net/npf/npf_bpf.c

/*-
 * Copyright (c) 2009-2013 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This material is based upon work partially supported by The
 * NetBSD Foundation under a contract with Mindaugas Rasiukevicius.
 *
 * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

/*
 * NPF byte-code processing.
 */

#ifdef _KERNEL
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: npf_bpf.c,v 1.14 2018/09/29 14:41:36 rmind Exp $");

#include <sys/types.h>
#include <sys/param.h>

#include <sys/bitops.h>
#include <sys/mbuf.h>
#include <net/bpf.h>
#endif

#define NPF_BPFCOP
#include "npf_impl.h"

#if defined(_NPF_STANDALONE)
#define   m_length(m)                   (nbuf)->nb_mops->getchainlen(m)
#endif

/*
 * BPF context and the coprocessor.
 */

static bpf_ctx_t *npf_bpfctx __read_mostly;

static uint32_t     npf_cop_l3(const bpf_ctx_t *, bpf_args_t *, uint32_t);
static uint32_t     npf_cop_table(const bpf_ctx_t *, bpf_args_t *, uint32_t);

static const bpf_copfunc_t npf_bpfcop[] = {
          [NPF_COP_L3]        = npf_cop_l3,
          [NPF_COP_TABLE]     = npf_cop_table,
};

#define   BPF_MW_ALLMASK \
    ((1U << BPF_MW_IPVER) | (1U << BPF_MW_L4OFF) | (1U << BPF_MW_L4PROTO))

void
npf_bpf_sysinit(void)
{
          npf_bpfctx = bpf_create();
          bpf_set_cop(npf_bpfctx, npf_bpfcop, __arraycount(npf_bpfcop));
          bpf_set_extmem(npf_bpfctx, NPF_BPF_NWORDS, BPF_MW_ALLMASK);
}

void
npf_bpf_sysfini(void)
{
          bpf_destroy(npf_bpfctx);
}

void
npf_bpf_prepare(npf_cache_t *npc, bpf_args_t *args, uint32_t *M)
{
          nbuf_t *nbuf = npc->npc_nbuf;
          const struct mbuf *mbuf = nbuf_head_mbuf(nbuf);
          const size_t pktlen = m_length(mbuf);

          /* Prepare the arguments for the BPF programs. */
#ifdef _NPF_STANDALONE
          args->pkt = (const uint8_t *)nbuf_dataptr(nbuf);
          args->wirelen = args->buflen = pktlen;
#else
          args->pkt = (const uint8_t *)mbuf;
          args->wirelen = pktlen;
          args->buflen = 0;
#endif
          args->mem = M;
          args->arg = npc;

          /*
           * Convert address length to IP version.  Just mask out
           * number 4 or set 6 if higher bits set, such that:
           *
           *        0         =>        0
           *        4         =>        4 (IPVERSION)
           *        16        =>        6 (IPV6_VERSION >> 4)
           */
          const u_int alen = npc->npc_alen;
          const uint32_t ver = (alen & 4) | ((alen >> 4) * 6);

          /*
           * Output words in the memory store:
           *        BPF_MW_IPVER        IP version (4 or 6).
           *        BPF_MW_L4OFF        L4 header offset.
           *        BPF_MW_L4PROTO      L4 protocol.
           */
          M[BPF_MW_IPVER] = ver;
          M[BPF_MW_L4OFF] = npc->npc_hlen;
          M[BPF_MW_L4PROTO] = npc->npc_proto;
}

int
npf_bpf_filter(bpf_args_t *args, const void *code, bpfjit_func_t jcode)
{
          /* Execute JIT-compiled code. */
          if (__predict_true(jcode)) {
                    return jcode(npf_bpfctx, args);
          }

          /* Execute BPF byte-code. */
          return bpf_filter_ext(npf_bpfctx, code, args);
}

void *
npf_bpf_compile(void *code, size_t size)
{
          return bpf_jit_generate(npf_bpfctx, code, size);
}

bool
npf_bpf_validate(const void *code, size_t len)
{
          const size_t icount = len / sizeof(struct bpf_insn);
          return bpf_validate_ext(npf_bpfctx, code, icount) != 0;
}

/*
 * NPF_COP_L3: fetches layer 3 information.
 */
static uint32_t
npf_cop_l3(const bpf_ctx_t *bc, bpf_args_t *args, uint32_t A)
{
          const npf_cache_t * const npc = (const npf_cache_t *)args->arg;
          const uint32_t ver = (npc->npc_alen & 4) | ((npc->npc_alen >> 4) * 6);
          uint32_t * const M = args->mem;

          M[BPF_MW_IPVER] = ver;
          M[BPF_MW_L4OFF] = npc->npc_hlen;
          M[BPF_MW_L4PROTO] = npc->npc_proto;
          return ver; /* A <- IP version */
}

#define   SRC_FLAG_BIT        (1U << 31)

/*
 * NPF_COP_TABLE: perform NPF table lookup.
 *
 *        A <- non-zero (true) if found and zero (false) otherwise
 */
static uint32_t
npf_cop_table(const bpf_ctx_t *bc, bpf_args_t *args, uint32_t A)
{
          const npf_cache_t * const npc = (const npf_cache_t *)args->arg;
          npf_tableset_t *tblset = npf_config_tableset(npc->npc_ctx);
          const uint32_t tid = A & (SRC_FLAG_BIT - 1);
          const npf_addr_t *addr;
          npf_table_t *t;

          if (!npf_iscached(npc, NPC_IP46)) {
                    return 0;
          }
          t = npf_tableset_getbyid(tblset, tid);
          if (__predict_false(!t)) {
                    return 0;
          }
          addr = npc->npc_ips[(A & SRC_FLAG_BIT) ? NPF_SRC : NPF_DST];
          return npf_table_lookup(t, npc->npc_alen, addr) == 0;
}