Forwarder returns servfail on upstream response noerror no data

**Describe the bug**

unbound 1.18.0 configured as forwarder : when upstream server replies with rcode NOERROR and zero answers, the forwarder replies to the client with rcode SERVFAIL.

**To reproduce**
- an unbound server configured as recursive resolver on interface 127.0.0.1@8053, configured with 
		`local-zone: "example.com" always_nodata` 
- an unbound server configured as forwarder on interface 127.0.0.1@7053, config:
```
server:
    username: ""
    chroot: ""
    directory: "/var/lib"
    do-daemonize: no
    do-not-query-localhost: no
    module-config: "iterator"
    interface: 127.0.0.1@7053
    interface-action: 127.0.0.1@7053 allow
    use-syslog: no

forward-zone:
    name: "."
    forward-addr: 127.0.0.1@8053
```
- query the forwarder : status SERVFAIL
```
$ dig @127.0.0.1 -p 7053 example.com

; DiG 9.16.42-Debian @127.0.0.1 -p 7053 example.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; -HEADER- opcode: QUERY, status: SERVFAIL, id: 28215
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;example.com.			IN	A
```
- query the recursive resolver : status NOERROR

```
$ dig @127.0.0.1 -p 8053 example.com 

;  DiG 9.16.42-Debian  @127.0.0.1 -p 8053 example.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; -HEADER- opcode: QUERY, status: NOERROR, id: 53473
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;example.com.			IN	A
```

**Expected behavior**
return rcode NOERROR with zero answers to the client as did unbound 1.17.1.

**System:**
 - OS: Debian 11
 - `unbound -V` output:
```
Version 1.18.0

Configure line: 
Linked libs: mini-event internal (it uses select), OpenSSL 1.1.1n  15 Mar 2022
Linked modules: dns64 respip validator iterator

```
**Additional information**

log for unbound forwarder 1.18.0
```
[1696431803] unbound[112655:0] info: iterator operate: query example.com. A IN
[1696431803] unbound[112655:0] info: response for example.com. A IN
[1696431803] unbound[112655:0] info: reply from <.> 127.0.0.1#8053
[1696431803] unbound[112655:0] info: query response was THROWAWAY
```

log for unbound forwarder 1.17.1
```
[1696431738] unbound[112637:0] info: iterator operate: query example.com. A IN
[1696431738] unbound[112637:0] info: response for example.com. A IN
[1696431738] unbound[112637:0] info: reply from <.> 127.0.0.1#8053
[1696431738] unbound[112637:0] info: query response was nodata ANSWER
```

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Uh oh!

Forwarder returns servfail on upstream response noerror no data #946

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Uh oh!

Forwarder returns servfail on upstream response noerror no data #946

Description

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions