main.c

   1 /*
   2 netmon - a simple network connectivity monitor
   3 Copyright © 2008-2016 Mikko Rasa, Mikkosoft Productions
   4 Distributed under the GPL
   5 */
   6
   7 #include <stdint.h>
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <unistd.h>
  12 #include <errno.h>
  13 #include <syslog.h>
  14 #include <sys/poll.h>
  15 #include <sys/socket.h>
  16 #include <sys/time.h>
  17 #include <sys/wait.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>
  23 #include <netdb.h>
  24 #include <arpa/inet.h>
  25 #include <pcap/pcap.h>
  26
  27 typedef unsigned long long Time;
  28
  29 typedef struct
  30 {
  31         struct sockaddr_storage address;
  32         struct sockaddr_storage mask;
  33 } Address;
  34
  35 typedef struct
  36 {
  37         char *interface_name;
  38         pcap_t *pcap;
  39         unsigned n_addresses;
  40         Address *addresses;
  41         Time last_receive;
  42         Time last_transmit;
  43         int connection_status;
  44         Time connection_down_time;
  45 } Monitor;
  46
  47 typedef struct
  48 {
  49         Monitor *monitor;
  50         Time delay;
  51         Time interval;
  52         const char *command;
  53         Time next;
  54         pid_t child_pid;
  55 } Trigger;
  56
  57 typedef struct
  58 {
  59         const char *target_name;
  60         struct sockaddr_in target_addr;
  61         int socket;
  62         struct pollfd pfd;
  63         Time next;
  64         uint16_t id;
  65         uint16_t seq;
  66         uint16_t pending;
  67         unsigned count;
  68         unsigned lost;
  69 } Pinger;
  70
  71 Time current_time();
  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 *);
  84
  85 int no_daemon;
  86 int verbose;
  87
  88 int main(int argc, char **argv)
  89 {
  90         Monitor monitor;
  91         Trigger trigger;
  92         Pinger pinger;
  93         int o;
  94         char *endp;
  95         Time stats_interval = 1800000000ULL;
  96
  97         no_daemon = 0;
  98         verbose = 0;
  99         monitor.interface_name = NULL;
 100         trigger.monitor = &monitor;
 101         trigger.delay = 60000000ULL;
 102         trigger.interval = 600000000ULL;
 103         pinger.target_name = NULL;
 104
 105         /* Parse options */
 106         while((o = getopt(argc, argv, "fvs:t:c:i:p:"))!=-1)
 107                 switch(o)
 108                 {
 109                 case 'f':
 110                         no_daemon = 1;
 111                         break;
 112                 case 'v':
 113                         verbose = 1;
 114                         break;
 115                 case 's':
 116                         stats_interval = strtoul(optarg, NULL, 10)*1000000;
 117                         break;
 118                 case 't':
 119                         trigger.delay = strtoul(optarg, &endp, 10)*1000000;
 120                         if(*endp==',')
 121                                 trigger.interval = strtoul(endp+1, NULL, 10)*1000000;
 122                         else
 123                                 trigger.interval = trigger.delay;
 124                         break;
 125                 case 'c':
 126                         trigger.command = optarg;
 127                         break;
 128                 case 'i':
 129                         monitor.interface_name = strdup(optarg);
 130                         break;
 131                 case 'p':
 132                         pinger.target_name = strdup(optarg);
 133                         break;
 134                 }
 135
 136         if(monitor.interface_name)
 137         {
 138                 monitor_init(&monitor);
 139
 140                 if(trigger.command)
 141                         trigger_init(&trigger);
 142         }
 143
 144         if(pinger.target_name)
 145                 pinger_init(&pinger);
 146
 147         if(!no_daemon && daemon(1, 0)==-1)
 148                 perror("daemon");
 149
 150         openlog("netmon", 0, LOG_LOCAL7);
 151
 152         Time next_stats = current_time()+stats_interval;
 153         while(1)
 154         {
 155                 Time time = current_time();
 156
 157                 if(monitor.interface_name)
 158                 {
 159                         monitor_check(&monitor, time);
 160
 161                         if(trigger.command)
 162                                 trigger_check(&trigger, time);
 163                 }
 164
 165                 if(pinger.target_name)
 166                 {
 167                         pinger_check(&pinger, time);
 168
 169                         if(time>=next_stats)
 170                         {
 171                                 if(pinger.count)
 172                                 {
