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resolve: synthesize empty domain only when A and/or AAAA key is requested

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Follow-up for 3b2ac14ac45bef01cf489c3231b868936866444b (#22231).

Before this commit.
---
$ dig -t SRV '.'

; <<>> DiG 9.16.24-RH <<>> -t SRV .
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 16836
;; flags: qr aa rd ra ad; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;.				IN	SRV

;; Query time: 1 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Fri Feb 04 12:01:09 JST 2022
;; MSG SIZE  rcvd: 28
---

After this commit.
---
$ dig -t SRV '.'

; <<>> DiG 9.16.24-RH <<>> -t SRV .
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19861
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;.				IN	SRV

;; AUTHORITY SECTION:
.			86394	IN	SOA	a.root-servers.net. nstld.verisign-grs.com. 2022020302 1800 900 604800 86400

;; Query time: 20 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Fri Feb 04 12:00:12 JST 2022
;; MSG SIZE  rcvd: 103
---

Fixes #22401.
This commit is contained in:
Yu Watanabe 2022-02-04 12:05:33 +09:00
parent 176a9a2cca
commit 30fa3aa1fa
1 changed files with 16 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
src/resolve/resolved-dns-scope.c
View File

@ -626,10 +626,6 @@ DnsScopeMatch dns_scope_good_domain(
if ((SD_RESOLVED_FLAGS_MAKE(s->protocol, s->family, false, false) & flags) == 0)
return DNS_SCOPE_NO;
/* Never resolve empty name. */
if (dns_name_is_empty(domain))
return DNS_SCOPE_NO;
/* Never resolve any loopback hostname or IP address via DNS, LLMNR or mDNS. Instead, always rely on
* synthesized RRs for these. */
if (is_localhost(domain) ||
@ -652,6 +648,22 @@ DnsScopeMatch dns_scope_good_domain(
DnsScopeMatch m;
int n_best = -1;
if (dns_name_is_empty(domain)) {
DnsResourceKey *t;
bool found = false;
/* Refuse empty name if only A and/or AAAA records are requested. */
DNS_QUESTION_FOREACH(t, question)
if (!IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_AAAA)) {
found = true;
break;
}
if (!found)
return DNS_SCOPE_NO;
}
/* Never route things to scopes that lack DNS servers */
if (!dns_scope_get_dns_server(s))
return DNS_SCOPE_NO;