Merge pull request #3549 from poettering/resolved-more

resolved: more fixes, among them "systemctl-resolve --status" to see DNS configuration in effect, and a local DNS stub listener on 127.0.0.53

Makefile.am

@@ -125,6 +125,7 @@ dist_systemunit_DATA_busnames =
 dist_sysusers_DATA =
 check_PROGRAMS =
 check_DATA =
+dist_rootlibexec_DATA =
 tests=
 manual_tests =
 TEST_EXTENSIONS = .py
@@ -5147,7 +5148,7 @@ systemd_export_LDADD = \
 	$(ZLIB_LIBS) \
 	-lbz2
 
-dist_rootlibexec_DATA = \
+dist_rootlibexec_DATA += \
 	src/import/import-pubring.gpg
 
 nodist_systemunit_DATA += \
@@ -5259,6 +5260,8 @@ systemd_resolved_SOURCES = \
 	src/resolve/resolved-dns-stream.c \
 	src/resolve/resolved-dns-trust-anchor.h \
 	src/resolve/resolved-dns-trust-anchor.c \
+	src/resolve/resolved-dns-stub.h \
+	src/resolve/resolved-dns-stub.c \
 	src/resolve/resolved-etc-hosts.h \
 	src/resolve/resolved-etc-hosts.c \
 	src/shared/gcrypt-util.c \
@@ -5411,6 +5414,9 @@ EXTRA_DIST += \
 	units/systemd-resolved.service.m4.in \
 	src/resolve/resolved.conf.in
 
+dist_rootlibexec_DATA += \
+	src/resolve/resolv.conf
+
 # ------------------------------------------------------------------------------
 if ENABLE_NETWORKD
 rootlibexec_PROGRAMS += \

man/systemd-resolve.xml

@@ -294,8 +294,15 @@
         <listitem><para>Flushes all DNS resource record caches the service maintains locally.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><option>--status</option></term>
+
+        <listitem><para>Shows the global and per-link DNS settings in currently in effect.</para></listitem>
+      </varlistentry>
+
       <xi:include href="standard-options.xml" xpointer="help" />
       <xi:include href="standard-options.xml" xpointer="version" />
+      <xi:include href="standard-options.xml" xpointer="no-pager" />
     </variablelist>
   </refsect1>
 

man/systemd-resolved.service.xml

@@ -58,27 +58,45 @@
 
     <para><command>systemd-resolved</command> is a system service that provides network name resolution to local
     applications. It implements a caching and validating DNS/DNSSEC stub resolver, as well as an LLMNR resolver and
-    responder. In addition it maintains the <filename>/run/systemd/resolve/resolv.conf</filename> file for
-    compatibility with traditional Linux programs. This file may be symlinked from
-    <filename>/etc/resolv.conf</filename>.</para>
+    responder. Local applications may submit network name resolution requests via three interfaces:</para>
 
-    <para>The glibc NSS module
-    <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry> is required to
-    permit glibc's NSS resolver functions to resolve host names via <command>systemd-resolved</command>.</para>
+    <itemizedlist>
+      <listitem><para>The native, fully-featured API <command>systemd-resolved</command> exposes on the bus. See the
+      <ulink url="http://www.freedesktop.org/wiki/Software/systemd/resolved">API Documentation</ulink> for
+      details. Usage of this API is generally recommended to clients as it is asynchronous and fully featured (for
+      example, properly returns DNSSEC validation status and interface scope for addresses as necessary for supporting
+      link-local networking).</para></listitem>
 
-    <para>The DNS servers contacted are determined from the global
-    settings in <filename>/etc/systemd/resolved.conf</filename>, the
-    per-link static settings in <filename>/etc/systemd/network/*.network</filename> files,
-    and the per-link dynamic settings received over DHCP. See
-    <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
-    and
-    <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry>
-    for details. To improve compatibility,
-    <filename>/etc/resolv.conf</filename> is read in order to discover
-    configured system DNS servers, but only if it is not a symlink
-    to <filename>/run/systemd/resolve/resolv.conf</filename> (see above).</para>
+      <listitem><para>The glibc
+      <citerefentry><refentrytitle>getaddrinfo</refentrytitle><manvolnum>3</manvolnum></citerefentry> API (as defined
+      by <ulink url="https://tools.ietf.org/html/rfc3493">RFC3493</ulink>) and its related resolver functions,
+      including <citerefentry><refentrytitle>gethostbyname</refentrytitle><manvolnum>3</manvolnum></citerefentry>. This
+      API is widely supported, including beyond the Linux platform. In its current form it does not expose DNSSEC
+      validation status information however, and is synchronous only. This API is backed by the glibc Name Service
+      Switch (<citerefentry><refentrytitle>nss</refentrytitle><manvolnum>5</manvolnum></citerefentry>). Usage of the
+      glibc NSS module <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+      is required in order to allow glibc's NSS resolver functions to resolve host names via
+      <command>systemd-resolved</command>.</para></listitem>
 
