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[icmpmonitor] / icmpmonitor.c
/*
* 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
* See LICENSE file for copyright and license details.
*/
#include <sys/param.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <signal.h>
#include <string.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <stddef.h>
#include <errno.h>
#include "cfg.h"
/* return codes */
#define RET_OK 0
#define RET_NO_HOSTS 1
#define RET_INIT_ERROR 2
#define RET_BAD_CFG 3
#define RET_BAD_OPT 4
#define MAXPACKET (65536 - 60 - 8) /* max packet size */
#define DEFDATALEN (64 - 8) /* default data length */
#define VERSION "ICMPmonitor v1.2 by lord@crocodile.org"
# define icmphdr icmp
/* typedefs */
typedef struct monitor_host
{
/* following are coming from cfg */
char *name;
int ping_interval;
int max_delay;
char *upcmd;
char *downcmd;
/* following values are calculated */
int socket;
struct timeval last_ping_received;
struct timeval last_ping_sent;
int up;
int down;
struct sockaddr_in dest;
unsigned int sentpackets ;
unsigned int recvdpackets;
/* linked list */
struct monitor_host *next;
} monitor_host_t;
/* 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(u_short *addr, int len);
static void read_icmp_data(monitor_host_t *p);
static void tvsub(struct timeval *out, struct timeval *in);
static int gcd(int x, int y);
/* globals */
static monitor_host_t **hosts = NULL;
static int isVerbose = 0;
static int keepBanging = 0;
static unsigned short ident;
static int send_delay = 1;
int main(int ac, char **av)
{
extern char* optarg;
extern int optind;
char *cfgfile=NULL;
int param;
while((param = getopt(ac, av, "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;
(void)signal(SIGALRM, pinger);
alarm(send_delay);
get_response();
exit(EXIT_SUCCESS);
}
/*
* in_cksum --
* Checksum routine for Internet Protocol family headers (C Version)
*/
static int
in_cksum(u_short *addr, int len)
{
register int nleft = len;
register u_short *w = addr;
register int sum = 0;
u_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
* carry bits from the top 16 bits into the lower 16 bits.
*/
while (nleft > 1) {
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 */
answer = ~sum; /* truncate to 16 bits */
return(answer);
}
/*
* pinger --
* 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,
* and the sequence number is an ascending integer. The first 8 bytes
* of the data portion are used to hold a UNIX "timeval" struct in VAX
* byte-order, to compute the round-trip time.
*/
static void pinger(int ignore)
{
register struct icmphdr *icp;
register int cc;
int i;
monitor_host_t *p;
u_char outpack[MAXPACKET];
p=hosts[0];
while(p)
{
if(p->socket!=-1)
{
struct timeval now;
(void)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(!fork())
{
system(p->downcmd);
exit(0);
} else
{
wait(NULL);
}
}
}
(void)gettimeofday(&now,(struct timezone *)NULL);
tvsub(&now, &p->last_ping_sent);
if(now.tv_sec > p->ping_interval)
{
/* Time to send ping */
icp = (struct icmphdr *)outpack;
icp->icmp_type = ICMP_ECHO;
icp->icmp_code = 0;
icp->icmp_cksum = 0;
icp->icmp_seq = p->socket;
icp->icmp_id = ident;
if (isVerbose) printf("INFO: Sending ICMP packet to %s.\n", p->name);
(void)gettimeofday((struct timeval *)&outpack[8],
(struct timezone *)NULL);
cc = DEFDATALEN + 8; /* skips ICMP portion */
/* compute ICMP checksum here */
icp->icmp_cksum = in_cksum((u_short *)icp, cc);
i = sendto(p->socket, (char *)outpack, cc, 0, (const struct sockaddr *)(&p->dest),
sizeof(struct sockaddr));
(void)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->sentpackets++;
}
}
p=p->next;
}
(void)signal(SIGALRM, pinger); /* restore handler */
alarm(send_delay);
}
static void get_response(void)
{
fd_set rfds;
int retval;
monitor_host_t *p;
int maxd=-1;
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)
{
/* we get her in case we are interrupted by signal.
