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authorLuke Shumaker <lukeshu@lukeshu.com>2017-05-10 17:35:20 -0400
committerLuke Shumaker <lukeshu@lukeshu.com>2017-05-10 17:35:20 -0400
commit0f84dd566f9a09ff2bf9c421c57f92c0940720f3 (patch)
treead55de626764ceb7056299d6f54048af2bc60e9e /src/grp-resolve/nss-resolve
parent113d1861d5730e1e61e6583317f1c6baa9deb333 (diff)
./tools/notsd-move
Diffstat (limited to 'src/grp-resolve/nss-resolve')
l---------src/grp-resolve/nss-resolve/GNUmakefile1
-rw-r--r--src/grp-resolve/nss-resolve/Makefile46
-rw-r--r--src/grp-resolve/nss-resolve/nss-resolve.c681
-rw-r--r--src/grp-resolve/nss-resolve/nss-resolve.sym19
-rw-r--r--src/grp-resolve/nss-resolve/nss-resolve.xml114
5 files changed, 861 insertions, 0 deletions
diff --git a/src/grp-resolve/nss-resolve/GNUmakefile b/src/grp-resolve/nss-resolve/GNUmakefile
new file mode 120000
index 0000000000..95e5924740
--- /dev/null
+++ b/src/grp-resolve/nss-resolve/GNUmakefile
@@ -0,0 +1 @@
+../../../GNUmakefile \ No newline at end of file
diff --git a/src/grp-resolve/nss-resolve/Makefile b/src/grp-resolve/nss-resolve/Makefile
new file mode 100644
index 0000000000..310f816b06
--- /dev/null
+++ b/src/grp-resolve/nss-resolve/Makefile
@@ -0,0 +1,46 @@
+# -*- Mode: makefile; indent-tabs-mode: t -*-
+#
+# This file is part of systemd.
+#
+# Copyright 2010-2012 Lennart Poettering
+# Copyright 2010-2012 Kay Sievers
+# Copyright 2013 Zbigniew Jędrzejewski-Szmek
+# Copyright 2013 David Strauss
+# Copyright 2016 Luke Shumaker
+#
+# systemd is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation; either version 2.1 of the License, or
+# (at your option) any later version.
+#
+# systemd is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with systemd; If not, see <http://www.gnu.org/licenses/>.
+include $(dir $(lastword $(MAKEFILE_LIST)))/../../../config.mk
+include $(topsrcdir)/build-aux/Makefile.head.mk
+
+libnss_resolve_la_SOURCES = \
+ src/nss-resolve/nss-resolve.sym \
+ src/nss-resolve/nss-resolve.c
+
+libnss_resolve_la_LDFLAGS = \
+ -module \
+ -export-dynamic \
+ -avoid-version \
+ -shared \
+ -shrext .so.2 \
+ -Wl,--version-script=$(srcdir)/nss-resolve.sym
+
+libnss_resolve_la_LIBADD = \
+ libsystemd-internal.la \
+ libsystemd-basic.la \
+ -ldl
+
+rootlib_LTLIBRARIES += \
+ libnss_resolve.la
+
+include $(topsrcdir)/build-aux/Makefile.tail.mk
diff --git a/src/grp-resolve/nss-resolve/nss-resolve.c b/src/grp-resolve/nss-resolve/nss-resolve.c
new file mode 100644
index 0000000000..681416e18f
--- /dev/null
+++ b/src/grp-resolve/nss-resolve/nss-resolve.c
@@ -0,0 +1,681 @@
+/***
+ This file is part of systemd.
