Changeset 3344 for pjproject

Timestamp:

Oct 14, 2010 7:22:04 AM (14 years ago)

Author:

bennylp

Message:

Misc (re #1134): fixed failure in resolving DNS A resolution if the answer contains more than one CNAME redirection before an A record is found (thanks Régis Montoya for the report)

File:

• pjproject/trunk/pjlib-util/src/pjlib-util/resolver.c (modified) (3 diffs)

pjproject/trunk/pjlib-util/src/pjlib-util/resolver.c

@@ -842 +842 @@
                                             pj_dns_a_record *rec)
 {
-    pj_str_t hostname, alias, *res_name;
+    enum { MAX_SEARCH = 20 };
+    pj_str_t hostname, alias = {NULL, 0};
     unsigned bufstart = 0;
     unsigned bufleft = sizeof(rec->buf_);
-    unsigned i, ansidx;
+    unsigned i, ansidx, search_cnt=0;
 
     PJ_ASSERT_RETURN(pkt && rec, PJ_EINVAL);
@@ -888 +889 @@
         return PJLIB_UTIL_EDNSNOANSWERREC;
 
-    /* If hostname is a CNAME, get the alias. */
-    if (pkt->ans[ansidx].type == PJ_DNS_TYPE_CNAME) {
-        alias = pkt->ans[ansidx].rdata.cname.name;
-        res_name = &alias;
-    } else if (pkt->ans[ansidx].type == PJ_DNS_TYPE_A) {
-        alias.ptr = NULL;
-        alias.slen = 0;
-        res_name = &hostname;
-    } else {
+    /* Keep following CNAME records. */
+    while (pkt->ans[ansidx].type == PJ_DNS_TYPE_CNAME &&
+           search_cnt++ < MAX_SEARCH)
+    {
+        if (!alias.slen)
+            alias = pkt->ans[ansidx].rdata.cname.name;
+
+        for (i=ansidx+1; i < pkt->hdr.anscount; ++i) {
+            if (pj_stricmp(&pkt->ans[ansidx].rdata.cname.name,
+                           &pkt->ans[i].name)==0)
+            {
+                break;
+            }
+        }
+
+        if (i==pkt->hdr.anscount)
+            return PJLIB_UTIL_EDNSINANSWER;
+
+        ansidx = i;
+    }
+
+    if (search_cnt >= MAX_SEARCH)
         return PJLIB_UTIL_EDNSINANSWER;
-    }
+
+    if (pkt->ans[ansidx].type != PJ_DNS_TYPE_A)
+        return PJLIB_UTIL_EDNSINANSWER;
 
     /* Copy alias to the record, if present. */
@@ -913 +929 @@
     }
 
-    /* Now scan the answer for all type A RRs where the name matches
-     * hostname or alias.
-     */
-    for (i=0; i<pkt->hdr.anscount; ++i) {
-        if (pkt->ans[i].type == PJ_DNS_TYPE_A &&
-            pj_stricmp(&pkt->ans[i].name, res_name)==0 &&
-            rec->addr_count < PJ_DNS_MAX_IP_IN_A_REC)
-        {
-            rec->addr[rec->addr_count].s_addr = 
-                pkt->ans[i].rdata.a.ip_addr.s_addr;
-            ++rec->addr_count;
-        }
+    /* Retrieve the IP address. */
+    if (rec->addr_count < PJ_DNS_MAX_IP_IN_A_REC) {
+        rec->addr[rec->addr_count++].s_addr =
+            pkt->ans[i].rdata.a.ip_addr.s_addr;
     }