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resolvectl: clarify IDNA and search path logic in combination with "resolvectl query --type="

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When low-level RR resolution is requested from "resolvectl query" via
"--type=" or "--class=" no search domain logic is applied and no IDNA
translation.

Explain this in detail in the documentation, and also mentions this when
users attempt to resolve single-label names or names with international
characters in the output.

I believe the current behaviour is correct, but it is indeed surprising.
Hence the documentation and output improvement.

Fixes: #11325 #10737
This commit is contained in:
Lennart Poettering 2020-11-06 20:10:40 +01:00
parent e557c82dd5
commit 018b642a98
2 changed files with 65 additions and 11 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

40
man/resolvectl.xml
View file

@ -55,7 +55,19 @@
<varlistentry>
<term><command>query</command> <replaceable>HOSTNAME|ADDRESS</replaceable>…</term>
<listitem><para>Resolve domain names, IPv4 and IPv6 addresses.</para></listitem>
<listitem><para>Resolve domain names, as well as IPv4 and IPv6 addresses. When used in conjuntion
with <option>--type=</option> or <option>--class=</option> (see below), resolves low-level DNS
resource records.</para>
<para>If a single-label domain name is specified it is searched for according to the configured
search domains — unless <option>--search=no</option> or
<option>--type=</option>/<option>--class=</option> are specified, both of which turn this logic
off.</para>
<para>If an international domain name is specified, it is automatically translated according to IDNA
rules when resolved via classic DNS — but not for look-ups via MulticastDNS or LLMNR. If
<option>--type=</option>/<option>--class=</option> is used IDNA translation is turned off and domain
names are processed as specified.</para></listitem>
</varlistentry>
<varlistentry>
@ -233,11 +245,19 @@
<term><option>-c</option> <replaceable>CLASS</replaceable></term>
<term><option>--class=</option><replaceable>CLASS</replaceable></term>
<listitem><para>Specifies the DNS resource record type (e.g. A, AAAA, MX, …) and class (e.g. IN, ANY, …) to
look up. If these options are used a DNS resource record set matching the specified class and type is
requested. The class defaults to IN if only a type is specified.
The special value <literal>help</literal> may be used to list known values.
</para></listitem>
<listitem><para>When used in conjunction with the <command>query</command> command, specifies the DNS
resource record type (e.g. A, AAAA, MX, …) and class (e.g. IN, ANY, …) to look up. If these options
are used a DNS resource record set matching the specified class and type is requested. The class
defaults to IN if only a type is specified. The special value <literal>help</literal> may be used to
list known values.</para>
<para>Without these options <command>resolvectl query</command> provides high-level domain name to
address and address to domain name resolution. With these options it provides low-level DNS resource
record resolution. The search domain logic is automatically turned off when these options are used,
i.e. specified domain names need to be fully qualified domain names. Moreover, IDNA internal domain
name translation is turned off as well, i.e. international domain names should be specified in
<literal>xn--…</literal> notation, unless look-up in MulticastDNS/LLMNR is desired, in which case
UTF-8 characters should be used.</para></listitem>
</varlistentry>
<varlistentry>
@ -324,9 +344,11 @@
<varlistentry>
<term><option>--search=</option><replaceable>BOOL</replaceable></term>
<listitem><para>Takes a boolean parameter. If true (the default), any specified single-label hostnames will be
searched in the domains configured in the search domain list, if it is non-empty. Otherwise, the search domain
logic is disabled.</para></listitem>
<listitem><para>Takes a boolean parameter. If true (the default), any specified single-label
hostnames will be searched in the domains configured in the search domain list, if it is
non-empty. Otherwise, the search domain logic is disabled. Note that this option has no effect if
<option>--type=</option> is used (see above), in which case the search domain logic is
unconditionally turned off.</para></listitem>
</varlistentry>
<varlistentry>

36
src/resolve/resolvectl.c
View file

@ -407,19 +407,51 @@ static int output_rr_packet(const void *d, size_t l, int ifindex) {
return 0;
}
static int idna_candidate(const char *name, char **ret) {
_cleanup_free_ char *idnafied = NULL;
int r;
assert(name);
assert(ret);
r = dns_name_apply_idna(name, &idnafied);
if (r < 0)
return log_error_errno(r, "Failed to apply IDNA to name '%s': %m", name);
if (r > 0 && !streq(name, idnafied)) {
*ret = TAKE_PTR(idnafied);
return true;
}
*ret = NULL;
return false;
}
static int resolve_record(sd_bus *bus, const char *name, uint16_t class, uint16_t type, bool warn_missing) {
_cleanup_(sd_bus_message_unrefp) sd_bus_message *req = NULL, *reply = NULL;
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_free_ char *idnafied = NULL;
bool needs_authentication = false;
unsigned n = 0;
uint64_t flags;
int r;
usec_t ts;
bool needs_authentication = false;
int r;
assert(name);
log_debug("Resolving %s %s %s (interface %s).", name, dns_class_to_string(class), dns_type_to_string(type), isempty(arg_ifname) ? "*" : arg_ifname);
if (dns_name_is_single_label(name))
log_notice("(Note that search domains are not appended when resolving raw record types. "
"Please specify fully qualified domain names when resolving raw records, or remove --type= switch from invocation in order to request regular hostname resolution.)");
r = idna_candidate(name, &idnafied);
if (r < 0)
return r;
if (r > 0)
log_notice("(Note that IDNA translation is not applied when resolving raw record types. "
"Please specify translated domain names — i.e. '%s' — when resolving raw records, or remove --type= switch from invocation in order to request regular hostname resolution.",
idnafied);
r = bus_message_new_method_call(bus, &req, bus_resolve_mgr, "ResolveRecord");
if (r < 0)
return bus_log_create_error(r);