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)