sgsn: Integrate c-ares with the osmocom event loop
c-ares is an asynchronous DNS resolver and we need it to
resolve the GGSN address. This is integrating the library
into our infrastructure. We will create and maintain a list
of registered FDs (c-ares is currently only using one of
them) and (re-)schedule the timer after events occurred.
diff --git a/openbsc/src/gprs/sgsn_ares.c b/openbsc/src/gprs/sgsn_ares.c
new file mode 100644
index 0000000..825b01c
--- /dev/null
+++ b/openbsc/src/gprs/sgsn_ares.c
@@ -0,0 +1,168 @@
+/* C-ARES DNS resolver integration */
+
+/*
+ * (C) 2015 by Holger Hans Peter Freyther
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <openbsc/sgsn.h>
+#include <openbsc/debug.h>
+
+#include <netdb.h>
+
+struct cares_event_fd {
+ struct llist_head head;
+ struct osmo_fd fd;
+};
+
+struct cares_cb_data {
+ ares_host_callback cb;
+ void *data;
+};
+
+static void osmo_ares_reschedule(struct sgsn_instance *sgsn);
+static void ares_cb(void *_arg, int status, int timeouts, struct hostent *hostent)
+{
+ struct cares_cb_data *arg = _arg;
+
+ arg->cb(arg->data, status, timeouts, hostent);
+ osmo_ares_reschedule(sgsn);
+ talloc_free(arg);
+}
+
+static int ares_osmo_fd_cb(struct osmo_fd *fd, unsigned int what)
+{
+ LOGP(DGPRS, LOGL_DEBUG, "C-ares fd(%d) ready(%d)\n", fd->fd, what);
+
+ ares_process_fd(sgsn->ares_channel,
+ (what & BSC_FD_READ) ? fd->fd : ARES_SOCKET_BAD,
+ (what & BSC_FD_WRITE) ? fd->fd : ARES_SOCKET_BAD);
+ osmo_ares_reschedule(sgsn);
+ return 0;
+}
+
+static void ares_timeout_cb(void *data)
+{
+ struct sgsn_instance *sgsn = data;
+
+ LOGP(DGPRS, LOGL_DEBUG, "C-ares triggering timeout\n");
+ ares_process_fd(sgsn->ares_channel, ARES_SOCKET_BAD, ARES_SOCKET_BAD);
+ osmo_ares_reschedule(sgsn);
+}
+
+static void osmo_ares_reschedule(struct sgsn_instance *sgsn)
+{
+ struct timeval *timeout, tv;
+
+ osmo_timer_del(&sgsn->ares_timer);
+ timeout = ares_timeout(sgsn->ares_channel, NULL, &tv);
+ if (timeout) {
+ sgsn->ares_timer.cb = ares_timeout_cb;
+ sgsn->ares_timer.data = sgsn;
+
+ LOGP(DGPRS, LOGL_DEBUG, "C-ares scheduling timeout %llu.%llu\n",
+ (unsigned long long) tv.tv_sec,
+ (unsigned long long) tv.tv_usec);
+ osmo_timer_schedule(&sgsn->ares_timer, tv.tv_sec, tv.tv_usec);
+ }
+}
+
+static void setup_ares_osmo_fd(void *data, int fd, int read, int write)
+{
+ struct cares_event_fd *ufd, *tmp;
+
+ /* delete the entry */
+ if (read == 0 && write == 0) {
+ llist_for_each_entry_safe(ufd, tmp, &sgsn->ares_fds, head) {
+ if (ufd->fd.fd != fd)
+ continue;
+
+ LOGP(DGPRS, LOGL_DEBUG,
+ "Removing C-ares watched fd (%d)\n", fd);
+ osmo_fd_unregister(&ufd->fd);
+ llist_del(&ufd->head);
+ talloc_free(ufd);
+ return;
+ }
+ }
+
+ /* Search for the fd or create a new one */
+ llist_for_each_entry(ufd, &sgsn->ares_fds, head) {
+ if (ufd->fd.fd != fd)
+ continue;
+
+ LOGP(DGPRS, LOGL_DEBUG, "Updating C-ares fd (%d)\n", fd);
+ goto update_fd;
+ }
+
+ LOGP(DGPRS, LOGL_DEBUG, "Registering C-ares fd (%d)\n", fd);
+ ufd = talloc_zero(tall_bsc_ctx, struct cares_event_fd);
+ ufd->fd.fd = fd;
+ ufd->fd.cb = ares_osmo_fd_cb;
+ ufd->fd.data = data;
+ osmo_fd_register(&ufd->fd);
+ llist_add(&ufd->head, &sgsn->ares_fds);
+
+update_fd:
+ if (read)
+ ufd->fd.when |= BSC_FD_READ;
+ else
+ ufd->fd.when &= ~BSC_FD_READ;
+
+ if (write)
+ ufd->fd.when |= BSC_FD_WRITE;
+ else
+ ufd->fd.when &= ~BSC_FD_WRITE;
+
+ osmo_ares_reschedule(sgsn);
+}
+
+int sgsn_ares_query(struct sgsn_instance *sgsn, const char *name,
+ ares_host_callback cb, void *data)
+{
+ struct cares_cb_data *cb_data;
+
+ cb_data = talloc_zero(tall_bsc_ctx, struct cares_cb_data);
+ cb_data->cb = cb;
+ cb_data->data = data;
+ ares_gethostbyname(sgsn->ares_channel, name, AF_INET, ares_cb, cb_data);
+ osmo_ares_reschedule(sgsn);
+ return 0;
+}
+
+int sgsn_ares_init(struct sgsn_instance *sgsn)
+{
+ struct ares_options options;
+ int optmask;
+ int rc;
+
+ INIT_LLIST_HEAD(&sgsn->ares_fds);
+ memset(&options, 0, sizeof(options));
+ options.sock_state_cb = setup_ares_osmo_fd;
+ options.sock_state_cb_data = sgsn;
+
+ optmask = ARES_OPT_FLAGS | ARES_OPT_SOCK_STATE_CB;
+
+ /*| ARES_OPT_SERVERS ... TODO..*/
+
+ ares_library_init(ARES_LIB_INIT_ALL);
+ rc = ares_init_options(&sgsn->ares_channel, &options, optmask);
+
+ return rc;
+}
+
+osmo_static_assert(ARES_SUCCESS == 0, ares_success_zero);