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/*
* Copyright (c) 2026 Stormshield
*
* SPDX-License-Identifier: BSD-2-Clause
*/
/*
* A dead-simple IPv6 multicast routing daemon. It registers itself with the
* multicast routing code and then waits for messages from the kernel. Received
* messages are handled by installing multicast routes.
*/
#include <sys/types.h>
#include <sys/event.h>
#include <sys/queue.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet6/ip6_mroute.h>
#include <arpa/inet.h>
#include <assert.h>
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
struct mif {
const char *name;
int mifi;
int pifi;
STAILQ_ENTRY(mif) next;
};
static STAILQ_HEAD(, mif) miflist = STAILQ_HEAD_INITIALIZER(miflist);
static void *
xmalloc(size_t size)
{
void *ptr;
ptr = malloc(size);
if (ptr == NULL)
err(1, "malloc");
return (ptr);
}
static void
usage(void)
{
fprintf(stderr,
"usage: %s [-i <iface>] [-m <srcaddr>/<groupaddr>/<iface>]\n",
getprogname());
exit(1);
}
static void
add_route(int sd, const struct in6_addr *src, const struct in6_addr *group,
mifi_t mifi)
{
struct mf6cctl mfcc;
struct mif *mif;
int error;
memset(&mfcc, 0, sizeof(mfcc));
mfcc.mf6cc_parent = mifi;
mfcc.mf6cc_origin.sin6_family = AF_INET6;
mfcc.mf6cc_origin.sin6_len = sizeof(struct sockaddr_in6);
mfcc.mf6cc_origin.sin6_addr = *src;
mfcc.mf6cc_mcastgrp.sin6_family = AF_INET6;
mfcc.mf6cc_mcastgrp.sin6_len = sizeof(struct sockaddr_in6);
mfcc.mf6cc_mcastgrp.sin6_addr = *group;
STAILQ_FOREACH(mif, &miflist, next) {
if (mif->mifi != mifi)
IF_SET(mif->mifi, &mfcc.mf6cc_ifset);
}
error = setsockopt(sd, IPPROTO_IPV6, MRT6_ADD_MFC,
&mfcc, sizeof(mfcc));
if (error != 0)
err(1, "setsockopt(MRT6_ADD_MFC)");
}
static void
handle_upcalls(int sd)
{
struct kevent ev;
int kq;
kq = kqueue();
if (kq < 0)
err(1, "kqueue");
EV_SET(&ev, sd, EVFILT_READ, EV_ADD | EV_ENABLE, 0, 0, NULL);
if (kevent(kq, &ev, 1, NULL, 0, NULL) < 0)
err(1, "kevent");
for (;;) {
char buf1[INET6_ADDRSTRLEN], buf2[INET6_ADDRSTRLEN];
struct mrt6msg msg;
ssize_t len;
int n;
n = kevent(kq, NULL, 0, &ev, 1, NULL);
if (n < 0) {
if (errno == EINTR)
break;
err(1, "kevent");
}
if (n == 0)
continue;
assert(n == 1);
assert(ev.filter == EVFILT_READ);
len = recv(sd, &msg, sizeof(msg), 0);
if (len < 0)
err(1, "recv");
if ((size_t)len < sizeof(msg)) {
warnx("short read on upcall, %zd bytes", len);
continue;
}
printf("upcall received:\n");
printf("msgtype=%d mif=%d src=%s dst=%s\n",
msg.im6_msgtype, msg.im6_mif,
inet_ntop(AF_INET6, &msg.im6_src, buf1, sizeof(buf1)),
inet_ntop(AF_INET6, &msg.im6_dst, buf2, sizeof(buf2)));
add_route(sd, &msg.im6_src, &msg.im6_dst, msg.im6_mif);
}
close(kq);
}
int
main(int argc, char **argv)
{
struct mif *mif;
int ch, error, mifi, sd, v;
mifi = 0;
while ((ch = getopt(argc, argv, "i:m:")) != -1) {
switch (ch) {
case 'i':
mif = xmalloc(sizeof(*mif));
mif->name = strdup(optarg);
mif->mifi = mifi++;
mif->pifi = if_nametoindex(optarg);
if (mif->pifi == 0)
errx(1, "unknown interface %s", optarg);
STAILQ_INSERT_TAIL(&miflist, mif, next);
break;
default:
usage();
/* NOTREACHED */
}
}
argc -= optind;
argv += optind;
sd = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
if (sd < 0)
err(1, "socket");
v = 1;
error = setsockopt(sd, IPPROTO_IPV6, MRT6_INIT, &v, sizeof(v));
if (error != 0)
err(1, "setsockopt(MRT6_INIT)");
STAILQ_FOREACH(mif, &miflist, next) {
struct mif6ctl mifc;
mifc.mif6c_mifi = mif->mifi;
mifc.mif6c_pifi = mif->pifi;
mifc.mif6c_flags = 0;
error = setsockopt(sd, IPPROTO_IPV6, MRT6_ADD_MIF,
&mifc, sizeof(mifc));
if (error != 0)
err(1, "setsockopt(MRT6_ADD_MIF) on %s", mif->name);
}
handle_upcalls(sd);
error = setsockopt(sd, IPPROTO_IPV6, MRT6_DONE, NULL, 0);
if (error != 0)
err(1, "setsockopt(MRT6_DONE)");
return (0);
}
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