 173                                         float loss_ratio = (float)pinger.lost/pinger.count;
 174                                         if(no_daemon)
 175                                                 printf("Packet loss: %.2f%%\n", loss_ratio*100);
 176                                         else
 177                                                 syslog(LOG_INFO, "Packet loss: %.2f%%", loss_ratio*100);
 178                                 }
 179
 180                                 pinger.count = 0;
 181                                 pinger.lost = 0;
 182                                 next_stats += stats_interval;
 183                         }
 184                 }
 185         }
 186
 187         closelog();
 188
 189         return 0;
 190 }
 191
 192 Time current_time()
 193 {
 194         struct timeval tv;
 195         gettimeofday(&tv, NULL);
 196         return tv.tv_sec*1000000ULL+tv.tv_usec;
 197 }
 198
 199 int monitor_init(Monitor *monitor)
 200 {
 201         char err[PCAP_ERRBUF_SIZE];
 202         pcap_if_t *devs;
 203         if(pcap_findalldevs(&devs, err)==-1)
 204         {
 205                 fprintf(stderr, "pcap_findalldevs: %s\n", err);
 206                 return -1;
 207         }
 208
 209         monitor->pcap = pcap_open_live(monitor->interface_name, 64, 0, 10, err);
 210         if(!monitor->pcap)
 211         {
 212                 fprintf(stderr, "pcap_findalldevs: %s\n", err);
 213                 return -1;
 214         }
 215
 216         if(pcap_setnonblock(monitor->pcap, 1, err)==-1)
 217         {
 218                 fprintf(stderr, "pcap_findalldevs: %s\n", err);
 219                 return -1;
 220         }
 221
 222         monitor->n_addresses = 0;
 223         monitor->addresses = NULL;
 224         for(pcap_if_t *d=devs; d; d=d->next)
 225                 for(pcap_addr_t *a=d->addresses; a; a=a->next)
 226                         if(a->addr->sa_family==AF_INET || a->addr->sa_family==AF_INET6)
 227                         {
 228                                 monitor->addresses = (Address *)realloc(monitor->addresses, (monitor->n_addresses+1)*sizeof(Address));
 229                                 unsigned size = (a->addr->sa_family==AF_INET6 ? sizeof(struct sockaddr_in6) : sizeof(struct sockaddr_in));
 230                                 memcpy(&monitor->addresses[monitor->n_addresses].address, a->addr, size);
 231                                 memcpy(&monitor->addresses[monitor->n_addresses].mask, a->netmask, size);
 232                                 ++monitor->n_addresses;
 233                         }
 234
 235         pcap_freealldevs(devs);
 236
 237         monitor->last_receive = 0;
 238         monitor->last_transmit = 0;
 239         monitor->connection_status = 1;
 240
 241         return 0;
 242 }
 243
 244 void monitor_check(Monitor *monitor, Time timestamp)
 245 {
 246         pcap_dispatch(monitor->pcap, -1, &capture_handler, (uint8_t *)monitor);
 247
 248         if(monitor->last_transmit && monitor->last_receive)
 249         {
 250                 /* If packets have been transmitted more recently than received, there
 251                 might be a problem */
 252                 if(monitor->last_transmit>monitor->last_receive)
 253                 {
 254                         if(monitor->connection_status && timestamp>=monitor->last_receive+10000000)
 255                         {
 256                                 monitor->connection_status = 0;
 257                                 monitor->connection_down_time = monitor->last_receive;
 258                                 if(no_daemon)
 259                                         printf("Connection is down\n");
 260                                 else
 261                                         syslog(LOG_INFO, "Connection is down");
 262                         }
 263                 }
 264                 else if(!monitor->connection_status)
 265                 {
 266                         Time duration = timestamp-monitor->connection_down_time;
 267                         monitor->connection_status = 1;
 268                         if(no_daemon)
 269                                 printf("Connection is up (was down for %lld seconds)\n", duration/1000000);
 270                         else
 271                                 syslog(LOG_INFO, "Connection is up (was down for %lld seconds)", duration/1000000);
 272                 }
 273         }
 274 }
 275
 276 void capture_handler(uint8_t *user, const struct pcap_pkthdr *header, const uint8_t *data)
 277 {
 278         Monitor *monitor = (Monitor *)user;
 279         const struct ether_header *eth = (const struct ether_header *)(data);
 280
 281         int src_scope = 0;
 282         int dst_scope = 0;
 283         int proto = ntohs(eth->ether_type);
