Mirror/redirect action in tc(8)	     Linux     Mirror/redirect action in tc(8)



NAME
       mirred - mirror/redirect action

SYNOPSIS
       tc ... action mirred DIRECTION ACTION [ index INDEX ]  TARGET

       DIRECTION := {  ingress | egress }

       TARGET := { DEV | BLOCK }

       DEV :=	dev DEVICENAME

       BLOCK :=	  blockid BLOCKID

       ACTION := {  mirror | redirect }

DESCRIPTION
       The mirred action allows packet mirroring (copying) or redirecting
       (stealing) the packet it receives. Mirroring is what is sometimes
       referred to as Switch Port Analyzer (SPAN) and is commonly used to
       analyze and/or debug flows.  When mirroring to a tc block, the packet
       will be mirrored to all the ports in the block with exception of the
       port where the packet ingressed, if that port is part of the tc block.
       Redirecting is similar to mirroring except that the behaviour is to
       mirror to the first N - 1 ports in the block and redirect to the last
       one (note that the port in which the packet arrived is not going to be
       mirrored or redirected to).

OPTIONS
       ingress
       egress Specify the direction in which the packet shall appear on the
	      destination interface.

       mirror
       redirect
	      Define whether the packet should be copied (mirror) or moved
	      (redirect) to the destination interface or block.

       index INDEX
	      Assign a unique ID to this action instead of letting the kernel
	      choose one automatically.	 INDEX is a 32bit unsigned integer
	      greater than zero.

       dev DEVICENAME
	      Specify the network interface to redirect or mirror to.

       blockid BLOCKID
	      Specify the tc block to redirect or mirror to.

EXAMPLES
       Limit ingress bandwidth on eth0 to 1mbit/s, redirect exceeding traffic
       to lo for debugging purposes:

	      # tc qdisc add dev eth0 handle ffff: clsact
	      # tc filter add dev eth0 ingress u32 \
		   match u32 0 0 \
		   action police rate 1mbit burst 100k conform-exceed pipe \
		   action mirred egress redirect dev lo

       Mirror all incoming ICMP packets on eth0 to a dummy interface for
       examination with e.g. tcpdump:

	      # ip link add dummy0 type dummy
	      # ip link set dummy0 up
	      # tc qdisc add dev eth0 handle ffff: clsact
	      # tc filter add dev eth0 ingress protocol ip \
		   u32 match ip protocol 1 0xff \
		   action mirred egress mirror dev dummy0

       Using an ifb interface, it is possible to send ingress traffic through
       an instance of sfq:

	      # modprobe ifb
	      # ip link set ifb0 up
	      # tc qdisc add dev ifb0 root sfq
	      # tc qdisc add dev eth0 handle ffff: clsact
	      # tc filter add dev eth0 ingress u32 \
		   match u32 0 0 \
		   action mirred egress redirect dev ifb0


LIMITATIONS
       The kernel restricts nesting to four levels to avoid the chance of
       nesting loops.

       Do not redirect for one IFB device to another.  IFB is a very
       specialized case of packet redirecting device.  Redirecting from
       ifbX->ifbY will cause all packets to be dropped.


SEE ALSO
       tc(8), tc-u32(8)

iproute2			  11 Jan 2015  Mirror/redirect action in tc(8)