/*
* arpd.c ARP helper daemon.
*
* 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.
*
* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
*/
#include <stdio.h>
#include <syslog.h>
#include <malloc.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <netdb.h>
#include <db_185.h>
#include <sys/ioctl.h>
#include <sys/poll.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/uio.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <time.h>
#include <signal.h>
#include <linux/if.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <linux/if_packet.h>
#include <linux/filter.h>
#include "libnetlink.h"
#include "utils.h"
#include "rt_names.h"
DB *dbase;
char *dbname = "/var/lib/arpd/arpd.db";
int ifnum;
int *ifvec;
char **ifnames;
struct dbkey {
__u32 iface;
__u32 addr;
};
#define IS_NEG(x) (((__u8 *)(x))[0] == 0xFF)
#define NEG_TIME(x) (((x)[2]<<24)|((x)[3]<<16)|((x)[4]<<8)|(x)[5])
#define NEG_AGE(x) ((__u32)time(NULL) - NEG_TIME((__u8 *)x))
#define NEG_VALID(x) (NEG_AGE(x) < negative_timeout)
#define NEG_CNT(x) (((__u8 *)(x))[1])
struct rtnl_handle rth;
struct pollfd pset[2];
int udp_sock = -1;
volatile int do_exit;
volatile int do_sync;
volatile int do_stats;
struct {
unsigned long arp_new;
unsigned long arp_change;
unsigned long app_recv;
unsigned long app_success;
unsigned long app_bad;
unsigned long app_neg;
unsigned long app_suppressed;
unsigned long kern_neg;
unsigned long kern_new;
unsigned long kern_change;
unsigned long probes_sent;
unsigned long probes_suppressed;
} stats;
int active_probing;
int negative_timeout = 60;
int no_kernel_broadcasts;
int broadcast_rate = 1000;
int broadcast_burst = 3000;
int poll_timeout = 30000;
static void usage(void)
{
fprintf(stderr,
"Usage: arpd [ -lkh? ] [ -a N ] [ -b dbase ] [ -B number ] [ -f file ] [ -n time ] [-p interval ] [ -R rate ] [ interfaces ]\n");
exit(1);
}
static int handle_if(int ifindex)
{
int i;
if (ifnum == 0)
return 1;
for (i = 0; i < ifnum; i++)
if (ifvec[i] == ifindex)
return 1;
return 0;
}
int sysctl_adjusted;
static void do_sysctl_adjustments(void)
{
int i;
if (!ifnum)
return;
for (i = 0; i < ifnum; i++) {
char buf[128];
FILE *fp;
if (active_probing) {
sprintf(buf, "/proc/sys/net/ipv4/neigh/%s/mcast_solicit", ifnames[i]);
if ((fp = fopen(buf, "w")) != NULL) {
if (no_kernel_broadcasts)
strcpy(buf, "0\n");
else
sprintf(buf, "%d\n", active_probing >= 2 ? 1 : 3-active_probing);
fputs(buf, fp);
fclose(fp);
}
}
sprintf(buf, "/proc/sys/net/ipv4/neigh/%s/app_solicit", ifnames[i]);
if ((fp = fopen(buf, "w")) != NULL) {
sprintf(buf, "%d\n", active_probing <= 1 ? 1 : active_probing);
fputs(buf, fp);
fclose(fp);
}
}
sysctl_adjusted = 1;
}
static void undo_sysctl_adjustments(void)
{
int i;
if (!sysctl_adjusted)
return;
for (i = 0; i < ifnum; i++) {
char buf[128];
FILE *fp;
if (active_probing) {
sprintf(buf, "/proc/sys/net/ipv4/neigh/%s/mcast_solicit", ifnames[i]);
if ((fp = fopen(buf, "w")) != NULL) {
strcpy(buf, "3\n");
fputs(buf, fp);
fclose(fp);
}
}
sprintf(buf, "/proc/sys/net/ipv4/neigh/%s/app_solicit", ifnames[i]);
if ((fp = fopen(buf, "w")) != NULL) {
