Provided by: libnftables1_1.0.6-2_amd64 
NAME
libnftables-json - Supported JSON schema by libnftables
SYNOPSIS
{ "nftables": [ OBJECTS ] }
OBJECTS := LIST_OBJECTS | CMD_OBJECTS
LIST_OBJECTS := LIST_OBJECT [ , LIST_OBJECTS ]
CMD_OBJECTS := CMD_OBJECT [ , CMD_OBJECTS ]
CMD_OBJECT := { CMD: LIST_OBJECT } | METAINFO_OBJECT
CMD := "add" | "replace" | "create" | "insert" | "delete" | "list" | "reset" | "flush" |
"rename"
LIST_OBJECT := TABLE | CHAIN | RULE | SET | MAP | ELEMENT | FLOWTABLE | COUNTER | QUOTA |
CT_HELPER | LIMIT | METAINFO_OBJECT | CT_TIMEOUT | CT_EXPECTATION
DESCRIPTION
libnftables supports JSON formatted input and output. This is implemented as an
alternative frontend to the standard CLI syntax parser, therefore basic behaviour is
identical and, for (almost) any operation available in standard syntax, there should be an
equivalent one in JSON.
JSON input may be provided in a single string as parameter to nft_run_cmd_from_buffer() or
in a file identified by the filename parameter of the nft_run_cmd_from_filename()
function.
JSON output has to be enabled via the nft_ctx_output_set_json() function, turning library
standard output into JSON format. Error output remains unaffected.
GLOBAL STRUCTURE
In general, any JSON input or output is enclosed in an object with a single property named
nftables. Its value is an array containing commands (for input) or ruleset elements (for
output).
A command is an object with a single property whose name identifies the command. Its value
is a ruleset element - basically identical to output elements, apart from certain
properties which may be interpreted differently or are required when output generally
omits them.
METAINFO OBJECT
In output, the first object in an nftables array is a special one containing library
information. Its content is as follows:
{ "metainfo": {
"version": STRING,
"release_name": STRING,
"json_schema_version": NUMBER
}}
The values of version and release_name properties are equal to the package version and
release name as printed by nft -v. The value of the json_schema_version property is an
integer indicating the schema version.
If supplied in library input, the parser will verify the json_schema_version value to not
exceed the internally hardcoded one (to make sure the given schema is fully understood).
In future, a lower number than the internal one may activate compatibility mode to parse
outdated and incompatible JSON input.
COMMAND OBJECTS
The structure accepts an arbitrary amount of commands which are interpreted in order of
appearance. For instance, the following standard syntax input:
flush ruleset
add table inet mytable
add chain inet mytable mychain
add rule inet mytable mychain tcp dport 22 accept
translates into JSON as such:
{ "nftables": [
{ "flush": { "ruleset": null }},
{ "add": { "table": {
"family": "inet",
"name": "mytable"
}}},
{ "add": { "chain": {
"family": "inet",
"table": "mytable",
"name": "mychain"
}}},
{ "add": { "rule": {
"family": "inet",
"table": "mytable",
"chain": "mychain",
"expr": [
{ "match": {
"op": "==",
"left": { "payload": {
"protocol": "tcp",
"field": "dport"
}},
"right": 22
}},
{ "accept": null }
]
}}}
]}
ADD
{ "add": ADD_OBJECT }
ADD_OBJECT := TABLE | CHAIN | RULE | SET | MAP | ELEMENT |
FLOWTABLE | COUNTER | QUOTA | CT_HELPER | LIMIT |
CT_TIMEOUT | CT_EXPECTATION
Add a new ruleset element to the kernel.
REPLACE
{ "replace": RULE }
Replace a rule. In RULE, the handle property is mandatory and identifies the rule to be
replaced.
CREATE
{ "create": ADD_OBJECT }
Identical to add command, but returns an error if the object already exists.
INSERT
{ "insert": RULE }
This command is identical to add for rules, but instead of appending the rule to the chain
by default, it inserts at first position. If a handle or index property is given, the rule
is inserted before the rule identified by those properties.
DELETE
{ "delete": ADD_OBJECT }
Delete an object from the ruleset. Only the minimal number of properties required to
uniquely identify an object is generally needed in ADD_OBJECT. For most ruleset elements,
this is family and table plus either handle or name (except rules since they don’t have a
name).
