/*
* Monitor hosts using ICMP "echo" and notify when down.
- *
+ *
* © 2019 Aaron Taylor <ataylor at subgeniuskitty dot com>
* © 1999 Vadim Zaliva <lord@crocodile.org>
* © 1989 The Regents of the University of California & Mike Muuss
#include <stdio.h>
#include <stdlib.h>
+#include <stdbool.h>
#include <signal.h>
#include <string.h>
#include <sys/time.h>
int socket;
struct timeval last_ping_received;
struct timeval last_ping_sent;
- /* TODO: Replace the following two values with a single boolean */
- int up;
- int down;
+ bool hostup;
struct sockaddr_in dest;
unsigned int sentpackets;
unsigned int recvdpackets;
-
+
/* linked list */
struct monitor_host * next;
};
-/* protos */
-static int gethostaddr(const char * name);
-static void read_hosts(const char * cfg_file_name);
-static void init_hosts(void);
-static void get_response(void);
-static void pinger(int);
-static int in_cksum(unsigned short * addr, int len);
-static void read_icmp_data(struct monitor_host * p);
-static void tvsub(struct timeval * out, struct timeval * in);
-static int gcd(int x, int y);
-
/* globals */
static struct monitor_host ** hosts = NULL;
static int isVerbose = 0;
static unsigned short ident;
static int send_delay = 1;
-int
-main(int argc, char ** argv)
-{
- extern char * optarg;
- extern int optind;
- char * cfgfile = NULL;
- int param;
-
- while ((param = getopt(argc, argv, "rvf:")) != -1) {
- switch(param) {
- case 'v':
- isVerbose = 1;
- break;
- case 'r':
- keepBanging = 1;
- break;
- case 'f':
- cfgfile=strdup(optarg);
- break;
- default:
- fprintf(stderr,"Usage: icmpmonitor [-v] [-r] [-f cfgfile]\n");
- exit(EXIT_FAILURE);
- }
- }
-
- if (!cfgfile) {
- fprintf(stderr, "ERROR: No config file specified.\n");
- exit(EXIT_FAILURE);
- }
-
- read_hosts(cfgfile);
-
- init_hosts();
-
- ident = getpid() & 0xFFFF;
-
- signal(SIGALRM, pinger);
- alarm(send_delay);
-
- get_response();
-
- exit(EXIT_SUCCESS);
-}
-
/*
* Checksum routine for Internet Protocol family headers
*/
unsigned short * w = addr;
int sum = 0;
unsigned short answer = 0;
-
+
/*
* Our algorithm is simple, using a 32 bit accumulator (sum), we add
* sequential 16 bit words to it, and at the end, fold back all the
sum += *w++;
nleft -= 2;
}
-
+
/* mop up an odd byte, if necessary */
if (nleft == 1) {
*(u_char *)(&answer) = *(u_char *)w;
sum += answer;
}
-
+
/* add back carry outs from top 16 bits to low 16 bits */
sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
sum += (sum >> 16); /* add carry */
return(answer);
}
+/*
+ * Subtracts two timeval structs.
+ * Ensure out >= in.
+ * Modifies out = out - in.
+ */
+static void
+tvsub(register struct timeval * out, register struct timeval * in)
+{
+ if ((out->tv_usec -= in->tv_usec) < 0) {
+ --out->tv_sec;
+ out->tv_usec += 1000000;
+ }
+ out->tv_sec -= in->tv_sec;
+}
+
/*
* Compose and transmit an ICMP ECHO REQUEST packet. The IP packet
* will be added on by the kernel. The ID field is our UNIX process ID,
while (p) {
if (p->socket != -1) {
struct timeval now;
-
+
gettimeofday(&now, (struct timezone *) NULL);
tvsub(&now, &p->last_ping_received);
- if (now.tv_sec > (p->max_delay + p->ping_interval)) {
- p->up = 0;
- if ((!p->down) || keepBanging) {
- p->down = 1;
-
- if (isVerbose) printf("INFO: Host %s is down. Executing DOWN command.\n", p->name);
+ if (now.tv_sec > (p->max_delay + p->ping_interval)) {
+ if ((p->hostup) || keepBanging) {
+ if (isVerbose) printf("INFO: Host %s stopped responding. Executing DOWN command.\n", p->name);
+ p->hostup = false;
if (!fork()) {
