DNS sites support - SRV DNS lookup plugin

https://fedorahosted.org/sssd/ticket/1032

This plugin mimics the current behaviour.

If discovery_domain is set it is the only domain that is tried.
If discovery_domain is not set, we try to autodetect domain first
and if that fails or SRV lookup on this domain fails, we fallback
to SSSD domain name.

5 files changed, 522 insertions, 0 deletions

diff --git a/Makefile.am b/Makefile.am
index 4e331098..7a352333 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -325,6 +325,7 @@ endif
 
 SSSD_FAILOVER_OBJ = \
     src/providers/fail_over.c \
+    src/providers/fail_over_srv.c \
     $(SSSD_RESOLV_OBJ)
 
 SSSD_LIBS = \
diff --git a/src/providers/data_provider_fo.c b/src/providers/data_provider_fo.c
index 232717e7..83294b59 100644
--- a/src/providers/data_provider_fo.c
+++ b/src/providers/data_provider_fo.c
@@ -254,6 +254,40 @@ void be_fo_set_srv_lookup_plugin(struct be_ctx *ctx,
     }
 }
 
+errno_t be_fo_set_dns_srv_lookup_plugin(struct be_ctx *be_ctx,
+                                        const char *hostname)
+{
+    struct fo_resolve_srv_dns_ctx *srv_ctx = NULL;
+    char resolved_hostname[HOST_NAME_MAX];
+    errno_t ret;
+
+    if (hostname == NULL) {
+        ret = gethostname(resolved_hostname, HOST_NAME_MAX);
+        if (ret != EOK) {
+            ret = errno;
+            DEBUG(SSSDBG_CRIT_FAILURE,
+                  ("gethostname() failed: [%d]: %s\n", ret, strerror(ret)));
+            return ret;
+        }
+        resolved_hostname[HOST_NAME_MAX-1] = '\0';
+        hostname = resolved_hostname;
+    }
+
+    srv_ctx = fo_resolve_srv_dns_ctx_init(be_ctx, be_ctx->be_res->resolv,
+                                          be_ctx->be_res->family_order,
+                                          default_host_dbs, hostname,
+                                          be_ctx->domain->name);
+    if (srv_ctx == NULL) {
+        DEBUG(SSSDBG_FATAL_FAILURE, ("Out of memory?\n"));
+        return ENOMEM;
+    }
+
+    be_fo_set_srv_lookup_plugin(be_ctx, fo_resolve_srv_dns_send,
+                                fo_resolve_srv_dns_recv, srv_ctx, "DNS");
+
+    return EOK;
+}
+
 int be_fo_add_srv_server(struct be_ctx *ctx,
                          const char *service_name,
                          const char *query_service,
diff --git a/src/providers/dp_backend.h b/src/providers/dp_backend.h
index 1b8a59e6..e0e2210c 100644
--- a/src/providers/dp_backend.h
+++ b/src/providers/dp_backend.h
@@ -218,6 +218,9 @@ void be_fo_set_srv_lookup_plugin(struct be_ctx *ctx,
                                  void *pvt,
                                  const char *plugin_name);
 