strcpy(buf, "0\n");
fputs(buf, fp);
fclose(fp);
}
}
sysctl_adjusted = 0;
}
static int send_probe(int ifindex, __u32 addr)
{
struct ifreq ifr = { .ifr_ifindex = ifindex };
struct sockaddr_in dst = {
.sin_family = AF_INET,
.sin_port = htons(1025),
.sin_addr.s_addr = addr,
};
socklen_t len;
unsigned char buf[256];
struct arphdr *ah = (struct arphdr *)buf;
unsigned char *p = (unsigned char *)(ah+1);
struct sockaddr_ll sll = {
.sll_family = AF_PACKET,
.sll_ifindex = ifindex,
.sll_protocol = htons(ETH_P_ARP),
};
if (ioctl(udp_sock, SIOCGIFNAME, &ifr))
return -1;
if (ioctl(udp_sock, SIOCGIFHWADDR, &ifr))
return -1;
if (ifr.ifr_hwaddr.sa_family != ARPHRD_ETHER)
return -1;
if (setsockopt(udp_sock, SOL_SOCKET, SO_BINDTODEVICE, ifr.ifr_name, strlen(ifr.ifr_name)+1) < 0)
return -1;
if (connect(udp_sock, (struct sockaddr *)&dst, sizeof(dst)) < 0)
return -1;
len = sizeof(dst);
if (getsockname(udp_sock, (struct sockaddr *)&dst, &len) < 0)
return -1;
ah->ar_hrd = htons(ifr.ifr_hwaddr.sa_family);
ah->ar_pro = htons(ETH_P_IP);
ah->ar_hln = 6;
ah->ar_pln = 4;
ah->ar_op = htons(ARPOP_REQUEST);
memcpy(p, ifr.ifr_hwaddr.sa_data, ah->ar_hln);
p += ah->ar_hln;
memcpy(p, &dst.sin_addr, 4);
p += 4;
memset(sll.sll_addr, 0xFF, sizeof(sll.sll_addr));
memcpy(p, &sll.sll_addr, ah->ar_hln);
p += ah->ar_hln;
memcpy(p, &addr, 4);
p += 4;
if (sendto(pset[0].fd, buf, p-buf, 0, (struct sockaddr *)&sll, sizeof(sll)) < 0)
return -1;
stats.probes_sent++;
return 0;
}
/* Be very tough on sending probes: 1 per second with burst of 3. */
static int queue_active_probe(int ifindex, __u32 addr)
{
static struct timeval prev;
static int buckets;
struct timeval now;
gettimeofday(&now, NULL);
if (prev.tv_sec) {
int diff = (now.tv_sec-prev.tv_sec)*1000+(now.tv_usec-prev.tv_usec)/1000;
buckets += diff;
} else {
buckets = broadcast_burst;
}
if (buckets > broadcast_burst)
buckets = broadcast_burst;
if (buckets >= broadcast_rate && !send_probe(ifindex, addr)) {
buckets -= broadcast_rate;
prev = now;
return 0;
}
stats.probes_suppressed++;
return -1;
}
static int respond_to_kernel(int ifindex, __u32 addr, char *lla, int llalen)
{
struct {
struct nlmsghdr n;
struct ndmsg ndm;
char buf[256];
} req = {
.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ndmsg)),
.n.nlmsg_flags = NLM_F_REQUEST,
.n.nlmsg_type = RTM_NEWNEIGH,
.ndm.ndm_family = AF_INET,
.ndm.ndm_state = NUD_STALE,
.ndm.ndm_ifindex = ifindex,
.ndm.ndm_type = RTN_UNICAST,
};
addattr_l(&req.n, sizeof(req), NDA_DST, &addr, 4);
addattr_l(&req.n, sizeof(req), NDA_LLADDR, lla, llalen);
return rtnl_send(&rth, &req, req.n.nlmsg_len) <= 0;
}
static void prepare_neg_entry(__u8 *ndata, __u32 stamp)
{
ndata[0] = 0xFF;
ndata[1] = 0;
ndata[2] = stamp>>24;
ndata[3] = stamp>>16;
ndata[4] = stamp>>8;
ndata[5] = stamp;
}
static int do_one_request(struct nlmsghdr *n)
{
struct ndmsg *ndm = NLMSG_DATA(n);
int len = n->nlmsg_len;
struct rtattr *tb[NDA_MAX+1];
struct dbkey key;
DBT dbkey, dbdat;
int do_acct = 0;
if (n->nlmsg_type == NLMSG_DONE) {
dbase->sync(dbase, 0);
/* Now we have at least mirror of kernel db, so that
* may start real resolution.
