2 netmon - a simple network connectivity monitor
3 Copyright © 2008-2016 Mikko Rasa, Mikkosoft Productions
4 Distributed under the GPL
15 #include <sys/socket.h>
18 #include <net/ethernet.h>
19 #include <netinet/in.h>
20 #include <netinet/ip.h>
21 #include <netinet/ip_icmp.h>
22 #include <netinet/ip6.h>
24 #include <arpa/inet.h>
25 #include <pcap/pcap.h>
27 typedef unsigned long long Time;
31 struct sockaddr_storage address;
32 struct sockaddr_storage mask;
43 int connection_status;
44 Time connection_down_time;
59 const char *target_name;
60 struct sockaddr_in target_addr;
72 int monitor_init(Monitor *);
73 void monitor_check(Monitor *, Time);
74 void capture_handler(uint8_t *, const struct pcap_pkthdr *, const uint8_t *);
75 int trigger_init(Trigger *);
76 void trigger_check(Trigger *, Time);
77 int get_inet_scope(uint32_t, const Address *);
78 int get_inet6_scope(const struct in6_addr *, const Address *);
79 int pinger_init(Pinger *);
80 void pinger_check(Pinger *, Time);
81 unsigned checksum(const char *, unsigned);
82 void send_ping(Pinger *);
83 pid_t run_command(const char *);
88 int main(int argc, char **argv)
95 Time stats_interval = 1800000000ULL;
99 monitor.interface_name = NULL;
100 trigger.monitor = &monitor;
101 trigger.delay = 60000000ULL;
102 trigger.interval = 600000000ULL;
103 pinger.target_name = NULL;
106 while((o = getopt(argc, argv, "fvs:t:c:i:p:"))!=-1)
116 stats_interval = strtoul(optarg, NULL, 10)*1000000;
119 trigger.delay = strtoul(optarg, &endp, 10)*1000000;
121 trigger.interval = strtoul(endp+1, NULL, 10)*1000000;
123 trigger.interval = trigger.delay;
126 trigger.command = optarg;
129 monitor.interface_name = strdup(optarg);
132 pinger.target_name = strdup(optarg);
136 if(monitor.interface_name)
138 if(monitor_init(&monitor))
142 if(trigger_init(&trigger))
146 if(pinger.target_name)
147 if(pinger_init(&pinger))
150 if(!no_daemon && daemon(1, 0)==-1)
156 openlog("netmon", 0, LOG_LOCAL7);
158 Time next_stats = current_time()+stats_interval;
161 Time time = current_time();
163 if(monitor.interface_name)
165 monitor_check(&monitor, time);
168 trigger_check(&trigger, time);
171 if(pinger.target_name)
173 pinger_check(&pinger, time);
179 float loss_ratio = (float)pinger.lost/pinger.count;
181 printf("Packet loss: %.2f%%\n", loss_ratio*100);
183 syslog(LOG_INFO, "Packet loss: %.2f%%", loss_ratio*100);
188 next_stats += stats_interval;
201 gettimeofday(&tv, NULL);
202 return tv.tv_sec*1000000ULL+tv.tv_usec;
205 int monitor_init(Monitor *monitor)
207 char err[PCAP_ERRBUF_SIZE];
209 if(pcap_findalldevs(&devs, err)==-1)
211 fprintf(stderr, "pcap_findalldevs: %s\n", err);
215 monitor->pcap = pcap_open_live(monitor->interface_name, 64, 0, 10, err);
218 fprintf(stderr, "pcap_findalldevs: %s\n", err);
222 if(pcap_setnonblock(monitor->pcap, 1, err)==-1)
224 fprintf(stderr, "pcap_findalldevs: %s\n", err);
228 monitor->n_addresses = 0;
229 monitor->addresses = NULL;
230 for(pcap_if_t *d=devs; d; d=d->next)
231 for(pcap_addr_t *a=d->addresses; a; a=a->next)
232 if(a->addr->sa_family==AF_INET || a->addr->sa_family==AF_INET6)