+errno_t be_fo_set_dns_srv_lookup_plugin(struct be_ctx *be_ctx,
+                                        const char *hostname);
+
 int be_fo_add_srv_server(struct be_ctx *ctx,
                          const char *service_name,
                          const char *query_service,
diff --git a/src/providers/fail_over_srv.c b/src/providers/fail_over_srv.c
new file mode 100644
index 00000000..aa0bccb2
--- /dev/null
+++ b/src/providers/fail_over_srv.c
@@ -0,0 +1,444 @@
+/*
+    Authors:
+        Pavel B??ezina <pbrezina@redhat.com>
+
+    Copyright (C) 2013 Red Hat
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    This program 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 General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <string.h>
+#include <talloc.h>
+#include <tevent.h>
+
+#include "util/util.h"
+#include "resolv/async_resolv.h"
+#include "providers/fail_over_srv.h"
+
+struct fo_discover_srv_state {
+    char *dns_domain;
+    struct fo_server_info *servers;
+    size_t num_servers;
+};
+
+static void fo_discover_srv_done(struct tevent_req *subreq);
+
+struct tevent_req *fo_discover_srv_send(TALLOC_CTX *mem_ctx,
+                                        struct tevent_context *ev,
+                                        struct resolv_ctx *resolv_ctx,
+                                        const char *service,
+                                        const char *protocol,
+                                        const char **discovery_domains)
+{
+    struct fo_discover_srv_state *state = NULL;
+    struct tevent_req *req = NULL;
+    struct tevent_req *subreq = NULL;
+    errno_t ret;
+
+    req = tevent_req_create(mem_ctx, &state, struct fo_discover_srv_state);
+    if (req == NULL) {
+        DEBUG(SSSDBG_CRIT_FAILURE, ("tevent_req_create() failed\n"));
+        return NULL;
+    }
+
+    subreq = resolv_discover_srv_send(state, ev, resolv_ctx, service,
+                                      protocol, discovery_domains);
+    if (subreq == NULL) {
+        ret = ENOMEM;
+        goto immediately;
+    }
+
+    tevent_req_set_callback(subreq, fo_discover_srv_done, req);
+
+    return req;
+
+immediately:
+    tevent_req_error(req, ret);
+    tevent_req_post(req, ev);
+
+    return req;
+}
+
+static void fo_discover_srv_done(struct tevent_req *subreq)
+{
+    struct fo_discover_srv_state *state = NULL;
+    struct tevent_req *req = NULL;
+    struct ares_srv_reply *reply_list = NULL;
+    struct ares_srv_reply *record = NULL;
+    int i;
+    errno_t ret;
+
+    req = tevent_req_callback_data(subreq, struct tevent_req);
+    state = tevent_req_data(req, struct fo_discover_srv_state);
+
+    ret = resolv_discover_srv_recv(state, subreq,
+                                   &reply_list, &state->dns_domain);
+    talloc_zfree(subreq);
+    if (ret == ENOENT) {
+        ret = ERR_SRV_NOT_FOUND;
+        goto done;
+    } else if (ret == EIO) {
+        ret = ERR_SRV_LOOKUP_ERROR;
+        goto done;
+    } else if (ret != EOK) {
+        goto done;
+    }
+
+    DEBUG(SSSDBG_TRACE_FUNC, ("Got answer. Processing...\n"));
+
+    /* sort and store the answer */
+    ret = resolv_sort_srv_reply(state, &reply_list);
+    if (ret != EOK) {
+        DEBUG(SSSDBG_CRIT_FAILURE, ("Could not sort the answers from DNS "
+                                    "[%d]: %s\n", ret, strerror(ret)));
+        goto done;
+    }
+
+    state->num_servers = 0;
+    for (record = reply_list; record != NULL; record = record->next) {
+        state->num_servers++;
+    }
+
+    DEBUG(SSSDBG_TRACE_FUNC, ("Got %lu servers\n", state->num_servers));
+
+    state->servers = talloc_array(state, struct fo_server_info,
+                                  state->num_servers);
+    if (state->servers == NULL) {
+        ret = ENOMEM;
+        goto done;
+    }
+
+    for (record = reply_list, i = 0;
+         record != NULL;
+         record = record->next, i++) {
+        state->servers[i].host = talloc_steal(state->servers, record->host);
+        state->servers[i].port = record->port;
+    }
+
+    talloc_zfree(reply_list);
+
+    ret = EOK;
+
+done:
+    if (ret != EOK) {
+        tevent_req_error(req, ret);
+        return;
+    }
+
+    tevent_req_done(req);
+}
+
+errno_t fo_discover_srv_recv(TALLOC_CTX *mem_ctx,
+                             struct tevent_req *req,
+                             char **_dns_domain,
+                             struct fo_server_info **_servers,
