
38.Op Fl t Ar timeout
39.Op Fl p
40.Op Fl d
41.Sh DESCRIPTION
42The
43.Nm
44command implements a simple ethernet packet reflector using the
45.Xr pcap 3
46library and
47.Xr bpf 4 ,
48the Berkeley Packet Filter.
49The program is useful primarily to test the low level round trip time
50of packets through an Ethernet interface and/or a switch.
51Network protocols, such as IP, and the network stack in general are never
52invoked, only the device driver that implements the particular interface
53is executed.
54As the
55.Nm
56command uses the
57.Xr bpf 4
58device the user must have root privileges to execute this program.
59.Pp
60The options are as follows:
61.Bl -tag -width ".Fl d Ar argument"
62.It Fl a Ar address
63Instead of reversing the ethernet destination and source addresses
64supply a different destination ethernet address for each packet
65received.
66.It Fl e Ar ether type
67Use a different ethertype than the default, 0x8822, which is the IEEE
68ether type for driver testing.
69.It Fl i Ar interface
70Network interface, which can be found with ifconfig(1).
71.It Fl t Ar timeout
72The time, in milliseconds, to wait for a packet.
73Lower times decrease latency at the cost of CPU.
74.It Fl p
75Set the device into promiscuous mode before testing.
76This is not usually necessary.
77.It Fl d
78Debug output.
79Print various small pieces of debug information.
80.El
81.Sh EXAMPLES
82The following is an example of a typical usage
83of the
84.Nm
85command:
86.Pp
87.Dl "ether_reflect -i em0 -t 1"
88.Pp
89Reflect all test packets, those with an ether type of 0x8822, which
90are seen on ineterface em0.
91The timeout is 1 millisecond.
92.Pp
93.Dl "ether_reflect -i em0 -a 00:00:00:aa:bb:cc -t 1"
94.Pp
95Rewrite the destination address in each packet to 00:00:00:aa:bb:cc
96before reflecting the packet.
97.Sh SEE ALSO
98.Xr tcpdump 1 ,
99.Xr bpf 4 ,
100.Xr pcap 3 ,
101.Xr ifconfig 8
102.Sh HISTORY
103The
104.Nm
105program first appeared in
106.Fx 8.0 .
107.Sh AUTHORS
108This
109manual page was written by
110.An George V. Neville-Neil Aq Mt gnn@FreeBSD.org .
111.Sh BUGS
112Should be reported to the author or to
113.Aq Mt net@FreeBSD.org .
114