LIST
{ "list": LIST_OBJECT }
LIST_OBJECT := TABLE | TABLES | CHAIN | CHAINS | SET | SETS |
MAP | MAPS | COUNTER | COUNTERS | QUOTA | QUOTAS |
CT_HELPER | CT_HELPERS | LIMIT | LIMITS | RULESET |
METER | METERS | FLOWTABLE | FLOWTABLES |
CT_TIMEOUT | CT_EXPECTATION
List ruleset elements. The plural forms are used to list all objects of that kind,
optionally filtered by family and for some, also table.
RESET
{ "reset": RESET_OBJECT }
RESET_OBJECT := COUNTER | COUNTERS | QUOTA | QUOTAS
Reset state in suitable objects, i.e. zero their internal counter.
FLUSH
{ "flush": FLUSH_OBJECT }
FLUSH_OBJECT := TABLE | CHAIN | SET | MAP | METER | RULESET
Empty contents in given object, e.g. remove all chains from given table or remove all
elements from given set.
RENAME
{ "rename": CHAIN }
Rename a chain. The new name is expected in a dedicated property named newname.
RULESET ELEMENTS
TABLE
{ "table": {
"family": STRING,
"name": STRING,
"handle": NUMBER
}}
This object describes a table.
family
The table’s family, e.g. "ip" or "ip6".
name
The table’s name.
handle
The table’s handle. In input, it is used only in delete command as alternative to
name.
CHAIN
{ "chain": {
"family": STRING,
"table": STRING,
"name": STRING,
"newname": STRING,
"handle": NUMBER,
"type": STRING,
"hook": STRING,
"prio": NUMBER,
"dev": STRING,
"policy": STRING
}}
This object describes a chain.
family
The table’s family.
table
The table’s name.
name
The chain’s name.
handle
The chain’s handle. In input, it is used only in delete command as alternative to
name.
newname
A new name for the chain, only relevant in the rename command.
The following properties are required for base chains:
type
The chain’s type.
hook
The chain’s hook.
prio
The chain’s priority.
dev
The chain’s bound interface (if in the netdev family).
policy
The chain’s policy.
RULE
{ "rule": {
"family": STRING,
"table": STRING,
"chain": STRING,
"expr": [ STATEMENTS ],
"handle": NUMBER,
"index": NUMBER,
"comment": STRING
}}
STATEMENTS := STATEMENT [, STATEMENTS ]
This object describes a rule. Basic building blocks of rules are statements. Each rule
consists of at least one.
family
The table’s family.
table
The table’s name.
chain
The chain’s name.
expr
An array of statements this rule consists of. In input, it is used in
add/insert/replace commands only.
handle
The rule’s handle. In delete/replace commands, it serves as an identifier of the rule
to delete/replace. In add/insert commands, it serves as an identifier of an existing
rule to append/prepend the rule to.
index
The rule’s position for add/insert commands. It is used as an alternative to handle
then.
comment
Optional rule comment.
SET / MAP
{ "set": {
"family": STRING,
"table": STRING,
"name": STRING,
"handle": NUMBER,
"type": SET_TYPE,
"policy": SET_POLICY,
"flags": [ SET_FLAG_LIST ],
"elem": SET_ELEMENTS,
"timeout": NUMBER,
"gc-interval": NUMBER,
"size": NUMBER
}}
{ "map": {
"family": STRING,
"table": STRING,
"name": STRING,
"handle": NUMBER,
"type": SET_TYPE,
"map": STRING,
"policy": SET_POLICY,
"flags": [ SET_FLAG_LIST ],
"elem": SET_ELEMENTS,
"timeout": NUMBER,
"gc-interval": NUMBER,
"size": NUMBER
}}
SET_TYPE := STRING | [ SET_TYPE_LIST ]
SET_TYPE_LIST := STRING [, SET_TYPE_LIST ]
SET_POLICY := "performance" | "memory"
SET_FLAG_LIST := SET_FLAG [, SET_FLAG_LIST ]
SET_FLAG := "constant" | "interval" | "timeout"
SET_ELEMENTS := EXPRESSION | [ EXPRESSION_LIST ]
EXPRESSION_LIST := EXPRESSION [, EXPRESSION_LIST ]
These objects describe a named set or map. Maps are a special form of sets in that they
translate a unique key to a value.
family
The table’s family.
table
The table’s name.
name
The set’s name.
handle
The set’s handle. For input, it is used in the delete command only.
type
The set’s datatype, see below.
map
Type of values this set maps to (i.e. this set is a map).
policy
The set’s policy.
flags
The set’s flags.
elem
Initial set element(s), see below.
timeout
Element timeout in seconds.
gc-interval
Garbage collector interval in seconds.
size
Maximum number of elements supported.
