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/*
This software is copyrighted (c) 2002 Rick van Rein, the Netherlands.
This software has been modified by Michel de Boer. 2005
*/
#include "dnssrv.h"
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include <errno.h>
#include <stdlib.h>
#include <netdb.h>
#include <sys/socket.h>
#include <string.h>
#include <signal.h>
/* Common offsets into an SRV RR */
#define SRV_COST (RRFIXEDSZ+0)
#define SRV_WEIGHT (RRFIXEDSZ+2)
#define SRV_PORT (RRFIXEDSZ+4)
#define SRV_SERVER (RRFIXEDSZ+6)
#define SRV_FIXEDSZ (RRFIXEDSZ+6)
/* Data structures */
typedef struct {
unsigned char buf [PACKETSZ];
int len;
} iobuf;
typedef char name [MAXDNAME];
#define MAXNUM_SRV PACKETSZ
/* Local variable for SRV options */
static unsigned long int srv_flags = 0L;
/* Setup the SRV options when initialising -- invocation optional */
void insrv_init (unsigned long flags) {
#ifdef HAVE_RES_INIT
srv_flags = flags;
res_init ();
#endif
}
/* Test the given SRV options to see if all are set */
int srv_testflag (unsigned long flags) {
return ((srv_flags & flags) == flags) ? 1 : 0;
}
/* Compare two SRV records by priority and by (scattered) weight */
int srvcmp (const void *left, const void *right) {
int lcost = ntohs (((unsigned short **) left ) [0][5]);
int rcost = ntohs (((unsigned short **) right) [0][5]);
if (lcost == rcost) {
lcost = -ntohs (((unsigned short **) left ) [0][6]);
rcost = -ntohs (((unsigned short **) right) [0][6]);
}
if (lcost < rcost) {
return -1;
} else if (lcost > rcost) {
return +1;
} else {
return 0;
}
}
/* Setup a client socket for the named service over the given protocol under
* the given domain name.
*/
int insrv_lookup (const char *service, const char *proto, const char *domain,
list<t_dns_result> &result)
{
// 1. convert service/proto to svcnm
// 2. construct SRV query for _service._proto.domain
iobuf names;
name svcnm;
int ctr;
int rnd;
HEADER *nameshdr;
unsigned char *here, *srv[MAXNUM_SRV];
int num_srv=0;
// Storage for fallback SRV list, constructed when DNS gives no SRV
//unsigned char fallbacksrv [2*(MAXCDNAME+SRV_FIXEDSZ+MAXCDNAME)];
// srv_flags &= ~SRV_GOT_MASK;
// srv_flags |= SRV_GOT_SRV;
strcpy (svcnm, "_");
strcat (svcnm, service);
strcat (svcnm, "._");
strcat (svcnm, proto);
// Note that SRV records are only defined for class IN
if (domain) {
names.len=res_querydomain (svcnm, domain,
C_IN, T_SRV,
names.buf, PACKETSZ);
} else {
names.len=res_query (svcnm,
C_IN, T_SRV,
names.buf, PACKETSZ);
}
if (names.len < 0) {
return -ENOENT;
}
nameshdr=(HEADER *) names.buf;
here=names.buf + HFIXEDSZ;
rnd=nameshdr->id; // Heck, gimme one reason why not!
if ((names.len < HFIXEDSZ) || nameshdr->tc) {
return -EMSGSIZE;
}
switch (nameshdr->rcode) {
case 1:
return -EFAULT;
case 2:
return -EAGAIN;
case 3:
return -ENOENT;
case 4:
return -ENOSYS;
case 5:
return -EPERM;
default:
break;
}
if (ntohs (nameshdr->ancount) == 0) {
return -ENOENT;
}
if (ntohs (nameshdr->ancount) > MAXNUM_SRV) {
return -ERANGE;
}
for (ctr=ntohs (nameshdr->qdcount); ctr>0; ctr--) {
int strlen=dn_skipname (here, names.buf+names.len);
here += strlen + QFIXEDSZ;
}
for (ctr=ntohs (nameshdr->ancount); ctr>0; ctr--) {
int strlen=dn_skipname (here, names.buf+names.len);
here += strlen;
srv [num_srv++] = here;
here += SRV_FIXEDSZ;
here += dn_skipname (here, names.buf+names.len);
}
// Overwrite weight with rnd-spread version to divide load over weights
for (ctr=0; ctr<num_srv; ctr++) {
*(unsigned short *) (srv [ctr]+SRV_WEIGHT)
= htons(rnd % (1+ns_get16 (srv [ctr]+SRV_WEIGHT)));
}
qsort (srv, num_srv, sizeof (*srv), srvcmp);
result.clear();
for (ctr=0; ctr<num_srv; ctr++) {
name srvname;
if (ns_name_ntop (srv [ctr]+SRV_SERVER, srvname, MAXDNAME) < 0) {
return -errno;
}
t_dns_result r;
r.hostname = srvname;
r.port = ns_get16(srv [ctr]+SRV_PORT);
result.push_back(r);
}
return 0;
}
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