bfcli

bfcli is a command line tool to communicate with the bpfilter daemon. It provides supports for extended features compared to the iptables client.

Commands

bfcli commands are structured as bfcli OBJECT ACTION. The commands and actions supported by bfcli are described below.

ruleset set

Define a new ruleset: replace all the existing chains with the ruleset provided. Replacement is not atomic.

Chains with valid hook options defined are attached to their hook. Chains without hook options are only loaded into the kernel.

Options

• --from-str RULESET: read and apply the ruleset defining from the command line.

• --from-file FILE: read FILE and apply the ruleset contained in it.

--from-str and --from-file are mutually exclusive.

Example

bfcli ruleset set --from-file myruleset.txt
bfcli ruleset set --from-str "chain my_xdp_chain BF_HOOK_XDP ACCEPT rule ip4.saddr in {192.168.1.1} ACCEPT"

ruleset get

Print the ruleset: request all the chains and rules from the daemon with counters values.

Example

$ sudo bfcli ruleset get
  chain my_tc_chain BF_HOOK_TC_INGRESS{ifindex=2} ACCEPT
      counters policy 87 packets 9085 bytes; error 0 packets 0 bytes
      rule
          ip4.saddr eq 0xc0 0xa8 0x01 0x01 0xff 0xff 0xff 0xff
          counters 2 packets 196 bytes
          ACCEPT

ruleset flush

Remove all the chains and rules defined by the daemon. Once this command completes, the daemon doesn’t contain any filtering rules, as if it was freshly started.

Examples

$ sudo bfcli ruleset get
  chain my_tc_chain BF_HOOK_TC_INGRESS{ifindex=2} ACCEPT
      counters policy 87 packets 9085 bytes; error 0 packets 0 bytes
      rule
          ip4.saddr eq 0xc0 0xa8 0x01 0x01 0xff 0xff 0xff 0xff
          counters 2 packets 196 bytes
          ACCEPT
$ sudo bfcli ruleset flush
$ sudo bfcli ruleset get
$ # Empty ruleset

chain set

Generate and load a chain into the kernel. If the chain definition contains hook options, the daemon will attach it to its hook. Any existing chain with the same name (attached or not) will be discarded and replaced with the new one.

If you want to update an existing chain without downtime, use bfcli chain update instead.

Options

• --from-str CHAIN: read the chain to set from the command line arguments.

• --from-file FILEPATH: read the chain from a file.

• --name NAME: if --from-str or --from-file provide multiple chains, NAME specify which one to send to the daemon.

Examples

$ # Create an empty XDP chain, do not attach it
$ sudo bfcli chain set --from-str "chain my_xdp_chain BF_HOOK_XDP ACCEPT"
$ sudo bfcli chain get --name my_xdp_chain
  chain my_xdp_chain BF_HOOK_XDP ACCEPT
      counters policy 0 packets 0 bytes; error 0 packets 0 bytes

# Create an empty TC chain and attach it
$ sudo bfcli chain set --from-str "chain my_tc_chain BF_HOOK_TC_INGRESS{ifindex=2} ACCEPT"
$ sudo bfcli chain get --name my_tc_chain
  chain my_tc_chain BF_HOOK_TC_INGRESS{ifindex=2} ACCEPT
      counters policy 35 packets 4091 bytes; error 0 packets 0 bytes

chain get

Print a chain.

Options

• --name NAME: name of the chain to print.

Examples

$ # Create a Netfilter chain and print it
$ sudo bfcli chain set --from-str "chain my_input_chain BF_HOOK_NF_LOCAL_IN{family=inet4,priorities=101-102} ACCEPT"
$ sudo bfcli chain get --name my_input_chain
  chain my_input_chain BF_HOOK_NF_LOCAL_IN{family=inet4,priorities=101-102} ACCEPT
      counters policy 1161 packets 149423 bytes; error 0 packets 0 bytes

chain load

Generate and load a chain into the kernel. Hook options are ignored.

If a chain with the same name already exist, it won’t be replaced. See bfcli chain set or bfcli chain update to replace an existing chain.

Options

• --from-str CHAIN: read the chain to set from the command line arguments.

• --from-file FILEPATH: read the chain from a file.

• --name NAME: if --from-str or --from-file provide multiple chains, NAME specify which one to send to the daemon.

