s4-resolv: fix dns_ex so as to fail correctly when a name does not exist

Without this, netbios name lookups do not work, as we never fall back to them.

This caused segfaults from e38d97e0424f7e5b21c8b7ac0b1f1bac33f19d69 to
251209bd6f6e66ca9bcf28cd652d85d1cd729fdc and then name lookup failure
or timeouts until this patch.

Andrew Bartlett

Autobuild-User: Andrew Bartlett <abartlet@samba.org>
Autobuild-Date: Wed Dec 14 01:16:37 CET 2011 on sn-devel-104

diff --git a/source4/libcli/resolve/dns_ex.c b/source4/libcli/resolve/dns_ex.c
index 9467521394efb2afa5f4b9dcd11e9ed1d69a03dc..4f46235a9ff57ae885ba020d75e1c94c00e4ac37 100644 (file)
--- a/source4/libcli/resolve/dns_ex.c
+++ b/source4/libcli/resolve/dns_ex.c
@@ -393,6 +393,12 @@ static void run_child_dns_lookup(struct dns_ex_state *state, int fd)
                c = get_a_aaaa_records(state, state->name.name, state->port);
        }
 
+       /* This line in critical - if we return without writing to the
+        * pipe, this is the signal that the name did not exist */
+       if (c.count == 0) {
+               goto done;
+       }
+
        addrs = talloc_strdup(state, "");
        if (!addrs) {
                goto done;
@@ -521,6 +527,9 @@ static void pipe_handler(struct tevent_context *ev, struct tevent_fd *fde,
        }
 
        if (ret <= 0) {
+               /* The check for ret == 0 here is important, if the
+                * name does not exist, then no bytes are written to
+                * the pipe */
                DEBUG(3,("dns child failed to find name '%s' of type %s\n",
                         state->name.name, (state->flags & RESOLVE_NAME_FLAG_DNS_SRV)?"SRV":"A"));
                composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);