TYPE
The set type might be a string, such as "ipv4_addr" or an array consisting of strings
(for concatenated types).
ELEM
A single set element might be given as string, integer or boolean value for simple
cases. If additional properties are required, a formal elem object may be used.
Multiple elements may be given in an array.
ELEMENT
{ "element": {
"family": STRING,
"table": STRING,
"name": STRING,
"elem": SET_ELEM
}}
SET_ELEM := EXPRESSION | [ EXPRESSION_LIST ]
EXPRESSION_LIST := EXPRESSION [, EXPRESSION ]
Manipulate element(s) in a named set.
family
The table’s family.
table
The table’s name.
name
The set’s name.
elem
See elem property of set object.
FLOWTABLE
{ "flowtable": {
"family": STRING,
"table": STRING,
"name": STRING,
"handle": NUMBER,
"hook": STRING,
"prio": NUMBER,
"dev": FT_INTERFACE
}}
FT_INTERFACE := STRING | [ FT_INTERFACE_LIST ]
FT_INTERFACE_LIST := STRING [, STRING ]
This object represents a named flowtable.
family
The table’s family.
table
The table’s name.
name
The flow table’s name.
handle
The flow table’s handle. In input, it is used by the delete command only.
hook
The flow table’s hook.
prio
The flow table’s priority.
dev
The flow table’s interface(s).
COUNTER
{ "counter": {
"family": STRING,
"table": STRING,
"name": STRING,
"handle": NUMBER,
"packets": NUMBER,
"bytes": NUMBER
}}
This object represents a named counter.
family
The table’s family.
table
The table’s name.
name
The counter’s name.
handle
The counter’s handle. In input, it is used by the delete command only.
packets
Packet counter value.
bytes
Byte counter value.
QUOTA
{ "quota": {
"family": STRING,
"table": STRING,
"name": STRING,
"handle": NUMBER,
"bytes": NUMBER,
"used": NUMBER,
"inv": BOOLEAN
}}
This object represents a named quota.
family
The table’s family.
table
The table’s name.
name
The quota’s name.
handle
The quota’s handle. In input, it is used by the delete command only.
bytes
Quota threshold.
used
Quota used so far.
inv
If true, match if the quota has been exceeded.
CT HELPER
{ "ct helper": {
"family": STRING,
"table": STRING,
"name": STRING,
"handle": ... ',
"type": 'STRING,
"protocol": CTH_PROTO,
"l3proto": STRING
}}
CTH_PROTO := "tcp" | "udp"
This object represents a named conntrack helper.
family
The table’s family.
table
The table’s name.
name
The ct helper’s name.
handle
The ct helper’s handle. In input, it is used by the delete command only.
type
The ct helper type name, e.g. "ftp" or "tftp".
protocol
The ct helper’s layer 4 protocol.
l3proto
The ct helper’s layer 3 protocol, e.g. "ip" or "ip6".
LIMIT
{ "limit": {
"family": STRING,
"table": STRING,
"name": STRING,
"handle": NUMBER,
"rate": NUMBER,
"per": STRING,
"burst": NUMBER,
"unit": LIMIT_UNIT,
"inv": BOOLEAN
}}
LIMIT_UNIT := "packets" | "bytes"
This object represents a named limit.
family
The table’s family.
table
The table’s name.
name
The limit’s name.
handle
The limit’s handle. In input, it is used by the delete command only.
rate
The limit’s rate value.
per
Time unit to apply the limit to, e.g. "week", "day", "hour", etc. If omitted,
defaults to "second".
burst
The limit’s burst value. If omitted, defaults to 0.
unit
Unit of rate and burst values. If omitted, defaults to "packets".
inv
If true, match if limit was exceeded. If omitted, defaults to false.
