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
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 out‐
put 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
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)
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