Merge of r4611, r4620: resolver fixes. *) Fixed segmentation fault in ngx_resolver_create_name_query(). If name passed for resolution was { 0, NULL } (e.g. as a result of name server returning CNAME pointing to ".") pointer wrapped to (void *) -1 resulting in segmentation fault on an attempt to dereference it. Reported by Lanshun Zhou. *) Resolver: protection from duplicate responses. If we already had CNAME in resolver node (i.e. rn->cnlen and rn->u.cname set), and got additional response with A record, it resulted in rn->cnlen set and rn->u.cname overwritten by rn->u.addr (or rn->u.addrs), causing segmentation fault later in ngx_resolver_free_node() on an attempt to free overwritten rn->u.cname. The opposite (i.e. CNAME got after A) might cause similar problems as well.