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