Examples

$ # Create an XDP chain and print it
$ sudo bfcli chain load --from-str "chain my_xdp_chain BF_HOOK_XDP ACCEPT"
$ sudo bfcli chain get --name my_xdp_chain
  chain my_xdp_chain BF_HOOK_XDP ACCEPT
      counters policy 0 packets 0 bytes; error 0 packets 0 bytes

$ # Create a single chain from a string containing 2 chains. Hook options are ignored.
$ sudo bfcli chain load --name my_other_xdp_chain --from-str "
    chain my_next_xdp_chain BF_HOOK_XDP DROP
    chain my_other_xdp_chain BF_HOOK_XDP ACCEPT"
$ sudo bfcli chain get --name my_other_xdp_chain
  chain my_other_xdp_chain BF_HOOK_XDP ACCEPT
      counters policy 0 packets 0 bytes; error 0 packets 0 bytes

chain attach

Attach a loaded chain to its hook.

Only loaded chains (not attached) can be attached. See bfcli chain set and bfcli chain update if you want to update an existing chain.

See below for a list of available hook options.

Options

• --name NAME: name of the chain to attach.

• --option OPTION: hook-specific options to attach the chain to its hook. See hook options below.

Examples

$ # Load and attach an XDP chain, print it
$ sudo bfcli chain load --from-str "chain my_xdp_chain BF_HOOK_XDP ACCEPT"
$ sudo bfcli chain attach --name my_xdp_chain --option ifindex=2
$ sudo bfcli chain get --name my_xdp_chain
  chain my_xdp_chain BF_HOOK_XDP{ifindex=2} ACCEPT
      counters policy 101 packets 11714 bytes; error 0 packets 0 bytes

chain update

Update an existing chain. The new chain will atomically update the existing one. Hook options are ignored. The new chain will replace the existing chain with the same name.

If you want to modify the hook options, use bfcli chain set instead.

Options

• --from-str CHAIN: read the chain to set from the command line arguments.

• --from-file FILEPATH: read the chain from a file.

• --name NAME: if --from-str or --from-file provide multiple chains, NAME specify which one to send to the daemon.

Examples

$ # Set an XDP chain and update it
$ sudo bfcli chain set --from-str "chain my_xdp_chain BF_HOOK_XDP{ifindex=2} ACCEPT"
$ sudo bfcli chain get --name my_xdp_chain
  chain my_xdp_chain BF_HOOK_XDP{ifindex=2} ACCEPT
      counters policy 307 packets 36544 bytes; error 0 packets 0 bytes
$ sudo bfcli chain update --from-str "
      chain my_xdp_chain BF_HOOK_XDP{ifindex=2} ACCEPT
          rule
              ip4.proto eq icmp
              counter
              DROP"
$ sudo bfcli chain get --name my_xdp_chain
  chain my_xdp_chain BF_HOOK_XDP{ifindex=2} ACCEPT
      counters policy 204 packets 24074 bytes; error 0 packets 0 bytes
      rule
          ip4.proto eq 0x01
          counters 0 packets 0 bytes
          DROP

chain flush

Detach, unload, and discard an existing chain.

Options

• --name NAME: name of the chain to flush.

Examples

$ # Set an XDP chain and update it
$ sudo bfcli chain set --from-str "chain my_xdp_chain BF_HOOK_XDP ACCEPT"
$ sudo bfcli chain get --name my_xdp_chain
  chain my_xdp_chain BF_HOOK_XDP ACCEPT
      counters policy 0 packets 0 bytes; error 0 packets 0 bytes
$ sudo bfcli chain flush --name my_xdp_chain
$ sudo bfcli chain get --name my_xdp_chain
$ # No output, chain doesn't exist

Filters definition

The following sections will use the dollar sign ($) to prefix values that should be replaced by the user, and brackets ([]) for optional values (whether it’s a literal or a user-provided value).

Example of a ruleset:

chain $NAME $HOOK $HOOK_OPTIONS $POLICY
    rule
        $MATCHER
        $VERDICT
    [...]
[...]

A ruleset is composed of chain(s), rule(s), and matcher(s):

• A chain is a set of rule(s) to match the packet against. It will use the rules to filter packets at a specific location in the kernel: a $HOOK. There can be only one chain defined for a given kernel hook. Chains also have a $POLICY which specify the action to take with the packet if none of the rules matches.