+
+ Copyright 2014 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <dlfcn.h>
+#include <errno.h>
+#include <netdb.h>
+#include <nss.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <systemd/sd-bus.h>
+
+#include "sd-bus/bus-common-errors.h"
+#include "systemd-basic/in-addr-util.h"
+#include "systemd-basic/macro.h"
+#include "systemd-basic/nss-util.h"
+#include "systemd-basic/signal-util.h"
+#include "systemd-basic/string-util.h"
+#include "systemd-basic/util.h"
+
+NSS_GETHOSTBYNAME_PROTOTYPES(resolve);
+NSS_GETHOSTBYADDR_PROTOTYPES(resolve);
+
+#define DNS_CALL_TIMEOUT_USEC (45*USEC_PER_SEC)
+
+typedef void (*voidfunc_t)(void);
+
+static voidfunc_t find_fallback(const char *module, const char *symbol) {
+ void *dl;
+
+ /* Try to find a fallback NSS module symbol */
+
+ dl = dlopen(module, RTLD_LAZY|RTLD_NODELETE);
+ if (!dl)
+ return NULL;
+
+ return dlsym(dl, symbol);
+}
+
+static bool bus_error_shall_fallback(sd_bus_error *e) {
+ return sd_bus_error_has_name(e, SD_BUS_ERROR_SERVICE_UNKNOWN) ||
+ sd_bus_error_has_name(e, SD_BUS_ERROR_NAME_HAS_NO_OWNER) ||
+ sd_bus_error_has_name(e, SD_BUS_ERROR_NO_REPLY) ||
+ sd_bus_error_has_name(e, SD_BUS_ERROR_ACCESS_DENIED);
+}
+
+static int count_addresses(sd_bus_message *m, int af, const char **canonical) {
+ int c = 0, r;
+
+ assert(m);
+ assert(canonical);
+
+ r = sd_bus_message_enter_container(m, 'a', "(iiay)");
+ if (r < 0)
+ return r;
+
+ while ((r = sd_bus_message_enter_container(m, 'r', "iiay")) > 0) {
+ int family, ifindex;
+
+ assert_cc(sizeof(int32_t) == sizeof(int));
+
+ r = sd_bus_message_read(m, "ii", &ifindex, &family);
+ if (r < 0)
+ return r;
+
+ r = sd_bus_message_skip(m, "ay");
+ if (r < 0)
+ return r;
+
+ r = sd_bus_message_exit_container(m);
+ if (r < 0)
+ return r;
+
+ if (af != AF_UNSPEC && family != af)
+ continue;
+
+ c++;
+ }
+ if (r < 0)
+ return r;
+
+ r = sd_bus_message_exit_container(m);
+ if (r < 0)
+ return r;
+
+ r = sd_bus_message_read(m, "s", canonical);
+ if (r < 0)
+ return r;
+
+ r = sd_bus_message_rewind(m, true);
+ if (r < 0)
+ return r;
+
+ return c;
+}
+
+enum nss_status _nss_resolve_gethostbyname4_r(
+ const char *name,
+ struct gaih_addrtuple **pat,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp) {
+
+ _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;
+ struct gaih_addrtuple *r_tuple, *r_tuple_first = NULL;
+ _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+ enum nss_status ret = NSS_STATUS_UNAVAIL;
+ const char *canonical = NULL;
+ size_t l, ms, idx;
+ char *r_name;
+ int c, r, i = 0;
+
+ BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
+
+ assert(name);
+ assert(pat);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ r = sd_bus_open_system(&bus);
+ if (r < 0)
+ goto fallback;
+
+ r = sd_bus_message_new_method_call(
+ bus,
+ &req,
+ "org.freedesktop.resolve1",
+ "/org/freedesktop/resolve1",
+ "org.freedesktop.resolve1.Manager",
+ "ResolveHostname");
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_set_auto_start(req, false);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_append(req, "isit", 0, name, AF_UNSPEC, (uint64_t) 0);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_call(bus, req, DNS_CALL_TIMEOUT_USEC, &error, &reply);
+ if (r < 0) {
+ if (sd_bus_error_has_name(&error, _BUS_ERROR_DNS "NXDOMAIN")) {
+ *errnop = ESRCH;
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+ }
+
+ if (bus_error_shall_fallback(&error))
+ goto fallback;
+
+ /* Treat all other error conditions as NOTFOUND, and fail. This includes DNSSEC errors and
+ suchlike. (We don't use UNAVAIL in this case so that the nsswitch.conf configuration can distuingish
