| 1 |
Implement priority/weight for DNS SRV records |
| 2 |
|
| 3 |
From RFC 2782: |
| 4 |
|
| 5 |
A client MUST attempt to contact the target host with the |
| 6 |
lowest-numbered priority it can reach. |
| 7 |
|
| 8 |
This patch sorts the DNS SRV records by their priority, and |
| 9 |
additionally gives records with a larger weight a higher probability |
| 10 |
of appearing earlier. This way, the DNS SRV records are tried in the |
| 11 |
order of their priority. |
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|
| 13 |
Author: James M Leddy <james.leddy@redhat.com> |
| 14 |
Upstream ITS: #7027 |
| 15 |
Resolves: #733078 |
| 16 |
|
| 17 |
--- |
| 18 |
libraries/libldap/dnssrv.c | 106 ++++++++++++++++++++++++++++++++++---------- |
| 19 |
1 files changed, 83 insertions(+), 23 deletions(-) |
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|
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diff --git a/libraries/libldap/dnssrv.c b/libraries/libldap/dnssrv.c |
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index 16b1544..40f93b4 100644 |
| 23 |
--- a/libraries/libldap/dnssrv.c |
| 24 |
+++ b/libraries/libldap/dnssrv.c |
| 25 |
@@ -174,6 +174,46 @@ int ldap_domain2dn( |
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return LDAP_SUCCESS; |
| 27 |
} |
| 28 |
|
| 29 |
+#ifdef HAVE_RES_QUERY |
| 30 |
+#define DNSBUFSIZ (64*1024) |
| 31 |
+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; |
| 35 |
+ char hostname[DNSBUFSIZ]; |
| 36 |
+} srv_record; |
| 37 |
+ |
| 38 |
+ |
| 39 |
+static int srv_cmp(const void *aa, const void *bb){ |
| 40 |
+ srv_record *a=(srv_record *)aa; |
| 41 |
+ srv_record *b=(srv_record *)bb; |
| 42 |
+ u_long total; |
| 43 |
+ |
| 44 |
+ if(a->priority < b->priority) { |
| 45 |
+ return -1; |
| 46 |
+ } |
| 47 |
+ if(a->priority > b->priority) { |
| 48 |
+ return 1; |
| 49 |
+ } |
| 50 |
+ if(a->priority == b->priority){ |
| 51 |
+ /* targets with same priority are in psudeo random order */ |
| 52 |
+ if (a->weight == 0 && b->weight == 0) { |
| 53 |
+ if (rand() % 2) { |
| 54 |
+ return -1; |
| 55 |
+ } else { |
| 56 |
+ return 1; |
| 57 |
+ } |
| 58 |
+ } |
| 59 |
+ total = a->weight + b->weight; |
| 60 |
+ if (rand() % total < a->weight) { |
| 61 |
+ return -1; |
| 62 |
+ } else { |
| 63 |
+ return 1; |
| 64 |
+ } |
| 65 |
+ } |
| 66 |
+} |
| 67 |
+#endif /* HAVE_RES_QUERY */ |
| 68 |
+ |
| 69 |
/* |
| 70 |
* Lookup and return LDAP servers for domain (using the DNS |
| 71 |
* SRV record _ldap._tcp.domain). |
| 72 |
@@ -183,15 +223,16 @@ int ldap_domain2hostlist( |
| 73 |
char **list ) |
| 74 |
{ |
| 75 |
#ifdef HAVE_RES_QUERY |
| 76 |
-#define DNSBUFSIZ (64*1024) |
| 77 |
- char *request; |
| 78 |
- char *hostlist = NULL; |
| 79 |
+ char *request; |
| 80 |
+ char *hostlist = NULL; |
| 81 |
+ srv_record *hostent_head=NULL; |
| 82 |
+ int i; |
| 83 |
int rc, len, cur = 0; |
| 84 |
unsigned char reply[DNSBUFSIZ]; |
| 85 |
+ int hostent_count=0; |
| 86 |
|
| 87 |
assert( domain != NULL ); |
| 88 |
assert( list != NULL ); |
| 89 |
- |
| 90 |
if( *domain == '\0' ) { |
| 91 |
return LDAP_PARAM_ERROR; |
| 92 |
} |
| 93 |
@@ -223,8 +264,7 @@ int ldap_domain2hostlist( |
| 94 |
unsigned char *p; |
| 95 |
char host[DNSBUFSIZ]; |
| 96 |
int status; |
| 97 |
- u_short port; |
| 98 |
- /* int priority, weight; */ |
| 99 |
+ u_short port, priority, weight; |
| 100 |
|
| 101 |
/* Parse out query */ |
| 102 |
p = reply; |