+                             size_t *_num_servers)
+{
+    struct fo_discover_srv_state *state = NULL;
+    state = tevent_req_data(req, struct fo_discover_srv_state);
+
+    TEVENT_REQ_RETURN_ON_ERROR(req);
+
+    if (_dns_domain != NULL) {
+        *_dns_domain = talloc_steal(mem_ctx, state->dns_domain);
+    }
+
+    if (_servers != NULL) {
+        *_servers = talloc_steal(mem_ctx, state->servers);
+    }
+
+    if (_num_servers != NULL) {
+        *_num_servers = state->num_servers;
+    }
+
+    return EOK;
+}
+
+struct fo_resolve_srv_dns_ctx {
+    struct resolv_ctx *resolv_ctx;
+    enum restrict_family family_order;
+    enum host_database *host_dbs;
+    char *hostname;
+    char *sssd_domain;
+    char *detected_domain;
+};
+
+struct fo_resolve_srv_dns_state {
+    struct tevent_context *ev;
+    struct fo_resolve_srv_dns_ctx *ctx;
+    const char *service;
+    const char *protocol;
+    const char *discovery_domain;
+
+    char *dns_domain;
+    struct fo_server_info *servers;
+    size_t num_servers;
+};
+
+static void fo_resolve_srv_dns_domain_done(struct tevent_req *subreq);
+static errno_t fo_resolve_srv_dns_discover(struct tevent_req *req);
+static void fo_resolve_srv_dns_done(struct tevent_req *subreq);
+
+struct fo_resolve_srv_dns_ctx *
+fo_resolve_srv_dns_ctx_init(TALLOC_CTX *mem_ctx,
+                            struct resolv_ctx *resolv_ctx,
+                            enum restrict_family family_order,
+                            enum host_database *host_dbs,
+                            const char *hostname,
+                            const char *sssd_domain)
+{
+    struct fo_resolve_srv_dns_ctx *ctx = NULL;
+
+    ctx = talloc_zero(mem_ctx, struct fo_resolve_srv_dns_ctx);
+    if (ctx == NULL) {
+        return NULL;
+    }
+
+    ctx->resolv_ctx = resolv_ctx;
+    ctx->family_order = family_order;
+    ctx->host_dbs = host_dbs;
+
+    ctx->hostname = talloc_strdup(ctx, hostname);
+    if (ctx->hostname == NULL) {
+        goto fail;
+    }
+
+    ctx->sssd_domain = talloc_strdup(ctx, sssd_domain);
+    if (ctx->sssd_domain == NULL) {
+        goto fail;
+    }
+
+    return ctx;
+
+fail:
+    talloc_free(ctx);
+    return NULL;
+}
+
+struct tevent_req *fo_resolve_srv_dns_send(TALLOC_CTX *mem_ctx,
+                                           struct tevent_context *ev,
+                                           const char *service,
+                                           const char *protocol,
+                                           const char *discovery_domain,
+                                           void *pvt)
+{
+    struct fo_resolve_srv_dns_state *state = NULL;
+    struct fo_resolve_srv_dns_ctx *ctx = NULL;
+    struct tevent_req *req = NULL;
+    struct tevent_req *subreq = NULL;
+    errno_t ret;
+
+    req = tevent_req_create(mem_ctx, &state, struct fo_resolve_srv_dns_state);
+    if (req == NULL) {
+        DEBUG(SSSDBG_CRIT_FAILURE, ("tevent_req_create() failed\n"));
+        return NULL;
+    }
+
+    ctx = talloc_get_type(pvt, struct fo_resolve_srv_dns_ctx);
+    if (ctx == NULL) {
+        ret = EINVAL;
+        goto immediately;
+    }
+
+    state->ev = ev;
+    state->ctx = ctx;
+    state->service = service;
+    state->protocol = protocol;
+
+    if (discovery_domain == NULL) {
+        state->discovery_domain = NULL;
+    } else {
+        state->discovery_domain = discovery_domain;
+    }
+
+    if (discovery_domain == NULL && ctx->detected_domain == NULL) {
+        /* we will try to detect proper discovery domain */
+        subreq = resolv_get_domain_send(state, state->ev, ctx->resolv_ctx,
+                                        ctx->hostname, ctx->host_dbs,
+                                        ctx->family_order);
+        if (subreq == NULL) {
+            ret = ENOMEM;
+            goto immediately;
+        }
+
+        tevent_req_set_callback(subreq, fo_resolve_srv_dns_domain_done, req);
+    } else {
+        /* we will use either provided or previously detected
+         * discovery domain */
+        ret = fo_resolve_srv_dns_discover(req);
+        if (ret != EAGAIN) {
+            goto immediately;
+        }
+    }
+
+    return req;
+
+immediately:
+    if (ret == EOK) {
+        tevent_req_done(req);
+    } else {
+        tevent_req_error(req, ret);
+    }
+    tevent_req_post(req, ev);
+
+    return req;
+}
+
+static void fo_resolve_srv_dns_domain_done(struct tevent_req *subreq)
+{
