msg_in.c

《嵌入式网络系统设计-基于Atmel ARM7 系列》这个本书的光盘资料

  }
  derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, SNMP_COMMUNITY_STR_LEN, m_stat->community);
  if (derr != ERR_OK)
  {
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  /* add zero terminator */
  len = ((len < (SNMP_COMMUNITY_STR_LEN))?(len):(SNMP_COMMUNITY_STR_LEN));
  m_stat->community[len] = 0;
  m_stat->com_strlen = len;
  if (strncmp(snmp_publiccommunity, (const char*)m_stat->community, SNMP_COMMUNITY_STR_LEN) != 0)
  {
    /** @todo: move this if we need to check more names */
    snmp_inc_snmpinbadcommunitynames();
    snmp_authfail_trap();
    return ERR_ARG;
  }
  ofs += (1 + len_octets + len);
  snmp_asn1_dec_type(p, ofs, &type);
  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
  if (derr != ERR_OK)
  {
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  switch(type)
  {
    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_REQ):
      /* GetRequest PDU */
      snmp_inc_snmpingetrequests();
      derr = ERR_OK;
      break;
    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_NEXT_REQ):
      /* GetNextRequest PDU */
      snmp_inc_snmpingetnexts();
      derr = ERR_OK;
      break;
    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_RESP):
      /* GetResponse PDU */
      snmp_inc_snmpingetresponses();
      derr = ERR_ARG;
      break;
    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_SET_REQ):
      /* SetRequest PDU */
      snmp_inc_snmpinsetrequests();
      derr = ERR_OK;
      break;
    case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_TRAP):
      /* Trap PDU */
      snmp_inc_snmpintraps();
      derr = ERR_ARG;
      break;
    default:
      snmp_inc_snmpinasnparseerrs();
      derr = ERR_ARG;
      break;
  }
  if (derr != ERR_OK)
  {
    /* unsupported input PDU for this agent (no parse error) */
    return ERR_ARG;
  }
  m_stat->rt = type & 0x1F;
  ofs += (1 + len_octets);
  if (len != (pdu_len - (ofs - ofs_base)))
  {
    /* decoded PDU length does not equal actual payload length */
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  snmp_asn1_dec_type(p, ofs, &type);
  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
  if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
  {
    /* can't decode or no integer (request ID) */
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->rid);
  if (derr != ERR_OK)
  {
    /* can't decode */
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  ofs += (1 + len_octets + len);
  snmp_asn1_dec_type(p, ofs, &type);
  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
  if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
  {
    /* can't decode or no integer (error-status) */
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  /* must be noError (0) for incoming requests.
     log errors for mib-2 completeness and for debug purposes */
  derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->error_status);
  if (derr != ERR_OK)
  {
    /* can't decode */
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  switch (m_stat->error_status)
  {
    case SNMP_ES_TOOBIG:
      snmp_inc_snmpintoobigs();
      break;
    case SNMP_ES_NOSUCHNAME:
      snmp_inc_snmpinnosuchnames();
      break;
    case SNMP_ES_BADVALUE:
      snmp_inc_snmpinbadvalues();
      break;
    case SNMP_ES_READONLY:
      snmp_inc_snmpinreadonlys();
      break;
    case SNMP_ES_GENERROR:
      snmp_inc_snmpingenerrs();
      break;
  }
  ofs += (1 + len_octets + len);
  snmp_asn1_dec_type(p, ofs, &type);
  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
  if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
  {
    /* can't decode or no integer (error-index) */
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  /* must be 0 for incoming requests.
     decode anyway to catch bad integers (and dirty tricks) */
  derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->error_index);
  if (derr != ERR_OK)
  {
    /* can't decode */
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  ofs += (1 + len_octets + len);
  *ofs_ret = ofs;
  return ERR_OK;
}

static err_t
snmp_pdu_dec_varbindlist(struct pbuf *p, u16_t ofs, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat)
{
  err_t derr;
  u16_t len, vb_len;
  u8_t  len_octets;
  u8_t type;

  /* variable binding list */
  snmp_asn1_dec_type(p, ofs, &type);
  derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &vb_len);
  if ((derr != ERR_OK) ||
      (type != (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ)))
  {
    snmp_inc_snmpinasnparseerrs();
    return ERR_ARG;
  }
  ofs += (1 + len_octets);

