NG_MACFILTER(4) FreeBSD Kernel Interfaces Manual NG_MACFILTER(4)
NAME
ng_macfilter - packet filtering netgraph node using ethernet MAC
addresses
SYNOPSIS
#include <sys/types.h>
#include <netgraph/ng_macfilter.h>
DESCRIPTION
The macfilter allows routing ethernet packets over different hooks based
on the sender MAC address.
This processing is done when traffic flows from the "ether" hook through
macfilter to one of the outgoing hooks. Outbound hooks can be added to
and remove from macfilter and arbitrarily named. By default one hook
called "default" is present and used for all packets which have no MAC
address in the MAC table. By adding MAC addresses to the MAC table
traffic coming from this host can be directed out other hooks. macfilter
keeps track of packets and bytes from and to this MAC address in the MAC
table.
Packets are not altered in any way. If hooks are not connected, packets
are dropped.
HOOKS
This node type by default has an ether hook, to be connected to the lower
hook of the NIC, and a default hook where packets are sent if the MAC
adddress is not found in the table. macfilter supports up to
NG_MACFILTER_UPPER_NUM hooks to be connected to the NIC's upper hook.
Other nodes can be inserted to provide additional processing. All
outbound can be combined back into one by using ng_one2many.
CONTROL MESSAGES
This node type supports the generic control messages, plus the following:
NGM_MACFILTER_RESET (reset)
Resets the MAC table in the node.
NGM_MACFILTER_DIRECT (direct)
Takes the following argument struct:
struct ngm_macfilter_direct {
u_char ether[ETHER_ADDR_LEN]; /* MAC address */
u_char hookname[NG_HOOKSIZ]; /* Upper hook name*/
};
The given ethernet MAC address will be forwarded out the named hook.
NGM_MACFILTER_DIRECT_HOOKID (directi)
Takes the following argument struct:
struct ngm_macfilter_direct_hookid {
u_char ether[ETHER_ADDR_LEN]; /* MAC address */
u_int16_t hookid; /* Upper hook hookid */
};
The given ethernet MAC address will be forwarded out the hook at id
hookid.
NGM_MACFILTER_GET_MACS (getmacs)
Returns the list of MAC addresses in the node in the following
structure:
struct ngm_macfilter_mac {
u_char ether[ETHER_ADDR_LEN]; /* MAC address */
u_int16_t hookid; /* Upper hook hookid */
u_int64_t packets_in; /* packets in from downstream */
u_int64_t bytes_in; /* bytes in from upstream */
u_int64_t packets_out; /* packets out towards downstream */
u_int64_t bytes_out; /* bytes out towards downstream */
};
struct ngm_macfilter_macs {
u_int32_t n; /* Number of entries in macs */
struct ngm_macfilter_mac macs[]; /* Macs table */
};
NGM_MACFILTER_GETCLR_MACS (getclrmacs)
Same as above, but will also atomically clear the packets_in,
bytes_in, packets_out, and bytes_out fields in the table.
NGM_MACFILTER_CLR_STATS (clrmacs)
Will clear the per MAC address packet and byte counters.
NGM_MACFILTER_GET_HOOKS (gethooks)
Will return a list of hooks and their hookids in an array of the
following struct's:
struct ngm_macfilter_hook {
u_char hookname[NG_HOOKSIZ]; /* Upper hook name*/
u_int16_t hookid; /* Upper hook hookid */
u_int32_t maccnt; /* Number of mac addresses associated with hook */
};
SHUTDOWN
This node shuts down upon receipt of a NGM_SHUTDOWN control message or
when all have been disconnected.
EXAMPLES
The following netgraph configuration will apply ipfw(8) tag 42 to each
packet that is routed over the "accepted" hook. The graph looks like the
following:
/------<one>-[combiner]-<many1>--------\
<upper> | <out>
/ <many0> \
[em0] | [tagger]
\ <default> /
<lower> | <in>
\----<ether>-[macfilter]-<accepted>-----/
Commands:
ngctl mkpeer em0: macfilter lower ether
ngctl name em0:lower macfilter
# Funnel both streams back into ether:upper
ngctl mkpeer em0: one2many upper one
ngctl name em0:upper recombiner
# Connect macfilter:default to recombiner:many0
ngctl connect macfilter: recombiner: default many0
# Connect macfilter:accepted to tagger:in
ngctl mkpeer macfilter: tag accepted in
ngctl name macfilter:accepted tagger
# Connect tagger:out to recombiner:many1
ngctl connect tagger: recombiner: out many1
# Mark tag all traffic through tagger in -> out with an ipfw tag 42
ngctl msg tagger: sethookin '{ thisHook="in" ifNotMatch="out" }'
ngctl msg tagger: sethookout '{ thisHook="out" tag_cookie=1148380143 tag_id=42 }'
# Pass traffic from ether:upper / combiner:one via combiner:many0 on to
# macfilter:default and on to ether:lower.
ngctl msg recombiner: setconfig '{ xmitAlg=3 failAlg=1 enabledLinks=[ 1 1 ] }'
Note: The tag_cookie 1148380143 was retrieved from MTAG_IPFW in
/usr/include/netinet/ip_var.h.
The following command can be used to add a MAC address to be output via
macfilter:accepted:
ngctl msg macfilter: direct '{ hookname="known" ether=08:00:27:92:eb:aa }'
The following command can be used to retrieve the packet and byte
counters :
ngctl msg macfilter: getmacs
It will return the contents of the MAC table:
Rec'd response "getmacs" (4) from "[54]:":
Args: { n=1 macs=[ { ether=08:00:27:92:eb:aa hookid=1 packets_in=3571 bytes_in=592631 packets_out=3437 bytes_out=777142 } ] }
SEE ALSO
divert(4), ipfw(4), netgraph(4), ng_ether(4), ng_one2many(4), ng_tag(4),
ngctl(8)
AUTHORS
The original version of this code was written by Pekka Nikander, and
subsequently modified heavily by Nick Hibma <n_hibma@FreeBSD.org>.
BUGS
None known.
FreeBSD 13.1-RELEASE-p6 December 10, 2018 FreeBSD 13.1-RELEASE-p6
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