CT TIMEOUT
{ "ct timeout": {
"family": STRING,
"table": STRING,
"name": STRING,
"handle": NUMBER,
"protocol": CTH_PROTO,
"state": STRING,
"value: NUMBER,
"l3proto": STRING
}}
CTH_PROTO := "tcp" | "udp" | "dccp" | "sctp" | "gre" | "icmpv6" | "icmp" | "generic"
This object represents a named conntrack timeout policy.
family
The table’s family.
table
The table’s name.
name
The ct timeout object’s name.
handle
The ct timeout object’s handle. In input, it is used by delete command only.
protocol
The ct timeout object’s layer 4 protocol.
state
The connection state name, e.g. "established", "syn_sent", "close" or "close_wait",
for which the timeout value has to be updated.
value
The updated timeout value for the specified connection state.
l3proto
The ct timeout object’s layer 3 protocol, e.g. "ip" or "ip6".
CT EXPECTATION
{ "ct expectation": {
"family": STRING,
"table": STRING,
"name": STRING,
"handle": NUMBER,
"l3proto": STRING
"protocol":* CTH_PROTO,
"dport": NUMBER,
"timeout: NUMBER,
"size: NUMBER,
*}}
CTH_PROTO := "tcp" | "udp" | "dccp" | "sctp" | "gre" | "icmpv6" | "icmp" | "generic"
This object represents a named conntrack expectation.
family
The table’s family.
table
The table’s name.
name
The ct expectation object’s name.
handle
The ct expectation object’s handle. In input, it is used by delete command only.
l3proto
The ct expectation object’s layer 3 protocol, e.g. "ip" or "ip6".
protocol
The ct expectation object’s layer 4 protocol.
dport
The destination port of the expected connection.
timeout
The time in millisecond that this expectation will live.
size
The maximum count of expectations to be living in the same time.
STATEMENTS
Statements are the building blocks for rules. Each rule consists of at least one.
VERDICT
{ "accept": null }
{ "drop": null }
{ "continue": null }
{ "return": null }
{ "jump": { "target": * STRING *}}
{ "goto": { "target": * STRING *}}
A verdict either terminates packet traversal through the current chain or delegates to a
different one.
jump and goto statements expect a target chain name.
MATCH
{ "match": {
"left": EXPRESSION,
"right": EXPRESSION,
"op": STRING
}}
This matches the expression on left hand side (typically a packet header or packet meta
info) with the expression on right hand side (typically a constant value). If the
statement evaluates to true, the next statement in this rule is considered. If not,
processing continues with the next rule in the same chain.
left
Left hand side of this match.
right
Right hand side of this match.
op
Operator indicating the type of comparison.
OPERATORS
& Binary AND
| Binary OR
^ Binary XOR
<< Left shift
>> Right shift
== Equal
!= Not equal
< Less than
> Greater than
⇐ Less than or equal to
>= Greater than or equal to
in Perform a lookup, i.e. test if
bits on RHS are contained in LHS
value
Unlike with the standard API, the operator is mandatory here. In the standard API, a
missing operator may be resolved in two ways, depending on the type of expression on
the RHS:
• If the RHS is a bitmask or a list of bitmasks, the expression resolves into a
binary operation with the inequality operator, like this: LHS & RHS != 0.
• In any other case, the equality operator is simply inserted.
For the non-trivial first case, the JSON API supports the in operator.
COUNTER
{ "counter": {
"packets": NUMBER,
"bytes": NUMBER
}}
{ "counter": STRING }
This object represents a byte/packet counter. In input, no properties are required. If
given, they act as initial values for the counter.
The first form creates an anonymous counter which lives in the rule it appears in. The
second form specifies a reference to a named counter object.
packets
Packets counted.
bytes
Bytes counted.
MANGLE
{ "mangle": {
"key": EXPRESSION,
"value": EXPRESSION
}}
This changes the packet data or meta info.
key
The packet data to be changed, given as an exthdr, payload, meta, ct or ct helper
expression.
value
Value to change data to.
