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Add subnet blacklist feature, use defines for socket/blacklist limit
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@kennylevinsen
kennylevinsen committed Dec 7, 2016
1 parent df5f748 commit 50dc26b
Showing 1 changed file with 94 additions and 10 deletions.
104 changes: 94 additions & 10 deletions mdns-repeater.c
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Original file line number Diff line number Diff line change
@@ -1,17 +1,17 @@
/*
* mdns-repeater.c - mDNS repeater daemon
* Copyright (C) 2011 Darell Tan
*
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
Expand Down Expand Up @@ -39,6 +39,9 @@

#define PIDFILE "/var/run/" PACKAGE ".pid"

#define MAX_SOCKS 16
#define MAX_SUBNETS 16

struct if_sock {
const char *ifname; /* interface name */
int sockfd; /* socket filedesc */
Expand All @@ -47,10 +50,19 @@ struct if_sock {
struct in_addr net; /* interface network (computed) */
};

struct subnet {
struct in_addr addr; /* subnet addr */
struct in_addr mask; /* subnet mask */
struct in_addr net; /* subnet net (computed) */
};

int server_sockfd = -1;

int num_socks = 0;
struct if_sock socks[5];
struct if_sock socks[MAX_SOCKS];

int num_subnets = 0;
struct subnet subnets[MAX_SUBNETS];

#define PACKET_SIZE 65536
void *pkt_data = NULL;
Expand Down Expand Up @@ -217,7 +229,7 @@ static pid_t already_running() {
FILE *f;
int count;
pid_t pid;

f = fopen(pid_file, "r");
if (f != NULL) {
count = fscanf(f, "%d", &pid);
Expand Down Expand Up @@ -299,16 +311,17 @@ static void show_help(const char *progname) {
"\n"
" flags:\n"
" -f runs in foreground for debugging\n"
" -b blacklist subnet (eg. 192.168.1.1/24)\n"
" -p specifies the pid file path (default: " PIDFILE ")\n"
" -h shows this help\n"
"\n"
);
}

static int parse_opts(int argc, char *argv[]) {
int c;
int c, delim, end;
int help = 0;
while ((c = getopt(argc, argv, "hfp:")) != -1) {
while ((c = getopt(argc, argv, "hfp:b:")) != -1) {
switch (c) {
case 'h': help = 1; break;
case 'f': foreground = 1; break;
Expand All @@ -319,6 +332,57 @@ static int parse_opts(int argc, char *argv[]) {
pid_file = optarg;
break;

case 'b':
if (num_subnets >= MAX_SUBNETS) {
log_message(LOG_ERR, "too many blacklisted subnets (maximum is %d)", MAX_SUBNETS);
exit(2);
}

delim = 0;
end = 0;
while (optarg[end] != 0) {
if (optarg[end] == '/')
delim = end;
end++;
}

if (end == 0 || delim == 0 || end == delim) {
log_message(LOG_ERR, "invalid blacklist argument");
exit(2);
}

struct subnet *ss = &subnets[num_subnets++];
char *addr = (char*) malloc(end);

// Copy the subnet identifier out and parse
memset(addr, 0, end);
strncpy(addr, optarg, delim);
if (inet_pton(AF_INET, addr, &ss->addr) != 1) {
log_message(LOG_ERR, "could not parse netmask");
exit(2);
}

// Copy the mask out and parse
memset(addr, 0, end);
strncpy(addr, optarg+delim+1, end-delim-1);
int mask = atoi(addr);
free(addr);

if (mask < 0 || mask > 32) {
log_message(LOG_ERR, "invalid netmask");
exit(2);
}

ss->mask.s_addr = ntohl((uint32_t)0xFFFFFFFF << (32 - mask));
ss->net.s_addr = ss->addr.s_addr & ss->mask.s_addr;
char *addr_str = strdup(inet_ntoa(ss->addr));
char *mask_str = strdup(inet_ntoa(ss->mask));
char *net_str = strdup(inet_ntoa(ss->net));
log_message(LOG_INFO, "blacklist addr %s mask %s net %s", addr_str, mask_str, net_str);
free(addr_str);
free(mask_str);
free(net_str);
break;
case '?':
case ':':
fputs("\n", stderr);
Expand Down Expand Up @@ -374,6 +438,11 @@ int main(int argc, char *argv[]) {
// create sending sockets
int i;
for (i = optind; i < argc; i++) {
if (num_socks >= MAX_SOCKS) {
log_message(LOG_ERR, "too many sockets (maximum is %d)", MAX_SOCKS);
exit(2);
}

int sockfd = create_send_sock(server_sockfd, argv[i], &socks[num_socks]);
if (sockfd < 0) {
log_message(LOG_ERR, "unable to create socket for interface %s", argv[i]);
Expand Down Expand Up @@ -406,7 +475,7 @@ int main(int argc, char *argv[]) {
struct sockaddr_in fromaddr;
socklen_t sockaddr_size = sizeof(struct sockaddr_in);

ssize_t recvsize = recvfrom(server_sockfd, pkt_data, PACKET_SIZE, 0,
ssize_t recvsize = recvfrom(server_sockfd, pkt_data, PACKET_SIZE, 0,
(struct sockaddr *) &fromaddr, &sockaddr_size);
if (recvsize < 0) {
log_message(LOG_ERR, "recv(): %m");
Expand All @@ -425,6 +494,21 @@ int main(int argc, char *argv[]) {
if (self_generated_packet)
continue;

char blacklisted_packet = 0;
for (j = 0; j < num_subnets; j++) {
// check for blacklist
if ((fromaddr.sin_addr.s_addr & subnets[j].mask.s_addr) == subnets[j].net.s_addr) {
blacklisted_packet = 1;
break;
}
}

if (blacklisted_packet) {
if (foreground)
printf("skipping packet from=%s\n", inet_ntoa(fromaddr.sin_addr));
continue;
}

if (foreground)
printf("data from=%s size=%ld\n", inet_ntoa(fromaddr.sin_addr), recvsize);

Expand Down Expand Up @@ -453,13 +537,13 @@ int main(int argc, char *argv[]) {

end_main:

if (pkt_data != NULL)
if (pkt_data != NULL)
free(pkt_data);

if (server_sockfd >= 0)
close(server_sockfd);

for (i = 0; i < num_socks; i++)
for (i = 0; i < num_socks; i++)
close(socks[i].sockfd);

// remove pid file if it belongs to us
Expand Down

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