src/tcpedit/plugins/dlt_null/null.c
/* $Id$ */
/*
* Copyright (c) 2001-2010 Aaron Turner <aturner at synfin dot net>
* Copyright (c) 2013-2022 Fred Klassen <tcpreplay at appneta dot com> - AppNeta
*
* The Tcpreplay Suite of tools is free software: you can redistribute it
* and/or modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or with the authors permission any later version.
*
* The Tcpreplay Suite is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with the Tcpreplay Suite. If not, see <http://www.gnu.org/licenses/>.
*/
#include "null.h"
#include "dlt_utils.h"
#include "tcpedit.h"
#include "tcpedit_stub.h"
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h> // PF_* values
static char dlt_name[] = "null";
static char _U_ dlt_prefix[] = "null";
static uint16_t dlt_value = DLT_NULL;
/*
* From the libpcap man page:
* DLT_NULL aka BSD loopback encapsulation; the link layer header is a 4-byte
* field, in host byte order, containing a PF_ value from
* socket.h for the network-layer protocol of the packet.
*
* Note that ``host byte order'' is the byte order of the
* machine on which the packets are captured, and the PF_ values
* are for the OS of the machine on which the packets are captured;
* if a live capture is being done, ``host byte order''
* is the byte order of the machine capturing the packets, and
* the PF_ values are those of the OS of the machine capturing
* the packets, but if a ``savefile'' is being read, the byte
* order and PF_ values are not necessarily those of the machine
* reading the capture file.
*/
/*
* Function to register ourselves. This function is always called, regardless
* of what DLT types are being used, so it shouldn't be allocating extra buffers
* or anything like that (use the dlt_null_init() function below for that).
* Tasks:
* - Create a new plugin struct
* - Fill out the provides/requires bit masks. Note: Only specify which fields are
* actually in the header.
* - Add the plugin to the context's plugin chain
* Returns: TCPEDIT_ERROR | TCPEDIT_OK | TCPEDIT_WARN
*/
int
dlt_null_register(tcpeditdlt_t *ctx)
{
tcpeditdlt_plugin_t *plugin;
assert(ctx);
/* create a new plugin structure */
plugin = tcpedit_dlt_newplugin();
/* set what we provide & require */
plugin->provides += PLUGIN_MASK_PROTO;
plugin->
requires
+= 0;
/* what is our DLT value? */
plugin->dlt = dlt_value;
/* set the prefix name of our plugin. This is also used as the prefix for our options */
plugin->name = safe_strdup(dlt_prefix);
/*
* Point to our functions, note, you need a function for EVERY method.
* Even if it is only an empty stub returning success.
*/
plugin->plugin_init = dlt_null_init;
plugin->plugin_cleanup = dlt_null_cleanup;
plugin->plugin_parse_opts = dlt_null_parse_opts;
plugin->plugin_decode = dlt_null_decode;
plugin->plugin_encode = dlt_null_encode;
plugin->plugin_proto = dlt_null_proto;
plugin->plugin_l2addr_type = dlt_null_l2addr_type;
plugin->plugin_l2len = dlt_null_l2len;
plugin->plugin_get_layer3 = dlt_null_get_layer3;
plugin->plugin_merge_layer3 = dlt_null_merge_layer3;
/* add it to the available plugin list */
return tcpedit_dlt_addplugin(ctx, plugin);
}
/*
* Initializer function. This function is called only once, if and only if
* this plugin will be utilized. Remember, if you need to keep track of any state,
* store it in your plugin->config, not a global!
* Returns: TCPEDIT_ERROR | TCPEDIT_OK | TCPEDIT_WARN
*/
int
dlt_null_init(tcpeditdlt_t *ctx)
{
tcpeditdlt_plugin_t *plugin;
assert(ctx);
if ((plugin = tcpedit_dlt_getplugin(ctx, dlt_value)) == NULL) {
tcpedit_seterr(ctx->tcpedit, "Unable to initialize unregistered plugin %s", dlt_name);
return TCPEDIT_ERROR;
}
return TCPEDIT_OK; /* success */
}
/*
* Since this is used in a library, we should manually clean up after ourselves
* Unless you allocated some memory in dlt_null_init(), this is just an stub.
* Returns: TCPEDIT_ERROR | TCPEDIT_OK | TCPEDIT_WARN
*/
int
dlt_null_cleanup(tcpeditdlt_t *ctx)
{
tcpeditdlt_plugin_t *plugin;
assert(ctx);
if ((plugin = tcpedit_dlt_getplugin(ctx, dlt_value)) == NULL) {
tcpedit_seterr(ctx->tcpedit, "Unable to cleanup unregistered plugin %s", dlt_name);
return TCPEDIT_ERROR;
}
safe_free(plugin->name);
plugin->name = NULL;
safe_free(plugin->config);
plugin->config = NULL;
plugin->config_size = 0;
return TCPEDIT_OK; /* success */
}
/*
* This is where you should define all your AutoGen AutoOpts option parsing.
* Any user specified option should have it's bit turned on in the 'provides'
* bit mask.
