event_tagging.c

/*
 * Copyright (c) 2003, 2004 Niels Provos <provos@citi.umich.edu>
 * All rights reserved.
 *
 * 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.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 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.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif

#ifdef WIN32
#define WIN32_LEAN_AND_MEAN
#include <winsock2.h>
#include <windows.h>
#undef WIN32_LEAN_AND_MEAN
#else
#include <sys/ioctl.h>
#endif

#include <sys/queue.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifndef WIN32
#include <syslog.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "event.h"
#include "evutil.h"
#include "log.h"

int evtag_decode_int(ev_uint32_t* pnumber, struct evbuffer* evbuf);
int evtag_encode_tag(struct evbuffer* evbuf, ev_uint32_t tag);
int evtag_decode_tag(ev_uint32_t* ptag, struct evbuffer* evbuf);

static struct evbuffer* _buf;   /* not thread safe */

void
evtag_init(void)
{
    if (_buf != NULL)
        return;

    if ((_buf = evbuffer_new()) == NULL)
        event_err(1, "%s: malloc", __func__);
}

/*
 * We encode integer's by nibbles; the first nibble contains the number
 * of significant nibbles - 1;  this allows us to encode up to 64-bit
 * integers.  This function is byte-order independent.
 */

void
encode_int(struct evbuffer* evbuf, ev_uint32_t number)
{
    int off = 1, nibbles = 0;
    ev_uint8_t data[5];

    memset(data, 0, sizeof(ev_uint32_t) + 1);
    while (number) {
        if (off & 0x1)
            data[off / 2] = (data[off / 2] & 0xf0) | (number & 0x0f);
        else
            data[off / 2] = (data[off / 2] & 0x0f) |
                            ((number & 0x0f) << 4);
        number >>= 4;
        off++;
    }

    if (off > 2)
        nibbles = off - 2;

    /* Off - 1 is the number of encoded nibbles */
    data[0] = (data[0] & 0x0f) | ((nibbles & 0x0f) << 4);

    evbuffer_add(evbuf, data, (off + 1) / 2);
}

/*
 * Support variable length encoding of tags; we use the high bit in each
 * octet as a continuation signal.
 */

int
evtag_encode_tag(struct evbuffer* evbuf, ev_uint32_t tag)
{
    int bytes = 0;
    ev_uint8_t data[5];

    memset(data, 0, sizeof(data));
    do {
        ev_uint8_t lower = tag & 0x7f;
        tag >>= 7;

        if (tag)
            lower |= 0x80;

        data[bytes++] = lower;
    } while (tag);

    if (evbuf != NULL)
        evbuffer_add(evbuf, data, bytes);

    return (bytes);
}

static int
decode_tag_internal(ev_uint32_t* ptag, struct evbuffer* evbuf, int dodrain)
{
    ev_uint32_t number = 0;
    ev_uint8_t* data = EVBUFFER_DATA(evbuf);
    int len = EVBUFFER_LENGTH(evbuf);
    int count = 0, shift = 0, done = 0;

    while (count++ < len) {
        ev_uint8_t lower = *data++;
        number |= (lower & 0x7f) << shift;
        shift += 7;

        if (!(lower & 0x80)) {
            done = 1;
            break;
        }
    }

    if (!done)
        return (-1);

    if (dodrain)
        evbuffer_drain(evbuf, count);

    if (ptag != NULL)
        *ptag = number;

    return (count);
}

int
evtag_decode_tag(ev_uint32_t* ptag, struct evbuffer* evbuf)
{
    return (decode_tag_internal(ptag, evbuf, 1 /* dodrain */));
}

/*
 * Marshal a data type, the general format is as follows:
 *
 * tag number: one byte; length: var bytes; payload: var bytes
 */

void
evtag_marshal(struct evbuffer* evbuf, ev_uint32_t tag,
              const void* data, ev_uint32_t len)
{
    evtag_encode_tag(evbuf, tag);
    encode_int(evbuf, len);
    evbuffer_add(evbuf, (void*)data, len);
}

/* Marshaling for integers */
void
evtag_marshal_int(struct evbuffer* evbuf, ev_uint32_t tag, ev_uint32_t integer)
{
    evbuffer_drain(_buf, EVBUFFER_LENGTH(_buf));
    encode_int(_buf, integer);

    evtag_encode_tag(evbuf, tag);
    encode_int(evbuf, EVBUFFER_LENGTH(_buf));
    evbuffer_add_buffer(evbuf, _buf);
}

void
evtag_marshal_string(struct evbuffer* buf, ev_uint32_t tag, const char* string)
{
    evtag_marshal(buf, tag, string, strlen(string));
}

void
evtag_marshal_timeval(struct evbuffer* evbuf, ev_uint32_t tag, struct timeval* tv)
{
    evbuffer_drain(_buf, EVBUFFER_LENGTH(_buf));

    encode_int(_buf, tv->tv_sec);
    encode_int(_buf, tv->tv_usec);

    evtag_marshal(evbuf, tag, EVBUFFER_DATA(_buf),
                  EVBUFFER_LENGTH(_buf));
}

static int
decode_int_internal(ev_uint32_t* pnumber, struct evbuffer* evbuf, int dodrain)
{
    ev_uint32_t number = 0;
    ev_uint8_t* data = EVBUFFER_DATA(evbuf);
    int len = EVBUFFER_LENGTH(evbuf);
    int nibbles = 0;

    if (!len)
        return (-1);

    nibbles = ((data[0] & 0xf0) >> 4) + 1;
    if (nibbles > 8 || (nibbles >> 1) + 1 > len)
        return (-1);
    len = (nibbles >> 1) + 1;

    while (nibbles > 0) {
        number <<= 4;
        if (nibbles & 0x1)
            number |= data[nibbles >> 1] & 0x0f;
        else
            number |= (data[nibbles >> 1] & 0xf0) >> 4;
        nibbles--;
    }

    if (dodrain)
        evbuffer_drain(evbuf, len);

