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/*
* Copyright (c) 2016-2023, OARC, Inc.
* 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 name of the copyright holder 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 BY THE COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDER 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.
*/
#include "config.h"
#include "bpft.h"
#include "iaddr.h"
#include <ldns/ldns.h>
void prepare_bpft(void)
{
unsigned udp10_mbs, udp10_mbc, udp11_mbc; // udp11_mbs
text_list bpfl;
text_ptr text;
size_t len;
char* p;
/* Prepare the must-be-set and must-be-clear tests. */
udp10_mbs = udp10_mbc = udp11_mbc = 0U; // udp11_mbs
if ((dir_wanted & DIR_INITIATE) != 0) {
if ((dir_wanted & DIR_RESPONSE) == 0)
udp10_mbc |= UDP10_QR_MASK;
} else if ((dir_wanted & DIR_RESPONSE) != 0) {
udp10_mbs |= UDP10_QR_MASK;
}
if ((msg_wanted & MSG_UPDATE) != 0) {
if ((msg_wanted & (MSG_QUERY | MSG_NOTIFY)) == 0)
udp10_mbs |= (LDNS_PACKET_UPDATE << UDP10_OP_SHIFT);
} else if ((msg_wanted & MSG_NOTIFY) != 0) {
if ((msg_wanted & (MSG_QUERY | MSG_UPDATE)) == 0)
udp10_mbs |= (LDNS_PACKET_NOTIFY << UDP10_OP_SHIFT);
} else if ((msg_wanted & MSG_QUERY) != 0) {
udp10_mbc |= UDP10_OP_MASK;
}
if (err_wanted == ERR_NO) {
udp10_mbc |= UDP10_TC_MASK;
udp11_mbc |= UDP11_RC_MASK;
}
/*
* Model
* (vlan) and (transport)
* (vlan) and ((icmp) or (frags) or (dns))
* (vlan) and ((icmp) or (frags) or ((ports) and (hosts)))
* (vlan) and ((icmp) or (frags) or (((tcp) or (udp)) and (hosts)))
* [(vlan) and] ( [(icmp) or] [(frags) or] ( ( [(tcp) or] (udp) ) [and (hosts)] ) )
*/
/* Make a BPF program to do early course kernel-level filtering. */
INIT_LIST(bpfl);
len = 0;
if (!EMPTY(vlans_excl))
len += text_add(&bpfl, "vlan and ("); /* vlan and ( transports ... */
else
len += text_add(&bpfl, "("); /* ( transports ... */
if (wanticmp) {
len += text_add(&bpfl, " ( ip proto 1 or ip proto 58 ) or");
}
if (wantfrags) {
len += text_add(&bpfl, " ( ip[6:2] & 0x1fff != 0 or ip6[6] = 44 ) or");
}
len += text_add(&bpfl, " ("); /* ( dns ... */
len += text_add(&bpfl, " ("); /* ( ports ... */
if (wanttcp) {
len += text_add(&bpfl, " ( tcp port %d ) or", dns_port);
/* tcp packets can be filtered by initiators/responders, but
* not mbs/mbc. */
}
len += text_add(&bpfl, " ( udp port %d and ( ip6 or ( ip", dns_port);
if (udp10_mbc != 0)
len += text_add(&bpfl, " and udp[10] & 0x%x = 0",
udp10_mbc);
if (udp10_mbs != 0)
len += text_add(&bpfl, " and udp[10] & 0x%x = 0x%x",
udp10_mbs, udp10_mbs);
if (udp11_mbc != 0)
len += text_add(&bpfl, " and udp[11] & 0x%x = 0",
udp11_mbc);
/* Dead code, udp11_mbs never set
if (udp11_mbs != 0)
len += text_add(&bpfl, " and udp[11] & 0x%x = 0x%x",
udp11_mbs, udp11_mbs);
*/
if (err_wanted != ERR_NO) {
len += text_add(&bpfl, " and (");
if ((err_wanted & ERR_TRUNC) != 0) {
len += text_add(&bpfl, " udp[10] & 0x%x = 0x%x or", UDP10_TC_MASK, UDP10_TC_MASK);
}
len += text_add(&bpfl, " 0x%x << (udp[11] & 0xf) & 0x%x != 0 )", ERR_RCODE_BASE, err_wanted);
}
len += text_add(&bpfl, " )))"); /* ... udp 53 ) */
len += text_add(&bpfl, " )"); /* ... ports ) */
if (options.bpf_hosts_apply_all) {
len += text_add(&bpfl, " )"); /* ... dns ) */
len += text_add(&bpfl, " )"); /* ... transport ) */
}
if (!EMPTY(initiators) || !EMPTY(responders)) {
const char* or = "or", *lp = "(", *sep;
endpoint_ptr ep;
len += text_add(&bpfl, " and host");
sep = lp;
for (ep = HEAD(initiators);
ep != NULL;
ep = NEXT(ep, link)) {
len += text_add(&bpfl, " %s %s", sep, ia_str(ep->ia));
sep = or ;
}
for (ep = HEAD(responders);
ep != NULL;
ep = NEXT(ep, link)) {
len += text_add(&bpfl, " %s %s", sep, ia_str(ep->ia));
sep = or ;
}
len += text_add(&bpfl, " )");
}
if (!EMPTY(not_initiators) || !EMPTY(not_responders)) {
const char* or = "or", *lp = "(", *sep;
endpoint_ptr ep;
len += text_add(&bpfl, " and not host");
sep = lp;
for (ep = HEAD(not_initiators);
ep != NULL;
ep = NEXT(ep, link)) {
len += text_add(&bpfl, " %s %s", sep, ia_str(ep->ia));
sep = or ;
}
for (ep = HEAD(not_responders);
ep != NULL;
ep = NEXT(ep, link)) {
len += text_add(&bpfl, " %s %s", sep, ia_str(ep->ia));
sep = or ;
}
len += text_add(&bpfl, " )");
}
if (!options.bpf_hosts_apply_all) {
len += text_add(&bpfl, " )"); /* ... dns ) */
len += text_add(&bpfl, " )"); /* ... transport ) */
}
if (extra_bpf)
len += text_add(&bpfl, " and ( %s )", extra_bpf);
bpft = calloc(len + 1, sizeof(char));
assert(bpft != NULL);
p = bpft;
for (text = HEAD(bpfl); text != NULL; text = NEXT(text, link)) {
memcpy(p, text->text, text->len);
p += text->len;
}
text_free(&bpfl);
if (!EMPTY(vlans_incl)) {
char* bpft_vlan;
len = (2 * len) + 64; /* add enough for the extra in snprintf() below */
bpft_vlan = calloc(len, sizeof(char));
assert(bpft_vlan != NULL);
snprintf(bpft_vlan, len, "( %s ) or ( vlan and ( %s ) )", bpft, bpft);
free(bpft);
bpft = bpft_vlan;
}
if (dumptrace >= 1)
fprintf(stderr, "%s: \"%s\"\n", ProgramName, bpft);
}
size_t text_add(text_list* list, const char* fmt, ...)
{
text_ptr text;
va_list ap;
int len;
text = calloc(1, sizeof *text);
assert(text != NULL);
INIT_LINK(text, link);
va_start(ap, fmt);
len = vasprintf(&text->text, fmt, ap);
assert(len >= 0);
va_end(ap);
text->len = len;
APPEND(*list, text, link);
return (text->len);
}
void text_free(text_list* list)
{
text_ptr at, text;
for (at = HEAD(*list); at;) {
text = at;
at = NEXT(text, link);
UNLINK(*list, text, link);
free(text->text);
assert(text != (void*)-1);
free(text);
}
}
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