*/
do_sysctl_adjustments();
return 0;
}
if (n->nlmsg_type != RTM_GETNEIGH && n->nlmsg_type != RTM_NEWNEIGH)
return 0;
len -= NLMSG_LENGTH(sizeof(*ndm));
if (len < 0)
return -1;
if (ndm->ndm_family != AF_INET ||
(ifnum && !handle_if(ndm->ndm_ifindex)) ||
ndm->ndm_flags ||
ndm->ndm_type != RTN_UNICAST ||
!(ndm->ndm_state&~NUD_NOARP))
return 0;
parse_rtattr(tb, NDA_MAX, NDA_RTA(ndm), len);
if (!tb[NDA_DST])
return 0;
key.iface = ndm->ndm_ifindex;
memcpy(&key.addr, RTA_DATA(tb[NDA_DST]), 4);
dbkey.data = &key;
dbkey.size = sizeof(key);
if (dbase->get(dbase, &dbkey, &dbdat, 0) != 0) {
dbdat.data = 0;
dbdat.size = 0;
}
if (n->nlmsg_type == RTM_GETNEIGH) {
if (!(n->nlmsg_flags&NLM_F_REQUEST))
return 0;
if (!(ndm->ndm_state&(NUD_PROBE|NUD_INCOMPLETE))) {
stats.app_bad++;
return 0;
}
if (ndm->ndm_state&NUD_PROBE) {
/* If we get this, kernel still has some valid
* address, but unicast probing failed and host
* is either dead or changed its mac address.
* Kernel is going to initiate broadcast resolution.
* OK, we invalidate our information as well.
*/
if (dbdat.data && !IS_NEG(dbdat.data))
stats.app_neg++;
dbase->del(dbase, &dbkey, 0);
} else {
/* If we get this kernel does not have any information.
* If we have something tell this to kernel. */
stats.app_recv++;
if (dbdat.data && !IS_NEG(dbdat.data)) {
stats.app_success++;
respond_to_kernel(key.iface, key.addr, dbdat.data, dbdat.size);
return 0;
}
/* Sheeit! We have nothing to tell. */
/* If we have recent negative entry, be silent. */
if (dbdat.data && NEG_VALID(dbdat.data)) {
if (NEG_CNT(dbdat.data) >= active_probing) {
stats.app_suppressed++;
return 0;
}
do_acct = 1;
}
}
if (active_probing &&
queue_active_probe(ndm->ndm_ifindex, key.addr) == 0 &&
do_acct) {
NEG_CNT(dbdat.data)++;
dbase->put(dbase, &dbkey, &dbdat, 0);
}
} else if (n->nlmsg_type == RTM_NEWNEIGH) {
if (n->nlmsg_flags&NLM_F_REQUEST)
return 0;
if (ndm->ndm_state&NUD_FAILED) {
/* Kernel was not able to resolve. Host is dead.
