Rewrote the function that lists for responses to pings.

[icmpmonitor] / icmpmonitor.c

diff --git a/icmpmonitor.c b/icmpmonitor.c
index 898fc80..a53538f 100644 (file)
--- a/icmpmonitor.c
+++ b/icmpmonitor.c
@@ -171,89 +171,78 @@ pinger(int ignore) /* Dummy parameter since this function registers as a signal
     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. */

         }
     }
 }
         }
     }
 }