    *pnumber = number;

    return (len);
}

int
evtag_decode_int(ev_uint32_t* pnumber, struct evbuffer* evbuf)
{
    return (decode_int_internal(pnumber, evbuf, 1) == -1 ? -1 : 0);
}

int
evtag_peek(struct evbuffer* evbuf, ev_uint32_t* ptag)
{
    return (decode_tag_internal(ptag, evbuf, 0 /* dodrain */));
}

int
evtag_peek_length(struct evbuffer* evbuf, ev_uint32_t* plength)
{
    struct evbuffer tmp;
    int res, len;

    len = decode_tag_internal(NULL, evbuf, 0 /* dodrain */);
    if (len == -1)
        return (-1);

    tmp = *evbuf;
    tmp.buffer += len;
    tmp.off -= len;

    res = decode_int_internal(plength, &tmp, 0);
    if (res == -1)
        return (-1);

    *plength += res + len;

    return (0);
}

int
evtag_payload_length(struct evbuffer* evbuf, ev_uint32_t* plength)
{
    struct evbuffer tmp;
    int res, len;

    len = decode_tag_internal(NULL, evbuf, 0 /* dodrain */);
    if (len == -1)
        return (-1);

    tmp = *evbuf;
    tmp.buffer += len;
    tmp.off -= len;

    res = decode_int_internal(plength, &tmp, 0);
    if (res == -1)
        return (-1);

    return (0);
}

int
evtag_consume(struct evbuffer* evbuf)
{
    ev_uint32_t len;
    if (decode_tag_internal(NULL, evbuf, 1 /* dodrain */) == -1)
        return (-1);
    if (evtag_decode_int(&len, evbuf) == -1)
        return (-1);
    evbuffer_drain(evbuf, len);

    return (0);
}

/* Reads the data type from an event buffer */

int
evtag_unmarshal(struct evbuffer* src, ev_uint32_t* ptag, struct evbuffer* dst)
{
    ev_uint32_t len;
    ev_uint32_t integer;

    if (decode_tag_internal(ptag, src, 1 /* dodrain */) == -1)
        return (-1);
    if (evtag_decode_int(&integer, src) == -1)
        return (-1);
    len = integer;

    if (EVBUFFER_LENGTH(src) < len)
        return (-1);

    if (evbuffer_add(dst, EVBUFFER_DATA(src), len) == -1)
        return (-1);

    evbuffer_drain(src, len);

    return (len);
}

/* Marshaling for integers */

int
evtag_unmarshal_int(struct evbuffer* evbuf, ev_uint32_t need_tag,
                    ev_uint32_t* pinteger)
{
    ev_uint32_t tag;
    ev_uint32_t len;
    ev_uint32_t integer;

    if (decode_tag_internal(&tag, evbuf, 1 /* dodrain */) == -1)
        return (-1);
    if (need_tag != tag)
        return (-1);
    if (evtag_decode_int(&integer, evbuf) == -1)
        return (-1);
    len = integer;

    if (EVBUFFER_LENGTH(evbuf) < len)
        return (-1);

    evbuffer_drain(_buf, EVBUFFER_LENGTH(_buf));
    if (evbuffer_add(_buf, EVBUFFER_DATA(evbuf), len) == -1)
        return (-1);

    evbuffer_drain(evbuf, len);

    return (evtag_decode_int(pinteger, _buf));
}

/* Unmarshal a fixed length tag */

int
evtag_unmarshal_fixed(struct evbuffer* src, ev_uint32_t need_tag, void* data,
                      size_t len)
{
    ev_uint32_t tag;

    /* Initialize this event buffer so that we can read into it */
    evbuffer_drain(_buf, EVBUFFER_LENGTH(_buf));

    /* Now unmarshal a tag and check that it matches the tag we want */
    if (evtag_unmarshal(src, &tag, _buf) == -1 || tag != need_tag)
        return (-1);

    if (EVBUFFER_LENGTH(_buf) != len)
        return (-1);

    memcpy(data, EVBUFFER_DATA(_buf), len);
    return (0);
}

int
evtag_unmarshal_string(struct evbuffer* evbuf, ev_uint32_t need_tag,
                       char** pstring)
{
    ev_uint32_t tag;

    evbuffer_drain(_buf, EVBUFFER_LENGTH(_buf));

    if (evtag_unmarshal(evbuf, &tag, _buf) == -1 || tag != need_tag)
        return (-1);

    *pstring = calloc(EVBUFFER_LENGTH(_buf) + 1, 1);
    if (*pstring == NULL)
        event_err(1, "%s: calloc", __func__);
    evbuffer_remove(_buf, *pstring, EVBUFFER_LENGTH(_buf));

    return (0);
}

int
evtag_unmarshal_timeval(struct evbuffer* evbuf, ev_uint32_t need_tag,
                        struct timeval* ptv)
{
    ev_uint32_t tag;
    ev_uint32_t integer;

    evbuffer_drain(_buf, EVBUFFER_LENGTH(_buf));
    if (evtag_unmarshal(evbuf, &tag, _buf) == -1 || tag != need_tag)
        return (-1);

    if (evtag_decode_int(&integer, _buf) == -1)
        return (-1);
    ptv->tv_sec = integer;
    if (evtag_decode_int(&integer, _buf) == -1)
        return (-1);
    ptv->tv_usec = integer;

    return (0);
}