system(p->downcmd);
exit(EXIT_SUCCESS);
}
}
}
-
+
gettimeofday(&now, (struct timezone *) NULL);
tvsub(&now, &p->last_ping_sent);
-
+
if (now.tv_sec > p->ping_interval) { /* Time to send ping */
icp = (struct icmp *) outpack;
icp->icmp_type = ICMP_ECHO;
icp->icmp_id = ident;
if (isVerbose) printf("INFO: Sending ICMP packet to %s.\n", p->name);
-
+
gettimeofday((struct timeval *) &outpack[8], (struct timezone *) NULL);
-
+
cc = DEFAULTDATALEN + 8; /* skips ICMP portion */
-
+
/* compute ICMP checksum */
icp->icmp_cksum = in_cksum((unsigned short *) icp, cc);
-
+
i = sendto(p->socket, (char *) outpack, cc, 0, (const struct sockaddr *) (&p->dest), sizeof(struct sockaddr));
-
+
gettimeofday(&p->last_ping_sent, (struct timezone *) NULL);
-
+
if (i < 0 || i != cc) {
if (i<0) fprintf(stderr, "WARN: Failed sending ICMP packet to %s.\n", p->name);
}
}
p = p->next;
}
-
+
signal(SIGALRM, pinger); /* restore handler */
alarm(send_delay);
}
-static void
-get_response(void)
-{
- fd_set rfds;
- int retval, maxd = -1;
- struct monitor_host * p;
-
- while (1) {
- p = hosts[0];
- FD_ZERO(&rfds);
- while (p) {
- if (p->socket != -1) {
- if (p->socket > maxd) maxd=p->socket;
- FD_SET(p->socket, &rfds);
- }
- p=p->next;
- }
-
- retval = select(maxd+1, &rfds, NULL, NULL, NULL);
- if (retval < 0) {
- /* Intentionally empty. We arrive here when interrupted by a signal. No action should be taken. */
- } else {
- if (retval > 0) {
- p = hosts[0];
- while (p) {
- if (p->socket!=-1 && FD_ISSET(p->socket, &rfds)) read_icmp_data(p);
- p = p->next;
- }
- } else {
- /* TODO: How to handle this error? */
- }
- }
- }
-}
-
static void
read_icmp_data(struct monitor_host * p)
{
struct sockaddr_in from;
struct ip * ip;
struct icmp * icmp;
- struct timeval tv ;
+ struct timeval tv;
unsigned char buf[MAXPACKETSIZE];
gettimeofday(&tv, (struct timezone *) NULL);
-
+
fromlen = sizeof(from);
if ((cc = recvfrom(p->socket, buf, sizeof(buf), 0, (struct sockaddr *)&from, &fromlen)) < 0) {
if (errno != EINTR) fprintf(stderr, "WARN: Error reading ICMP data from %s.\n", p->name);
return;
- }
+ }
- /* check IP header actual len */
- ip = (struct ip *) buf;
- iphdrlen = ip->ip_hl << 2;
+ /* check IP header actual len */
+ ip = (struct ip *) buf;
+ iphdrlen = ip->ip_hl << 2;
icmp = (struct icmp *) (buf + iphdrlen);
-
+
if (cc < iphdrlen + ICMP_MINLEN) {
fprintf(stderr, "WARN: Received short packet from %s.\n", p->name);
return;
}
-
+
if (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == ident && icmp->icmp_seq == p->socket) {
p->recvdpackets++;
memcpy(&p->last_ping_received, &tv, sizeof(tv));
-
+
tvsub(&tv, (struct timeval *) &icmp->icmp_data[0]);
delay = tv.tv_sec * 1000 + (tv.tv_usec / 1000);
-
+
if (isVerbose) printf("INFO: Got ICMP reply from %s in %d ms.\n", p->name, delay);
- p->down = 0;
- if (!p->up) {
- p->up = 1;
- if (isVerbose) printf("INFO: Host %s is up. Executing UP command.\n", p->name);
+ if (!p->hostup) {
+ if (isVerbose) printf("INFO: Host %s started responding. Executing UP command.\n", p->name);
+ p->hostup = true;
if (!fork()) {
system(p->upcmd);
exit(EXIT_SUCCESS);
}
}
+static void
+get_response(void)
+{
+ fd_set rfds;
+ int retval, maxd = -1;
+ struct monitor_host * p;
+
+ while (1) {
+ p = hosts[0];
+ FD_ZERO(&rfds);
+ while (p) {
+ if (p->socket != -1) {
+ if (p->socket > maxd) maxd=p->socket;
+ FD_SET(p->socket, &rfds);
+ }
+ p = p->next;
+ }
+
+ retval = select(maxd+1, &rfds, NULL, NULL, NULL);
+ if (retval < 0) {
+ /* Intentionally empty. We arrive here when interrupted by a signal. No action should be taken. */
