Removed gcd().

[icmpmonitor] / icmpmonitor.c

diff --git a/icmpmonitor.c b/icmpmonitor.c
index efa6d71..f7e4a47 100644 (file)
--- a/icmpmonitor.c
+++ b/icmpmonitor.c
@@ -39,20 +39,19 @@
 
 #define VERSION 2
 
 
 #define VERSION 2
 

-#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
 /* 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

+#define IP_PACKET_MAX_BYTES     65535

 
 /* 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
 
 
 /* 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 (not value). */
+/* For example: MAX_CONF_KEY_LEN > strlen("start_condition")                    */
+#define MAX_CONF_KEY_LEN       20

 
 /* One struct per host as listed in the config file. */
 struct host_entry {
 
 /* One struct per host as listed in the config file. */
 struct host_entry {


@@ -76,10 +75,10 @@ struct host_entry {
 
 /* Globals */
     /* Since the program is based around signals, a linked list of hosts is maintained here. */
 
 /* Globals */
     /* Since the program is based around signals, a linked list of hosts is maintained here. */

-    static struct host_entry * first_host_in_list = NULL;
+    struct host_entry * first_host_in_list = NULL;

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

-    static bool                  verbose        = false;
-    static bool                  retry_down_cmd = false;
+    bool                verbose            = false;
+    bool                retry_down_cmd     = false;

 
 /*
  * Generate an Internet Checksum per RFC 1071.
 
 /*
  * Generate an Internet Checksum per RFC 1071.


@@ -100,173 +99,158 @@ checksum(const uint16_t * data)
 }
 
 /*
 }
 
 /*

- * Calculate difference between two timeval structs to within one second.
+ * Calculate difference (a-b) between two timeval structs.

  */
 void
 timeval_diff(struct timeval * a, const struct timeval * b)
 {
  */
 void
 timeval_diff(struct timeval * a, const struct timeval * b)
 {

-    assert(a->tv_sec >= b->tv_sec);
+    if (a->tv_usec < b->tv_usec) {
+        a->tv_sec--;
+        a->tv_usec += 1000000;
+    }
+    a->tv_usec -= b->tv_usec;

     a->tv_sec -= b->tv_sec;
 }
 
 /*
     a->tv_sec -= b->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,
- * 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.
+ * This function iterates over the list of hosts, pinging any which are due.

  */
  */

-static void
-pinger(int ignore)
+void
+pinger(int ignore) /* Dummy parameter since this function registers as a signal handler. */

 {
 {

-    int i;
-    struct icmp * icp;
-    struct host_entry * p = first_host_in_list;
-    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);
-            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 (verbose) printf("INFO: Host %s stopped responding. Executing DOWN command.\n", p->name);
-                    p->host_up = false;
-                    if (!fork()) {
-                        system(p->down_cmd);
-                        exit(EXIT_SUCCESS);
-                    } else {
-                        wait(NULL);
-                    }
-                }
-            }
+    assert(first_host_in_list);

 
 

-            gettimeofday(&now, (struct timezone *) NULL);
-            timeval_diff(&now, &p->last_ping_sent);
+    struct icmp * icmp_packet;
+    struct host_entry * host = first_host_in_list;
+    unsigned char packet[IP_PACKET_MAX_BYTES]; /* Use char so this can be aliased later. */

 
 

-            if (now.tv_sec > p->ping_interval) { /* Time to send ping */
-                icp = (struct icmp *) outpack;
-                icp->icmp_type  = ICMP_ECHO;
-                icp->icmp_code  = 0;
-                icp->icmp_cksum = 0;
-                icp->icmp_seq   = p->socket;
-                icp->icmp_id    = getpid() & 0xFFFF;
+    while (host) {
+        struct timeval elapsed_time;
+        gettimeofday(&elapsed_time, NULL);
+        timeval_diff(&elapsed_time, &host->last_ping_received);

 
 

-                if (verbose) printf("INFO: Sending ICMP packet to %s.\n", p->name);
+        if ((elapsed_time.tv_sec > host->max_delay) && (host->host_up || retry_down_cmd)) {
+            if (verbose) printf("INFO: Host %s stopped responding. Executing DOWN command.\n", host->name);
+            host->host_up = false;
+            if (!fork()) {
+                system(host->down_cmd);
+                exit(EXIT_SUCCESS);
+            }
+        }

 
 

-                gettimeofday((struct timeval *) &outpack[8], (struct timezone *) NULL);
+        if (elapsed_time.tv_sec > host->ping_interval) {
+            if (verbose) printf("INFO: Sending ICMP packet to %s.\n", host->name);

 
 

-                int cc = DEFAULTDATALEN + 8;  /* skips ICMP portion */
+            icmp_packet = (struct icmp *) packet;
+            icmp_packet->icmp_type  = ICMP_ECHO;
+            icmp_packet->icmp_code  = 0;
+            icmp_packet->icmp_cksum = 0;
+            icmp_packet->icmp_seq   = host->socket;
+            icmp_packet->icmp_id    = getpid() & 0xFFFF;

