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33 .\" Author: Archie Cobbs <archie@FreeBSD.org>
36 .\" $Whistle: ng_bpf.8,v 1.2 1999/12/03 01:57:12 archie Exp $
43 .Nd Berkeley packet filter netgraph node type
45 .Fd #include <net/bpf.h>
46 .Fd #include <netgraph/ng_bpf.h>
50 node type allows Berkeley Packet Filter (see
52 filters to be applied to data travelling through a Netgraph network.
53 Each node allows an arbitrary number of connections to arbitrarily
54 named hooks. With each hook is associated a
56 filter program which is applied to incoming data only, a destination hook
57 for matching packets, a destination hook for non-matching packets,
58 and various statistics counters.
62 program returns an unsigned integer, which is normally interpreted as
63 the length of the prefix of the packet to return. In the context of this
64 node type, returning zero is considered a non-match, in which case the
65 entire packet is delivered out the non-match destination hook.
66 Returning a value greater than zero causes the packet to be truncated
67 to that length and delivered out the match destination hook.
68 Either or both destination hooks may be the empty string, or may
69 not exist, in which case the packet is dropped.
71 New hooks are initially configured to drop all packets.
72 A new filter program may be installed using the
73 .Dv NGM_BPF_SET_PROGRAM
76 This node type supports any number of hooks having arbitrary names.
78 This node type supports the generic control messages, plus the following:
80 .It Dv NGM_BPF_SET_PROGRAM
81 This command sets the filter program that will be applied to incoming
82 data on a hook. The following structure must be supplied as an argument:
83 .Bd -literal -offset 4n
84 struct ngm_bpf_hookprog {
85 char thisHook[NG_HOOKLEN+1]; /* name of hook */
86 char ifMatch[NG_HOOKLEN+1]; /* match dest hook */
87 char ifNotMatch[NG_HOOKLEN+1]; /* !match dest hook */
88 int32_t bpf_prog_len; /* #isns in program */
89 struct bpf_insn bpf_prog[0]; /* bpf program */
93 The hook to be updated is specified in
95 The BPF program is the sequence of instructions in the
100 Matching and non-matching incoming packets are delivered out the hooks named
104 respectively. The program must be a valid
109 .It Dv NGM_BPF_GET_PROGRAM
110 This command takes an
112 string argument, the hook name, and returns the
114 .Dv "struct ngm_bpf_hookprog"
116 .It Dv NGM_BPF_GET_STATS
117 This command takes an
119 string argument, the hook name, and returns the
120 statistics associated with the hook as a
121 .Dv "struct ng_bpf_hookstat" .
122 .It Dv NGM_BPF_CLR_STATS
123 This command takes an
125 string argument, the hook name, and clears the
126 statistics associated with the hook.
127 .It Dv NGM_BPF_GETCLR_STATS
128 This command is identical to
129 .Dv NGM_BPF_GET_STATS ,
130 except that the statistics are also atomically cleared.
133 This node shuts down upon receipt of a
135 control message, or when all hooks have been disconnected.
137 When built as a loadable kernel module, this module includes the file
138 .Pa net/bpf_filter.c .
139 Although loading the module should fail if
141 already exists in the kernel, currently it does not, and the duplicate
142 copies of the file do not interfere.
143 However, this may change in the future.
147 node type was implemented in
154 .An Archie Cobbs Aq archie@FreeBSD.org