Manual: tc-mirred

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.   Redi‐
       recting 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)