 
 

-                icp->icmp_cksum = checksum((uint16_t *) outpack);
+            /* Write a timestamp struct in the packet's data segment for use in calculating travel times. */
+            gettimeofday((struct timeval *) &packet[ICMP_ECHO_HEADER_BYTES], NULL);

 
 

-                i = sendto(p->socket, (char *) outpack, cc, 0, (const struct sockaddr *) (&p->dest), sizeof(struct sockaddr));
+            icmp_packet->icmp_cksum = checksum((uint16_t *) packet);

 
 

-                gettimeofday(&p->last_ping_sent, (struct timezone *) NULL);
+            size_t bytes_sent = sendto(host->socket, packet, ICMP_ECHO_PACKET_BYTES, 0,
+                                       (const struct sockaddr *) &host->dest,
+                                       sizeof(struct sockaddr));

 
 

-                if (i < 0 || i != cc) {
-                    if (i<0) fprintf(stderr, "WARN: Failed sending ICMP packet to %s.\n", p->name);
-                }
+            if (bytes_sent == ICMP_ECHO_PACKET_BYTES) {
+                gettimeofday(&host->last_ping_sent, NULL);
+            } else {
+                fprintf(stderr, "WARN: Failed sending ICMP packet to %s.\n", host->name);

             }
         }
             }
         }

-        p = p->next;
+        host = host->next;

     }
 
     }
 

-    signal(SIGALRM, pinger); /* restore handler */
+    signal(SIGALRM, pinger);

     alarm(TIMER_RESOLUTION);
 }
 
     alarm(TIMER_RESOLUTION);
 }
 

-static void
-read_icmp_data(struct host_entry * p)
+void
+read_icmp_data(struct host_entry * host)

 {
 {

-    int cc, iphdrlen, delay;
-    socklen_t fromlen;
-    struct sockaddr_in from;
-    struct ip * ip;
-    struct icmp * icmp;
-    struct timeval tv;
-    unsigned char buf[MAXPACKETSIZE];
+    struct timeval now;
+    gettimeofday(&now, NULL);

 
 

-    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);
+    struct sockaddr_in from;
+    socklen_t fromlen = sizeof(from);
+    int bytes;
+    unsigned char packet[IP_PACKET_MAX_BYTES]; /* Use char so this can be aliased later. */
+    if ((bytes = recvfrom(host->socket, packet, sizeof(packet), 0, (struct sockaddr *) &from, &fromlen)) < 0) {
+        if (errno != EINTR) fprintf(stderr, "WARN: Error reading ICMP data from %s.\n", host->name);

         return;
     }
 
         return;
     }
 

-    /* check IP header actual len */
-    ip       = (struct ip *) buf;
-    iphdrlen = ip->ip_hl << 2;
-    icmp     = (struct icmp *) (buf + iphdrlen);
+    struct ip * ip     = (struct ip *) packet;
+    int iphdrlen       = ip->ip_hl << 2;
+    struct icmp * icmp = (struct icmp *) (packet + iphdrlen);

 
 

-    if (cc < iphdrlen + ICMP_MINLEN) {
-        fprintf(stderr, "WARN: Received short packet from %s.\n", p->name);
+    if (bytes < iphdrlen + ICMP_MINLEN) {
+        fprintf(stderr, "WARN: Received short packet from %s.\n", host->name);

         return;
     }
 
         return;
     }
 

-    if (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == (getpid() & 0xFFFF) && icmp->icmp_seq == p->socket) {
-
-        memcpy(&p->last_ping_received, &tv, sizeof(tv));
-
-        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.\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 (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == (getpid() & 0xFFFF) && icmp->icmp_seq == host->socket) {
+        memcpy(&host->last_ping_received, &now, sizeof(now));
+        if (verbose) printf("INFO: Got ICMP reply from %s.\n", host->name);
+        if (!host->host_up) {
+            if (verbose) printf("INFO: Host %s started responding. Executing UP command.\n", host->name);
+            host->host_up = true;

             if (!fork()) {
             if (!fork()) {

-                system(p->up_cmd);
+                system(host->up_cmd);

                 exit(EXIT_SUCCESS);
                 exit(EXIT_SUCCESS);

-            } else {
-                wait(NULL);

             }
         }
     } else {
             }
         }
     } else {

-        /* TODO: Do anything here? */
+        /* The packet isn't what we expected. Ignore it and move on. */

     }
 }
 
     }
 }
 

-static void
+/*
+ * This function contains the main program loop, listening for replies to pings
+ * sent from the signal-driven pinger().
+ */
+void

 get_response(void)
 {
 get_response(void)
 {

-    fd_set rfds;
-    int retval, maxd = -1;
-    struct host_entry * p;
-
-    while (1) {
-        p = first_host_in_list;
+    while (true) {
+        fd_set rfds;

         FD_ZERO(&rfds);
         FD_ZERO(&rfds);