+ such executed but negative replies from complete failure to talk to resolved. */
+ ret = NSS_STATUS_NOTFOUND;
+ goto fail;
+ }
+
+ c = count_addresses(reply, AF_UNSPEC, &canonical);
+ if (c < 0) {
+ r = c;
+ goto fail;
+ }
+ if (c == 0) {
+ *errnop = ESRCH;
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+ }
+
+ if (isempty(canonical))
+ canonical = name;
+
+ l = strlen(canonical);
+ ms = ALIGN(l+1) + ALIGN(sizeof(struct gaih_addrtuple)) * c;
+ if (buflen < ms) {
+ *errnop = ENOMEM;
+ *h_errnop = TRY_AGAIN;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ /* First, append name */
+ r_name = buffer;
+ memcpy(r_name, canonical, l+1);
+ idx = ALIGN(l+1);
+
+ /* Second, append addresses */
+ r_tuple_first = (struct gaih_addrtuple*) (buffer + idx);
+
+ r = sd_bus_message_enter_container(reply, 'a', "(iiay)");
+ if (r < 0)
+ goto fail;
+
+ while ((r = sd_bus_message_enter_container(reply, 'r', "iiay")) > 0) {
+ int family, ifindex;
+ const void *a;
+ size_t sz;
+
+ assert_cc(sizeof(int32_t) == sizeof(int));
+
+ r = sd_bus_message_read(reply, "ii", &ifindex, &family);
+ if (r < 0)
+ goto fail;
+
+ if (ifindex < 0) {
+ r = -EINVAL;
+ goto fail;
+ }
+
+ r = sd_bus_message_read_array(reply, 'y', &a, &sz);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_exit_container(reply);
+ if (r < 0)
+ goto fail;
+
+ if (!IN_SET(family, AF_INET, AF_INET6))
+ continue;
+
+ if (sz != FAMILY_ADDRESS_SIZE(family)) {
+ r = -EINVAL;
+ goto fail;
+ }
+
+ r_tuple = (struct gaih_addrtuple*) (buffer + idx);
+ r_tuple->next = i == c-1 ? NULL : (struct gaih_addrtuple*) ((char*) r_tuple + ALIGN(sizeof(struct gaih_addrtuple)));
+ r_tuple->name = r_name;
+ r_tuple->family = family;
+ r_tuple->scopeid = ifindex;
+ memcpy(r_tuple->addr, a, sz);
+
+ idx += ALIGN(sizeof(struct gaih_addrtuple));
+ i++;
+ }
+ if (r < 0)
+ goto fail;
+
+ assert(i == c);
+ assert(idx == ms);
+
+ if (*pat)
+ **pat = *r_tuple_first;
+ else
+ *pat = r_tuple_first;
+
+ if (ttlp)
+ *ttlp = 0;
+
+ /* Explicitly reset all error variables */
+ *errnop = 0;
+ *h_errnop = NETDB_SUCCESS;
+ h_errno = 0;
+
+ return NSS_STATUS_SUCCESS;
+
+fallback:
+ {
+ _nss_gethostbyname4_r_t fallback;
+
+ fallback = (_nss_gethostbyname4_r_t)
+ find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname4_r");
+
+ if (fallback)
+ return fallback(name, pat, buffer, buflen, errnop, h_errnop, ttlp);
+ }
+
+fail:
+ *errnop = -r;
+ *h_errnop = NO_RECOVERY;
+ return ret;
+}
+
+enum nss_status _nss_resolve_gethostbyname3_r(
+ const char *name,
+ int af,
+ struct hostent *result,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp,
+ char **canonp) {
+
+ _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;
+ char *r_name, *r_aliases, *r_addr, *r_addr_list;
+ _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+ enum nss_status ret = NSS_STATUS_UNAVAIL;
+ size_t l, idx, ms, alen;
+ const char *canonical;
+ int c, r, i = 0;
+
+ BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
+
+ assert(name);
+ assert(result);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ if (af == AF_UNSPEC)
+ af = AF_INET;
+
+ if (af != AF_INET && af != AF_INET6) {
+ r = -EAFNOSUPPORT;
+ goto fail;
+ }
+
+ r = sd_bus_open_system(&bus);
+ if (r < 0)
+ goto fallback;
+
+ r = sd_bus_message_new_method_call(
+ bus,
+ &req,
+ "org.freedesktop.resolve1",
+ "/org/freedesktop/resolve1",
+ "org.freedesktop.resolve1.Manager",
+ "ResolveHostname");
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_set_auto_start(req, false);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_append(req, "isit", 0, name, af, (uint64_t) 0);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_call(bus, req, DNS_CALL_TIMEOUT_USEC, &error, &reply);