* Create negative entry if it is not present
* or renew it if it is too old. */
if (!dbdat.data ||
!IS_NEG(dbdat.data) ||
!NEG_VALID(dbdat.data)) {
__u8 ndata[6];
stats.kern_neg++;
prepare_neg_entry(ndata, time(NULL));
dbdat.data = ndata;
dbdat.size = sizeof(ndata);
dbase->put(dbase, &dbkey, &dbdat, 0);
}
} else if (tb[NDA_LLADDR]) {
if (dbdat.data && !IS_NEG(dbdat.data)) {
if (memcmp(RTA_DATA(tb[NDA_LLADDR]), dbdat.data, dbdat.size) == 0)
return 0;
stats.kern_change++;
} else {
stats.kern_new++;
}
dbdat.data = RTA_DATA(tb[NDA_LLADDR]);
dbdat.size = RTA_PAYLOAD(tb[NDA_LLADDR]);
dbase->put(dbase, &dbkey, &dbdat, 0);
}
}
return 0;
}
static void load_initial_table(void)
{
if (rtnl_neighdump_req(&rth, AF_INET, NULL) < 0) {
perror("dump request failed");
exit(1);
}
}
static void get_kern_msg(void)
{
int status;
struct nlmsghdr *h;
struct sockaddr_nl nladdr = {};
struct iovec iov;
char buf[8192];
struct msghdr msg = {
(void *)&nladdr, sizeof(nladdr),
&iov, 1,
NULL, 0,
0
};
iov.iov_base = buf;
iov.iov_len = sizeof(buf);
status = recvmsg(rth.fd, &msg, MSG_DONTWAIT);
if (status <= 0)
return;
if (msg.msg_namelen != sizeof(nladdr))
return;
if (nladdr.nl_pid)
return;
for (h = (struct nlmsghdr *)buf; status >= sizeof(*h); ) {
int len = h->nlmsg_len;
int l = len - sizeof(*h);
if (l < 0 || len > status)
return;
if (do_one_request(h) < 0)
return;
status -= NLMSG_ALIGN(len);
h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
}
}
/* Receive gratuitous ARP messages and store them, that's all. */
static void get_arp_pkt(void)
{
unsigned char buf[1024];
struct sockaddr_ll sll;
socklen_t sll_len = sizeof(sll);
struct arphdr *a = (struct arphdr *)buf;
struct dbkey key;
DBT dbkey, dbdat;
int n;
n = recvfrom(pset[0].fd, buf, sizeof(buf), MSG_DONTWAIT,
(struct sockaddr *)&sll, &sll_len);
if (n < 0) {
if (errno != EINTR && errno != EAGAIN)
syslog(LOG_ERR, "recvfrom: %m");
return;
}
if (ifnum && !handle_if(sll.sll_ifindex))
return;
/* Sanity checks */
if (n < sizeof(*a) ||
(a->ar_op != htons(ARPOP_REQUEST) &&
a->ar_op != htons(ARPOP_REPLY)) ||
a->ar_pln != 4 ||
a->ar_pro != htons(ETH_P_IP) ||
a->ar_hln != sll.sll_halen ||
sizeof(*a) + 2*4 + 2*a->ar_hln > n)
return;
key.iface = sll.sll_ifindex;
memcpy(&key.addr, (char *)(a+1) + a->ar_hln, 4);
/* DAD message, ignore. */
if (key.addr == 0)
return;
dbkey.data = &key;
dbkey.size = sizeof(key);
if (dbase->get(dbase, &dbkey, &dbdat, 0) == 0 && !IS_NEG(dbdat.data)) {
if (memcmp(dbdat.data, a+1, dbdat.size) == 0)
return;
stats.arp_change++;
} else {
stats.arp_new++;
}
dbdat.data = a+1;
dbdat.size = a->ar_hln;
dbase->put(dbase, &dbkey, &dbdat, 0);
}
