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prime_hash.c 5.73 KB
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/*
* $Id$
*
* Copyright (C) 2007 1&1 Internet AG
*
* This file is part of opensips, a free SIP server.
*
* opensips 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 2 of the License, or
* (at your option) any later version
*
* opensips 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, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*!
* \file
* \brief
* Functions for determinung a pseudo random number over a message's
* header field, based on CRC32 or a prime number algorithm.
*/
#include "sr_module.h"
#include "parser/parse_uri.h"
#include "parser/parse_to.h"
#include "parser/parse_from.h"
#include "crc.h"
#include <ctype.h>
#include "prime_hash.h"
static int determine_source(struct sip_msg *msg, enum hash_source source,
str *source_string);
static int validate_msg(struct sip_msg * msg);
static int determine_call_id (struct sip_msg *msg, str *source_string);
static int determine_fromto_uri (struct to_body *fromto, str *source_string);
static int determine_fromto_user (struct to_body *fromto, str *source_string);
static int first_token (str *source_string);
int hash_func (struct sip_msg * msg,
enum hash_source source, int denominator) {
int ret;
unsigned int hash;
str source_string;
if(determine_source (msg, source, &source_string) == -1) {
return -1;
}
crc32_uint(&source_string, &hash);
ret = hash % denominator;
LM_DBG("hash: %u %% %i = %i\n", hash, denominator, ret);
return ret;
}
int prime_hash_func(struct sip_msg * msg,
enum hash_source source, int denominator) {
str source_string;
if(source != shs_from_user && source != shs_to_user) {
LM_ERR("chosen hash source not usable (may contain letters)\n");
return -1;
}
if (determine_source (msg, source, &source_string) == -1) {
return -1;
}
static const int INT_DIGIT_LIMIT = 18;
static const int PRIME_NUMBER = 51797;
uint64_t number = 0;
uint64_t p10;
int i, j, limit = 0;
int ret;
char source_number_s[INT_DIGIT_LIMIT + 1];
i = INT_DIGIT_LIMIT - 1;
j = source_string.len - 1;
source_number_s[INT_DIGIT_LIMIT] ='\0';
while(i >= 0 && j >= 0) {
if(isdigit(source_string.s[j])) {
source_number_s[i] = source_string.s[j];
i--;
}
j--;
}
limit = i;
for(i=INT_DIGIT_LIMIT - 1, p10=1; i>limit; i--, p10=p10*10) {
number += (source_number_s[i] - '0') * p10;
}
LM_DBG("source_string is %.*s, source_number_s "
"is: %s, number is %llu\n", source_string.len, source_string.s,
source_number_s + (limit + 1), (long long unsigned int)number);
ret = number % PRIME_NUMBER;
ret = ret % denominator + 1;
LM_DBG("calculated hash is: %i\n", ret);
return ret;
}
static int determine_source (struct sip_msg *msg, enum hash_source source,
str *source_string) {
source_string->s = NULL;
source_string->len = 0;
if(validate_msg(msg) < 0) {
return -1;
}
switch (source) {
case shs_call_id:
return determine_call_id (msg, source_string);
case shs_from_uri:
return determine_fromto_uri (get_from(msg), source_string);
case shs_from_user:
return determine_fromto_user (get_from(msg), source_string);
case shs_to_uri:
return determine_fromto_uri (get_to(msg), source_string);
case shs_to_user:
return determine_fromto_user (get_to(msg), source_string);
default:
LM_ERR("unknown hash source %i.\n",
(int) source);
return -1;
}
}
static int validate_msg(struct sip_msg * msg) {
if(!msg->callid && ((parse_headers(msg, HDR_CALLID_F, 0) == -1) || !msg->callid)) {
LM_ERR("Message has no Call-ID header\n");
return -1;
}
if(!msg->to && ((parse_headers(msg, HDR_TO_F, 0) == -1) || !msg->to)) {
LM_ERR("Message has no To header\n");
return -1;
}
if(!msg->from && ((parse_headers(msg, HDR_FROM_F, 0) == -1) || !msg->from)) {
LM_ERR("Message has no From header\n");
return -1;
}
//TODO it would make more sense to do the parsing just if its needed
// but parse_from_header is smart enough, so its probably not a huge problem
if (parse_from_header(msg) < 0) {
LM_ERR("Error while parsing From header field\n");
return -1;
}
return 0;
}
static int determine_call_id (struct sip_msg *msg, str *source_string) {
source_string->s = msg->callid->body.s;
source_string->len = msg->callid->body.len;
first_token (source_string);
return 0;
}
static int determine_fromto_uri (struct to_body *fromto, str *source_string) {
if (fromto == NULL) {
LM_ERR("fromto is NULL!\n");
return -1;
}
source_string->s = fromto->uri.s;
source_string->len = fromto->uri.len;
return 0;
}
static int determine_fromto_user (struct to_body *fromto, str *source_string) {
struct sip_uri uri;
if (fromto == NULL) {
LM_ERR("fromto is NULL!\n");
return -1;
}
if (parse_uri (fromto->uri.s, fromto->uri.len, &uri) < 0) {
LM_ERR("Failed to parse From or To URI.\n");
return -1;
}
source_string->s = uri.user.s;
source_string->len = uri.user.len;
return 0;
}
static int first_token (str *source_string) {
size_t len;
if (source_string->s == NULL || source_string->len == 0) {
return 0;
}
while (source_string->len > 0 && isspace (*source_string->s)) {
++source_string->s;
--source_string->len;
}
for (len = 0; len < source_string->len; ++len) {
if (isspace (source_string->s[len])) {
source_string->len = len;
break;
}
}
return 0;
}
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