+ if (r < 0) {
+ if (sd_bus_error_has_name(&error, _BUS_ERROR_DNS "NXDOMAIN")) {
+ *errnop = ESRCH;
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+ }
+
+ if (bus_error_shall_fallback(&error))
+ goto fallback;
+
+ ret = NSS_STATUS_NOTFOUND;
+ goto fail;
+ }
+
+ c = count_addresses(reply, af, &canonical);
+ if (c < 0) {
+ r = c;
+ goto fail;
+ }
+ if (c == 0) {
+ *errnop = ESRCH;
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+ }
+
+ if (isempty(canonical))
+ canonical = name;
+
+ alen = FAMILY_ADDRESS_SIZE(af);
+ l = strlen(canonical);
+
+ ms = ALIGN(l+1) + c * ALIGN(alen) + (c+2) * sizeof(char*);
+
+ if (buflen < ms) {
+ *errnop = ENOMEM;
+ *h_errnop = TRY_AGAIN;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ /* First, append name */
+ r_name = buffer;
+ memcpy(r_name, canonical, l+1);
+ idx = ALIGN(l+1);
+
+ /* Second, create empty aliases array */
+ r_aliases = buffer + idx;
+ ((char**) r_aliases)[0] = NULL;
+ idx += sizeof(char*);
+
+ /* Third, append addresses */
+ r_addr = buffer + idx;
+
+ r = sd_bus_message_enter_container(reply, 'a', "(iiay)");
+ if (r < 0)
+ goto fail;
+
+ while ((r = sd_bus_message_enter_container(reply, 'r', "iiay")) > 0) {
+ int ifindex, family;
+ const void *a;
+ size_t sz;
+
+ r = sd_bus_message_read(reply, "ii", &ifindex, &family);
+ if (r < 0)
+ goto fail;
+
+ if (ifindex < 0) {
+ r = -EINVAL;
+ goto fail;
+ }
+
+ r = sd_bus_message_read_array(reply, 'y', &a, &sz);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_exit_container(reply);
+ if (r < 0)
+ goto fail;
+
+ if (family != af)
+ continue;
+
+ if (sz != alen) {
+ r = -EINVAL;
+ goto fail;
+ }
+
+ memcpy(r_addr + i*ALIGN(alen), a, alen);
+ i++;
+ }
+ if (r < 0)
+ goto fail;
+
+ assert(i == c);
+ idx += c * ALIGN(alen);
+
+ /* Fourth, append address pointer array */
+ r_addr_list = buffer + idx;
+ for (i = 0; i < c; i++)
+ ((char**) r_addr_list)[i] = r_addr + i*ALIGN(alen);
+
+ ((char**) r_addr_list)[i] = NULL;
+ idx += (c+1) * sizeof(char*);
+
+ assert(idx == ms);
+
+ result->h_name = r_name;
+ result->h_aliases = (char**) r_aliases;
+ result->h_addrtype = af;
+ result->h_length = alen;
+ result->h_addr_list = (char**) r_addr_list;
+
+ /* Explicitly reset all error variables */
+ *errnop = 0;
+ *h_errnop = NETDB_SUCCESS;
+ h_errno = 0;
+
+ if (ttlp)
+ *ttlp = 0;
+
+ if (canonp)
+ *canonp = r_name;
+
+ return NSS_STATUS_SUCCESS;
+
+fallback:
+ {
+ _nss_gethostbyname3_r_t fallback;
+
+ fallback = (_nss_gethostbyname3_r_t)
+ find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyname3_r");
+ if (fallback)
+ return fallback(name, af, result, buffer, buflen, errnop, h_errnop, ttlp, canonp);
+ }
+
+fail:
+ *errnop = -r;
+ *h_errnop = NO_RECOVERY;
+ return ret;
+}
+
+enum nss_status _nss_resolve_gethostbyaddr2_r(
+ const void* addr, socklen_t len,
+ int af,
+ struct hostent *result,
+ char *buffer, size_t buflen,
+ int *errnop, int *h_errnop,
+ int32_t *ttlp) {
+
+ _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;
+ char *r_name, *r_aliases, *r_addr, *r_addr_list;
+ _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+ enum nss_status ret = NSS_STATUS_UNAVAIL;
+ unsigned c = 0, i = 0;
+ size_t ms = 0, idx;
+ const char *n;
+ int r, ifindex;
+
+ BLOCK_SIGNALS(NSS_SIGNALS_BLOCK);
+
+ assert(addr);
+ assert(result);
+ assert(buffer);
+ assert(errnop);
+ assert(h_errnop);
+
+ if (!IN_SET(af, AF_INET, AF_INET6)) {
+ *errnop = EAFNOSUPPORT;
+ *h_errnop = NO_DATA;
+ return NSS_STATUS_UNAVAIL;