+ } else {
+ if (retval > 0) {
+ p = hosts[0];
+ while (p) {
+ if (p->socket!=-1 && FD_ISSET(p->socket, &rfds)) read_icmp_data(p);
+ p = p->next;
+ }
+ } else {
+ /* TODO: How to handle this error? */
+ }
+ }
+ }
+}
+
static void
read_hosts(const char * cfg_file_name)
{
int i, n = 0;
struct Cfg * cfg;
-
+
if ((cfg = readcfg(cfg_file_name)) == NULL) {
fprintf(stderr, "ERROR: Failed to read config.\n");
exit(EXIT_FAILURE);
}
-
+
if (cfg->nelements) {
hosts = malloc(sizeof(struct monitor_host *) * cfg->nelements);
for (i = 0; i < cfg->nelements; i++) {
fprintf(stderr, "ERROR: Too many fields in record %d of cfg file. Got %d.\n", n, cfg->dict[i]->nvalues+1);
exit(EXIT_FAILURE);
}
-
+
hosts[n] = malloc(sizeof(struct monitor_host));
hosts[n]->name = strdup(cfg->dict[i]->name);
hosts[n]->ping_interval = atoi (cfg->dict[i]->value[0]);
hosts[n]->max_delay = atoi (cfg->dict[i]->value[1]);
hosts[n]->upcmd = strdup(cfg->dict[i]->value[2]);
hosts[n]->downcmd = strdup(cfg->dict[i]->value[3]);
-
+
if (cfg->dict[i]->nvalues == 4) {
- hosts[n]->down = 0;
- hosts[n]->up = 1;
+ hosts[n]->hostup = true;
} else if (strcmp(cfg->dict[i]->value[4], "up") == 0) {
- hosts[n]->down = 0;
- hosts[n]->up = 1;
+ hosts[n]->hostup = true;
} else if (strcmp(cfg->dict[i]->value[4], "down") == 0) {
- hosts[n]->down = 1;
- hosts[n]->up = 0;
+ hosts[n]->hostup = false;
} else if (strcmp(cfg->dict[i]->value[4], "auto") == 0) {
- hosts[n]->down = 1;
- hosts[n]->up = 1;
- } else if (strcmp(cfg->dict[i]->value[4], "none") == 0) {
- hosts[n]->down = 0;
- hosts[n]->up = 0;
+ /* TODO: Send a ping and set initial state accordingly. */
} else {
fprintf(stderr, "ERROR: Illegal value %s in record %d for startup condition.\n", cfg->dict[i]->value[4], n);
exit(EXIT_FAILURE);
gettimeofday(&(hosts[n]->last_ping_received), (struct timezone *)NULL);
n++;
- }
+ }
}
freecfg(cfg);
{
static int res;
struct hostent * he;
-
+
if ((res = inet_addr(name)) < 0) {
he = gethostbyname(name);
if (!he) return -1;
memcpy(&res, he->h_addr, he->h_length);
- }
+ }
return(res);
}
+static int
+gcd(int x, int y)
+{
+ int remainder = x % y;
+ if (remainder == 0) return y;
+ return gcd(y, remainder);
+}
+
static void
init_hosts(void)
{
fprintf(stderr, "ERROR: Unknown protocol: icmp.\n");
exit(EXIT_FAILURE);
}
-
+
while (p) {
bzero(&p->dest, sizeof(p->dest));
p->dest.sin_family = AF_INET;
}
}
-/*
- * Subtracts two timeval structs.
- * Ensure out >= in.
- * Modifies out = out - in.
- */
-static void
-tvsub(register struct timeval * out, register struct timeval * in)
+int
+main(int argc, char ** argv)
{
- if ((out->tv_usec -= in->tv_usec) < 0) {
- --out->tv_sec;
- out->tv_usec += 1000000;
+ extern char * optarg;
+ extern int optind;
+ char * cfgfile = NULL;
+ int param;
+
+ while ((param = getopt(argc, argv, "rvf:")) != -1) {
+ switch(param) {
+ case 'v':
+ isVerbose = 1;
+ break;
+ case 'r':
+ keepBanging = 1;
+ break;
+ case 'f':
+ cfgfile=strdup(optarg);
+ break;
+ default:
+ fprintf(stderr,"Usage: icmpmonitor [-v] [-r] [-f cfgfile]\n");
+ exit(EXIT_FAILURE);
+ }
}
- out->tv_sec -= in->tv_sec;
-}
-static int
-gcd(int x, int y)
-{
- int remainder = x % y;
- if (remainder == 0) return y;
- return gcd(y, remainder);
+ if (!cfgfile) {
+ fprintf(stderr, "ERROR: No config file specified.\n");
+ exit(EXIT_FAILURE);
+ }
+
+ read_hosts(cfgfile);
+
+ init_hosts();
+
+ ident = getpid() & 0xFFFF;
+
+ signal(SIGALRM, pinger);
+ alarm(send_delay);
+
+ get_response();
+
+ exit(EXIT_SUCCESS);
}
projects / icmpmonitor / commitdiff