* Returns: TCPEDIT_ERROR | TCPEDIT_OK | TCPEDIT_WARN
*/
int
dlt_null_parse_opts(tcpeditdlt_t *ctx)
{
assert(ctx);
/* nothing to parse here, move along */
return TCPEDIT_OK; /* success */
}
/*
* Function to decode the layer 2 header in the packet.
* You need to fill out:
* - ctx->l2len
* - ctx->srcaddr
* - ctx->dstaddr
* - ctx->proto
* - ctx->decoded_extra
* Returns: TCPEDIT_ERROR | TCPEDIT_OK | TCPEDIT_WARN
*/
int
dlt_null_decode(tcpeditdlt_t *ctx, const u_char *packet, int pktlen)
{
int proto;
assert(ctx);
assert(packet);
if ((proto = dlt_null_proto(ctx, packet, pktlen)) == TCPEDIT_ERROR)
return TCPEDIT_ERROR;
ctx->proto = (uint16_t)proto;
ctx->l2len = 4;
return TCPEDIT_OK; /* success */
}
/*
* Function to encode the layer 2 header back into the packet.
* Returns: total packet len or TCPEDIT_ERROR
*/
int
dlt_null_encode(tcpeditdlt_t *ctx, u_char *packet, _U_ int pktlen, _U_ tcpr_dir_t dir)
{
assert(ctx);
assert(packet);
tcpedit_seterr(ctx->tcpedit, "%s", "DLT_NULL and DLT_LOOP plugins do not support packet encoding");
return TCPEDIT_ERROR;
}
/*
* Function returns the Layer 3 protocol type of the given packet, or TCPEDIT_ERROR on error
*/
int
dlt_null_proto(tcpeditdlt_t *ctx, const u_char *packet, int pktlen)
{
assert(ctx);
assert(packet);
uint32_t *af_type;
int protocol = 0;
if (pktlen < 4)
return TCPEDIT_ERROR;
/* PF_INET is always 2 but PF_INET6 varies based on platform, i.e
* Linux - 10
* NetBSD,OpenBSD,BSD/OS - 24
* NetBSD,OpenBSD,BSD/OS - 28
* Darwin/macOS - 30
* See https://gitlab.com/wireshark/wireshark/-/wikis/NullLoopback
*/
af_type = (uint32_t *)packet;
if (*af_type == PF_INET || SWAPLONG(*af_type) == PF_INET) {
protocol = ETHERTYPE_IP;
} else if (*af_type == PF_INET6 || SWAPLONG(*af_type) == PF_INET6 || *af_type == 10 || SWAPLONG(*af_type) == 10 ||
*af_type == 24 || SWAPLONG(*af_type) == 24 || *af_type == 28 || SWAPLONG(*af_type) == 28 ||
*af_type == 30 || SWAPLONG(*af_type) == 30) {
protocol = ETHERTYPE_IP6;
} else {
tcpedit_seterr(ctx->tcpedit, "Unsupported DLT_NULL/DLT_LOOP PF_ type: 0x%04x", *af_type);
return TCPEDIT_ERROR;
}
return htons(protocol);
}
/*
* Function returns a pointer to the layer 3 protocol header or NULL on error
*/
u_char *
dlt_null_get_layer3(tcpeditdlt_t *ctx, u_char *packet, int pktlen)
{
int l2len;
assert(ctx);
assert(packet);
l2len = dlt_null_l2len(ctx, packet, pktlen);
if (pktlen < l2len)
return NULL;
return tcpedit_dlt_l3data_copy(ctx, packet, pktlen, l2len);
}
/*
* function merges the packet (containing L2 and old L3) with the l3data buffer
* containing the new l3 data. Note, if L2 % 4 == 0, then they're pointing to the
* same buffer, otherwise there was a memcpy involved on strictly aligned architectures
* like SPARC
*/
u_char *
dlt_null_merge_layer3(tcpeditdlt_t *ctx, u_char *packet, int pktlen, u_char *ipv4_data, u_char *ipv6_data)
{
int l2len;
assert(ctx);
assert(packet);
assert(ipv4_data || ipv6_data);
l2len = dlt_null_l2len(ctx, packet, pktlen);
if (pktlen < l2len)
return NULL;
return tcpedit_dlt_l3data_merge(ctx, packet, pktlen, ipv4_data ?: ipv6_data, l2len);
}
/*
* return the length of the L2 header of the current packet
*/
int
dlt_null_l2len(tcpeditdlt_t *ctx, const u_char *packet, int pktlen)
{
assert(ctx);
assert(packet);
if (pktlen < 4)
return 0;
/* always is 4 */
return 4;
}
/*
* return a static pointer to the source/destination MAC address
* return NULL on error/address doesn't exist
*/
u_char *
dlt_null_get_mac(tcpeditdlt_t *ctx, _U_ tcpeditdlt_mac_type_t mac, const u_char *packet, _U_ int pktlen)
{
assert(ctx);
assert(packet);
return (NULL);
}
tcpeditdlt_l2addr_type_t
dlt_null_l2addr_type(void)
{
return NONE;
}