+ }
+
+ if (len != FAMILY_ADDRESS_SIZE(af)) {
+ *errnop = EINVAL;
+ *h_errnop = NO_RECOVERY;
+ return NSS_STATUS_UNAVAIL;
+ }
+
+ r = sd_bus_open_system(&bus);
+ if (r < 0)
+ goto fallback;
+
+ r = sd_bus_message_new_method_call(
+ bus,
+ &req,
+ "org.freedesktop.resolve1",
+ "/org/freedesktop/resolve1",
+ "org.freedesktop.resolve1.Manager",
+ "ResolveAddress");
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_set_auto_start(req, false);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_append(req, "ii", 0, af);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_append_array(req, 'y', addr, len);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_append(req, "t", (uint64_t) 0);
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_call(bus, req, DNS_CALL_TIMEOUT_USEC, &error, &reply);
+ if (r < 0) {
+ if (sd_bus_error_has_name(&error, _BUS_ERROR_DNS "NXDOMAIN")) {
+ *errnop = ESRCH;
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+ }
+
+ if (bus_error_shall_fallback(&error))
+ goto fallback;
+
+ ret = NSS_STATUS_NOTFOUND;
+ goto fail;
+ }
+
+ r = sd_bus_message_enter_container(reply, 'a', "(is)");
+ if (r < 0)
+ goto fail;
+
+ while ((r = sd_bus_message_read(reply, "(is)", &ifindex, &n)) > 0) {
+
+ if (ifindex < 0) {
+ r = -EINVAL;
+ goto fail;
+ }
+
+ c++;
+ ms += ALIGN(strlen(n) + 1);
+ }
+ if (r < 0)
+ goto fail;
+
+ r = sd_bus_message_rewind(reply, false);
+ if (r < 0)
+ return r;
+
+ if (c <= 0) {
+ *errnop = ESRCH;
+ *h_errnop = HOST_NOT_FOUND;
+ return NSS_STATUS_NOTFOUND;
+ }
+
+ ms += ALIGN(len) + /* the address */
+ 2 * sizeof(char*) + /* pointers to the address, plus trailing NULL */
+ c * sizeof(char*); /* pointers to aliases, plus trailing NULL */
+
+ if (buflen < ms) {
+ *errnop = ENOMEM;
+ *h_errnop = TRY_AGAIN;
+ return NSS_STATUS_TRYAGAIN;
+ }
+
+ /* First, place address */
+ r_addr = buffer;
+ memcpy(r_addr, addr, len);
+ idx = ALIGN(len);
+
+ /* Second, place address list */
+ r_addr_list = buffer + idx;
+ ((char**) r_addr_list)[0] = r_addr;
+ ((char**) r_addr_list)[1] = NULL;
+ idx += sizeof(char*) * 2;
+
+ /* Third, reserve space for the aliases array */
+ r_aliases = buffer + idx;
+ idx += sizeof(char*) * c;
+
+ /* Fourth, place aliases */
+ i = 0;
+ r_name = buffer + idx;
+ while ((r = sd_bus_message_read(reply, "(is)", &ifindex, &n)) > 0) {
+ char *p;
+ size_t l;
+
+ l = strlen(n);
+ p = buffer + idx;
+ memcpy(p, n, l+1);
+
+ if (i > 0)
+ ((char**) r_aliases)[i-1] = p;
+ i++;
+
+ idx += ALIGN(l+1);
+ }
+ if (r < 0)
+ goto fail;
+
+ ((char**) r_aliases)[c-1] = NULL;
+ assert(idx == ms);
+
+ result->h_name = r_name;
+ result->h_aliases = (char**) r_aliases;
+ result->h_addrtype = af;
+ result->h_length = len;
+ result->h_addr_list = (char**) r_addr_list;
+
+ if (ttlp)
+ *ttlp = 0;
+
+ /* Explicitly reset all error variables */
+ *errnop = 0;
+ *h_errnop = NETDB_SUCCESS;
+ h_errno = 0;
+
+ return NSS_STATUS_SUCCESS;
+
+fallback:
+ {
+ _nss_gethostbyaddr2_r_t fallback;
+
+ fallback = (_nss_gethostbyaddr2_r_t)
+ find_fallback("libnss_dns.so.2", "_nss_dns_gethostbyaddr2_r");
+
+ if (fallback)
+ return fallback(addr, len, af, result, buffer, buflen, errnop, h_errnop, ttlp);
+ }
+
+fail:
+ *errnop = -r;
+ *h_errnop = NO_RECOVERY;
+ return ret;
+}
+
+NSS_GETHOSTBYNAME_FALLBACKS(resolve);
+NSS_GETHOSTBYADDR_FALLBACKS(resolve);
diff --git a/src/grp-resolve/nss-resolve/nss-resolve.sym b/src/grp-resolve/nss-resolve/nss-resolve.sym
new file mode 100644
index 0000000000..df8dff2a20
--- /dev/null
+++ b/src/grp-resolve/nss-resolve/nss-resolve.sym
@@ -0,0 +1,19 @@
+/***
+ This file is part of systemd.
