openldap/openldap-dns-priority.patch
Jan Vcelak 81680b05fb new feature update: honor priority/weight with ldap_domain2hostlist
There was a typo in the patch. "weight" of the SRV records was not
taken correctly.

Resolves: #733078
2011-09-21 11:05:39 +02:00

193 lines
4.8 KiB
Diff

Implement priority/weight for DNS SRV records
From RFC 2782:
A client MUST attempt to contact the target host with the
lowest-numbered priority it can reach.
This patch sorts the DNS SRV records by their priority, and
additionally gives records with a larger weight a higher probability
of appearing earlier. This way, the DNS SRV records are tried in the
order of their priority.
Author: James M Leddy <james.leddy@redhat.com>
Upstream ITS: #7027
Resolves: #733078
---
libraries/libldap/dnssrv.c | 106 ++++++++++++++++++++++++++++++++++----------
1 files changed, 83 insertions(+), 23 deletions(-)
diff --git a/libraries/libldap/dnssrv.c b/libraries/libldap/dnssrv.c
index 16b1544..40f93b4 100644
--- a/libraries/libldap/dnssrv.c
+++ b/libraries/libldap/dnssrv.c
@@ -174,6 +174,46 @@ int ldap_domain2dn(
return LDAP_SUCCESS;
}
+#ifdef HAVE_RES_QUERY
+#define DNSBUFSIZ (64*1024)
+typedef struct srv_record {
+ u_short priority;
+ u_short weight;
+ u_short port;
+ char hostname[DNSBUFSIZ];
+} srv_record;
+
+
+static int srv_cmp(const void *aa, const void *bb){
+ srv_record *a=(srv_record *)aa;
+ srv_record *b=(srv_record *)bb;
+ u_long total;
+
+ if(a->priority < b->priority) {
+ return -1;
+ }
+ if(a->priority > b->priority) {
+ return 1;
+ }
+ if(a->priority == b->priority){
+ /* targets with same priority are in psudeo random order */
+ if (a->weight == 0 && b->weight == 0) {
+ if (rand() % 2) {
+ return -1;
+ } else {
+ return 1;
+ }
+ }
+ total = a->weight + b->weight;
+ if (rand() % total < a->weight) {
+ return -1;
+ } else {
+ return 1;
+ }
+ }
+}
+#endif /* HAVE_RES_QUERY */
+
/*
* Lookup and return LDAP servers for domain (using the DNS
* SRV record _ldap._tcp.domain).
@@ -183,15 +223,16 @@ int ldap_domain2hostlist(
char **list )
{
#ifdef HAVE_RES_QUERY
-#define DNSBUFSIZ (64*1024)
- char *request;
- char *hostlist = NULL;
+ char *request;
+ char *hostlist = NULL;
+ srv_record *hostent_head=NULL;
+ int i;
int rc, len, cur = 0;
unsigned char reply[DNSBUFSIZ];
+ int hostent_count=0;
assert( domain != NULL );
assert( list != NULL );
-
if( *domain == '\0' ) {
return LDAP_PARAM_ERROR;
}
@@ -223,8 +264,7 @@ int ldap_domain2hostlist(
unsigned char *p;
char host[DNSBUFSIZ];
int status;
- u_short port;
- /* int priority, weight; */
+ u_short port, priority, weight;
/* Parse out query */
p = reply;
@@ -263,40 +303,56 @@ int ldap_domain2hostlist(
size = (p[0] << 8) | p[1];
p += 2;
if (type == T_SRV) {
- int buflen;
status = dn_expand(reply, reply + len, p + 6, host, sizeof(host));
if (status < 0) {
goto out;
}
- /* ignore priority and weight for now */
- /* priority = (p[0] << 8) | p[1]; */
- /* weight = (p[2] << 8) | p[3]; */
+
+ /* Get priority weight and port */
+ priority = (p[0] << 8) | p[1];
+ weight = (p[2] << 8) | p[3];
port = (p[4] << 8) | p[5];
if ( port == 0 || host[ 0 ] == '\0' ) {
goto add_size;
}
- buflen = strlen(host) + STRLENOF(":65355 ");
- hostlist = (char *) LDAP_REALLOC(hostlist, cur + buflen + 1);
- if (hostlist == NULL) {
- rc = LDAP_NO_MEMORY;
- goto out;
+ hostent_head = (srv_record *) LDAP_REALLOC(hostent_head, (hostent_count+1)*(sizeof(srv_record)));
+ if(hostent_head==NULL){
+ rc=LDAP_NO_MEMORY;
+ goto out;
+
}
- if (cur > 0) {
- /* not first time around */
- hostlist[cur++] = ' ';
- }
- cur += sprintf(&hostlist[cur], "%s:%hu", host, port);
+ hostent_head[hostent_count].priority=priority;
+ hostent_head[hostent_count].weight=weight;
+ hostent_head[hostent_count].port=port;
+ strncpy(hostent_head[hostent_count].hostname, host,255);
+ hostent_count=hostent_count+1;
}
add_size:;
p += size;
}
}
+ qsort(hostent_head, hostent_count, sizeof(srv_record), srv_cmp);
+
+ for(i=0; i<hostent_count; i++){
+ int buflen;
+ buflen = strlen(hostent_head[i].hostname) + STRLENOF(":65355" );
+ hostlist = (char *) LDAP_REALLOC(hostlist, cur+buflen+1);
+ if (hostlist == NULL) {
+ rc = LDAP_NO_MEMORY;
+ goto out;
+ }
+ if(cur>0){
+ hostlist[cur++]=' ';
+ }
+ cur += sprintf(&hostlist[cur], "%s:%hd", hostent_head[i].hostname, hostent_head[i].port);
+ }
+
if (hostlist == NULL) {
- /* No LDAP servers found in DNS. */
- rc = LDAP_UNAVAILABLE;
- goto out;
+ /* No LDAP servers found in DNS. */
+ rc = LDAP_UNAVAILABLE;
+ goto out;
}
rc = LDAP_SUCCESS;
@@ -308,8 +364,12 @@ add_size:;
if (request != NULL) {
LDAP_FREE(request);
}
+ if (hostent_head != NULL) {
+ LDAP_FREE(hostent_head);
+ }
if (rc != LDAP_SUCCESS && hostlist != NULL) {
LDAP_FREE(hostlist);
+
}
return rc;
#else
--
1.7.6