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resolved: introduce the _localdnsstub and _localdnsproxy special hostnames for 127.0.0.54 + 127.0.0.53
Let's give these special IP addresses names. After all name resolution is our job here. Fixes: #23623
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@ -323,11 +323,12 @@
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<listitem><para>Takes a boolean parameter; used in conjunction with <command>query</command>. If true
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(the default), select domains are resolved on the local system, among them
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<literal>localhost</literal>, <literal>_gateway</literal> and <literal>_outbound</literal>, or
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entries from <filename>/etc/hosts</filename>. If false these domains are not resolved locally, and
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either fail (in case of <literal>localhost</literal>, <literal>_gateway</literal> or
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<literal>_outbound</literal> and suchlike) or go to the network via regular DNS/mDNS/LLMNR lookups
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(in case of <filename>/etc/hosts</filename> entries).</para></listitem>
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<literal>localhost</literal>, <literal>_gateway</literal>, <literal>_outbound</literal>,
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<literal>_localdnsstub</literal> and <literal>_localdnsproxy</literal> or entries from
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<filename>/etc/hosts</filename>. If false these domains are not resolved locally, and either fail (in
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case of <literal>localhost</literal>, <literal>_gateway</literal> or <literal>_outbound</literal> and
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suchlike) or go to the network via regular DNS/mDNS/LLMNR lookups (in case of
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<filename>/etc/hosts</filename> entries).</para></listitem>
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</varlistentry>
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<varlistentry>
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@ -118,6 +118,12 @@
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local default gateway configured. This assigns a stable hostname to the local outbound IP addresses,
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useful for referencing them independently of the current network configuration state.</para></listitem>
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<listitem><para>The hostname <literal>_localdnsstub</literal> is resolved to the IP address 127.0.0.53,
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i.e. the address the local DNS stub (see above) is listening on.</para></listitem>
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<listitem><para>The hostname <literal>_localdnsproxy</literal> is resolved to the IP address 127.0.0.54,
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i.e. the address the local DNS proxy (see above) is listening on.</para></listitem>
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<listitem><para>The mappings defined in <filename>/etc/hosts</filename> are resolved to their
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configured addresses and back, but they will not affect lookups for non-address types (like MX).
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Support for <filename>/etc/hosts</filename> may be disabled with <varname>ReadEtcHosts=no</varname>,
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@ -60,4 +60,12 @@ static inline bool is_outbound_hostname(const char *hostname) {
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return STRCASE_IN_SET(hostname, "_outbound", "_outbound.");
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}
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static inline bool is_dns_stub_hostname(const char *hostname) {
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return STRCASE_IN_SET(hostname, "_localdnsstub", "_localdnsstub.");
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}
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static inline bool is_dns_proxy_stub_hostname(const char *hostname) {
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return STRCASE_IN_SET(hostname, "_localdnsproxy", "_localdnsproxy.");
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}
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int get_pretty_hostname(char **ret);
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@ -480,7 +480,11 @@ static bool single_label_nonsynthetic(const char *name) {
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if (!dns_name_is_single_label(name))
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return false;
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if (is_localhost(name) || is_gateway_hostname(name))
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if (is_localhost(name) ||
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is_gateway_hostname(name) ||
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is_outbound_hostname(name) ||
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is_dns_stub_hostname(name) ||
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is_dns_proxy_stub_hostname(name))
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return false;
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r = resolve_system_hostname(NULL, &first_label);
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@ -635,8 +635,11 @@ DnsScopeMatch dns_scope_good_domain(
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if (dns_name_dont_resolve(domain))
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return DNS_SCOPE_NO;
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/* Never go to network for the _gateway or _outbound domain — they're something special, synthesized locally. */
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if (is_gateway_hostname(domain) || is_outbound_hostname(domain))
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/* Never go to network for the _gateway, _outbound, _localdnsstub, _localdnsproxy domain — they're something special, synthesized locally. */
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if (is_gateway_hostname(domain) ||
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is_outbound_hostname(domain) ||
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is_dns_stub_hostname(domain) ||
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is_dns_proxy_stub_hostname(domain))
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return DNS_SCOPE_NO;
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switch (s->protocol) {
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@ -341,7 +341,90 @@ static int synthesize_gateway_rr(
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return 1; /* > 0 means: we have some gateway */
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}
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static int synthesize_gateway_ptr(Manager *m, int af, const union in_addr_union *address, int ifindex, DnsAnswer **answer) {
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static int synthesize_dns_stub_rr(
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Manager *m,
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const DnsResourceKey *key,
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in_addr_t addr,
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DnsAnswer **answer) {
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_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
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int r;
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assert(m);
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assert(key);
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assert(answer);
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if (!IN_SET(key->type, DNS_TYPE_A, DNS_TYPE_ANY))
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return 1; /* we still consider ourselves the owner of this name */
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r = dns_answer_reserve(answer, 1);
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if (r < 0)
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return r;
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rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_A, dns_resource_key_name(key));
