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/*
Unix SMB/CIFS implementation.
Copyright (C) Stefan Metzmacher 2015
This program 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
(at your option) any later version.
This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "replace.h"
#include "lib/util/charset/charset.h"
#include "lib/util/fault.h"
#include "lib/util/dns_cmp.h"
/*
* this function assumes names are well formed DNS names.
* it doesn't validate them
*
* It allows strings up to a length of UINT16_MAX - 1
* with up to UINT8_MAX components. On overflow this
* just returns the result of strcasecmp_m().
*
* Trailing dots (only one) are ignored.
*
* The DNS names are compared per component, starting from
* the last one.
*
* The function is usable in a sort, but the return value contains more
* information than a simple comparison. There are 5 return values, defined
* above.
*
* DNS_CMP_FIRST_IS_CHILD (-2) means the first argument is a sub-domain of the
* second. e.g. dns_cmp("foo.example.org", "example.org")
*
* DNS_CMP_FIRST_IS_LESS (-1) means the first argument sorts before the
* second, but is not a sub-domain. e.g. dns_cmp("eggsample.org", "example.org").
*
* DNS_CMP_SECOND_IS_CHILD (+2) and DNS_CMP_SECOND_IS_LESS (+1) have the
* similar expected meanings. DNS_CMP_MATCH (0) means equality.
*
* NULL values are the parent of all addresses, which means comparisons
* between a string and NULL will return +2 or -2.
*/
int dns_cmp(const char *s1, const char *s2)
{
size_t l1 = 0;
const char *p1 = NULL;
size_t num_comp1 = 0;
uint16_t comp1[UINT8_MAX] = {0};
size_t l2 = 0;
const char *p2 = NULL;
size_t num_comp2 = 0;
uint16_t comp2[UINT8_MAX] = {0};
size_t i;
if (s1 == s2) {
/* this includes the both NULL case */
return DNS_CMP_MATCH;
}
if (s1 == NULL) {
return DNS_CMP_SECOND_IS_CHILD;
}
if (s2 == NULL) {
return DNS_CMP_FIRST_IS_CHILD;
}
l1 = strlen(s1);
l2 = strlen(s2);
/*
* trailing '.' are ignored.
*/
if (l1 > 1 && s1[l1 - 1] == '.') {
l1--;
}
if (l2 > 1 && s2[l2 - 1] == '.') {
l2--;
}
for (i = 0; i < ARRAY_SIZE(comp1); i++) {
char *p;
if (i == 0) {
p1 = s1;
if (l1 == 0 || l1 >= UINT16_MAX) {
/* just use one single component on overflow */
break;
}
}
comp1[num_comp1++] = PTR_DIFF(p1, s1);
p = strchr_m(p1, '.');
if (p == NULL) {
p1 = NULL;
break;
}
p1 = p + 1;
}
if (p1 != NULL) {
/* just use one single component on overflow */
num_comp1 = 0;
comp1[num_comp1++] = 0;
p1 = NULL;
}
for (i = 0; i < ARRAY_SIZE(comp2); i++) {
char *p;
if (i == 0) {
p2 = s2;
if (l2 == 0 || l2 >= UINT16_MAX) {
/* just use one single component on overflow */
break;
}
}
comp2[num_comp2++] = PTR_DIFF(p2, s2);
p = strchr_m(p2, '.');
if (p == NULL) {
p2 = NULL;
break;
}
p2 = p + 1;
}
if (p2 != NULL) {
/* just use one single component on overflow */
num_comp2 = 0;
comp2[num_comp2++] = 0;
p2 = NULL;
}
for (i = 0; i < UINT8_MAX; i++) {
int cmp;
if (i < num_comp1) {
size_t idx = num_comp1 - (i + 1);
p1 = s1 + comp1[idx];
} else {
p1 = NULL;
}
if (i < num_comp2) {
size_t idx = num_comp2 - (i + 1);
p2 = s2 + comp2[idx];
} else {
p2 = NULL;
}
if (p1 == NULL && p2 == NULL) {
return DNS_CMP_MATCH;
}
if (p1 != NULL && p2 == NULL) {
return DNS_CMP_FIRST_IS_CHILD;
}
if (p1 == NULL && p2 != NULL) {
return DNS_CMP_SECOND_IS_CHILD;
}
cmp = strcasecmp_m(p1, p2);
if (cmp < 0) {
return DNS_CMP_FIRST_IS_LESS;
}
if (cmp > 0) {
return DNS_CMP_SECOND_IS_LESS;
}
}
smb_panic(__location__);
return -1;
}
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