Eliminated send_delay global (file) variable.

[icmpmonitor] / icmpmonitor.c

diff --git a/icmpmonitor.c b/icmpmonitor.c
index bf5ab9b..f2bf43e 100644 (file)
--- a/icmpmonitor.c
+++ b/icmpmonitor.c
@@ -1,10 +1,13 @@
 /*
 /*

- * Monitor hosts using ICMP "echo" and notify when down.
- * TODO: Write a better description.
+ * ICMPmonitor
+ *
+ * Monitors hosts using ICMP 'echo', executing a user-specified command
+ * whenever hosts change state between responsive and unresponsive.

  *
  * © 2019 Aaron Taylor <ataylor at subgeniuskitty dot com>
  * © 1999 Vadim Zaliva <lord@crocodile.org>
  * © 1989 The Regents of the University of California & Mike Muuss
  *
  * © 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.
  */
 
  * See LICENSE file for copyright and license details.
  */
 


@@ -24,6 +27,8 @@
 #include <netinet/ip.h>
 #include <netinet/ip_icmp.h>
 #include <errno.h>
 #include <netinet/ip.h>
 #include <netinet/ip_icmp.h>
 #include <errno.h>

+#include <assert.h>
+

 #include "iniparser/iniparser.h"
 
 #define VERSION 2
 #include "iniparser/iniparser.h"
 
 #define VERSION 2


@@ -31,6 +36,15 @@
 #define MAXPACKETSIZE  (65536 - 60 - 8) /* TODO: What are the magic numbers? */
 #define DEFAULTDATALEN (64 - 8)         /* TODO: What are the magic numbers? */
 
 #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
 
 /* Must be larger than the length of the longest configuration key (currently 'start_condition'). */
 #define MAXCONFKEYLEN 20
 


@@ -49,70 +63,44 @@ struct monitor_host {
     struct timeval     last_ping_sent;
     bool               host_up;
     struct sockaddr_in dest;
     struct timeval     last_ping_sent;
     bool               host_up;
     struct sockaddr_in dest;

-    unsigned int       sent_packets;
-    unsigned int       recvd_packets;

 
 

-    /* TODO: Why are we using both a linked list AND an array for this data? */

     /* Linked list */
     struct monitor_host * next;
 };
 
 /* Globals */
     /* Since the program is based around signals, a linked list of hosts is maintained here. */
     /* Linked list */
     struct monitor_host * next;
 };
 
 /* Globals */
     /* Since the program is based around signals, a linked list of hosts is maintained here. */

-    static struct monitor_host ** hosts          = NULL;
+    static struct monitor_host * hosts          = NULL;

     /* Set by command line flags. */
     /* Set by command line flags. */

-    static bool                   verbose        = false;
-    static bool                   retry_down_cmd = false;
-    /* TODO: Get rid of this global. */
-    static int                    send_delay     = 1;
+    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;

 }
 
 /*
 }
 
 /*


@@ -125,18 +113,17 @@ tv_sub(register struct timeval * out, register struct timeval * in)
 static void
 pinger(int ignore)
 {
 static void
 pinger(int ignore)
 {

-    int cc, i;
+    int i;

     struct icmp * icp;
     struct icmp * icp;

-    struct monitor_host * p;
-    u_char outpack[MAXPACKETSIZE];
+    struct monitor_host * p = hosts;
+    unsigned char outpack[MAXPACKETSIZE]; /* Use char so this can be aliased later. */

 
 

-    p = hosts[0];

     while (p) {
         if (p->socket != -1) {
             struct timeval now;
 
             gettimeofday(&now, (struct timezone *) NULL);
     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) {
 
             if (now.tv_sec > (p->max_delay + p->ping_interval)) {
                 if ((p->host_up) || retry_down_cmd) {


@@ -152,7 +139,7 @@ pinger(int ignore)
             }
 
             gettimeofday(&now, (struct timezone *) NULL);
             }
 
             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;
 
             if (now.tv_sec > p->ping_interval) { /* Time to send ping */
                 icp = (struct icmp *) outpack;


@@ -166,10 +153,9 @@ pinger(int ignore)
 
                 gettimeofday((struct timeval *) &outpack[8], (struct timezone *) NULL);
 
 
                 gettimeofday((struct timeval *) &outpack[8], (struct timezone *) NULL);
 

