contrib/dhcpcd/src/bpf.h

   1 /* SPDX-License-Identifier: BSD-2-Clause */
   2 /*
   3  * dhcpcd: BPF arp and bootp filtering
   4  * Copyright (c) 2006-2023 Roy Marples <roy@marples.name>
   5  * All rights reserved
   6
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  */
  28
  29 #ifndef BPF_HEADER
  30 #define BPF_HEADER
  31
  32 #define BPF_EOF                 0x01U
  33 #define BPF_PARTIALCSUM         0x02U
  34 #define BPF_BCAST               0x04U
  35
  36 /*
  37  * Even though we program the BPF filter should we trust it?
  38  * On Linux at least there is a window between opening the socket,
  39  * binding the interface and setting the filter where we receive data.
  40  * This data is NOT checked OR flushed and IS returned when reading.
  41  * We have no way of flushing it other than reading these packets!
  42  * But we don't know if they passed the filter or not ..... so we need
  43  * to validate each and every packet that comes through ourselves as well.
  44  * Even if Linux does fix this sorry state, who is to say other kernels
  45  * don't have bugs causing a similar effect?
  46  *
  47  * As such, let's strive to keep the filters just for pattern matching
  48  * to avoid waking dhcpcd up.
  49  *
  50  * If you want to be notified of any packet failing the BPF filter,
  51  * define BPF_DEBUG below.
  52  */
  53 //#define       BPF_DEBUG
  54
  55 #include "dhcpcd.h"
  56
  57 struct bpf {
  58         const struct interface *bpf_ifp;
  59         int bpf_fd;
  60         unsigned int bpf_flags;
  61         void *bpf_buffer;
  62         size_t bpf_size;
  63         size_t bpf_len;
  64         size_t bpf_pos;
  65 };
  66
  67 extern const char *bpf_name;
  68 size_t bpf_frame_header_len(const struct interface *);
  69 void *bpf_frame_header_src(const struct interface *, void *, size_t *);
  70 void *bpf_frame_header_dst(const struct interface *, void *, size_t *);
  71 int bpf_frame_bcast(const struct interface *, const void *);
  72 struct bpf * bpf_open(const struct interface *,
  73     int (*)(const struct bpf *, const struct in_addr *),
  74     const struct in_addr *);
  75 void bpf_close(struct bpf *);
  76 int bpf_attach(int, void *, unsigned int);
  77 ssize_t bpf_send(const struct bpf *, uint16_t, const void *, size_t);
  78 ssize_t bpf_read(struct bpf *, void *, size_t);
  79 int bpf_arp(const struct bpf *, const struct in_addr *);
  80 int bpf_bootp(const struct bpf *, const struct in_addr *);
  81 #endif