#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <errno.h>
+#include <assert.h>
#include "iniparser/iniparser.h"
#define MAXPACKETSIZE (65536 - 60 - 8) /* TODO: What are the magic numbers? */
#define DEFAULTDATALEN (64 - 8) /* TODO: What are the magic numbers? */
+/* ICMP header contains: type, code, checksum, identifier and sequence number. */
+#define ICMP_ECHO_HEADER_BYTES 8
+#define ICMP_ECHO_DATA_BYTES sizeof(struct timeval)
+#define ICMP_ECHO_PACKET_BYTES ICMP_ECHO_HEADER_BYTES + ICMP_ECHO_DATA_BYTES
+
+/* Minimum time in seconds between pings. If this value is increased above the */
+/* `ping_interval` for a given host, some pings to that host may not be sent. */
+#define TIMER_RESOLUTION 1
+
/* Must be larger than the length of the longest configuration key (currently 'start_condition'). */
#define MAXCONFKEYLEN 20
/* Globals */
/* Since the program is based around signals, a linked list of hosts is maintained here. */
static struct monitor_host * hosts = NULL;
- static int send_delay = 1;
/* Set by command line flags. */
static bool verbose = false;
static bool retry_down_cmd = false;
/*
- * Checksum routine for Internet Protocol family headers
+ * Generate an Internet Checksum per RFC 1071.
+ *
+ * This is not a general purpose implementation of RFC 1071. Since we only
+ * send ICMP echo packets, we assume 'data' will contain a specific number of
+ * bytes.
*/
-static int
-in_cksum(unsigned short * addr, int len)
+uint16_t
+checksum(uint16_t * data)
{
- int nleft = len;
- 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
- * 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;
+ uint32_t accumulator = 0;
+ for (size_t i = 0; i < ICMP_ECHO_PACKET_BYTES / 2; i++) {
+ accumulator += ntohs(data[i]);
+ if (accumulator > 0xffff) accumulator -= 0xffff;
}
-
- /* 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);
+ return htons(~accumulator);
}
/*
- * Subtracts two timeval structs.
- * Ensure out >= in.
- * Modifies out = out - in.
+ * Calculate difference between two timeval structs to within one second.
*/
-static void
-tv_sub(register struct timeval * out, register struct timeval * in)
+void
+timeval_diff(struct timeval * a, const struct timeval * b)
{
- if ((out->tv_usec -= in->tv_usec) < 0) {
- --out->tv_sec;
- out->tv_usec += 1000000;
- }
- out->tv_sec -= in->tv_sec;
+ assert(a->tv_sec >= b->tv_sec);
+ a->tv_sec -= b->tv_sec;
}
/*
int i;
struct icmp * icp;
struct monitor_host * p = hosts;
- u_char outpack[MAXPACKETSIZE];
+ unsigned char outpack[MAXPACKETSIZE]; /* Use char so this can be aliased later. */
while (p) {
if (p->socket != -1) {
struct timeval now;
gettimeofday(&now, (struct timezone *) NULL);
- tv_sub(&now, &p->last_ping_received);
+ timeval_diff(&now, &p->last_ping_received);
if (now.tv_sec > (p->max_delay + p->ping_interval)) {
if ((p->host_up) || retry_down_cmd) {
}
gettimeofday(&now, (struct timezone *) NULL);
- tv_sub(&now, &p->last_ping_sent);
+ timeval_diff(&now, &p->last_ping_sent);
if (now.tv_sec > p->ping_interval) { /* Time to send ping */
icp = (struct icmp *) outpack;
int cc = DEFAULTDATALEN + 8; /* skips ICMP portion */
- /* compute ICMP checksum */
- icp->icmp_cksum = in_cksum((unsigned short *) icp, cc);
+ icp->icmp_cksum = checksum((uint16_t *) outpack);
i = sendto(p->socket, (char *) outpack, cc, 0, (const struct sockaddr *) (&p->dest), sizeof(struct sockaddr));
}
signal(SIGALRM, pinger); /* restore handler */
- alarm(send_delay);
+ alarm(TIMER_RESOLUTION);
}
static void
memcpy(&p->last_ping_received, &tv, sizeof(tv));
- tv_sub(&tv, (struct timeval *) &icmp->icmp_data[0]);
+ timeval_diff(&tv, (struct timeval *) &icmp->icmp_data[0]);
delay = tv.tv_sec * 1000 + (tv.tv_usec / 1000);
- if (verbose) printf("INFO: Got ICMP reply from %s in %d ms.\n", p->name, delay);
+ if (verbose) printf("INFO: Got ICMP reply from %s.\n", p->name);
if (!p->host_up) {
if (verbose) printf("INFO: Host %s started responding. Executing UP command.\n", p->name);
p->host_up = true;
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);
+ //if (ok == 0) send_delay = p->ping_interval;
+ //else send_delay = gcd(send_delay, p->ping_interval);
ok++;
}
}
init_hosts();
signal(SIGALRM, pinger);
- alarm(send_delay);
+ alarm(TIMER_RESOLUTION);
get_response();