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@@ -263,40 +303,56 @@ int ldap_domain2hostlist( |
| 104 |
size = (p[0] << 8) | p[1]; |
| 105 |
p += 2; |
| 106 |
if (type == T_SRV) { |
| 107 |
- int buflen; |
| 108 |
status = dn_expand(reply, reply + len, p + 6, host, sizeof(host)); |
| 109 |
if (status < 0) { |
| 110 |
goto out; |
| 111 |
} |
| 112 |
- /* ignore priority and weight for now */ |
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- /* priority = (p[0] << 8) | p[1]; */ |
| 114 |
- /* weight = (p[2] << 8) | p[3]; */ |
| 115 |
+ |
| 116 |
+ /* Get priority weight and port */ |
| 117 |
+ priority = (p[0] << 8) | p[1]; |
| 118 |
+ weight = (p[2] << 8) | p[3]; |
| 119 |
port = (p[4] << 8) | p[5]; |
| 120 |
|
| 121 |
if ( port == 0 || host[ 0 ] == '\0' ) { |
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goto add_size; |
| 123 |
} |
| 124 |
|
| 125 |
- buflen = strlen(host) + STRLENOF(":65355 "); |
| 126 |
- 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; |
| 130 |
+ hostent_head = (srv_record *) LDAP_REALLOC(hostent_head, (hostent_count+1)*(sizeof(srv_record))); |
| 131 |
+ if(hostent_head==NULL){ |
| 132 |
+ rc=LDAP_NO_MEMORY; |
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+ goto out; |
| 134 |
+ |
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} |
| 136 |
- if (cur > 0) { |
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- /* not first time around */ |
| 138 |
- hostlist[cur++] = ' '; |
| 139 |
- } |
| 140 |
- 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=weight; |
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+ hostent_head[hostent_count].port=port; |
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+ strncpy(hostent_head[hostent_count].hostname, host,255); |
| 145 |
+ hostent_count=hostent_count+1; |
| 146 |
} |
| 147 |
add_size:; |
| 148 |
p += size; |
| 149 |
} |
| 150 |
} |
| 151 |
+ qsort(hostent_head, hostent_count, sizeof(srv_record), srv_cmp); |
| 152 |
+ |
| 153 |
+ for(i=0; i<hostent_count; i++){ |
| 154 |
+ int buflen; |
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+ buflen = strlen(hostent_head[i].hostname) + STRLENOF(":65355" ); |
| 156 |
+ hostlist = (char *) LDAP_REALLOC(hostlist, cur+buflen+1); |
| 157 |
+ if (hostlist == NULL) { |
| 158 |
+ rc = LDAP_NO_MEMORY; |
| 159 |
+ goto out; |
| 160 |
+ } |
| 161 |
+ 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); |
| 165 |
+ } |
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+ |
| 167 |
if (hostlist == NULL) { |
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- /* No LDAP servers found in DNS. */ |
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- rc = LDAP_UNAVAILABLE; |
| 170 |
- goto out; |
| 171 |
+ /* No LDAP servers found in DNS. */ |
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+ rc = LDAP_UNAVAILABLE; |
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+ goto out; |
| 174 |
} |
| 175 |
|
| 176 |
rc = LDAP_SUCCESS; |
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@@ -308,8 +364,12 @@ add_size:; |
| 178 |
if (request != NULL) { |
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LDAP_FREE(request); |
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} |
| 181 |
+ if (hostent_head != NULL) { |
| 182 |
+ 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; |
| 189 |
#else |
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-- |
| 191 |
1.7.6 |
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