path: root/src/tcpedit/plugins/dlt_utils.c

/* $Id: dlt_utils.c 2423 2010-03-13 07:09:49Z aturner $ */

/*
 * Copyright (c) 2006-2010 Aaron Turner.
 * 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. Neither the names of the copyright owners nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``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 AUTHORS OR COPYRIGHT HOLDERS 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 <string.h>

#include "dlt_plugins-int.h"  
#include "dlt_utils.h"
#include "common.h"

/* from dlt_plugins.c */
extern const u_int32_t tcpeditdlt_bit_map[];
extern const char *tcpeditdlt_bit_info[];

/*
 * Call parse args on src & dst plugins
 */
int 
tcpedit_dlt_parse_opts(tcpeditdlt_t *ctx)
{
    assert(ctx);
    
    if (ctx->decoder->plugin_parse_opts(ctx) != TCPEDIT_OK)
        return TCPEDIT_ERROR;
        
    if (ctx->decoder->dlt != ctx->encoder->dlt) {
        if (ctx->encoder->plugin_parse_opts(ctx) != TCPEDIT_OK)
            return TCPEDIT_ERROR;
    }

    return TCPEDIT_OK;
}
 
/*
 * find a given plugin struct in the context for a given DLT.  Returns NULL on failure
 */
tcpeditdlt_plugin_t *
tcpedit_dlt_getplugin(tcpeditdlt_t *ctx, int dlt)
{
    tcpeditdlt_plugin_t *ptr;
    
    assert(ctx);

    ptr = ctx->plugins;
    if (ptr == NULL)
        return NULL;
    
    while (ptr->dlt != dlt && ptr->next != NULL) {
        ptr = ptr->next;
    }
    
    if (ptr->dlt == dlt)
        return ptr;
        
    return NULL;
}

/*
 * find a given plugin struct in the context for a given DLT.  Returns NULL on failure
 */
tcpeditdlt_plugin_t *
tcpedit_dlt_getplugin_byname(tcpeditdlt_t *ctx, const char *name)
{
    tcpeditdlt_plugin_t *ptr;
    
    assert(ctx);
    assert(name);

    ptr = ctx->plugins;
    if (ptr == NULL)
        return NULL;
    
    while ((strcmp(ptr->name, name) != 0) && ptr->next != NULL) {
        ptr = ptr->next;
    }
    
    if (strcmp(ptr->name, name) == 0)
        return ptr;
        
    return NULL;
}

/* 
 * Create a new plugin struct.  WILL NOT RETURN ON FAILURE! (out of memory is not recoverable)
 */
tcpeditdlt_plugin_t *
tcpedit_dlt_newplugin(void)
{
    tcpeditdlt_plugin_t *plugin;
    
    plugin = (tcpeditdlt_plugin_t *)safe_malloc(sizeof(tcpeditdlt_plugin_t));
    plugin->dlt = 0xffff; /* zero is a valid plugin, so use 0xffff */
    return plugin;
}

/*
 * Add a plugin to the plugin chain for the given context.  Return 0 on success,
 * -1 on failure
 */
int 
tcpedit_dlt_addplugin(tcpeditdlt_t *ctx, tcpeditdlt_plugin_t *new)
{
    tcpeditdlt_plugin_t *ptr;
    assert(ctx);
    assert(new);

    /* look for a dupe by DLT */
    if ((ptr = tcpedit_dlt_getplugin(ctx, new->dlt)) != NULL) {
        tcpedit_seterr(ctx->tcpedit, "Can only have one DLT plugin registered per-DLT: 0x%x", new->dlt);
        return TCPEDIT_ERROR;
    }
    
    /* dupe by name? */
    if ((ptr = tcpedit_dlt_getplugin_byname(ctx, new->name)) != NULL) {
        tcpedit_seterr(ctx->tcpedit, "Can only have one DLT plugin registered per-name: %s", new->name);
        return TCPEDIT_ERROR;
    }
    
    /* 
     * check that the plugin is properly constructed, note that the encoder
     * and decoder are optional!
     */
    assert(new->dlt < 0xffff);
    assert(new->plugin_init);
    assert(new->plugin_cleanup);
    assert(new->plugin_parse_opts);
    assert(new->plugin_proto);
    assert(new->plugin_l2addr_type);
    assert(new->plugin_l2len);
    assert(new->plugin_get_layer3);
    assert(new->plugin_merge_layer3);

    
    /* add it to the end of the chain */
    if (ctx->plugins == NULL) {
        ctx->plugins = new;
    } else {
        ptr = ctx->plugins;
        while (ptr->next != NULL)
            ptr = ptr->next;
        
        ptr->next = new;
    }
    
    /* we're done */
    return 0;
}


/*
 * validates that the decoder plugin provides all the fields that are required
 * by then encoding plugin. Returns TCPEDIT_OK | TCPEDIT_ERROR
 */
int
tcpedit_dlt_validate(tcpeditdlt_t *ctx)
{
    u_int32_t bit;
    
    /* loops from 1 -> UINT32_MAX by powers of 2 */
    for (bit = 1; bit != 0; bit = bit << 2) {
        if (ctx->encoder->requires & bit && ! ctx->decoder->provides & bit) {
            tcpedit_seterr(ctx->tcpedit, "%s", tcpeditdlt_bit_info[tcpeditdlt_bit_map[bit]]);
            return TCPEDIT_ERROR;
        }            
    }

    dbgx(1, "Input linktype is %s", 
        pcap_datalink_val_to_description(ctx->decoder->dlt));
    dbgx(1, "Output linktype is %s", 
        pcap_datalink_val_to_description(ctx->encoder->dlt));

    return TCPEDIT_OK;
}


/*
 * Utility function to extract the Layer 3 header and beyond in a single buffer
 * Since some CPU's like UltraSPARC are strictly aligned, they really don't like
 * it when you jump to an offset which isn't on a word boundry (like ethernet)
 */
u_char *
tcpedit_dlt_l3data_copy(tcpeditdlt_t *ctx, u_char *packet, int pktlen, int l2len)
{
    u_char *ptr;
    assert(ctx);
    assert(packet);
    assert(pktlen);

    if (pktlen <= l2len)
        return NULL;
    
#ifdef FORCE_ALIGN
    /* 
     * copy layer 3 and up to our temp packet buffer
     * for now on, we have to edit the packetbuff because
     * just before we send the packet, we copy the packetbuff 
     * back onto the pkt.data + l2len buffer
     * we do all this work to prevent byte alignment issues
     */
    if (l2len % 4 == 0) {
        ptr = (&(packet)[l2len]);
    } else {
        ptr = ctx->l3buff;
        memcpy(ptr, (&(packet)[l2len]), pktlen - l2len);
    }
#else
    /*
     * on non-strict byte align systems, don't need to memcpy(), 
     * just point to 14 bytes into the existing buffer
     */
    ptr = (&(packet)[l2len]);
#endif
    return ptr;
}

/*
 * reverse of tcpedit_dlt_l3data_copy
 */
u_char *
tcpedit_dlt_l3data_merge(tcpeditdlt_t *ctx, u_char *packet, int pktlen, const u_char *l3data, const int l2len)
{
    assert(ctx);
    assert(packet);
    assert(pktlen >= 0);
    assert(l3data);
    assert(l2len >= 0);
#ifdef FORCE_ALIGN
    /* 
     * put back the layer 3 and above back in the pkt.data buffer 
     * we can't edit the packet at layer 3 or above beyond this point
     */
     if (l2len % 4 != 0)
         memcpy((&(packet)[l2len]), l3data, pktlen - l2len);
#endif
    return packet;
}