 284         if(proto==ETHERTYPE_IP)
 285         {
 286                 const struct ip *ip = (const struct ip *)(eth+1);
 287                 if(ntohl(ip->ip_dst.s_addr)>>28==14)
 288                         dst_scope = 3;
 289
 290                 for(unsigned i=0; i<monitor->n_addresses; ++i)
 291                         if(monitor->addresses[i].address.ss_family==AF_INET)
 292                         {
 293                                 int s = get_inet_scope(ip->ip_src.s_addr, &monitor->addresses[i]);
 294                                 if(s>src_scope)
 295                                         src_scope = s;
 296
 297                                 s = get_inet_scope(ip->ip_dst.s_addr, &monitor->addresses[i]);
 298                                 if(s>dst_scope)
 299                                         dst_scope = s;
 300                         }
 301         }
 302         else if(proto==ETHERTYPE_IPV6)
 303         {
 304                 const struct ip6_hdr *ip6 = (const struct ip6_hdr *)(eth+1);
 305                 for(unsigned i=0; i<monitor->n_addresses; ++i)
 306                         if(monitor->addresses[i].address.ss_family==AF_INET6)
 307                         {
 308                                 int s = get_inet6_scope(&ip6->ip6_src, &monitor->addresses[i]);
 309                                 if(s>src_scope)
 310                                         src_scope = s;
 311
 312                                 s = get_inet6_scope(&ip6->ip6_dst, &monitor->addresses[i]);
 313                                 if(s>dst_scope)
 314                                         dst_scope = s;
 315                         }
 316         }
 317
 318         Time timestamp = header->ts.tv_sec*1000000ULL+header->ts.tv_usec;
 319         if(src_scope==0 && dst_scope>0)
 320                 monitor->last_receive = timestamp;
 321         else if(src_scope>0 && dst_scope==0)
 322                 monitor->last_transmit = timestamp;
 323 }
 324
 325 int trigger_init(Trigger *trigger)
 326 {
 327         trigger->next = trigger->delay;
 328         trigger->child_pid = 0;
 329
 330         return 0;
 331 }
 332
 333 void trigger_check(Trigger *trigger, Time time)
 334 {
 335         Monitor *monitor = trigger->monitor;
 336
 337         if(monitor->connection_status)
 338                 trigger->next = trigger->delay;
 339         else if(time>=monitor->last_receive+trigger->next)
 340         {
 341                 if(no_daemon)
 342                         printf("Running %s\n", trigger->command);
 343                 else
 344                         syslog(LOG_INFO, "Running %s", trigger->command);
 345                 trigger->child_pid = run_command(trigger->command);
 346                 trigger->next += trigger->interval;
 347         }
 348
 349         /* Reap any finished child process */
 350         if(trigger->child_pid)
 351         {
 352                 if(waitpid(trigger->child_pid, NULL, WNOHANG)==trigger->child_pid)
 353                         trigger->child_pid = 0;
 354         }
 355 }
 356
 357 int get_inet_scope(uint32_t addr, const Address *local_addr)
 358 {
 359         uint32_t diff = addr^((struct sockaddr_in *)&local_addr->address)->sin_addr.s_addr;
 360         if(!diff)
 361                 return 2;
 362         else if(!(diff&((struct sockaddr_in *)&local_addr->mask)->sin_addr.s_addr))
 363                 return 1;
 364         else
 365                 return 0;
 366 }
 367
 368 int get_inet6_scope(const struct in6_addr *addr, const Address *local_addr)
 369 {
 370         int result = 2;
 371         for(unsigned i=0; i<16; ++i)
 372         {
 373                 uint8_t diff = addr->s6_addr[i]^((struct sockaddr_in6 *)&local_addr->address)->sin6_addr.s6_addr[i];
 374                 if(diff)
 375                 {
 376                         diff &= ((struct sockaddr_in6 *)&local_addr->mask)->sin6_addr.s6_addr[i];
 377                         if(diff)
 378                                 return 0;
 379                         else
 380                                 result = 1;
 381                 }
 382         }
 383
 384         return result;
 385 }
 386
 387 int pinger_init(Pinger *pinger)
 388 {
 389         if(!pinger->target_name)
 390                 return -1;
 391
 392         struct hostent *host;
 393
 394         host = gethostbyname(pinger->target_name);
 395         if(!host)
 396         {
 397                 herror("gethostbyname");
 398                 return -1;
 399         }
 400
 401         if(host->h_addrtype!=AF_INET)
 402         {
 403                 fprintf(stderr, "Got a hostent, but it doesn't have an IPv4 address");
 404                 return -1;
 405         }
 406
 407         pinger->target_addr.sin_family = AF_INET;