+    struct fo_resolve_srv_dns_state *state = NULL;
+    struct tevent_req *req = NULL;
+    errno_t ret;
+
+    req = tevent_req_callback_data(subreq, struct tevent_req);
+    state = tevent_req_data(req, struct fo_resolve_srv_dns_state);
+
+    ret = resolv_get_domain_recv(state->ctx, subreq,
+                                 &state->ctx->detected_domain);
+    talloc_zfree(subreq);
+    if (ret != EOK) {
+        goto done;
+    }
+
+    ret = fo_resolve_srv_dns_discover(req);
+
+done:
+    if (ret == EOK) {
+        tevent_req_done(req);
+    } else if (ret != EAGAIN) {
+        tevent_req_error(req, ret);
+    }
+
+    return;
+}
+
+static errno_t fo_resolve_srv_dns_discover(struct tevent_req *req)
+{
+    struct fo_resolve_srv_dns_state *state = NULL;
+    struct fo_resolve_srv_dns_ctx *ctx = NULL;
+    struct tevent_req *subreq = NULL;
+    const char **domains = NULL;
+    errno_t ret;
+
+    state = tevent_req_data(req, struct fo_resolve_srv_dns_state);
+    ctx = state->ctx;
+
+    domains = talloc_zero_array(state, const char *, 3);
+    if (domains == NULL) {
+        ret = ENOMEM;
+        goto done;
+    }
+
+    if (state->discovery_domain == NULL) {
+        /* we will use detected domain with SSSD domain as fallback */
+        domains[0] = talloc_strdup(domains, ctx->detected_domain);
+        if (domains[0] == NULL) {
+            ret = ENOMEM;
+            goto done;
+        }
+
+        if (strcmp(ctx->detected_domain, ctx->sssd_domain) != 0) {
+            domains[1] = talloc_strdup(domains, ctx->sssd_domain);
+            if (domains[1] == NULL) {
+                ret = ENOMEM;
+                goto done;
+            }
+        }
+    } else {
+        /* We will use only discovery domain that was provided via plugin
+         * interface. We don't have to dup here because it is already on
+         * state. */
+        domains[0] = state->discovery_domain;
+    }
+
+    subreq = fo_discover_srv_send(state, state->ev, ctx->resolv_ctx,
+                                  state->service, state->protocol, domains);
+    if (subreq == NULL) {
+        ret = ENOMEM;
+        goto done;
+    }
+
+    tevent_req_set_callback(subreq, fo_resolve_srv_dns_done, req);
+
+    ret = EAGAIN;
+
+done:
+    if (ret != EAGAIN) {
+        talloc_free(domains);
+    }
+
+    return ret;
+}
+
+static void fo_resolve_srv_dns_done(struct tevent_req *subreq)
+{
+    struct fo_resolve_srv_dns_state *state = NULL;
+    struct tevent_req *req = NULL;
+    errno_t ret;
+
+    req = tevent_req_callback_data(subreq, struct tevent_req);
+    state = tevent_req_data(req, struct fo_resolve_srv_dns_state);
+
+    ret = fo_discover_srv_recv(state, subreq, &state->dns_domain,
+                               &state->servers, &state->num_servers);
+    talloc_zfree(subreq);
+    if (ret != EOK) {
+        goto done;
+    }
+
+done:
+    if (ret != EOK) {
+        tevent_req_error(req, ret);
+        return;
+    }
+
+    tevent_req_done(req);
+}
+
+errno_t fo_resolve_srv_dns_recv(TALLOC_CTX *mem_ctx,
+                                struct tevent_req *req,
+                                char **_dns_domain,
+                                struct fo_server_info **_primary_servers,
+                                size_t *_num_primary_servers,
+                                struct fo_server_info **_backup_servers,
+                                size_t *_num_backup_servers)
+{
+    struct fo_resolve_srv_dns_state *state = NULL;
+    state = tevent_req_data(req, struct fo_resolve_srv_dns_state);
+
+    TEVENT_REQ_RETURN_ON_ERROR(req);
+
+    if (_primary_servers) {
+        *_primary_servers = talloc_steal(mem_ctx, state->servers);
+    }
+
+    if (_num_primary_servers) {
+        *_num_primary_servers = state->num_servers;
+    }
+
+    /* backup servers are not supported by simple srv lookup */
+    if (_backup_servers) {
+        *_backup_servers = NULL;
+    }
+
+    if (_num_backup_servers) {
+        *_num_backup_servers = 0;
+    }
+
+    if (_dns_domain) {
+        *_dns_domain = talloc_steal(mem_ctx, state->dns_domain);
+    }
+
+    return EOK;
+}
diff --git a/src/providers/fail_over_srv.h b/src/providers/fail_over_srv.h
index 0796ad5a..4550b09d 100644
--- a/src/providers/fail_over_srv.h
+++ b/src/providers/fail_over_srv.h
@@ -69,4 +69,44 @@ typedef errno_t
                                struct fo_server_info **_backup_servers,
                                size_t *_num_backup_servers);
 
