/*
* Copyright (c) 2016 Chris Johns <chrisj@rtems.org>. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Useful functions to access the routing tables. Based on unpv13e from
* Stevens.
*/
#include <stdbool.h>
#include <errno.h>
#include <net/if.h>
#include <net/route.h>
#include <netinet/in.h>
#include <sys/socket.h>
/*
* Round up 'a' to next multiple of 'size', which must be a power of 2
*/
#define RR_ROUNDUP(a, size) (((a) & ((size)-1)) ? (1 + ((a) | ((size)-1))) : (a))
/*
* Step to next socket address structure;
* if sa_len is 0, assume it is sizeof(u_long).
*/
#define NEXT_SA(ap) \
ap = (struct sockaddr*) ((caddr_t) ap + \
(ap->sa_len ? RR_ROUNDUP(ap->sa_len, sizeof (u_long)) : sizeof(u_long)))
static void
get_rtaddrs(int addrs, struct sockaddr* sa, struct sockaddr** rti_info)
{
int i;
for (i = 0; i < RTAX_MAX; i++) {
if ((addrs & (1 << i)) != 0) {
rti_info[i] = sa;
NEXT_SA(sa);
} else
rti_info[i] = NULL;
}
}
/*
* Get a route.
*/
int rtems_get_route(const struct sockaddr_in* sin, struct sockaddr** rti_info)
{
int s;
char* buf;
const size_t buflen = sizeof(struct rt_msghdr) + 512;
pid_t pid;
struct rt_msghdr* rtm;
struct sockaddr_in* r_sin;
struct sockaddr* sa;
const int seq = (int) 0x28290817;
ssize_t r;
buf = calloc(1, buflen);
if (buf == NULL) {
errno = ENOMEM;
return -1;
}
s = socket(AF_ROUTE, SOCK_RAW, AF_UNSPEC);
if (s < 0)
return -1;
rtm = (struct rt_msghdr *) buf;
rtm->rtm_msglen = sizeof(struct rt_msghdr) + sizeof(struct sockaddr_in);
rtm->rtm_version = RTM_VERSION;
rtm->rtm_type = RTM_GET;
rtm->rtm_addrs = RTA_DST;
rtm->rtm_pid = pid = getpid();
rtm->rtm_seq = seq;
r_sin = (struct sockaddr_in *) (rtm + 1);
*r_sin = *sin;
r = write(s, rtm, rtm->rtm_msglen);
if (r < 0) {
int en = errno;
close(s);
free(buf);
errno = en;
return -1;
}
while (true) {
r = read(s, rtm, buflen);
if (r < 0) {
int en = errno;
close(s);
free(buf);
errno = en;
return -1;
}
/*
* The kernel sends all routing message to all routing sockets. We need to
* filter them for the one for us.
*/
if (rtm->rtm_type == RTM_GET &&
rtm->rtm_seq == seq &&
rtm->rtm_pid == pid)
break;
}
close(s);
rtm = (struct rt_msghdr*) buf;
sa = (struct sockaddr*) (rtm + 1);
get_rtaddrs(rtm->rtm_addrs, sa, rti_info);
free(buf);
return 0;
}