  /* start with empty list */
  m_stat->invb.count = 0;
  m_stat->invb.head = NULL;
  m_stat->invb.tail = NULL;

  while (vb_len > 0)
  {
    struct snmp_obj_id oid, oid_value;
    struct snmp_varbind *vb;

    snmp_asn1_dec_type(p, ofs, &type);
    derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
    if ((derr != ERR_OK) ||
        (type != (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ)) ||
        (len <= 0) || (len > vb_len))
    {
      snmp_inc_snmpinasnparseerrs();
      /* free varbinds (if available) */
      snmp_varbind_list_free(&m_stat->invb);
      return ERR_ARG;
    }
    ofs += (1 + len_octets);
    vb_len -= (1 + len_octets);

    snmp_asn1_dec_type(p, ofs, &type);
    derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
    if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OBJ_ID)))
    {
      /* can't decode object name length */
      snmp_inc_snmpinasnparseerrs();
      /* free varbinds (if available) */
      snmp_varbind_list_free(&m_stat->invb);
      return ERR_ARG;
    }
    derr = snmp_asn1_dec_oid(p, ofs + 1 + len_octets, len, &oid);
    if (derr != ERR_OK)
    {
      /* can't decode object name */
      snmp_inc_snmpinasnparseerrs();
      /* free varbinds (if available) */
      snmp_varbind_list_free(&m_stat->invb);
      return ERR_ARG;
    }
    ofs += (1 + len_octets + len);
    vb_len -= (1 + len_octets + len);

    snmp_asn1_dec_type(p, ofs, &type);
    derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
    if (derr != ERR_OK)
    {
      /* can't decode object value length */
      snmp_inc_snmpinasnparseerrs();
      /* free varbinds (if available) */
      snmp_varbind_list_free(&m_stat->invb);
      return ERR_ARG;
    }

    switch (type)
    {
      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG):
        vb = snmp_varbind_alloc(&oid, type, sizeof(s32_t));
        if (vb != NULL)
        {
          s32_t *vptr = vb->value;

          derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, vptr);
          snmp_varbind_tail_add(&m_stat->invb, vb);
        }
        else
        {
          derr = ERR_ARG;
        }
        break;
      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_COUNTER):
      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_GAUGE):
      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_TIMETICKS):
        vb = snmp_varbind_alloc(&oid, type, sizeof(u32_t));
        if (vb != NULL)
        {
          u32_t *vptr = vb->value;

          derr = snmp_asn1_dec_u32t(p, ofs + 1 + len_octets, len, vptr);
          snmp_varbind_tail_add(&m_stat->invb, vb);
        }
        else
        {
          derr = ERR_ARG;
        }
        break;
      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OC_STR):
      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_OPAQUE):
        vb = snmp_varbind_alloc(&oid, type, len);
        if (vb != NULL)
        {
          derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, vb->value_len, vb->value);
          snmp_varbind_tail_add(&m_stat->invb, vb);
        }
        else
        {
          derr = ERR_ARG;
        }
        break;
      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_NUL):
        vb = snmp_varbind_alloc(&oid, type, 0);
        if (vb != NULL)
        {
          snmp_varbind_tail_add(&m_stat->invb, vb);
          derr = ERR_OK;
        }
        else
        {
          derr = ERR_ARG;
        }
        break;
      case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OBJ_ID):
        derr = snmp_asn1_dec_oid(p, ofs + 1 + len_octets, len, &oid_value);
        if (derr == ERR_OK)
        {
          vb = snmp_varbind_alloc(&oid, type, oid_value.len * sizeof(s32_t));
          if (vb != NULL)
          {
            u8_t i = oid_value.len;
            s32_t *vptr = vb->value;