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if (!rr)
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return -ENOMEM;
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rr->a.in_addr.s_addr = htobe32(addr);
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r = dns_answer_add(*answer, rr, LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED, NULL);
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if (r < 0)
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return r;
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return 1;
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}
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static int synthesize_dns_stub_ptr(
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Manager *m,
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int af,
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const union in_addr_union *address,
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DnsAnswer **answer) {
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int r;
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assert(m);
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assert(address);
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assert(answer);
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if (af != AF_INET)
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return 0;
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if (address->in.s_addr == htobe32(INADDR_DNS_STUB)) {
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r = dns_answer_reserve(answer, 1);
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if (r < 0)
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return r;
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r = answer_add_ptr(answer, "53.0.0.127.in-addr.arpa", "_localdnsstub", LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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return 1;
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}
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if (address->in.s_addr == htobe32(INADDR_DNS_PROXY_STUB)) {
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r = dns_answer_reserve(answer, 1);
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if (r < 0)
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return r;
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r = answer_add_ptr(answer, "54.0.0.127.in-addr.arpa", "_localdnsproxy", LOOPBACK_IFINDEX, DNS_ANSWER_AUTHENTICATED);
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if (r < 0)
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return r;
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return 1;
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}
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return 0;
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}
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static int synthesize_gateway_ptr(
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Manager *m,
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int af,
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const union in_addr_union *address,
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int ifindex,
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DnsAnswer **answer) {
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_cleanup_free_ struct local_address *addresses = NULL;
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int n;
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@ -422,7 +505,22 @@ int dns_synthesize_answer(
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continue;
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}
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} else if ((dns_name_endswith(name, "127.in-addr.arpa") > 0 && dns_name_equal(name, "2.0.0.127.in-addr.arpa") == 0) ||
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} else if (is_dns_stub_hostname(name)) {
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r = synthesize_dns_stub_rr(m, key, INADDR_DNS_STUB, &answer);
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if (r < 0)
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return log_error_errno(r, "Failed to synthesize local DNS stub RRs: %m");
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} else if (is_dns_proxy_stub_hostname(name)) {
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r = synthesize_dns_stub_rr(m, key, INADDR_DNS_PROXY_STUB, &answer);
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if (r < 0)
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return log_error_errno(r, "Failed to synthesize local DNS stub RRs: %m");
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} else if ((dns_name_endswith(name, "127.in-addr.arpa") > 0 &&
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dns_name_equal(name, "2.0.0.127.in-addr.arpa") == 0 &&
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dns_name_equal(name, "53.0.0.127.in-addr.arpa") == 0 &&
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dns_name_equal(name, "54.0.0.127.in-addr.arpa") == 0) ||
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dns_name_equal(name, "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0) {
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r = synthesize_localhost_ptr(m, key, &answer);
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@ -430,7 +528,7 @@ int dns_synthesize_answer(
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return log_error_errno(r, "Failed to synthesize localhost PTR RRs: %m");
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} else if (dns_name_address(name, &af, &address) > 0) {
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int v, w;
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int v, w, u;
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if (getenv_bool("SYSTEMD_RESOLVED_SYNTHESIZE_HOSTNAME") == 0)
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continue;
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@ -443,7 +541,11 @@ int dns_synthesize_answer(
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if (w < 0)
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return log_error_errno(w, "Failed to synthesize gateway hostname PTR RR: %m");
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if (v == 0 && w == 0) /* This IP address is neither a local one nor a gateway */
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u = synthesize_dns_stub_ptr(m, af, &address, &answer);
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if (u < 0)
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return log_error_errno(u, "Failed to synthesize local stub hostname PTR PR: %m");
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if (v == 0 && w == 0 && u == 0) /* This IP address is neither a local one, nor a gateway, nor a stub address */
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continue;
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/* Note that we never synthesize reverse PTR for _outbound, since those are local
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@ -56,6 +56,17 @@ echo nameserver 10.0.3.3 10.0.3.4 | "$RESOLVCONF" -a hoge.foo.dhcp
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assert_in '10.0.3.1 10.0.3.2' "$(resolvectl dns hoge)"
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assert_in '10.0.3.3 10.0.3.4' "$(resolvectl dns hoge.foo)"
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# Tests for _localdnsstub and _localdnsproxy
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assert_in '127.0.0.53' "$(resolvectl query _localdnsstub)"
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assert_in '_localdnsstub' "$(resolvectl query 127.0.0.53)"
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assert_in '127.0.0.54' "$(resolvectl query _localdnsproxy)"
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assert_in '_localdnsproxy' "$(resolvectl query 127.0.0.54)"
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assert_in '127.0.0.53' "$(dig @127.0.0.53 _localdnsstub)"
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assert_in '_localdnsstub' "$(dig @127.0.0.53 -x 127.0.0.53)"
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assert_in '127.0.0.54' "$(dig @127.0.0.53 _localdnsproxy)"
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assert_in '_localdnsproxy' "$(dig @127.0.0.53 -x 127.0.0.54)"
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# Tests for mDNS and LLMNR settings
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mkdir -p /run/systemd/resolved.conf.d
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{
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