• A rule defines an action to take on a packet if it matches all its specified criteria. A rule will then apply a defined action to the packet if it’s matched.

• A matcher is a matching criterion within a rule. It can match a specific protocol, a specific field, a network interface… The number of matchers supported by bpfilter and bfcli is constantly growing.

Note

Lines starting with # are comments and bfcli will ignore them.

Chains

Chains are defined such as:

chain $NAME $HOOK{$OPTIONS} $POLICY

With:

• $NAME: user-defined name for the chain.

• $HOOK: hook in the kernel to attach the chain to:

  • BF_HOOK_XDP: XDP hook.

  • BF_HOOK_TC_INGRESS: ingress TC hook.

  • BF_HOOK_NF_PRE_ROUTING: similar to nftables and iptables prerouting hook.

  • BF_HOOK_NF_LOCAL_IN: similar to nftables and iptables input hook.

  • BF_HOOK_CGROUP_INGRESS: ingress cgroup hook.

  • BF_HOOK_CGROUP_EGRESS: egress cgroup hook.

  • BF_HOOK_NF_FORWARD: similar to nftables and iptables forward hook.

  • BF_HOOK_NF_LOCAL_OUT: similar to nftables and iptables output hook.

  • BF_HOOK_NF_POST_ROUTING: similar to nftables and iptables postrouting hook.

  • BF_HOOK_TC_EGRESS: egress TC hook.

• $POLICY: action taken if no rule matches the packet, either ACCEPT forward the packet to the kernel, or DROP to discard it. Note while CONTINUE is a valid verdict for rules, it is not supported for chain policy.

$OPTIONS are hook-specific comma separated key value pairs:

Option	Required by	Supported by	Notes
ifindex=$IFINDEX	BF_HOOK_XDP, BF_HOOK_TC	N/A	Interface index to attach the program to.
cgpath=$CGROUP_PATH	BF_HOOK_CGROUP_INGRESS, BF_HOOK_CGROUP_EGRESS	N/A	Path to the cgroup to attach to.
family=$FAMILY	BF_HOOK_NF_*	N/A	Netfilter hook version to attach the chain to: inet4 for IPv4 or inet6 for IPv6. Rules that are incompatible with the hook version will be ignored.
priorities=$INT1-$INT2	BF_HOOK_NF_*	N/A	INT1 and INT2 are different non-zero integers. Priority values to use when attaching the chain. Two values are required to ensure atomic update of the chain.

Rules

Rules are defined such as:

rule
    [$MATCHER...]
    [counter]
    $VERDICT

With:

• $MATCHER: zero or more matchers. Matchers are defined later.

• counter: optional literal. If set, the filter will counter the number of packets and bytes matched by the rule.

• $VERDICT: action taken by the rule if the packet is matched against all the criteria: either ACCEPT, DROP or CONTINUE. - ACCEPT: forward the packet to the kernel - DROP: discard the packet. - CONTINUE: continue processing subsequent rules.

In a chain, as soon as a rule matches a packet, its verdict is applied. If the verdict is ACCEPT or DROP, the subsequent rules are not processed. Hence, the rules’ order matters. If no rule matches the packet, the chain’s policy is applied.

Note CONTINUE means a packet can be counted more than once if multiple rules specify CONTINUE and counter.

Matchers

Matchers are defined such as:

$TYPE [$OP] $PAYLOAD

With:

• $TYPE: type of the matcher, defined which part of the processed network packet need to be compared against. All the exact matcher types are defined below.

• $OP: comparison operation, not all $TYPE of matchers support all the existing comparison operators:

  • eq: exact equality.

  • not: inequality.

  • any: match the packet against a set of data defined as the payload. If any of the member of the payload set is found in the packet, the matcher is positive. For example, if you want to match all the icmp and udp packets: ip4.proto any icmp,udp.

  • all: match the packet against a set of data defined as the payload. If all the member of the payload set are found in the packet, the matcher is positive, even if the packet contains more than only the members defined in the payload. For example, to match all the packets containing at least the ACK TCP flag: tcp.flags all ACK.

