source: rtems-libbsd/rtemsbsd/rtems/rtems-bsd-arp-processor.c @ dd35ec5

/*
 * Copyright (c) 2014 embedded brains GmbH.  All rights reserved.
 *
 *  embedded brains GmbH
 *  Dornierstr. 4
 *  82178 Puchheim
 *  Germany
 *  <rtems@embedded-brains.de>
 *
 * Copyright (c) 2006-2013 Roy Marples <roy@marples.name>
 *
 * Some parts are derived from the dhcpcd sources.
 *
 * http://roy.marples.name/projects/dhcpcd
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <rtems/bsd/util.h>

#include <sys/cdefs.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>

#include <net/bpf.h>
#include <net/if_dl.h>
#include <arpa/inet.h>

#include <errno.h>
#include <fcntl.h>
#include <ifaddrs.h>
#include <stdlib.h>
#include <string.h>

struct rtems_bsd_arp_processor_context {
        int fd;
        uint8_t eaddr[ETHER_ADDR_LEN];
        size_t buf_size;
        uint8_t buf[];
};

#ifndef BPF_ETHCOOK
# define BPF_ETHCOOK 0
#endif
#ifndef BPF_WHOLEPACKET
# define BPF_WHOLEPACKET ~0U
#endif
static const struct bpf_insn arp_bpf_filter[] = {
        /* Make sure this is an ARP packet... */
        BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
        BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_ARP, 0, 3),
        /* Make sure this is an ARP REQUEST... */
        BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20 + BPF_ETHCOOK),
        BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REQUEST, 2, 0),
        /* or ARP REPLY... */
        BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20 + BPF_ETHCOOK),
        BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REPLY, 0, 1),
        /* If we passed all the tests, ask for the whole packet. */
        BPF_STMT(BPF_RET + BPF_K, BPF_WHOLEPACKET),
        /* Otherwise, drop it. */
        BPF_STMT(BPF_RET + BPF_K, 0)
};

static const size_t arp_bpf_filter_len =
    sizeof(arp_bpf_filter) / sizeof(arp_bpf_filter[0]);

static void
process_arp_packet(const uint8_t *pkt, size_t pkt_size, int fd,
    const uint8_t eaddr[ETHER_ADDR_LEN], rtems_bsd_arp_processor processor,
    void *arg)
{
        struct arphdr ar;
        uint32_t spa;
        uint32_t tpa;
        const uint8_t *sha;
        const uint8_t *tha;

        /* We must have a full ARP header */
        if (pkt_size < sizeof(ar))
                return;

        memcpy(&ar, pkt, sizeof(ar));

        /* Protocol must be IP. */
        if (ar.ar_pro != htons(ETHERTYPE_IP))
                return;

        if (ar.ar_pln != sizeof(spa))
                return;

        /* Only these types are recognised */
        if (ar.ar_op != htons(ARPOP_REPLY) &&
            ar.ar_op != htons(ARPOP_REQUEST))
                return;

        /* Get pointers to the hardware addresses */
        sha = pkt + sizeof(ar);
        tha = sha + ar.ar_hln + ar.ar_pln;

        /* Ensure we got all the data */
        if ((tha + ar.ar_hln + ar.ar_pln) - pkt > pkt_size)
                return;

        /* Ignore messages from ourself */
        if (ar.ar_hln == ETHER_ADDR_LEN &&
            memcmp(sha, &eaddr[0], ETHER_ADDR_LEN) == 0)
                return;

        /* Copy out the IP addresses */
        memcpy(&spa, sha + ar.ar_hln, ar.ar_pln);
        memcpy(&tpa, tha + ar.ar_hln, ar.ar_pln);

        (*processor)(arg, fd, eaddr, &ar, spa, tpa, sha, tha);
}

rtems_bsd_arp_processor_context *
rtems_bsd_arp_processor_create(const char *ifname)
{
        rtems_bsd_arp_processor_context *ctx = NULL;
        int fd = -1;
        struct ifreq ifr;
        int buf_len;
        size_t buf_size;
        struct bpf_version pv;
        struct bpf_program pf;
        int flags;
        int rv;

        fd = open("/dev/bpf", O_RDWR);
        if (fd < 0) {
                goto error;
        }

        rv = ioctl(fd, BIOCVERSION, &pv);
        if (rv != 0 || pv.bv_major != BPF_MAJOR_VERSION ||
            pv.bv_minor < BPF_MINOR_VERSION) {
                goto error;
        }

        memset(&ifr, 0, sizeof(ifr));
        strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
        rv = ioctl(fd, BIOCSETIF, &ifr);
        if (rv != 0) {
                goto error;
        }

        rv = ioctl(fd, BIOCGBLEN, &buf_len);
        if (rv != 0 || buf_len <= 0) {
                goto error;
        }
        buf_size = (size_t) buf_len;

        flags = 1;
        rv = ioctl(fd, BIOCIMMEDIATE, &flags);
        if (rv != 0) {
                goto error;
        }

        pf.bf_insns = __DECONST(struct bpf_insn *, arp_bpf_filter);
        pf.bf_len = arp_bpf_filter_len;
        rv = ioctl(fd, BIOCSETF, &pf);
        if (rv != 0) {
                goto error;
        }

        ctx = malloc(sizeof(*ctx) + buf_size);
        if (ctx == NULL) {
                goto error;
        }

        rv = rtems_bsd_get_ethernet_addr(ifname, &ctx->eaddr[0]);
        if (rv != 0) {
                goto error;
        }

        ctx->fd = fd;
        ctx->buf_size = buf_size;

        return ctx;

error:
        close(fd);
        free(ctx);

        return NULL;
}

int
rtems_bsd_arp_processor_get_file_descriptor(
    const rtems_bsd_arp_processor_context *ctx)
{
        return ctx->fd;
}

int
rtems_bsd_arp_processor_process(
    rtems_bsd_arp_processor_context *ctx,
    rtems_bsd_arp_processor processor, void *arg)
{
        ssize_t n;
        size_t buf_avail;
        size_t buf_pos;

        n = read(ctx->fd, &ctx->buf[0], ctx->buf_size);
        if (n < 0) {
                return -1;
        }

        buf_avail = (size_t) n;
        buf_pos = 0;

        while (buf_pos < buf_avail) {
                const uint8_t *pkt = &ctx->buf[0] + buf_pos;
                struct bpf_hdr bp;

                memcpy(&bp, pkt, sizeof(bp));

                if (bp.bh_caplen == bp.bh_datalen &&
                    buf_pos + bp.bh_caplen + bp.bh_hdrlen <= buf_avail) {
                        const uint8_t *payload = pkt + bp.bh_hdrlen +
                            ETHER_HDR_LEN;
                        size_t payload_size = bp.bh_caplen - ETHER_HDR_LEN;

                        process_arp_packet(payload, payload_size, ctx->fd, ctx->eaddr,
                            processor, NULL);
                }

                buf_pos += BPF_WORDALIGN(bp.bh_hdrlen + bp.bh_caplen);
        }

        return 0;
}