-    <para><command>systemd-resolved</command> synthesizes DNS RRs for the following cases:</para>
+      <listitem><para>Additionally, <command>systemd-resolved</command> provides a local DNS stub listener on IP
+      address 127.0.0.53 on the local loopback interface. Programs issuing DNS requests directly, bypassing any local
+      API may be directed to this stub, in order to connect them <command>systemd-resolved</command>. Note however that
+      it is strongly recommended that local programs use the glibc NSS or bus APIs instead (as described above), as
+      various network resolution concepts (such as link-local addressing, or LLMNR Unicode domains) cannot be mapped to
+      the unicast DNS protocol.</para></listitem>
+    </itemizedlist>
+
+    <para>The DNS servers contacted are determined from the global settings in
+    <filename>/etc/systemd/resolved.conf</filename>, the per-link static settings in
+    <filename>/etc/systemd/network/*.network</filename> files, the per-link dynamic settings received over DHCP and any
+    DNS server information made available by other system services. See
+    <citerefentry><refentrytitle>resolved.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> and
+    <citerefentry><refentrytitle>systemd.network</refentrytitle><manvolnum>5</manvolnum></citerefentry> for details
+    about systemd's own configuration files for DNS servers. To improve compatibility,
+    <filename>/etc/resolv.conf</filename> is read in order to discover configured system DNS servers, but only if it is
+    not a symlink to <filename>/run/systemd/resolve/resolv.conf</filename> (see below).</para>
+
+    <para><command>systemd-resolved</command> synthesizes DNS resource records (RRs) for the following cases:</para>
 
     <itemizedlist>
       <listitem><para>The local, configured hostname is resolved to
@@ -137,14 +155,45 @@
     per-interface domains are exclusively routed to the matching
     interfaces.</para>
 
-    <para>Note that <filename>/run/systemd/resolve/resolv.conf</filename> should not be used directly by applications,
-    but only through a symlink from <filename>/etc/resolv.conf</filename>.</para>
-
     <para>See the <ulink url="http://www.freedesktop.org/wiki/Software/systemd/resolved"> resolved D-Bus API
     Documentation</ulink> for information about the APIs <filename>systemd-resolved</filename> provides.</para>
 
   </refsect1>
 
+  <refsect1>
+    <title><filename>/etc/resolv.conf</filename></title>
+
+    <para>Three modes of handling <filename>/etc/resolv.conf</filename> (see
+    <citerefentry><refentrytitle>resolv.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>) are
+    supported:</para>
+
+    <itemizedlist>
+      <listitem><para>A static file <filename>/usr/lib/systemd/resolv.conf</filename> is provided that lists
+      the 127.0.0.53 DNS stub (see above) as only DNS server. This file may be symlinked from
+      <filename>/etc/resolv.conf</filename> in order to connect all local clients that bypass local DNS APIs to
+      <command>systemd-resolved</command>. This mode of operation is recommended.</para></listitem>
+
+      <listitem><para><command>systemd-resolved</command> maintains the
+      <filename>/run/systemd/resolve/resolv.conf</filename> file for compatibility with traditional Linux
+      programs. This file may be symlinked from <filename>/etc/resolv.conf</filename> and is always kept up-to-date,
+      containing information about all known DNS servers. Note the file format's limitations: it does not know a
+      concept of per-interface DNS servers and hence only contains system-wide DNS server definitions. Note that
+      <filename>/run/systemd/resolve/resolv.conf</filename> should not be used directly by applications, but only
+      through a symlink from <filename>/etc/resolv.conf</filename>. If this mode of operation is used local clients
+      that bypass any local DNS API will also bypass <command>systemd-resolved</command> and will talk directly to the
+      known DNS servers.</para> </listitem>
+
+      <listitem><para>Alternatively, <filename>/etc/resolv.conf</filename> may be managed by other packages, in which
+      case <command>systemd-resolved</command> will read it for DNS configuration data. In this mode of operation
+      <command>systemd-resolved</command> is consumer rather than provider of this configuration
+      file. </para></listitem>
+    </itemizedlist>
+
+    <para>Note that the selected mode of operation for this file is detected fully automatically, depending on whether
+    <filename>/etc/resolv.conf</filename> is a symlink to <filename>/run/systemd/resolve/resolv.conf</filename> or
+    lists 127.0.0.53 as DNS server.</para>
+  </refsect1>
+
   <refsect1>
     <title>Signals</title>
 

