[OpenSER-Devel] bug in the dns failover??

[Bogdan-Andrei Iancu]

Hi Guang,

Not exactly correct. Let me explain:
    - a2dns_node() is called to store the additional results returned by 
SRV lookup. This results will be placed in *dn
    -srv2dns_node() is later called to store the additional res returned 
by NAPTR lookup. The function takes as param *dn, but if you look in the 
function code, you will see that a new dns_node is created and the 
original dn is attached to this new node. The function returns the new node:
         n->kids = *dn;
        *dn = n;

Regards,
Bogdan

Guang Hu wrote:
> Hi, I encountered this problem while trying to test the dns
> based failover supported in openSER 1.2.0.  I had a hard time
> trying to make it work and then I started looking at the code
> and below is what I found in resolve.c
>
> in sip_resolvehost(), the dn argument is non null if it is doing
> dns failover. after grabbing the naptr record it calls
> do_srv_lookup(). do_srv_lookup then calls a2dns_node() if there
> is a second record in the srv lookup. so now *dn is not null but
> then it calls srv2dns_node with the same dn and this smashes
> what was originally pointed to by *dn (malloc'ed in a2dns_node).
> what it needs to do is call the srv2dns_node with the address of
> (*dn)->kids if *dn is already pointing to something.
>
> here is the snippet of code from sip_resolvehost that I am
> talking about. 
>
>         head = get_record( tmp, T_NAPTR);
>         if (head) {
>                 /* filter and sort the records */
>                 filter_and_sort_naptr( &head, &rd, is_sips);
>                 /* free what is useless */
>                 free_rdata_list( rd );
>                 /* process the NAPTR records */
>                 for( rd=head ; rd ; rd=rd->next ) {
>                         *proto = get_naptr_proto( get_naptr(rd)
> );
>                         he = do_srv_lookup( get_naptr(rd)->repl,
> port, dn);
>                         if ( he ) {
>                                 DBG("DEBUG:sip_resolvehost2:
> found!\n");
>                                 if (dn) {
>                                         /* save the state of the
> resolver for failure cases */
>                                         if (*dn==NULL)
>                                                 rd = rd->next;
>                                         if (rd && srv2dns_node(
> rd, dn)!=0) {
>                                                 shm_free(*dn);
>                                                 *dn = 0;
>                                         }
>                                 }
>                                 free_rdata_list(head);
>                                 return he;
>                         }
>                 }
>                 if (head)
>                         free_rdata_list(head);
>         }
>
>
>
>
>
>
> I checked 1.2.0, 1.2.2, and 1.3.0 and they all look the same. so
> now my question is how did this ever work before?
>
>
> thanks,
> Guang
>
>
>
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