+struct tevent_req *fo_discover_srv_send(TALLOC_CTX *mem_ctx,
+                                        struct tevent_context *ev,
+                                        struct resolv_ctx *resolv_ctx,
+                                        const char *service,
+                                        const char *protocol,
+                                        const char **discovery_domains);
+
+errno_t fo_discover_srv_recv(TALLOC_CTX *mem_ctx,
+                             struct tevent_req *req,
+                             char **_dns_domain,
+                             struct fo_server_info **_servers,
+                             size_t *_num_servers);
+
+/* Simple SRV lookup plugin */
+
+struct fo_resolve_srv_dns_ctx;
+
+struct fo_resolve_srv_dns_ctx *
+fo_resolve_srv_dns_ctx_init(TALLOC_CTX *mem_ctx,
+                            struct resolv_ctx *resolv_ctx,
+                            enum restrict_family family_order,
+                            enum host_database *host_dbs,
+                            const char *hostname,
+                            const char *sssd_domain);
+
+struct tevent_req *fo_resolve_srv_dns_send(TALLOC_CTX *mem_ctx,
+                                           struct tevent_context *ev,
+                                           const char *service,
+                                           const char *protocol,
+                                           const char *discovery_domain,
+                                           void *pvt);
+
+errno_t fo_resolve_srv_dns_recv(TALLOC_CTX *mem_ctx,
+                                struct tevent_req *req,
+                                char **_dns_domain,
+                                struct fo_server_info **_primary_servers,
+                                size_t *_num_primary_servers,
+                                struct fo_server_info **_backup_servers,
+                                size_t *_num_backup_servers);
+
 #endif /* __FAIL_OVER_SRV_H__ */