QUOTA
{ "quota": {
"val": NUMBER,
"val_unit": STRING,
"used": NUMBER,
"used_unit": STRING,
"inv": BOOLEAN
}}
{ "quota": STRING }
The first form creates an anonymous quota which lives in the rule it appears in. The
second form specifies a reference to a named quota object.
val
Quota value.
val_unit
Unit of val, e.g. "kbytes" or "mbytes". If omitted, defaults to "bytes".
used
Quota used so far. Optional on input. If given, serves as initial value.
used_unit
Unit of used. Defaults to "bytes".
inv
If true, will match if quota was exceeded. Defaults to false.
LIMIT
{ "limit": {
"rate": NUMBER,
"rate_unit": STRING,
"per": STRING,
"burst": NUMBER,
"burst_unit": STRING,
"inv": BOOLEAN
}}
{ "limit": STRING }
The first form creates an anonymous limit which lives in the rule it appears in. The
second form specifies a reference to a named limit object.
rate
Rate value to limit to.
rate_unit
Unit of rate, e.g. "packets" or "mbytes". Defaults to "packets".
per
Denominator of rate, e.g. "week" or "minutes".
burst
Burst value. Defaults to 0.
burst_unit
Unit of burst, ignored if rate_unit is "packets". Defaults to "bytes".
inv
If true, matches if the limit was exceeded. Defaults to false.
FWD
{ "fwd": {
"dev": EXPRESSION,
"family": FWD_FAMILY,
"addr": EXPRESSION
}}
FWD_FAMILY := "ip" | "ip6"
Forward a packet to a different destination.
dev
Interface to forward the packet on.
family
Family of addr.
addr
IP(v6) address to forward the packet to.
Both family and addr are optional, but if at least one is given, both must be present.
NOTRACK
{ "notrack": null }
Disable connection tracking for the packet.
DUP
{ "dup": {
"addr": EXPRESSION,
"dev": EXPRESSION
}}
Duplicate a packet to a different destination.
addr
Address to duplicate packet to.
dev
Interface to duplicate packet on. May be omitted to not specify an interface
explicitly.
NETWORK ADDRESS TRANSLATION
{ "snat": {
"addr": EXPRESSION,
"family": STRING,
"port": EXPRESSION,
"flags": FLAGS
}}
{ "dnat": {
"addr": EXPRESSION,
"family": STRING,
"port": EXPRESSION,
"flags": FLAGS
}}
{ "masquerade": {
"port": EXPRESSION,
"flags": FLAGS
}}
{ "redirect": {
"port": EXPRESSION,
"flags": FLAGS
}}
FLAGS := FLAG | [ FLAG_LIST ]
FLAG_LIST := FLAG [, FLAG_LIST ]
FLAG := "random" | "fully-random" | "persistent"
Perform Network Address Translation.
addr
Address to translate to.
family
Family of addr, either ip or ip6. Required in inet table family.
port
Port to translate to.
flags
Flag(s).
All properties are optional and default to none.
REJECT
{ "reject": {
"type": STRING,
"expr": EXPRESSION
}}
Reject the packet and send the given error reply.
type
Type of reject, either "tcp reset", "icmpx", "icmp" or "icmpv6".
expr
ICMP code to reject with.
All properties are optional.
SET
{ "set": {
"op": STRING,
"elem": EXPRESSION,
"set": STRING
}}
Dynamically add/update elements to a set.
op
Operator on set, either "add" or "update".
elem
Set element to add or update.
set
Set reference.
LOG
{ "log": {
"prefix": STRING,
"group": NUMBER,
"snaplen": NUMBER,
"queue-threshold": NUMBER,
"level": LEVEL,
"flags": FLAGS
}}
LEVEL := "emerg" | "alert" | "crit" | "err" | "warn" | "notice" |
"info" | "debug" | "audit"
FLAGS := FLAG | [ FLAG_LIST ]
FLAG_LIST := FLAG [, FLAG_LIST ]
FLAG := "tcp sequence" | "tcp options" | "ip options" | "skuid" |
"ether" | "all"
Log the packet.
prefix
Prefix for log entries.
group
Log group.
snaplen
Snaplen for logging.
queue-threshold
Queue threshold.
level
Log level. Defaults to "warn".
flags
Log flags.
All properties are optional.
CT HELPER
{ "ct helper": EXPRESSION }
Enable the specified conntrack helper for this packet.
ct helper
CT helper reference.
METER
{ "meter": {
"name": STRING,
"key": EXPRESSION,
"stmt": STATEMENT
}}
Apply a given statement using a meter.
name
Meter name.
key
Meter key.
stmt
Meter statement.