src/basic/bitmap.c

@@ -50,6 +50,23 @@ Bitmap *bitmap_new(void) {
         return new0(Bitmap, 1);
 }
 
+Bitmap *bitmap_copy(Bitmap *b) {
+        Bitmap *ret;
+
+        ret = bitmap_new();
+        if (!ret)
+                return NULL;
+
+        ret->bitmaps = newdup(uint64_t, b->bitmaps, b->n_bitmaps);
+        if (!ret->bitmaps) {
+                free(ret);
+                return NULL;
+        }
+
+        ret->n_bitmaps = ret->bitmaps_allocated = b->n_bitmaps;
+        return ret;
+}
+
 void bitmap_free(Bitmap *b) {
         if (!b)
                 return;

src/basic/bitmap.h

@@ -27,10 +27,9 @@
 typedef struct Bitmap Bitmap;
 
 Bitmap *bitmap_new(void);
-
-void bitmap_free(Bitmap *b);
-
+Bitmap *bitmap_copy(Bitmap *b);
 int bitmap_ensure_allocated(Bitmap **b);
+void bitmap_free(Bitmap *b);
 
 int bitmap_set(Bitmap *b, unsigned n);
 void bitmap_unset(Bitmap *b, unsigned n);

src/basic/hashmap.c

@@ -1764,6 +1764,9 @@ void *ordered_hashmap_next(OrderedHashmap *h, const void *key) {
 int set_consume(Set *s, void *value) {
         int r;
 
+        assert(s);
+        assert(value);
+
         r = set_put(s, value);
         if (r <= 0)
                 free(value);
@@ -1791,6 +1794,8 @@ int set_put_strdupv(Set *s, char **l) {
         int n = 0, r;
         char **i;
 
+        assert(s);
+
         STRV_FOREACH(i, l) {
                 r = set_put_strdup(s, *i);
                 if (r < 0)
@@ -1801,3 +1806,23 @@ int set_put_strdupv(Set *s, char **l) {
 
         return n;
 }
+
+int set_put_strsplit(Set *s, const char *v, const char *separators, ExtractFlags flags) {
+        const char *p = v;
+        int r;
+
+        assert(s);
+        assert(v);
+
+        for (;;) {
+                char *word;
+
+                r = extract_first_word(&p, &word, separators, flags);
+                if (r <= 0)
+                        return r;
+
+                r = set_consume(s, word);
+                if (r < 0)
+                        return r;
+        }
+}

src/basic/process-util.c

@@ -553,7 +553,7 @@ int wait_for_terminate(pid_t pid, siginfo_t *status) {
                         if (errno == EINTR)
                                 continue;
 
-                        return -errno;
+                        return negative_errno();
                 }
 
                 return 0;

src/basic/set.h

@@ -19,6 +19,7 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include "extract-word.h"
 #include "hashmap.h"
 #include "macro.h"
 
@@ -122,6 +123,7 @@ static inline char **set_get_strv(Set *s) {
 int set_consume(Set *s, void *value);
 int set_put_strdup(Set *s, const char *p);
 int set_put_strdupv(Set *s, char **l);
+int set_put_strsplit(Set *s, const char *v, const char *separators, ExtractFlags flags);
 
