1 files changed, 89 insertions, 0 deletions
diff --git a/pimd/mtracebis_routeget.c b/pimd/mtracebis_routeget.c
new file mode 100644
index 0000000..20618fa
--- /dev/null
+++ b/pimd/mtracebis_routeget.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Multicast Traceroute for FRRouting
+ * Copyright (C) 2018  Mladen Sablic
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef __linux__
+
+#include <asm/types.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <sys/types.h>
+#include <stdio.h>
+#include <arpa/inet.h>
+#include <string.h>
+
+#include "mtracebis_netlink.h"
+#include "mtracebis_routeget.h"
+
+static int find_dst(struct nlmsghdr *n, struct in_addr *src, struct in_addr *gw)
+{
+	struct rtmsg *r = NLMSG_DATA(n);
+	int len = n->nlmsg_len;
+	struct rtattr *tb[RTA_MAX + 1];
+
+	len -= NLMSG_LENGTH(sizeof(*r));
+	if (len < 0) {
+		fprintf(stderr, "BUG: wrong nlmsg len %d\n", len);
+		return -1;
+	}
+
+	parse_rtattr(tb, RTA_MAX, RTM_RTA(r), len);
+	if (tb[RTA_PREFSRC])
+		src->s_addr = *(uint32_t *)RTA_DATA(tb[RTA_PREFSRC]);
+	if (tb[RTA_GATEWAY])
+		gw->s_addr = *(uint32_t *)RTA_DATA(tb[RTA_GATEWAY]);
+	if (tb[RTA_OIF])
+		return *(int *)RTA_DATA(tb[RTA_OIF]);
+	return 0;
+}
+
+int routeget(struct in_addr dst, struct in_addr *src, struct in_addr *gw)
+{
+	struct {
+		struct nlmsghdr n;
+		struct rtmsg r;
+		char buf[1024];
+	} req;
+	int ret;
+	struct rtnl_handle rth = {.fd = -1};
+
+	memset(&req, 0, sizeof(req));
+
+	req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
+	req.n.nlmsg_flags = NLM_F_REQUEST;
+	req.n.nlmsg_type = RTM_GETROUTE;
+	req.r.rtm_family = AF_INET;
+	req.r.rtm_table = 0;
+	req.r.rtm_protocol = 0;
+	req.r.rtm_scope = 0;
+	req.r.rtm_type = 0;
+	req.r.rtm_src_len = 0;
+	req.r.rtm_dst_len = 0;
+	req.r.rtm_tos = 0;
+
+	addattr_l(&req.n, sizeof(req), RTA_DST, &dst.s_addr, 4);
+	req.r.rtm_dst_len = 32;
+
+	ret = rtnl_open(&rth, 0);
+
+	if (ret < 0 || rth.fd <= 0)
+		return ret;
+
+	if (rtnl_talk(&rth, &req.n, 0, 0, &req.n, NULL, NULL) < 0) {
+		ret = -1;
+		goto close_rth;
+	}
+
+	ret = find_dst(&req.n, src, gw);
+close_rth:
+	rtnl_close(&rth);
+	return ret;
+}
+
+#endif /* __linux__ */