234 monitor->addresses = (Address *)realloc(monitor->addresses, (monitor->n_addresses+1)*sizeof(Address));
235 unsigned size = (a->addr->sa_family==AF_INET6 ? sizeof(struct sockaddr_in6) : sizeof(struct sockaddr_in));
236 memcpy(&monitor->addresses[monitor->n_addresses].address, a->addr, size);
237 memcpy(&monitor->addresses[monitor->n_addresses].mask, a->netmask, size);
238 ++monitor->n_addresses;
241 pcap_freealldevs(devs);
243 monitor->last_receive = 0;
244 monitor->last_transmit = 0;
245 monitor->connection_status = 1;
250 void monitor_check(Monitor *monitor, Time timestamp)
252 pcap_dispatch(monitor->pcap, -1, &capture_handler, (uint8_t *)monitor);
254 if(monitor->last_transmit && monitor->last_receive)
256 /* If packets have been transmitted more recently than received, there
257 might be a problem */
258 if(monitor->last_transmit>monitor->last_receive)
260 if(monitor->connection_status && timestamp>=monitor->last_receive+10000000)
262 monitor->connection_status = 0;
263 monitor->connection_down_time = monitor->last_receive;
265 printf("Connection is down\n");
267 syslog(LOG_INFO, "Connection is down");
270 else if(!monitor->connection_status)
272 Time duration = timestamp-monitor->connection_down_time;
273 monitor->connection_status = 1;
275 printf("Connection is up (was down for %lld seconds)\n", duration/1000000);
277 syslog(LOG_INFO, "Connection is up (was down for %lld seconds)", duration/1000000);
282 void capture_handler(uint8_t *user, const struct pcap_pkthdr *header, const uint8_t *data)
284 Monitor *monitor = (Monitor *)user;
285 const struct ether_header *eth = (const struct ether_header *)(data);
289 int proto = ntohs(eth->ether_type);
290 if(proto==ETHERTYPE_IP)
292 const struct ip *ip = (const struct ip *)(eth+1);
293 if(ntohl(ip->ip_dst.s_addr)>>28==14)
296 for(unsigned i=0; i<monitor->n_addresses; ++i)
297 if(monitor->addresses[i].address.ss_family==AF_INET)
299 int s = get_inet_scope(ip->ip_src.s_addr, &monitor->addresses[i]);
303 s = get_inet_scope(ip->ip_dst.s_addr, &monitor->addresses[i]);
308 else if(proto==ETHERTYPE_IPV6)
310 const struct ip6_hdr *ip6 = (const struct ip6_hdr *)(eth+1);
311 for(unsigned i=0; i<monitor->n_addresses; ++i)
312 if(monitor->addresses[i].address.ss_family==AF_INET6)
314 int s = get_inet6_scope(&ip6->ip6_src, &monitor->addresses[i]);
318 s = get_inet6_scope(&ip6->ip6_dst, &monitor->addresses[i]);
324 Time timestamp = header->ts.tv_sec*1000000ULL+header->ts.tv_usec;
325 if(src_scope==0 && dst_scope>0)
326 monitor->last_receive = timestamp;
327 else if(src_scope>0 && dst_scope==0)
328 monitor->last_transmit = timestamp;
331 int trigger_init(Trigger *trigger)
333 trigger->next = trigger->delay;
334 trigger->child_pid = 0;
339 void trigger_check(Trigger *trigger, Time time)
341 Monitor *monitor = trigger->monitor;
343 if(monitor->connection_status)
344 trigger->next = trigger->delay;
345 else if(time>=monitor->last_receive+trigger->next)
348 printf("Running %s\n", trigger->command);
350 syslog(LOG_INFO, "Running %s", trigger->command);
351 trigger->child_pid = run_command(trigger->command);