-                cc = DEFAULTDATALEN + 8;  /* skips ICMP portion */
+                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));
 
 
                 i = sendto(p->socket, (char *) outpack, cc, 0, (const struct sockaddr *) (&p->dest), sizeof(struct sockaddr));
 


@@ -178,14 +164,13 @@ pinger(int ignore)
                 if (i < 0 || i != cc) {
                     if (i<0) fprintf(stderr, "WARN: Failed sending ICMP packet to %s.\n", p->name);
                 }
                 if (i < 0 || i != cc) {
                     if (i<0) fprintf(stderr, "WARN: Failed sending ICMP packet to %s.\n", p->name);
                 }

-                p->sent_packets++;

             }
         }
         p = p->next;
     }
 
     signal(SIGALRM, pinger); /* restore handler */
             }
         }
         p = p->next;
     }
 
     signal(SIGALRM, pinger); /* restore handler */

-    alarm(send_delay);
+    alarm(TIMER_RESOLUTION);

 }
 
 static void
 }
 
 static void


@@ -218,14 +203,13 @@ read_icmp_data(struct monitor_host * p)
     }
 
     if (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == (getpid() & 0xFFFF) && icmp->icmp_seq == p->socket) {
     }
 
     if (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == (getpid() & 0xFFFF) && icmp->icmp_seq == p->socket) {

-        p->recvd_packets++;

 
         memcpy(&p->last_ping_received, &tv, sizeof(tv));
 
 
         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);
 
         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;
         if (!p->host_up) {
             if (verbose) printf("INFO: Host %s started responding. Executing UP command.\n", p->name);
             p->host_up = true;


@@ -249,7 +233,7 @@ get_response(void)
     struct monitor_host * p;
 
     while (1) {
     struct monitor_host * p;
 
     while (1) {

-        p = hosts[0];
+        p = hosts;

         FD_ZERO(&rfds);
         while (p) {
             if (p->socket != -1) {
         FD_ZERO(&rfds);
         while (p) {
             if (p->socket != -1) {


@@ -264,7 +248,7 @@ get_response(void)
             /* Intentionally empty. We arrive here when interrupted by a signal. No action should be taken. */
         } else {
             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];
+                p = hosts;

                 while (p) {
                     if (p->socket!=-1 && FD_ISSET(p->socket, &rfds)) read_icmp_data(p);
                     p = p->next;
                 while (p) {
                     if (p->socket!=-1 && FD_ISSET(p->socket, &rfds)) read_icmp_data(p);
                     p = p->next;


@@ -291,7 +275,7 @@ parse_config(const char * conf_file)
         exit(EXIT_FAILURE);
     }
 
         exit(EXIT_FAILURE);
     }
 

-    hosts = malloc(sizeof(struct monitor_host *) * host_count);
+    struct monitor_host * host_list_end = NULL;

     for (int i=0; i < host_count; i++) {
         /* Allocate a reusable buffer large enough to hold the full 'section:key' string. */
         int section_len = strlen(iniparser_getsecname(conf, i));
     for (int i=0; i < host_count; i++) {
         /* Allocate a reusable buffer large enough to hold the full 'section:key' string. */
         int section_len = strlen(iniparser_getsecname(conf, i));


@@ -299,45 +283,52 @@ parse_config(const char * conf_file)
         strcpy(key_buf, iniparser_getsecname(conf, i));
         key_buf[section_len++] = ':';
 
         strcpy(key_buf, iniparser_getsecname(conf, i));
         key_buf[section_len++] = ':';
 

-        hosts[i] = malloc(sizeof(struct monitor_host));
+        struct monitor_host * cur_host = malloc(sizeof(struct monitor_host));

 
         key_buf[section_len] = '\0';
         strncat(key_buf, "host", MAXCONFKEYLEN);
 
         key_buf[section_len] = '\0';
         strncat(key_buf, "host", MAXCONFKEYLEN);

-        hosts[i]->name = strdup(iniparser_getstring(conf, key_buf, NULL));
+        cur_host->name = strdup(iniparser_getstring(conf, key_buf, NULL));

 
         key_buf[section_len] = '\0';
         strncat(key_buf, "interval", MAXCONFKEYLEN);
 
         key_buf[section_len] = '\0';
         strncat(key_buf, "interval", MAXCONFKEYLEN);

