1 /*
2 * Multicast Traceroute for FRRouting
3 * Copyright (C) 2018 Mladen Sablic
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License along
16 * with this program; see the file COPYING; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18 */
19
20 #ifdef HAVE_CONFIG_H
21 #include "config.h"
22 #endif
23
24 #ifdef __linux__
25
26 #include <asm/types.h>
27 #include <linux/netlink.h>
28 #include <linux/rtnetlink.h>
29 #include <sys/types.h>
30 #include <stdio.h>
31 #include <arpa/inet.h>
32 #include <string.h>
33
34 #include "mtracebis_netlink.h"
35 #include "mtracebis_routeget.h"
36
find_dst(struct nlmsghdr * n,struct in_addr * src,struct in_addr * gw)37 static int find_dst(struct nlmsghdr *n, struct in_addr *src, struct in_addr *gw)
38 {
39 struct rtmsg *r = NLMSG_DATA(n);
40 int len = n->nlmsg_len;
41 struct rtattr *tb[RTA_MAX + 1];
42
43 len -= NLMSG_LENGTH(sizeof(*r));
44 if (len < 0) {
45 fprintf(stderr, "BUG: wrong nlmsg len %d\n", len);
46 return -1;
47 }
48
49 parse_rtattr(tb, RTA_MAX, RTM_RTA(r), len);
50 if (tb[RTA_PREFSRC])
51 src->s_addr = *(uint32_t *)RTA_DATA(tb[RTA_PREFSRC]);
52 if (tb[RTA_GATEWAY])
53 gw->s_addr = *(uint32_t *)RTA_DATA(tb[RTA_GATEWAY]);
54 if (tb[RTA_OIF])
55 return *(int *)RTA_DATA(tb[RTA_OIF]);
56 return 0;
57 }
58
routeget(struct in_addr dst,struct in_addr * src,struct in_addr * gw)59 int routeget(struct in_addr dst, struct in_addr *src, struct in_addr *gw)
60 {
61 struct {
62 struct nlmsghdr n;
63 struct rtmsg r;
64 char buf[1024];
65 } req;
66 int ret;
67 struct rtnl_handle rth = {.fd = -1};
68
69 memset(&req, 0, sizeof(req));
70
71 req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
72 req.n.nlmsg_flags = NLM_F_REQUEST;
73 req.n.nlmsg_type = RTM_GETROUTE;
74 req.r.rtm_family = AF_INET;
75 req.r.rtm_table = 0;
76 req.r.rtm_protocol = 0;
77 req.r.rtm_scope = 0;
78 req.r.rtm_type = 0;
79 req.r.rtm_src_len = 0;
80 req.r.rtm_dst_len = 0;
81 req.r.rtm_tos = 0;
82
83 addattr_l(&req.n, sizeof(req), RTA_DST, &dst.s_addr, 4);
84 req.r.rtm_dst_len = 32;
85
86 ret = rtnl_open(&rth, 0);
87
88 if (ret < 0 || rth.fd <= 0)
89 return ret;
90
91 if (rtnl_talk(&rth, &req.n, 0, 0, &req.n, NULL, NULL) < 0) {
92 ret = -1;
93 goto close_rth;
94 }
95
96 ret = find_dst(&req.n, src, gw);
97 close_rth:
98 rtnl_close(&rth);
99 return ret;
100 }
101
102 #endif /* __linux__ */
103