man: Add a man page for the mirred action

Signed-off-by: Phil Sutter <phil@nwl.cc>

man/man8/tc-mirred.8

+.TH "Mirror/redirect action in tc" 8 "11 Jan 2015" "iproute2" "Linux"
+
+.SH NAME
+mirred - mirror/redirect action
+.SH SYNOPSIS
+.in +8
+.ti -8
+.BR tc " ... " "action mirred"
+.I DIRECTION ACTION
+.RB "[ " index
+.IR INDEX " ] "
+.BI dev " DEVICENAME"
+
+.ti -8
+.IR DIRECTION " := { "
+.BR ingress " | " egress " }"
+
+.ti -8
+.IR ACTION " := { "
+.BR mirror " | " redirect " }"
+.SH DESCRIPTION
+The
+.B mirred
+action allows to redirect or mirror packets to another network interface on the
+same system. It is typically used in combination with the
+.B ifb
+pseudo device to create a shrared instance where QoS happens, but serves well
+for debugging or monitoring purposes, too.
+.SH OPTIONS
+.TP
+.B ingress
+.TQ
+.B egress
+Specify the direction in which the packet shall appear on the destination
+interface. Currently only
+.B egress
+is implemented.
+.TP
+.B mirror
+.TQ
+.B redirect
+Define whether the packet should be copied
+.RB ( mirror )
+or moved
+.RB ( redirect )
+to the destination interface.
+.TP
+.BI index " INDEX"
+Assign a unique ID to this action instead of letting the kernel choose one
+automatically.
+.I INDEX
+is a 32bit unsigned integer greater than zero.
+.TP
+.BI dev " DEVICENAME"
+Specify the network interface to redirect or mirror to.
+.SH EXAMPLES
+Limit ingress bandwidth on eth0 to 1mbit/s, redirect exceeding traffic to lo for
+debugging purposes:
+
+.RS
+.EX
+# tc qdisc add dev eth0 handle ffff: ingress
+# tc filter add dev eth0 parent ffff: u32 \\
+	match u32 0 0 \\
+	action police rate 1mbit burst 100k conform-exceed pipe \\
+	action mirred egress redirect dev lo
+.EE
+.RE
+
+Use an
+.B ifb
+interface to send ingress traffic on eth0 through an instance of
+.BR sfq :
+
+.RS
+.EX
+# modprobe ifb
+# ip link set ifb0 up
+# tc qdisc add dev ifb0 root sfq
+# tc qdisc add dev eth0 handle ffff: ingress
+# tc filter add dev eth0 parent ffff: u32 \\
+	match u32 0 0 \\
+	action mirred egress redirect dev ifb0
+.EE
+.RE
+
+.SH SEE ALSO
+.BR tc (8),
+.BR tc-u32 (8)