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psyced/utility/erq/srv.c

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/* SRV implementation by the PSYC developers at psyced.org
*
* REMINDER: when modifying anything about these files, remember
* that not only the psyced installer needs to be updated, you
* also have to manually update the gentoo tar.
*/
#include "srv.h"
#include <unistd.h>
#include <stdlib.h>
#include <strings.h>
#include <arpa/inet.h> // For solaris
#include <arpa/nameser.h>
#include <resolv.h>
#if !defined(__FreeBSD__) && !defined(__NetBSD__) && !defined(__OpenBSD__)
# include <malloc.h>
#else
# include <stdlib.h>
#endif
/* the biggest packet we'll send and receive */
#if PACKETSZ > 1024
#define MAXPACKET PACKETSZ
#else
#define MAXPACKET 1024
#endif
/* and what we send and receive */
typedef union {
HEADER hdr;
u_char buf[MAXPACKET];
} querybuf;
#ifndef T_SRV
#define T_SRV 33
#endif
void freesrvhost ( struct srvhost * s )
{
struct srvhost * n;
while( s ) {
n = s->next;
/* hack to make double-free visible by causing null dereference */
s->next = NULL;
free( (void *)s );
s = n;
}
}
static int compare( const void * a, const void * b )
{
struct srvhost * aa, * bb;
if ( !a )
return 1;
if ( !b )
return -1;
aa = (struct srvhost *) *(int*)a;
bb = (struct srvhost *) *(int*)b;
if ( aa->pref > bb->pref )
return 1;
if ( aa->pref < bb->pref )
return -1;
if ( aa->rweight > bb->rweight )
return -1;
if ( aa->rweight < bb->rweight )
return 1;
return 0;
}
struct srvhost * getsrv( const char * domain,
const char * service, const char * protocol ) {
querybuf answer; /* answer buffer from nameserver */
int n;
char * zone;
int ancount, qdcount; /* answer count and query count */
HEADER *hp; /* answer buffer header */
struct srvhost **replyarray;
struct srvhost * firsthost;
int answerno;
u_char hostbuf[256];
u_char *msg, *eom, *cp; /* answer buffer positions */
int dlen, type, pref, weight, port;
if ( !domain || !*domain ||
!service || !*service ||
!protocol || !*protocol )
return NULL;
zone = (char *)malloc( strlen( domain ) +
strlen( service ) +
strlen( protocol ) + 20 );
if (zone == NULL)
return NULL;
*zone = '\0';
if (*service != '_') // If service and protocol do not start with a
strcat(zone, "_"); // _, prepend the _ to them...
strcat(zone, service);
strcat(zone, ".");
if (*protocol != '_')
strcat(zone, "_");
strcat(zone, protocol);
strcat(zone, ".");
strcat(zone, domain);
n = res_query( zone, C_IN, T_SRV, (u_char *)&answer, sizeof( answer ) );
(void) free( zone );
zone = NULL;
if ( n < (int)sizeof(HEADER) )
return NULL;
/* valid answer received. skip the query record. */
hp = (HEADER *)&answer;
qdcount = ntohs(hp->qdcount);
ancount = ntohs(hp->ancount);
msg = (u_char *)&answer;
eom = (u_char *)&answer + n;
cp = (u_char *)&answer + sizeof(HEADER);
while ( qdcount-- > 0 && cp < eom ) {
n = dn_expand( msg, eom, cp, (char *)hostbuf, 256 );
if (n < 0)
return NULL;
cp += n + QFIXEDSZ;
}
/* make a big-enough (probably too big) reply array */
replyarray
= (struct srvhost **) malloc( ancount * sizeof(struct srvhost *) );
for( n = 0; n < ancount; n++ )
replyarray[n] = NULL;
answerno = 0;
/* loop through the answer buffer and extract SRV records */
while ( ancount-- > 0 && cp < eom ) {
n = dn_expand( msg, eom, cp, (char *)hostbuf, 256 );
if ( n < 0 ) {
for( n = 0; n < answerno; n++ )
(void) free( replyarray[n] );
(void)free( replyarray );
return NULL;
}
cp += n;
type = _getshort(cp);
cp += sizeof(u_short);
/* class = _getshort(cp); */
cp += sizeof(u_short);
/* ttl = _getlong(cp); */
cp += sizeof(u_long);
dlen = _getshort(cp);
cp += sizeof(u_short);
if ( type != T_SRV ) {
cp += dlen;
continue;
}
pref = _getshort(cp);
cp += sizeof(u_short);
weight = _getshort(cp);
cp += sizeof(u_short);
port = _getshort(cp);
cp += sizeof(u_short);
n = dn_expand( msg, eom, cp, (char *)hostbuf, 256 );
if (n < 0)
break;
cp += n;
replyarray[answerno]
= (struct srvhost *)malloc( sizeof( struct srvhost ) +
strlen( (char *)hostbuf ) );
replyarray[answerno]->pref = pref;
replyarray[answerno]->weight = weight;
if ( weight )
replyarray[answerno]->rweight = 1+random()%( 10000 * weight );
else
replyarray[answerno]->rweight = 0;
replyarray[answerno]->port = port;
replyarray[answerno]->next = NULL;
strcpy( replyarray[answerno]->name, (char *)hostbuf );
answerno++;
}
if (answerno == 0) return NULL;
qsort( replyarray, answerno, sizeof( struct srvhost * ),
compare );
// Recreate a linked list from the sorted array...
for( n = 0; n < answerno; n++ )
replyarray[n]->next = replyarray[n+1];
replyarray[answerno-1]->next = NULL;
firsthost = replyarray[0];
(void) free( replyarray );
return firsthost;
}