static void catch_signal(int sig, void (*handler)(int))
{
struct sigaction sa = { .sa_handler = handler };
#ifdef SA_INTERRUPT
sa.sa_flags = SA_INTERRUPT;
#endif
sigaction(sig, &sa, NULL);
}
#include <setjmp.h>
sigjmp_buf env;
volatile int in_poll;
static void sig_exit(int signo)
{
do_exit = 1;
if (in_poll)
siglongjmp(env, 1);
}
static void sig_sync(int signo)
{
do_sync = 1;
if (in_poll)
siglongjmp(env, 1);
}
static void sig_stats(int signo)
{
do_sync = 1;
do_stats = 1;
if (in_poll)
siglongjmp(env, 1);
}
static void send_stats(void)
{
syslog(LOG_INFO, "arp_rcv: n%lu c%lu app_rcv: tot %lu hits %lu bad %lu neg %lu sup %lu",
stats.arp_new, stats.arp_change,
stats.app_recv, stats.app_success,
stats.app_bad, stats.app_neg, stats.app_suppressed
);
syslog(LOG_INFO, "kern: n%lu c%lu neg %lu arp_send: %lu rlim %lu",
stats.kern_new, stats.kern_change, stats.kern_neg,
stats.probes_sent, stats.probes_suppressed
);
do_stats = 0;
}
int main(int argc, char **argv)
{
int opt;
int do_list = 0;
char *do_load = NULL;
while ((opt = getopt(argc, argv, "h?b:lf:a:n:p:kR:B:")) != EOF) {
switch (opt) {
case 'b':
dbname = optarg;
break;
case 'f':
if (do_load) {
fprintf(stderr, "Duplicate option -f\n");
usage();
}
do_load = optarg;
break;
case 'l':
do_list = 1;
break;
case 'a':
active_probing = atoi(optarg);
break;
case 'n':
negative_timeout = atoi(optarg);
break;
case 'k':
no_kernel_broadcasts = 1;
break;
case 'p':
if ((poll_timeout = 1000 * strtod(optarg, NULL)) < 100) {
fprintf(stderr, "Invalid poll timeout\n");
exit(-1);
}
break;
case 'R':
if ((broadcast_rate = atoi(optarg)) <= 0 ||
(broadcast_rate = 1000/broadcast_rate) <= 0) {
fprintf(stderr, "Invalid ARP rate\n");
exit(-1);
}
break;
case 'B':
if ((broadcast_burst = atoi(optarg)) <= 0 ||
(broadcast_burst = 1000*broadcast_burst) <= 0) {
fprintf(stderr, "Invalid ARP burst\n");
exit(-1);
}
break;
case 'h':
case '?':
default:
usage();
}
}
argc -= optind;
argv += optind;
if (argc > 0) {
ifnum = argc;
ifnames = argv;
ifvec = malloc(argc*sizeof(int));
if (!ifvec) {
perror("malloc");
exit(-1);
}
}
if ((udp_sock = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
perror("socket");
exit(-1);
}
if (ifnum) {
int i;
struct ifreq ifr = {};
for (i = 0; i < ifnum; i++) {
if (get_ifname(ifr.ifr_name, ifnames[i]))
invarg("not a valid ifname", ifnames[i]);
if (ioctl(udp_sock, SIOCGIFINDEX, &ifr)) {
perror("ioctl(SIOCGIFINDEX)");
exit(-1);
}
ifvec[i] = ifr.ifr_ifindex;
}
}
dbase = dbopen(dbname, O_CREAT|O_RDWR, 0644, DB_HASH, NULL);
if (dbase == NULL) {
perror("db_open");
exit(-1);
}
if (do_load) {
char buf[128];
FILE *fp;
struct dbkey k;
DBT dbkey, dbdat;
dbkey.data = &k;
dbkey.size = sizeof(k);
