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. If X is omitted, it is
	      assumed to be zero.

       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
	      offset  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 hash-
       ing  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  beforehand,
       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 1-257:

	      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)