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

       flow - flow based traffic control filter

       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 }

       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.

       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 omit‐
              ted, 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 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 op‐
              eration, NUM may be much more complex: It may be prefixed by a minus ('-') sign to cause subtraction instead of addi‐
              tion and for keys of src, dst, nfct-src and nfct-dst it may be given in IP address notation. See below for an  illus‐
              trating 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.

       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 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.

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

              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.

              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.

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

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

              Use the packet's vlan ID as key.

       rxhash Use the flow hash as key.

       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 to classids 1-256:

              tc filter add ... flow map \
                   key dst addend - 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

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

iproute2                                                    20 Oct 2015                                        Flow filter in tc(8)