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+***/
+
+{
+global:
+ _nss_resolve_gethostbyname_r;
+ _nss_resolve_gethostbyname2_r;
+ _nss_resolve_gethostbyname3_r;
+ _nss_resolve_gethostbyname4_r;
+ _nss_resolve_gethostbyaddr_r;
+ _nss_resolve_gethostbyaddr2_r;
+local: *;
+};
diff --git a/src/grp-resolve/nss-resolve/nss-resolve.xml b/src/grp-resolve/nss-resolve/nss-resolve.xml
new file mode 100644
index 0000000000..9f24f65019
--- /dev/null
+++ b/src/grp-resolve/nss-resolve/nss-resolve.xml
@@ -0,0 +1,114 @@
+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+ This file is part of systemd.
+
+ Copyright 2011 Lennart Poettering
+ Copyright 2013 Tom Gundersen
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="nss-resolve" conditional='ENABLE_RESOLVED'>
+
+ <refentryinfo>
+ <title>nss-resolve</title>
+ <productname>systemd</productname>
+
+ <authorgroup>
+ <author>
+ <contrib>Developer</contrib>
+ <firstname>Lennart</firstname>
+ <surname>Poettering</surname>
+ <email>lennart@poettering.net</email>
+ </author>
+ </authorgroup>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>nss-resolve</refentrytitle>
+ <manvolnum>8</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>nss-resolve</refname>
+ <refname>libnss_resolve.so.2</refname>
+ <refpurpose>Provide hostname resolution via <filename>systemd-resolved.service</filename></refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <para><filename>libnss_resolve.so.2</filename></para>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><command>nss-resolve</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of the
+ GNU C Library (<command>glibc</command>) enabling it to resolve host names via the
+ <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry> local network
+ name resolution service. It replaces the <command>nss-dns</command> plug-in module that traditionally resolves
+ hostnames via DNS.</para>
+
+ <para>To activate the NSS module, add <literal>resolve</literal> to the line starting with
+ <literal>hosts:</literal> in <filename>/etc/nsswitch.conf</filename>.</para>
+
+ <para>It is recommended to place <literal>resolve</literal> early in <filename>/etc/nsswitch.conf</filename>'
+ <literal>hosts:</literal> line (but after the <literal>files</literal> or <literal>mymachines</literal> entries),
+ replacing the <literal>dns</literal> entry if it exists, to ensure DNS queries are always routed via
+ <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
+
+ <para>Note that <command>nss-resolve</command> will chain-load <command>nss-dns</command> if
+ <filename>systemd-resolved.service</filename> is not running, ensuring that basic DNS resolution continues to work
+ if the service is down.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Example</title>
+
+ <para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables <command>nss-resolve</command>
+ correctly:</para>
+
+<programlisting>passwd: compat mymachines systemd
+group: compat mymachines systemd
+shadow: compat
+
+hosts: files mymachines <command>resolve [!UNAVAIL=return]</command> dns myhostname
+networks: files
+
+protocols: db files
+services: db files
+ethers: db files
+rpc: db files
+
+netgroup: nis</programlisting>
+
+ <para>This keeps the <command>dns</command> module as a fallback for cases where the <command>nss-resolve</command>
+ module is not installed.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd-resolved</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
+ <citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ </para>
+ </refsect1>
+
+</refentry>