QUEUE
{ "queue": {
"num": EXPRESSION,
"flags": FLAGS
}}
FLAGS := FLAG | [ FLAG_LIST ]
FLAG_LIST := FLAG [, FLAG_LIST ]
FLAG := "bypass" | "fanout"
Queue the packet to userspace.
num
Queue number.
flags
Queue flags.
VERDICT MAP
{ "vmap": {
"key": EXPRESSION,
"data": EXPRESSION
}}
Apply a verdict conditionally.
key
Map key.
data
Mapping expression consisting of value/verdict pairs.
CT COUNT
{ "ct count": {
"val": NUMBER,
"inv": BOOLEAN
}}
Limit the number of connections using conntrack.
val
Connection count threshold.
inv
If true, match if val was exceeded. If omitted, defaults to false.
CT TIMEOUT
{ "ct timeout": EXPRESSION }
Assign connection tracking timeout policy.
ct timeout
CT timeout reference.
CT EXPECTATION
{ "ct expectation": EXPRESSION }
Assign connection tracking expectation.
ct expectation
CT expectation reference.
XT
{ "xt": {
"type": TYPENAME,
"name": STRING
}}
TYPENAME := match | target | watcher
This represents an xt statement from xtables compat interface. It is a fallback if
translation is not available or not complete.
Seeing this means the ruleset (or parts of it) were created by iptables-nft and one should
use that to manage it.
BEWARE: nftables won’t restore these statements.
EXPRESSIONS
Expressions are the building blocks of (most) statements. In their most basic form, they
are just immediate values represented as a JSON string, integer or boolean type.
IMMEDIATES
STRING
NUMBER
BOOLEAN
Immediate expressions are typically used for constant values. For strings, there are two
special cases:
@STRING
The remaining part is taken as set name to create a set reference.
\*
Construct a wildcard expression.
LISTS
ARRAY
List expressions are constructed by plain arrays containing of an arbitrary number of
expressions.
CONCAT
{ "concat": CONCAT }
CONCAT := [ EXPRESSION_LIST ]
EXPRESSION_LIST := EXPRESSION [, EXPRESSION_LIST ]
Concatenate several expressions.
SET
{ "set": SET }
SET := EXPRESSION | [ EXPRESSION_LIST ]
This object constructs an anonymous set. For mappings, an array of arrays with exactly two
elements is expected.
MAP
{ "map": {
"key": EXPRESSION,
"data": EXPRESSION
}}
Map a key to a value.
key
Map key.
data
Mapping expression consisting of value/target pairs.
PREFIX
{ "prefix": {
"addr": EXPRESSION,
"len": NUMBER
}}
Construct an IPv4 or IPv6 prefix consisting of address part in addr and prefix length in
len.
RANGE
{ "range": [ EXPRESSION , EXPRESSION ] }
Construct a range of values. The first array item denotes the lower boundary, the second
one the upper boundary.
PAYLOAD
{ "payload": {
"base": BASE,
"offset": NUMBER,
"len": NUMBER
}}
{ "payload": {
"protocol": STRING,
"field": STRING
}}
BASE := "ll" | "nh" | "th"
Construct a payload expression, i.e. a reference to a certain part of packet data. The
first form creates a raw payload expression to point at a random number (len) of bytes at
a certain offset (offset) from a given reference point (base). The following base values
are accepted:
"ll"
The offset is relative to Link Layer header start offset.
"nh"
The offset is relative to Network Layer header start offset.
"th"
The offset is relative to Transport Layer header start offset.
The second form allows one to reference a field by name (field) in a named packet header
(protocol).
EXTHDR
{ "exthdr": {
"name": STRING,
"field": STRING,
"offset": NUMBER
}}
Create a reference to a field (field) in an IPv6 extension header (name). offset is used
only for rt0 protocol.
If the field property is not given, the expression is to be used as a header existence
check in a match statement with a boolean on the right hand side.
TCP OPTION
{ "tcp option": {
"name": STRING,
"field": STRING
}}
Create a reference to a field (field) of a TCP option header (name).
If the field property is not given, the expression is to be used as a TCP option existence
check in a match statement with a boolean on the right hand side.