 #define SET_FOREACH(e, s, i) \
         for ((i) = ITERATOR_FIRST; set_iterate((s), &(i), (void**)&(e)); )

src/basic/string-table.h

@@ -48,6 +48,8 @@ ssize_t string_table_lookup(const char * const *table, size_t len, const char *k
 #define _DEFINE_STRING_TABLE_LOOKUP_FROM_STRING_WITH_BOOLEAN(name,type,yes,scope) \
         scope type name##_from_string(const char *s) {                  \
                 int b;                                                  \
+                if (!s)                                                 \
+                        return -1;                                      \
                 b = parse_boolean(s);                                   \
                 if (b == 0)                                             \
                         return (type) 0;                                \

src/journal/mmap-cache.c

@@ -481,7 +481,7 @@ static int mmap_try_harder(MMapCache *m, void *addr, int fd, int prot, int flags
                 if (ptr != MAP_FAILED)
                         break;
                 if (errno != ENOMEM)
-                        return -errno;
+                        return negative_errno();
 
                 r = make_room(m);
                 if (r < 0)
@@ -571,7 +571,7 @@ static int add_mmap(
         return 1;
 
 outofmem:
-        munmap(d, wsize);
+        (void) munmap(d, wsize);
         return -ENOMEM;
 }
 

src/login/loginctl.c

@@ -290,7 +290,7 @@ typedef struct SessionStatusInfo {
         char *seat;
         char *tty;
         char *display;
-        bool remote;
+        int remote;
         char *remote_host;
         char *remote_user;
         char *service;
@@ -304,7 +304,7 @@ typedef struct SessionStatusInfo {
 
 typedef struct UserStatusInfo {
         uid_t uid;
-        bool linger;
+        int linger;
         char *name;
         struct dual_timestamp timestamp;
         char *state;

src/network/networkd-brvlan.c

@@ -58,7 +58,7 @@ static int append_vlan_info_data(Link *const link, sd_netlink_message *req, uint
         struct bridge_vlan_info br_vlan;
         int i, j, k, r, done, cnt;
         uint16_t begin, end;
-        bool untagged;
+        bool untagged = false;
 
         assert(link);
         assert(req);

src/network/networkd-network-gperf.gperf

@@ -52,7 +52,7 @@ Network.DNS,                            config_parse_strv,
 Network.LLMNR,                          config_parse_resolve_support,                   0,                             offsetof(Network, llmnr)
 Network.MulticastDNS,                   config_parse_resolve_support,                   0,                             offsetof(Network, mdns)
 Network.DNSSEC,                         config_parse_dnssec_mode,                       0,                             offsetof(Network, dnssec_mode)
-Network.DNSSECNegativeTrustAnchors,     config_parse_dnssec_negative_trust_anchors,     0,                             offsetof(Network, dnssec_negative_trust_anchors)
+Network.DNSSECNegativeTrustAnchors,     config_parse_dnssec_negative_trust_anchors,     0,                             0
 Network.NTP,                            config_parse_strv,                              0,                             offsetof(Network, ntp)
 Network.IPForward,                      config_parse_address_family_boolean_with_kernel,0,                             offsetof(Network, ip_forward)
 Network.IPMasquerade,                   config_parse_bool,                              0,                             offsetof(Network, ip_masquerade)

src/resolve/dns-type.c

@@ -96,6 +96,15 @@ bool dns_type_is_valid_query(uint16_t type) {
                        DNS_TYPE_RRSIG);
 }
 
+bool dns_type_is_zone_transer(uint16_t type) {
+
+        /* Zone transfers, either normal or incremental */
+
+        return IN_SET(type,
+                      DNS_TYPE_AXFR,
+                      DNS_TYPE_IXFR);
+}
+
 bool dns_type_is_valid_rr(uint16_t type) {
 
         /* The types valid as RR in packets (but not necessarily

src/resolve/dns-type.h

@@ -136,6 +136,7 @@ bool dns_type_is_obsolete(uint16_t type);
 bool dns_type_may_wildcard(uint16_t type);
 bool dns_type_apex_only(uint16_t type);
 bool dns_type_needs_authentication(uint16_t type);
+bool dns_type_is_zone_transer(uint16_t type);
 int dns_type_to_af(uint16_t type);
 
 bool dns_class_is_pseudo(uint16_t class);