 408         pinger->target_addr.sin_addr = *(struct in_addr *)host->h_addr_list[0];
 409
 410         if(verbose)
 411         {
 412                 char buf[64];
 413                 inet_ntop(AF_INET, &pinger->target_addr.sin_addr, buf, sizeof(buf));
 414                 printf("Ping target is %s\n", buf);
 415         }
 416
 417         pinger->socket = socket(PF_INET, SOCK_RAW, IPPROTO_ICMP);
 418         if(pinger->socket==-1)
 419         {
 420                 perror("socket");
 421                 return -1;
 422         }
 423
 424         pinger->next = 0;
 425         pinger->id = getpid();
 426         pinger->seq = 1;
 427         pinger->pending = 0;
 428         pinger->count = 0;
 429         pinger->lost = 0;
 430
 431         pinger->pfd.fd = pinger->socket;
 432         pinger->pfd.events = POLLIN;
 433
 434         return 0;
 435 }
 436
 437 void pinger_check(Pinger *pinger, Time time)
 438 {
 439         if(poll(&pinger->pfd, 1, 10)>0)
 440         {
 441                 struct sockaddr_in addr;
 442                 socklen_t alen = sizeof(addr);
 443
 444                 /* Receive a packet */
 445                 char data[1500];
 446                 int len = recvfrom(pinger->socket, data, sizeof(data), 0, (struct sockaddr *)&addr, &alen);
 447                 if(len==-1)
 448                         fprintf(stderr, "recvfrom error: %s\n", strerror(errno));
 449                 else
 450                 {
 451                         struct ip *ip = (struct ip *)data;
 452                         if(ip->ip_p==IPPROTO_ICMP)
 453                         {
 454                                 struct icmp *icmp = (struct icmp *)(ip+1);
 455                                 if(icmp->icmp_type==ICMP_ECHOREPLY && icmp->icmp_id==pinger->id)
 456                                 {
 457                                         /* It's an ICMP echo reply and ours, process it */
 458                                         if(verbose)
 459                                         {
 460                                                 char buf[64];
 461                                                 inet_ntop(AF_INET, &addr.sin_addr, buf, sizeof(buf));
 462                                                 printf("Ping reply from %s\n", buf);
 463                                         }
 464
 465                                         if(icmp->icmp_seq==pinger->pending)
 466                                                 pinger->pending = 0;
 467                                         else if(verbose)
 468                                                 printf("Sequence %d, expected %d\n", icmp->icmp_seq, pinger->pending);
 469                                 }
 470                         }
 471                 }
 472         }
 473
 474         if(time>=pinger->next)
 475         {
 476                 if(pinger->pending)
 477                 {
 478                         ++pinger->lost;
 479                         if(verbose)
 480                                 printf("Lost ping\n");
 481                 }
 482
 483                 send_ping(pinger);
 484                 pinger->next = time+1000000;
 485         }
 486 }
 487
 488 unsigned checksum(const char *data, unsigned len)
 489 {
 490         unsigned        sum = 0;
 491         for(unsigned i=0; i<len; i+=2)
 492                 sum += *(const unsigned short *)(data+i);
 493         while(sum>0xFFFF)
 494                 sum = (sum>>16)+(sum&0xFFFF);
 495
 496         return ~sum;
 497 }
 498
 499 void send_ping(Pinger *pinger)
 500 {
 501         char data[64];
 502         for(unsigned i=0; i<sizeof(data); ++i)
 503                 data[i] = i;
 504
 505         struct icmp *hdr = (struct icmp *)data;
 506         hdr->icmp_type = ICMP_ECHO;
 507         hdr->icmp_code = 0;
 508         hdr->icmp_cksum = 0;
 509         hdr->icmp_id = pinger->id;
 510         hdr->icmp_seq = pinger->seq;
 511         hdr->icmp_cksum = checksum(data, sizeof(data));
 512
 513         if(sendto(pinger->socket, data, sizeof(data), 0, (struct sockaddr *)&pinger->target_addr, sizeof(struct sockaddr_in))==-1)
 514                 fprintf(stderr, "sendto error: %s\n", strerror(errno));
 515
 516         pinger->pending = pinger->seq++;
 517         if(!pinger->seq)
 518                 ++pinger->seq;
 519         ++pinger->count;
 520 }
 521
 522 pid_t run_command(const char *cmd)
 523 {
 524         pid_t pid;
 525
 526         pid = fork();
 527         if(pid==0)
 528         {
 529                 const char *argv[2];
 530                 argv[0] = cmd;
 531                 argv[1] = 0;
 532                 execv(cmd, (char *const *)argv);
 533                 exit(127);
 534         }
 535         else
 536                 return pid;
 537 }