Flow filter in tc(8)						       Linux						      Flow filter in tc(8)

NAME

       flow - flow based traffic control filter

SYNOPSIS

       Mapping mode:

	      tc filter ... flow map key KEY [ OPS ] [ OPTIONS ]

       Hashing mode:

	      tc filter ... flow hash keys KEY_LIST [ perturb secs ] [ OPTIONS ]

       OPS := [ OPS ] OP

       OPTIONS := [ divisor NUM ] [ baseclass ID ] [ match EMATCH_TREE ] [ action ACTION_SPEC ]

       KEY_LIST := [ KEY_LIST ] KEY

       OP := { or | and | xor | rshift | addend } NUM

       ID := X:Y

       KEY := { src | dst | proto | proto-src | proto-dst | iif | priority | mark | nfct | nfct-src | nfct-dst | nfct-proto-src | nfct-proto-dst |
	       rt-classid | sk-uid | sk-gid | vlan-tag | rxhash }

DESCRIPTION

       The flow classifier is meant to extend the SFQ hashing capabilities without hard-coding new hash functions. It  also  allows  deterministic
       mappings of keys to classes.

OPTIONS

       action ACTION_SPEC
	      Apply an action from the generic actions framework on matching packets.

       baseclass ID
	      An  offset  for  the  resulting  class  ID.   ID	may  be  root,	none  or  a  hexadecimal  class ID in the form [X:]Y. X must match
	      qdisc's/class's major handle (if omitted, the correct value is chosen automatically). If the whole baseclass is omitted, Y  defaults
	      to 1.

       divisor NUM
	      Number of buckets to use for sorting into. Keys are calculated modulo NUM.

       hash keys KEY-LIST
	      Perform a jhash2 operation over the keys in KEY-LIST, the result (modulo the divisor if given) is taken as class ID, optionally off-
	      set by the value of baseclass.  It is possible to specify an interval (in seconds) after which jhash2's entropy source is  recreated
	      using the perturb parameter.

       map key KEY
	      Packet  data identified by KEY is translated into class IDs to push the packet into. The value may be mangled by OPS before using it
	      for the mapping. They are applied in the order listed here:

	      and NUM
		  Perform bitwise AND operation with numeric value NUM.

	      or NUM
		  Perform bitwise OR operation with numeric value NUM.

	      xor NUM
		  Perform bitwise XOR operation with numeric value NUM.

	      rshift NUM
		  Shift the value of KEY to the right by NUM bits.

	      addend NUM
		  Add NUM to the value of KEY.

	      For the or, and, xor and rshift operations, NUM is assumed to be an unsigned, 32bit integer value. For the addend operation, NUM may
	      be  much	more  complex: It may be prefixed by a minus ('-') sign to cause subtraction instead of addition and for keys of src, dst,
	      nfct-src and nfct-dst it may be given in IP address notation. See below for an illustrating example.

       match EMATCH_TREE
	      Match packets using the extended match infrastructure. See tc-ematch(8)  for  a  detailed  description  of  the  allowed	syntax	in
	      EMATCH_TREE.

KEYS

       In  mapping  mode,  a  single key is used (after optional permutation) to build a class ID. The resulting ID is deducible in most cases. In
       hashing more, a number of keys may be specified which are then hashed and the output used as class ID.  This ID is not deducible in before-
       hand, and may even change over time for a given flow if a perturb interval has been given.

       The range of class IDs can be limited by the divisor option, which is used for a modulus.

       src, dst
	      Use  source  or destination address as key. In case of IPv4 and TIPC, this is the actual address value. For IPv6, the 128bit address
	      is folded into a 32bit value by XOR'ing the four 32bit words. In all other cases, the kernel-internal socket address is used  (after
	      folding into 32bits on 64bit systems).

       proto  Use the layer four protocol number as key.

       proto-src
	      Use the layer four source port as key. If not available, the kernel-internal socket address is used instead.

       proto-dst
	      Use the layer four destination port as key. If not available, the associated kernel-internal dst_entry address is used after XOR'ing
	      with the packet's layer three protocol number.

       iif    Use the incoming interface index as key.

       priority
	      Use the packet's priority as key. Usually this is the IP header's DSCP/ECN value.

       mark   Use the netfilter fwmark as key.

       nfct   Use the associated conntrack entry address as key.

       nfct-src, nfct-dst, nfct-proto-src, nfct-proto-dst
	      These are conntrack-aware variants of src, dst, proto-src and proto-dst.	In case of NAT, these are basically  the  packet  header's
	      values before NAT was applied.

       rt-classid
	      Use the packet's destination routing table entry's realm as key.

       sk-uid
       sk-gid For locally generated packets, use the user or group ID the originating socket belongs to as key.

       vlan-tag
	      Use the packet's vlan ID as key.

       rxhash Use the flow hash as key.

EXAMPLES

       Classic SFQ hash:

	      tc filter add ... flow hash 
		   keys src,dst,proto,proto-src,proto-dst divisor 1024

       Classic SFQ hash, but using information from conntrack to work properly in combination with NAT:

	      tc filter add ... flow hash 
		   keys nfct-src,nfct-dst,proto,nfct-proto-src,nfct-proto-dst 
		   divisor 1024

       Map destination IPs of 192.168.0.0/24 to classids 1-256:

	      tc filter add ... flow map 
		   key dst addend -192.168.0.0 divisor 256

       Alternative to the above:

	      tc filter add ... flow map 
		   key dst and 0xff

       The same, but in reverse order:

	      tc filter add ... flow map 
		   key dst and 0xff xor 0xff

SEE ALSO

       tc(8), tc-ematch(8), tc-sfq(8)

iproute2							    20 Oct 2015 					      Flow filter in tc(8)