-        while (p) {
-            if (p->socket != -1) {
-                if (p->socket > maxd) maxd = p->socket;
-                FD_SET(p->socket, &rfds);
-            }
-            p = p->next;
+
+        assert(first_host_in_list);
+        struct host_entry * host = first_host_in_list;
+
+        int max_fd = -1;
+        while (host) {
+            if (host->socket > max_fd) max_fd = host->socket;
+            FD_SET(host->socket, &rfds);
+            host = host->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 = first_host_in_list;
-                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? */
+        int retval;
+        if ((retval = select(max_fd+1, &rfds, NULL, NULL, NULL)) > 0) {
+            assert(first_host_in_list);
+            host = first_host_in_list;
+            while (host) {
+                if (FD_ISSET(host->socket, &rfds)) read_icmp_data(host);
+                host = host->next;

             }
             }

+        } else {
+            /* An error or interruption occurred.                    */
+            /* We can't do anything about it, so loop and try again. */

         }
     }
 }
 
         }
     }
 }
 

-static void
+/*
+ * Parse a configuration file using the `iniparser` library.
+ * See `icmpmonitor.ini` and `README.md` for examples and reference.
+ */
+void

 parse_config(const char * conf_file)
 {
     dictionary * conf = iniparser_load(conf_file);
 parse_config(const char * conf_file)
 {
     dictionary * conf = iniparser_load(conf_file);


@@ -285,38 +269,37 @@ parse_config(const char * conf_file)
     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));

-        char * key_buf = malloc(section_len + 1 + MAXCONFKEYLEN + 1);
+        char * key_buf = malloc(section_len + 1 + MAX_CONF_KEY_LEN + 1); /* +1 for ':' and '\0' */

         strcpy(key_buf, iniparser_getsecname(conf, i));
         key_buf[section_len++] = ':';
 
         struct host_entry * cur_host = malloc(sizeof(struct host_entry));
 
         key_buf[section_len] = '\0';
         strcpy(key_buf, iniparser_getsecname(conf, i));
         key_buf[section_len++] = ':';
 
         struct host_entry * cur_host = malloc(sizeof(struct host_entry));
 
         key_buf[section_len] = '\0';

-        strncat(key_buf, "host", MAXCONFKEYLEN);
+        strncat(key_buf, "host", MAX_CONF_KEY_LEN);

         cur_host->name = strdup(iniparser_getstring(conf, key_buf, NULL));
 
         key_buf[section_len] = '\0';
         cur_host->name = strdup(iniparser_getstring(conf, key_buf, NULL));
 
         key_buf[section_len] = '\0';

-        strncat(key_buf, "interval", MAXCONFKEYLEN);
+        strncat(key_buf, "interval", MAX_CONF_KEY_LEN);

         cur_host->ping_interval = iniparser_getint(conf, key_buf, -1);
 
         key_buf[section_len] = '\0';
         cur_host->ping_interval = iniparser_getint(conf, key_buf, -1);
 
         key_buf[section_len] = '\0';

-        strncat(key_buf, "max_delay", MAXCONFKEYLEN);
+        strncat(key_buf, "max_delay", MAX_CONF_KEY_LEN);

         cur_host->max_delay = iniparser_getint(conf, key_buf, -1);
 
         key_buf[section_len] = '\0';
         cur_host->max_delay = iniparser_getint(conf, key_buf, -1);
 
         key_buf[section_len] = '\0';

-        strncat(key_buf, "up_cmd", MAXCONFKEYLEN);
+        strncat(key_buf, "up_cmd", MAX_CONF_KEY_LEN);

         cur_host->up_cmd = strdup(iniparser_getstring(conf, key_buf, NULL));
 
         key_buf[section_len] = '\0';
         cur_host->up_cmd = strdup(iniparser_getstring(conf, key_buf, NULL));
 
         key_buf[section_len] = '\0';

-        strncat(key_buf, "down_cmd", MAXCONFKEYLEN);
+        strncat(key_buf, "down_cmd", MAX_CONF_KEY_LEN);

         cur_host->down_cmd = strdup(iniparser_getstring(conf, key_buf, NULL));
 
         key_buf[section_len] = '\0';
         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. */
-        cur_host->host_up = true;
+        strncat(key_buf, "start_condition", MAX_CONF_KEY_LEN);
+        const char * value = iniparser_getstring(conf, key_buf, NULL);
+        if (value) cur_host->host_up = *value == 'u' ? true : false;

 
 

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

         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);
         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);


@@ -359,14 +342,6 @@ get_host_addr(const char * name)
     return result;
 }
 
     return result;
 }
 

-size_t
-gcd(const size_t x, const size_t y)
-{
-    size_t remainder = x % y;
-    if (remainder == 0) return y;
-    return gcd(y, remainder);
-}
-

 void
 remove_host_from_list(struct host_entry * host)
 {
 void
 remove_host_from_list(struct host_entry * host)
 {