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// 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__ */
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