it's ok. */
}
else
{
if(retval>0)
{
p=hosts[0];
while(p)
{
if(p->socket!=-1 && FD_ISSET(p->socket, &rfds))
{
/* Read data */
read_icmp_data(p);
}
p=p->next;
}
} else {
/* TODO: How to handle this error? */
}
}
}
}
static void read_icmp_data(monitor_host_t *p)
{
socklen_t fromlen ;
struct sockaddr_in from ;
int cc ;
struct ip *ip ;
struct icmp *icmp ;
int iphdrlen ;
int delay ;
struct timeval tv ;
unsigned char buf[MAXPACKET]; /* read buffer */
(void)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 ;
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(!fork())
{
system(p->upcmd);
exit(0);
} else
{
wait(NULL);
}
}
} else {
/* TODO: Do anything here? */
}
}
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(monitor_host_t *) * cfg->nelements);
for (i=0; i<cfg->nelements; i++) {
if (cfg->dict[i]->nvalues < 4) {
fprintf(stderr, "ERROR: Not enough fields in record %d of cfg file. Got %d.\n", n, cfg->dict[i]->nvalues+1);
exit(EXIT_FAILURE);
} else if (cfg->dict[i]->nvalues>5) {
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(monitor_host_t));
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;
} else if(strcmp(cfg->dict[i]->value[4], "up")==0)
{
hosts[n]->down = 0;
hosts[n]->up = 1;
} else if(strcmp(cfg->dict[i]->value[4], "down")==0)
{
hosts[n]->down = 1;
hosts[n]->up = 0;
} 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;
} else {
fprintf(stderr, "ERROR: Illegal value %s in record %n for startup condition.\n", cfg->dict[i]->value[4], n);
exit(EXIT_FAILURE);
}
hosts[n]->sentpackets = 0;
hosts[n]->recvdpackets = 0;
hosts[n]->socket = -1;
hosts[n]->next = NULL;
if (n > 0) hosts[n-1]->next=hosts[n];
gettimeofday(&(hosts[n]->last_ping_received), (struct timezone *)NULL);
n++;
}
}
freecfg(cfg);
if (n <= 0) {
fprintf(stderr, "ERROR: No hosts defined in cfg file, exiting.\n");
exit(EXIT_FAILURE);
}
}
static int gethostaddr(const char *name)
{
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 void init_hosts(void)
{
monitor_host_t *p=hosts[0];
struct protoent *proto;
int ok=0;
if ((proto = getprotobyname("icmp")) == NULL) {
fprintf(stderr, "ERROR: Unknown protocol: icmp.\n");
exit(EXIT_FAILURE);
}
while(p) {
bzero(&p->dest,sizeof(p->dest));
p->dest.sin_family=AF_INET;
if((p->dest.sin_addr.s_addr=gethostaddr(p->name))<=0)
{
fprintf(stderr, "WARN: Can't resolve host. Skipping client %s.\n", p->name);
p->socket=-1;
} else
{
if((p->socket=socket(AF_INET,SOCK_RAW,proto->p_proto))<0)
{
fprintf(stderr, "WARN: Can't create socket. Skipping client %s.\n", p->name);
p->socket=-1;
} else
{
if(ok==0)
send_delay = p->ping_interval;
else
send_delay = gcd(send_delay, p->ping_interval);
ok++;
}
}
p=p->next;
}
if(!ok)
{
fprintf(stderr, "ERROR: No hosts left to process.\n");
exit(EXIT_FAILURE);
}
}
/*
* tvsub --
* Subtract 2 timeval structs: out = out - in. Out is assumed to
* be >= 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;
}
static int gcd(int x, int y)
{
int remainder = x % y;
if (remainder == 0) return y;
return gcd(y, remainder);
}
Monitor hosts via ICMP ping and execute user hooks when host goes up/down.