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/*
* DNS lookup for SMTP sender
*
* Copyright (c) 1987-2011 by the citadel.org team
*
* This program is open source software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License, version 3.
*
* 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.
*/
#include "sysdep.h"
#include <stdio.h>
#include <syslog.h>
#ifdef HAVE_RESOLV_H
#include <arpa/nameser.h>
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#include <arpa/nameser_compat.h>
#endif
#include <resolv.h>
#endif
#include <libcitadel.h>
#include "sysdep_decls.h"
#include "citadel.h"
#include "domain.h"
#include "internet_addressing.h"
/*
* get_hosts() checks the Internet configuration for various types of
* entries and returns them in the same format as getmx() does -- fill the
* buffer with a delimited list of hosts and return the number of hosts.
*
* This is used to fetch MX smarthosts, SpamAssassin hosts, etc.
*/
int get_hosts(char *mxbuf, char *rectype) {
int config_lines;
int i;
char buf[256];
char host[256], type[256];
int total_smarthosts = 0;
if (inetcfg == NULL) return(0);
strcpy(mxbuf, "");
config_lines = num_tokens(inetcfg, '\n');
for (i=0; i<config_lines; ++i) {
extract_token(buf, inetcfg, i, '\n', sizeof buf);
extract_token(host, buf, 0, '|', sizeof host);
extract_token(type, buf, 1, '|', sizeof type);
if (!strcasecmp(type, rectype)) {
strcat(mxbuf, host);
strcat(mxbuf, "|");
++total_smarthosts;
}
}
return(total_smarthosts);
}
/*
* Compare the preference of two MX records. First check by the actual
* number listed in the MX record. If they're identical, randomize the
* result.
*/
int mx_compare_pref(const void *mx1, const void *mx2) {
int pref1;
int pref2;
pref1 = ((const struct mx *)mx1)->pref;
pref2 = ((const struct mx *)mx2)->pref;
if (pref1 > pref2) {
return(1);
}
else if (pref1 < pref2) {
return(0);
}
else {
return(rand() % 2);
}
}
/*
* getmx()
*
* Return one or more MX's for a mail destination.
*
* Upon success, it fills 'mxbuf' with one or more MX hosts, separated by
* vertical bar characters, and returns the number of hosts as its return
* value. If no MX's are found, it returns 0.
*
*/
int getmx(char *mxbuf, char *dest) {
#ifdef HAVE_RESOLV_H
union {
u_char bytes[1024];
HEADER header;
} answer;
#endif
int ret;
unsigned char *startptr, *endptr, *ptr;
char expanded_buf[1024];
unsigned short pref, type;
int n = 0;
int qdcount;
struct mx *mxrecs = NULL;
int num_mxrecs = 0;
/* If we're configured to send all mail to a smart-host, then our
* job here is really easy.
*/
n = get_hosts(mxbuf, "smarthost");
if (n > 0) return(n);
/*
* No smart-host? Look up the best MX for a site.
* Make a call to the resolver library.
*/
ret = res_query(
dest,
C_IN, T_MX, (unsigned char *)answer.bytes, sizeof(answer) );
if (ret < 0) {
mxrecs = malloc(sizeof(struct mx));
mxrecs[0].pref = 0;
strcpy(mxrecs[0].host, dest);
num_mxrecs = 1;
}
else {
/* If we had to truncate, shrink the number to avoid fireworks */
if (ret > sizeof(answer))
ret = sizeof(answer);
startptr = &answer.bytes[0]; /* start and end of buffer */
endptr = &answer.bytes[ret];
ptr = startptr + HFIXEDSZ; /* advance past header */
for (qdcount = ntohs(answer.header.qdcount); qdcount--; ptr += ret + QFIXEDSZ) {
if ((ret = dn_skipname(ptr, endptr)) < 0) {
syslog(LOG_DEBUG, "dn_skipname error\n");
return(0);
}
}
while(1) {
memset(expanded_buf, 0, sizeof(expanded_buf));
ret = dn_expand(startptr,
endptr,
ptr,
expanded_buf,
sizeof(expanded_buf)
);
if (ret < 0) break;
ptr += ret;
GETSHORT(type, ptr);
ptr += INT16SZ + INT32SZ;
GETSHORT(n, ptr);
if (type != T_MX) {
ptr += n;
}
else {
GETSHORT(pref, ptr);
ret = dn_expand(startptr,
endptr,
ptr,
expanded_buf,
sizeof(expanded_buf)
);
ptr += ret;
++num_mxrecs;
if (mxrecs == NULL) {
mxrecs = malloc(sizeof(struct mx));
}
else {
mxrecs = realloc(mxrecs,
(sizeof(struct mx) * num_mxrecs) );
}
mxrecs[num_mxrecs - 1].pref = pref;
strcpy(mxrecs[num_mxrecs - 1].host,
expanded_buf);
}
}
}
/* Sort the MX records by preference */
if (num_mxrecs > 1) {
qsort(mxrecs, num_mxrecs, sizeof(struct mx), mx_compare_pref);
}
strcpy(mxbuf, "");
for (n=0; n<num_mxrecs; ++n) {
strcat(mxbuf, mxrecs[n].host);
strcat(mxbuf, "|");
}
free(mxrecs);
/* Append any fallback smart hosts we have configured.
*/
num_mxrecs += get_hosts(&mxbuf[strlen(mxbuf)], "fallbackhost");
return(num_mxrecs);
}
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