1 files changed, 123 insertions, 0 deletions
diff --git a/src/osmo-bts-oc2g/misc/oc2gbts_nl.c b/src/osmo-bts-oc2g/misc/oc2gbts_nl.c
new file mode 100644
index 00000000..39f64aae
--- /dev/null
+++ b/src/osmo-bts-oc2g/misc/oc2gbts_nl.c
@@ -0,0 +1,123 @@
+/* Helper for netlink */
+
+/* Copyright (C) 2015 by Yves Godin <support@nuranwireless.com>
+ * 
+ * Based on sysmoBTS:
+ *     sysmobts_nl.c
+ *     (C) 2014 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 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 <arpa/inet.h>
+#include <netinet/ip.h>
+
+#include <sys/socket.h>
+
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#define NLMSG_TAIL(nmsg) \
+        ((struct rtattr *) (((void *) (nmsg)) + NLMSG_ALIGN((nmsg)->nlmsg_len)))
+
+/**
+ * In case one binds to 0.0.0.0/INADDR_ANY and wants to know which source
+ * address will be used when sending a message this function can be used.
+ * It will ask the routing code of the kernel for the PREFSRC
+ */
+int source_for_dest(const struct in_addr *dest, struct in_addr *loc_source)
+{
+	int fd, rc;
+	struct rtmsg *r;
+	struct rtattr *rta;
+        struct {
+		struct nlmsghdr         n;
+		struct rtmsg            r;
+		char                    buf[1024];
+        } req;
+
+	memset(&req, 0, sizeof(req));
+
+	fd = socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_ROUTE);
+	if (fd < 0) {
+		perror("nl socket");
+		return -1;
+	}
+
+	/* Send a rtmsg and ask for a response */
+        req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
+        req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+        req.n.nlmsg_type = RTM_GETROUTE;
+        req.n.nlmsg_seq = 1;
+
+	/* Prepare the routing request */
+        req.r.rtm_family = AF_INET;
+
+	/* set the dest */
+	rta = NLMSG_TAIL(&req.n);
+	rta->rta_type = RTA_DST;
+	rta->rta_len = RTA_LENGTH(sizeof(*dest));
+	memcpy(RTA_DATA(rta), dest, sizeof(*dest));
+
+	/* update sizes for dest */
+	req.r.rtm_dst_len = sizeof(*dest) * 8;
+	req.n.nlmsg_len = NLMSG_ALIGN(req.n.nlmsg_len) + RTA_ALIGN(rta->rta_len);
+
+	rc = send(fd, &req, req.n.nlmsg_len, 0);
+	if (rc != req.n.nlmsg_len) {
+		perror("short write");
+		close(fd);
+		return -2;
+	}
+
+
+	/* now receive a response and parse it */
+	rc = recv(fd, &req, sizeof(req), 0);
+	if (rc <= 0) {
+		perror("short read");
+		close(fd);
+		return -3;
+	}
+
+	if (!NLMSG_OK(&req.n, rc) || req.n.nlmsg_type != RTM_NEWROUTE) {
+		close(fd);
+		return -4;
+	}
+
+	r = NLMSG_DATA(&req.n);
+	rc -= NLMSG_LENGTH(sizeof(*r));
+	rta = RTM_RTA(r);
+	while (RTA_OK(rta, rc)) {
+		if (rta->rta_type != RTA_PREFSRC) {
+			rta = RTA_NEXT(rta, rc);
+			continue;
+		}
+
+		/* we are done */
+		memcpy(loc_source, RTA_DATA(rta), RTA_PAYLOAD(rta));
+		close(fd);
+		return 0;
+	}
+
+	close(fd);
+	return -5;
+}