  • in: matches the packet against a hashed set of reference values. Using the in operator is useful when the packet’s data needs to be compared against a large set of different values. Let’s say you want to filter 1000 different IPv4 addresses, you can either define 1000 ip4.saddr eq $IP matcher, in which case bpfilter will compare the packet against every IP one after the other. Or you can use ip4.saddr in {$IP0,IP1,...} in which case bpfilter will compare the packet’s data against the hashed set as a whole in 1 operation.

  • range: matches in a range of values. Formatted as $START-$END. Both $START and $END are included in the range.

• $PAYLOAD: payload to compare to the processed network packet. The exact payload format depends on $TYPE.

Meta

Matches	Type	Operator	Payload	Notes
Interface index	meta.ifindex	eq	$IFINDEX	For chains attached to an ingress hook, $IFINDEX is the input interface index. For chains attached to an egress hook, $IFINDEX is the output interface index.
L3 protocol	meta.l3_proto	eq	$PROTOCOL	ipv4 and ipv6 are supported.
L4 protocol	meta.l4_proto	eq	$PROTOCOL	icmp, icmpv6, tcp, udp are supported.
Source port	meta.sport	eq	$PORT	$PORT is a valid port value, as a decimal integer.
		not
		range	$START-$END	$START and $END are valid port values, as decimal integers.
Destination port	meta.dport	eq	$PORT	$PORT is a valid port value, as a decimal integer.
		not
		range	$START-$END	$START and $END are valid port values, as decimal integers.
Probability	meta.probability	eq	$PROBABILITY	$PROBABILITY is an integer between 0 and 100 followed by the % sign.

IPv4

Matches	Type	Operator	Payload	Notes
Source address	ip4.saddr	eq	$IP/$MASK	/$MASK is optional, /32 is used by default.
		not
		in	{$IP[,...]}	Only support /32 mask.
Destination address	ip4.daddr	eq	$IP/$MASK	/$MASK is optional, /32 is used by default.
		not
		in	{$IP[,...]}	Only support /32 mask.
Source network	ip4.snet	in	{$IP/$MASK[,...]}
Destination network	ip4.dnet	in	{$IP/$MASK[,...]}
Protocol	ip4.proto	eq	$PROTOCOL	Only icmp is supported for now, more protocols will be added.

IPv6

Matches	Type	Operator	Payload	Notes
Source address	ip6.saddr	eq	$IP/$PREFIX	/$PREFIX is optional, /128 is used by default.
		not
Destination address	ip6.daddr	eq
		not
Source network	ip6.snet	in	{$IP/$MASK[,...]}
Destination network	ip6.dnet	in	{$IP/$MASK[,...]}

TCP

Matches	Type	Operator	Payload	Notes
Source port	tcp.sport	eq	$PORT	$PORT is a valid port value, as a decimal integer.
		not
		range	$START-$END	$START and $END are valid port values, as decimal integers.
Destination port	tcp.dport	eq	$PORT	$PORT is a valid port value, as a decimal integer.
		not
		range	$START-$END	$START and $END are valid port values, as decimal integers.
Flags	tcp.flags	eq	$FLAGS	$FLAGS is a comma-separated list of capitalized TCP flags (FIN, RST, ACK, ECE, SYN, PSH, URG, CWR).
		not
		any
		all

UDP

Matches	Type	Operator	Payload	Notes
Source port	udp.sport	eq	$PORT	$PORT is a valid port value, as a decimal integer.
		not
		range	$START-$END	$START and $END are valid port values, as decimal integers.
Destination port	udp.dport	eq	$PORT	$PORT is a valid port value, as a decimal integer.
		not
		range	$START-$END	$START and $END are valid port values, as decimal integers.

ICMP

Matches	Type	Operator	Payload	Notes
Type	icmp.type	eq	$ICMP_TYPE	$ICMP_TYPE is a valid ICMP message type as a decimal integer.
		not
Code	icmp.code	eq	$ICMP_CODE	$ICMP_CODE is a valid ICMP message code as a decimal integer.
		not

ICMPv6

Matches	Type	Operator	Payload	Notes
Type	icmpv6.type	eq	$ICMPV6_TYPE	$ICMPV6_TYPE is a valid ICMPv6 message type as a decimal integer.
		not
Code	icmpv6.code	eq	$ICMPV6_CODE	$ICMPV6_CODE is a valid ICMPv6 message code as a decimal integer.
		not