src/resolve/resolv.conf

@@ -0,0 +1,11 @@
+# This is a static resolv.conf file for connecting local clients to
+# systemd-resolved via its DNS stub listener on 127.0.0.53.
+#
+# Third party programs must not access this file directly, but only through the
+# symlink at /etc/resolv.conf. To manage resolv.conf(5) in a different way,
+# replace this symlink by a static file or a different symlink.
+#
+# See systemd-resolved.service(8) for details about the supported modes of
+# operation for /etc/resolv.conf.
+
+nameserver 127.0.0.53

src/resolve/resolved-bus.c

@@ -647,6 +647,8 @@ static int bus_method_resolve_record(sd_bus_message *message, void *userdata, sd
 
         if (!dns_type_is_valid_query(type))
                 return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Specified resource record type %" PRIu16 " may not be used in a query.", type);
+        if (dns_type_is_zone_transer(type))
+                return sd_bus_error_setf(error, SD_BUS_ERROR_NOT_SUPPORTED, "Zone transfers not permitted via this programming interface.");
         if (dns_type_is_obsolete(type))
                 return sd_bus_error_setf(error, SD_BUS_ERROR_NOT_SUPPORTED, "Specified DNS resource record type %" PRIu16 " is obsolete.", type);
 
@@ -670,6 +672,10 @@ static int bus_method_resolve_record(sd_bus_message *message, void *userdata, sd
         if (r < 0)
                 return r;
 
+        /* Let's request that the TTL is fixed up for locally cached entries, after all we return it in the wire format
+         * blob */
+        q->clamp_ttl = true;
+
         q->request = sd_bus_message_ref(message);
         q->complete = bus_method_resolve_record_complete;
 
@@ -1414,6 +1420,36 @@ static int bus_property_get_dnssec_supported(
         return sd_bus_message_append(reply, "b", manager_dnssec_supported(m));
 }
 
+static int bus_property_get_ntas(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+
+        Manager *m = userdata;
+        const char *domain;
+        Iterator i;
+        int r;
+
+        assert(reply);
+        assert(m);
+
+        r = sd_bus_message_open_container(reply, 'a', "s");
+        if (r < 0)
+                return r;
+
+        SET_FOREACH(domain, m->trust_anchor.negative_by_name, i) {
+                r = sd_bus_message_append(reply, "s", domain);
+                if (r < 0)
+                        return r;
+        }
+
+        return sd_bus_message_close_container(reply);
+}
+
 static int bus_method_reset_statistics(sd_bus_message *message, void *userdata, sd_bus_error *error) {
         Manager *m = userdata;
         DnsScope *s;
@@ -1540,6 +1576,7 @@ static const sd_bus_vtable resolve_vtable[] = {
         SD_BUS_PROPERTY("CacheStatistics", "(ttt)", bus_property_get_cache_statistics, 0, 0),
         SD_BUS_PROPERTY("DNSSECStatistics", "(tttt)", bus_property_get_dnssec_statistics, 0, 0),
         SD_BUS_PROPERTY("DNSSECSupported", "b", bus_property_get_dnssec_supported, 0, 0),
+        SD_BUS_PROPERTY("DNSSECNegativeTrustAnchors", "as", bus_property_get_ntas, 0, 0),
 
         SD_BUS_METHOD("ResolveHostname", "isit", "a(iiay)st", bus_method_resolve_hostname, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("ResolveAddress", "iiayt", "a(is)t", bus_method_resolve_address, SD_BUS_VTABLE_UNPRIVILEGED),

src/resolve/resolved-conf.c

@@ -37,6 +37,10 @@ int manager_add_dns_server_by_string(Manager *m, DnsServerType type, const char
         if (r < 0)
                 return r;
 
+        /* Silently filter out 0.0.0.0 and 127.0.0.53 (our own stub DNS listener) */
+        if (!dns_server_address_valid(family, &address))
+                return 0;
+
         /* Filter out duplicates */
         s = dns_server_find(manager_get_first_dns_server(m, type), family, &address, ifindex);
         if (s) {

src/resolve/resolved-dns-answer.h

@@ -87,6 +87,10 @@ static inline unsigned dns_answer_size(DnsAnswer *a) {
         return a ? a->n_rrs : 0;
 }
 
+static inline bool dns_answer_isempty(DnsAnswer *a) {
+        return dns_answer_size(a) <= 0;
+}
+
 void dns_answer_dump(DnsAnswer *answer, FILE *f);
 
 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsAnswer*, dns_answer_unref);