-        hosts[i]->ping_interval = iniparser_getint(conf, key_buf, -1);
+        cur_host->ping_interval = iniparser_getint(conf, key_buf, -1);

 
         key_buf[section_len] = '\0';
         strncat(key_buf, "max_delay", MAXCONFKEYLEN);
 
         key_buf[section_len] = '\0';
         strncat(key_buf, "max_delay", MAXCONFKEYLEN);

-        hosts[i]->max_delay = iniparser_getint(conf, key_buf, -1);
+        cur_host->max_delay = iniparser_getint(conf, key_buf, -1);

 
         key_buf[section_len] = '\0';
         strncat(key_buf, "up_cmd", MAXCONFKEYLEN);
 
         key_buf[section_len] = '\0';
         strncat(key_buf, "up_cmd", MAXCONFKEYLEN);

-        hosts[i]->up_cmd = strdup(iniparser_getstring(conf, key_buf, NULL));
+        cur_host->up_cmd = strdup(iniparser_getstring(conf, key_buf, NULL));

 
         key_buf[section_len] = '\0';
         strncat(key_buf, "down_cmd", MAXCONFKEYLEN);
 
         key_buf[section_len] = '\0';
         strncat(key_buf, "down_cmd", MAXCONFKEYLEN);

-        hosts[i]->down_cmd = strdup(iniparser_getstring(conf, key_buf, NULL));
+        cur_host->down_cmd = strdup(iniparser_getstring(conf, key_buf, NULL));

 
         key_buf[section_len] = '\0';
         /* TODO: Parse for up/down/auto in start_condition. */
         /* TODO: Do a host up/down check if necessary. */
 
         key_buf[section_len] = '\0';
         /* TODO: Parse for up/down/auto in start_condition. */
         /* TODO: Do a host up/down check if necessary. */

-        hosts[i]->host_up = true;
+        cur_host->host_up = true;

 
         /* TODO: Do I want to make any checks for start_condition? */
 
         /* TODO: Do I want to make any checks for start_condition? */

-        if (hosts[i]->name == NULL || hosts[i]->ping_interval == -1 || hosts[i]->max_delay == -1) {
+        if (cur_host->name == NULL || cur_host->ping_interval == -1 || cur_host->max_delay == -1) {

             fprintf(stderr, "ERROR: Problems parsing section %s.\n", iniparser_getsecname(conf, i));
             exit(EXIT_FAILURE);
         }
 
             fprintf(stderr, "ERROR: Problems parsing section %s.\n", iniparser_getsecname(conf, i));
             exit(EXIT_FAILURE);
         }
 

-        hosts[i]->sent_packets = 0;
-        hosts[i]->recvd_packets = 0;
-        hosts[i]->socket = -1;
-        hosts[i]->next = NULL;
-        if (i>0) hosts[i-1]->next = hosts[i];
-        gettimeofday(&(hosts[i]->last_ping_received), (struct timezone *) NULL);
+        cur_host->socket = -1;
+        cur_host->next = NULL;
+        gettimeofday(&(cur_host->last_ping_received), (struct timezone *) NULL);
+
+        if (hosts == NULL) {
+            hosts = cur_host;
+            host_list_end = cur_host;
+        } else {
+            host_list_end->next = cur_host;
+            host_list_end = cur_host;
+        }
+
+        free(key_buf);

     }
     iniparser_freedict(conf);
 }
     }
     iniparser_freedict(conf);
 }


@@ -367,7 +358,7 @@ gcd(int x, int y)
 static void
 init_hosts(void)
 {
 static void
 init_hosts(void)
 {

-    struct monitor_host * p = hosts[0];
+    struct monitor_host * p = hosts;

     struct protoent * proto;
     int ok = 0;
 
     struct protoent * proto;
     int ok = 0;
 


@@ -387,8 +378,8 @@ init_hosts(void)
                 fprintf(stderr, "WARN: Can't create socket. Skipping client %s.\n", p->name);
                 p->socket=-1;
             } else {
                 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++;
             }
         }
                 ok++;
             }
         }


@@ -450,7 +441,7 @@ main(int argc, char ** argv)
     init_hosts();
 
     signal(SIGALRM, pinger);
     init_hosts();
 
     signal(SIGALRM, pinger);

-    alarm(send_delay);
+    alarm(TIMER_RESOLUTION);

 
     get_response();
 
 
     get_response();