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