            while(i > 0)
            {
              i--;
              vptr[i] = oid_value.id[i];
            }
            snmp_varbind_tail_add(&m_stat->invb, vb);
            derr = ERR_OK;
          }
          else
          {
            derr = ERR_ARG;
          }
        }
        break;
      case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_IPADDR):
        if (len == 4)
        {
          /* must be exactly 4 octets! */
          vb = snmp_varbind_alloc(&oid, type, 4);
          if (vb != NULL)
          {
            derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, vb->value_len, vb->value);
            snmp_varbind_tail_add(&m_stat->invb, vb);
          }
          else
          {
            derr = ERR_ARG;
          }
        }
        else
        {
          derr = ERR_ARG;
        }
        break;
      default:
        derr = ERR_ARG;
        break;
    }
    if (derr != ERR_OK)
    {
      snmp_inc_snmpinasnparseerrs();
      /* free varbinds (if available) */
      snmp_varbind_list_free(&m_stat->invb);
      return ERR_ARG;
    }
    ofs += (1 + len_octets + len);
    vb_len -= (1 + len_octets + len);
  }

  if (m_stat->rt == SNMP_ASN1_PDU_SET_REQ)
  {
    snmp_add_snmpintotalsetvars(m_stat->invb.count);
  }
  else
  {
    snmp_add_snmpintotalreqvars(m_stat->invb.count);
  }

  *ofs_ret = ofs;
  return ERR_OK;
}

struct snmp_varbind*
snmp_varbind_alloc(struct snmp_obj_id *oid, u8_t type, u8_t len)
{
  struct snmp_varbind *vb;

  vb = (struct snmp_varbind *)mem_malloc(sizeof(struct snmp_varbind));
  LWIP_ASSERT("vb != NULL",vb != NULL);
  if (vb != NULL)
  {
    u8_t i;

    vb->next = NULL;
    vb->prev = NULL;
    i = oid->len;
    vb->ident_len = i;
    if (i > 0)
    {
      /* allocate array of s32_t for our object identifier */
      vb->ident = (s32_t*)mem_malloc(sizeof(s32_t) * i);
      LWIP_ASSERT("vb->ident != NULL",vb->ident != NULL);
      if (vb->ident == NULL)
      {
        mem_free(vb);
        return NULL;
      }
      while(i > 0)
      {
        i--;
        vb->ident[i] = oid->id[i];
      }
    }
    else
    {
      /* i == 0, pass zero length object identifier */
      vb->ident = NULL;
    }
    vb->value_type = type;
    vb->value_len = len;
    if (len > 0)
    {
      /* allocate raw bytes for our object value */
      vb->value = mem_malloc(len);
      LWIP_ASSERT("vb->value != NULL",vb->value != NULL);
      if (vb->value == NULL)
      {
        if (vb->ident != NULL)
        {
          mem_free(vb->ident);
        }
        mem_free(vb);
        return NULL;
      }
    }
    else
    {
      /* ASN1_NUL type, or zero length ASN1_OC_STR */
      vb->value = NULL;
    }
  }
  return vb;
}

void
snmp_varbind_free(struct snmp_varbind *vb)
{
  if (vb->value != NULL )
  {
    mem_free(vb->value);
  }
  if (vb->ident != NULL )
  {
    mem_free(vb->ident);
  }
  mem_free(vb);
}

void
snmp_varbind_list_free(struct snmp_varbind_root *root)
{
  struct snmp_varbind *vb, *prev;

  vb = root->tail;
  while ( vb != NULL )
  {
    prev = vb->prev;
    snmp_varbind_free(vb);
    vb = prev;
  }
  root->count = 0;
  root->head = NULL;
  root->tail = NULL;
}

void
snmp_varbind_tail_add(struct snmp_varbind_root *root, struct snmp_varbind *vb)
{
  if (root->count == 0)
  {
    /* add first varbind to list */
    root->head = vb;
    root->tail = vb;
  }
  else
  {
    /* add nth varbind to list tail */
    root->tail->next = vb;
    vb->prev = root->tail;
    root->tail = vb;
  }
  root->count += 1;
}

struct snmp_varbind*
snmp_varbind_tail_remove(struct snmp_varbind_root *root)
{
  struct snmp_varbind* vb;

  if (root->count > 0)
  {
    /* remove tail varbind */
    vb = root->tail;
    root->tail = vb->prev;
    vb->prev->next = NULL;
    root->count -= 1;
  }
  else
  {
    /* nothing to remove */
    vb = NULL;
  }
  return vb;
}

#endif /* LWIP_SNMP */