SCTP CHUNK
{ "sctp chunk": {
"name": STRING,
"field": STRING
}}
Create a reference to a field (field) of an SCTP chunk (name).
If the field property is not given, the expression is to be used as an SCTP chunk
existence check in a match statement with a boolean on the right hand side.
META
{ "meta": {
"key": META_KEY
}}
META_KEY := "length" | "protocol" | "priority" | "random" | "mark" |
"iif" | "iifname" | "iiftype" | "oif" | "oifname" |
"oiftype" | "skuid" | "skgid" | "nftrace" |
"rtclassid" | "ibriport" | "obriport" | "ibridgename" |
"obridgename" | "pkttype" | "cpu" | "iifgroup" |
"oifgroup" | "cgroup" | "nfproto" | "l4proto" |
"secpath"
Create a reference to packet meta data.
RT
{ "rt": {
"key": RT_KEY,
"family": RT_FAMILY
}}
RT_KEY := "classid" | "nexthop" | "mtu"
RT_FAMILY := "ip" | "ip6"
Create a reference to packet routing data.
The family property is optional and defaults to unspecified.
CT
{ "ct": {
"key": STRING,
"family": CT_FAMILY,
"dir": CT_DIRECTION
}}
CT_FAMILY := "ip" | "ip6"
CT_DIRECTION := "original" | "reply"
Create a reference to packet conntrack data.
Some CT keys do not support a direction. In this case, dir must not be given.
NUMGEN
{ "numgen": {
"mode": NG_MODE,
"mod": NUMBER,
"offset": NUMBER
}}
NG_MODE := "inc" | "random"
Create a number generator.
The offset property is optional and defaults to 0.
HASH
{ "jhash": {
"mod": NUMBER,
"offset": NUMBER,
"expr": EXPRESSION,
"seed": NUMBER
}}
{ "symhash": {
"mod": NUMBER,
"offset": NUMBER
}}
Hash packet data.
The offset and seed properties are optional and default to 0.
FIB
{ "fib": {
"result": FIB_RESULT,
"flags": FIB_FLAGS
}}
FIB_RESULT := "oif" | "oifname" | "type"
FIB_FLAGS := FIB_FLAG | [ FIB_FLAG_LIST ]
FIB_FLAG_LIST := FIB_FLAG [, FIB_FLAG_LIST ]
FIB_FLAG := "saddr" | "daddr" | "mark" | "iif" | "oif"
Perform kernel Forwarding Information Base lookups.
BINARY OPERATION
{ "|": [ EXPRESSION, EXPRESSION ] }
{ "^": [ EXPRESSION, EXPRESSION ] }
{ "&": [ EXPRESSION, EXPRESSION ] }
{ "<<": [ EXPRESSION, EXPRESSION ] }
{ ">>": [ EXPRESSION, EXPRESSION ] }
All binary operations expect an array of exactly two expressions, of which the first
element denotes the left hand side and the second one the right hand side.
VERDICT
{ "accept": null }
{ "drop": null }
{ "continue": null }
{ "return": null }
{ "jump": { "target": STRING }}
{ "goto": { "target": STRING }}
Same as the verdict statement, but for use in verdict maps.
jump and goto verdicts expect a target chain name.
ELEM
{ "elem": {
"val": EXPRESSION,
"timeout": NUMBER,
"expires": NUMBER,
"comment": STRING
}}
Explicitly set element object, in case timeout, expires or comment are desired. Otherwise,
it may be replaced by the value of val.
SOCKET
{ "socket": {
"key": SOCKET_KEY
}}
SOCKET_KEY := "transparent"
Construct a reference to packet’s socket.
OSF
{ "osf": {
"key": OSF_KEY,
"ttl": OSF_TTL
}}
OSF_KEY := "name"
OSF_TTL := "loose" | "skip"
Perform OS fingerprinting. This expression is typically used in the LHS of a match
statement.
key
Which part of the fingerprint info to match against. At this point, only the OS name
is supported.
ttl
Define how the packet’s TTL value is to be matched. This property is optional. If
omitted, the TTL value has to match exactly. A value of loose accepts TTL values less
than the fingerprint one. A value of skip omits TTL value comparison entirely.
AUTHOR
Phil Sutter <phil@nwl.cc>
Author.
01/29/2023 LIBNFTABLES-JSON(5)