flow

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 ] [ ac-
               tion 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 de-
              faults 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 us-
              ing  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 ad-
              dress  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)