352 trigger->next += trigger->interval;
355 /* Reap any finished child process */
356 if(trigger->child_pid)
358 if(waitpid(trigger->child_pid, NULL, WNOHANG)==trigger->child_pid)
359 trigger->child_pid = 0;
363 int get_inet_scope(uint32_t addr, const Address *local_addr)
365 uint32_t diff = addr^((struct sockaddr_in *)&local_addr->address)->sin_addr.s_addr;
368 else if(!(diff&((struct sockaddr_in *)&local_addr->mask)->sin_addr.s_addr))
374 int get_inet6_scope(const struct in6_addr *addr, const Address *local_addr)
377 for(unsigned i=0; i<16; ++i)
379 uint8_t diff = addr->s6_addr[i]^((struct sockaddr_in6 *)&local_addr->address)->sin6_addr.s6_addr[i];
382 diff &= ((struct sockaddr_in6 *)&local_addr->mask)->sin6_addr.s6_addr[i];
393 int pinger_init(Pinger *pinger)
395 if(!pinger->target_name)
398 struct hostent *host;
400 host = gethostbyname(pinger->target_name);
403 herror("gethostbyname");
407 if(host->h_addrtype!=AF_INET)
409 fprintf(stderr, "Got a hostent, but it doesn't have an IPv4 address");
413 pinger->target_addr.sin_family = AF_INET;
414 pinger->target_addr.sin_addr = *(struct in_addr *)host->h_addr_list[0];
419 inet_ntop(AF_INET, &pinger->target_addr.sin_addr, buf, sizeof(buf));
420 printf("Ping target is %s\n", buf);
423 pinger->socket = socket(PF_INET, SOCK_RAW, IPPROTO_ICMP);
424 if(pinger->socket==-1)
426 perror("socket(SOCK_RAW)");
431 pinger->id = getpid();
437 pinger->pfd.fd = pinger->socket;
438 pinger->pfd.events = POLLIN;
443 void pinger_check(Pinger *pinger, Time time)
445 if(poll(&pinger->pfd, 1, 10)>0)
447 struct sockaddr_in addr;
448 socklen_t alen = sizeof(addr);
450 /* Receive a packet */
452 int len = recvfrom(pinger->socket, data, sizeof(data), 0, (struct sockaddr *)&addr, &alen);
454 fprintf(stderr, "recvfrom error: %s\n", strerror(errno));
457 struct ip *ip = (struct ip *)data;
458 if(ip->ip_p==IPPROTO_ICMP)
460 struct icmp *icmp = (struct icmp *)(ip+1);
461 if(icmp->icmp_type==ICMP_ECHOREPLY && icmp->icmp_id==pinger->id)
463 /* It's an ICMP echo reply and ours, process it */
467 inet_ntop(AF_INET, &addr.sin_addr, buf, sizeof(buf));
468 printf("Ping reply from %s\n", buf);
471 if(icmp->icmp_seq==pinger->pending)
474 printf("Sequence %d, expected %d\n", icmp->icmp_seq, pinger->pending);
480 if(time>=pinger->next)
486 printf("Lost ping\n");
490 pinger->next = time+1000000;
494 unsigned checksum(const char *data, unsigned len)
497 for(unsigned i=0; i<len; i+=2)
498 sum += *(const unsigned short *)(data+i);
500 sum = (sum>>16)+(sum&0xFFFF);
505 void send_ping(Pinger *pinger)
508 for(unsigned i=0; i<sizeof(data); ++i)
511 struct icmp *hdr = (struct icmp *)data;
512 hdr->icmp_type = ICMP_ECHO;
515 hdr->icmp_id = pinger->id;
516 hdr->icmp_seq = pinger->seq;
517 hdr->icmp_cksum = checksum(data, sizeof(data));
519 if(sendto(pinger->socket, data, sizeof(data), 0, (struct sockaddr *)&pinger->target_addr, sizeof(struct sockaddr_in))==-1)
520 fprintf(stderr, "sendto error: %s\n", strerror(errno));
522 pinger->pending = pinger->seq++;
528 pid_t run_command(const char *cmd)
538 execv(cmd, (char *const *)argv);