man 8 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  re-
       ferred  to  as Switch Port Analyzer (SPAN) and is commonly used to ana-
       lyze 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. Redi-
       recting  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 mir-
       rored 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 exam-
       ination 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  special-
       ized  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)