if (strcmp(do_load, "-") == 0 || strcmp(do_load, "--") == 0) {
fp = stdin;
} else if ((fp = fopen(do_load, "r")) == NULL) {
perror("fopen");
goto do_abort;
}
buf[sizeof(buf)-1] = 0;
while (fgets(buf, sizeof(buf), fp)) {
__u8 b1[6];
char ipbuf[128];
char macbuf[128];
if (buf[0] == '#')
continue;
if (sscanf(buf, "%u%s%s", &k.iface, ipbuf, macbuf) != 3) {
fprintf(stderr, "Wrong format of input file \"%s\"\n", do_load);
goto do_abort;
}
if (strncmp(macbuf, "FAILED:", 7) == 0)
continue;
if (!inet_aton(ipbuf, (struct in_addr *)&k.addr)) {
fprintf(stderr, "Invalid IP address: \"%s\"\n", ipbuf);
goto do_abort;
}
if (ll_addr_a2n((char *) b1, 6, macbuf) != 6)
goto do_abort;
dbdat.size = 6;
if (dbase->put(dbase, &dbkey, &dbdat, 0)) {
perror("hash->put");
goto do_abort;
}
}
dbase->sync(dbase, 0);
if (fp != stdin)
fclose(fp);
}
if (do_list) {
DBT dbkey, dbdat;
printf("%-8s %-15s %s\n", "#Ifindex", "IP", "MAC");
while (dbase->seq(dbase, &dbkey, &dbdat, R_NEXT) == 0) {
struct dbkey *key = dbkey.data;
if (handle_if(key->iface)) {
if (!IS_NEG(dbdat.data)) {
char b1[18];
printf("%-8d %-15s %s\n",
key->iface,
inet_ntoa(*(struct in_addr *)&key->addr),
ll_addr_n2a(dbdat.data, 6, ARPHRD_ETHER, b1, 18));
} else {
printf("%-8d %-15s FAILED: %dsec ago\n",
key->iface,
inet_ntoa(*(struct in_addr *)&key->addr),
NEG_AGE(dbdat.data));
}
}
}
}
if (do_load || do_list)
goto out;
pset[0].fd = socket(PF_PACKET, SOCK_DGRAM, 0);
if (pset[0].fd < 0) {
perror("socket");
exit(-1);
}
if (1) {
struct sockaddr_ll sll = {
.sll_family = AF_PACKET,
.sll_protocol = htons(ETH_P_ARP),
.sll_ifindex = (ifnum == 1 ? ifvec[0] : 0),
};
if (bind(pset[0].fd, (struct sockaddr *)&sll, sizeof(sll)) < 0) {
perror("bind");
goto do_abort;
}
}
if (rtnl_open(&rth, RTMGRP_NEIGH) < 0) {
perror("rtnl_open");
goto do_abort;
}
pset[1].fd = rth.fd;
load_initial_table();
if (daemon(0, 0)) {
perror("arpd: daemon");
goto do_abort;
}
openlog("arpd", LOG_PID | LOG_CONS, LOG_DAEMON);
catch_signal(SIGINT, sig_exit);
catch_signal(SIGTERM, sig_exit);
catch_signal(SIGHUP, sig_sync);
catch_signal(SIGUSR1, sig_stats);
#define EVENTS (POLLIN|POLLPRI|POLLERR|POLLHUP)
pset[0].events = EVENTS;
pset[0].revents = 0;
pset[1].events = EVENTS;
pset[1].revents = 0;
sigsetjmp(env, 1);
for (;;) {
in_poll = 1;
if (do_exit)
break;
if (do_sync) {
in_poll = 0;
dbase->sync(dbase, 0);
do_sync = 0;
in_poll = 1;
}
if (do_stats)
send_stats();
if (poll(pset, 2, poll_timeout) > 0) {
in_poll = 0;
if (pset[0].revents&EVENTS)
get_arp_pkt();
if (pset[1].revents&EVENTS)
get_kern_msg();
} else {
do_sync = 1;
}
}
undo_sysctl_adjustments();
out:
dbase->close(dbase);
exit(0);
do_abort:
dbase->close(dbase);
exit(-1);
}