Rewrote get_host_addr() to use getaddrinfo().

[icmpmonitor] / icmpmonitor.c

diff --git a/icmpmonitor.c b/icmpmonitor.c
index cc141b5..6dede30 100644 (file)
--- a/icmpmonitor.c
+++ b/icmpmonitor.c
@@ -27,6 +27,7 @@
 #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"
 
 
 #include "iniparser/iniparser.h"
 


@@ -35,11 +36,20 @@
 #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
 
 /* One struct per host as listed in the config file. */
 /* Must be larger than the length of the longest configuration key (currently 'start_condition'). */
 #define MAXCONFKEYLEN 20
 
 /* One struct per host as listed in the config file. */

-struct monitor_host {
+struct host_entry {

     /* From the config file */
     char * name;
     int    ping_interval;
     /* From the config file */
     char * name;
     int    ping_interval;


@@ -55,64 +65,42 @@ struct monitor_host {
     struct sockaddr_in dest;
 
     /* Linked list */
     struct sockaddr_in dest;
 
     /* Linked list */

-    struct monitor_host * next;
+    struct host_entry * next;

 };
 
 /* 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 monitor_host * hosts          = NULL;
-    static int                   send_delay     = 1;
+    static struct host_entry * first_host_in_list = NULL;

     /* Set by command line flags. */
     static bool                  verbose        = false;
     static bool                  retry_down_cmd = false;
 
 /*
     /* 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(const 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;

 }
 
 /*
 }
 
 /*


@@ -127,15 +115,15 @@ pinger(int ignore)
 {
     int i;
     struct icmp * icp;
 {
     int i;
     struct icmp * icp;

-    struct monitor_host * p = hosts;
-    u_char outpack[MAXPACKETSIZE];
+    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);
 
     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) {


@@ -151,7 +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;


@@ -167,8 +155,7 @@ pinger(int ignore)
 
                 int 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));
 


@@ -183,11 +170,11 @@ pinger(int ignore)
     }
 
     signal(SIGALRM, pinger); /* restore handler */
     }
 
     signal(SIGALRM, pinger); /* restore handler */

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

 }
 
 static void
 }
 
 static void

-read_icmp_data(struct monitor_host * p)
+read_icmp_data(struct host_entry * p)

 {
     int cc, iphdrlen, delay;
     socklen_t fromlen;
 {
     int cc, iphdrlen, delay;
     socklen_t fromlen;


@@ -219,10 +206,10 @@ read_icmp_data(struct monitor_host * p)
 
         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;


@@ -243,10 +230,10 @@ get_response(void)
 {
     fd_set rfds;
     int retval, maxd = -1;
 {
     fd_set rfds;
     int retval, maxd = -1;

-    struct monitor_host * p;
+    struct host_entry * p;

 
     while (1) {
 
     while (1) {

-        p = hosts;
+        p = first_host_in_list;

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


@@ -261,7 +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;
+                p = first_host_in_list;

                 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;


@@ -288,7 +275,7 @@ parse_config(const char * conf_file)
         exit(EXIT_FAILURE);
     }
 
         exit(EXIT_FAILURE);
     }
 

-    struct monitor_host * host_list_end = NULL;
+    struct host_entry * 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));


@@ -296,7 +283,7 @@ 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++] = ':';
 

-        struct monitor_host * cur_host = malloc(sizeof(struct monitor_host));
+        struct host_entry * cur_host = malloc(sizeof(struct host_entry));

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


@@ -333,8 +320,8 @@ parse_config(const char * conf_file)
         cur_host->next = NULL;
         gettimeofday(&(cur_host->last_ping_received), (struct timezone *) NULL);
 
         cur_host->next = NULL;
         gettimeofday(&(cur_host->last_ping_received), (struct timezone *) NULL);
 

-        if (hosts == NULL) {
-            hosts = cur_host;
+        if (first_host_in_list == NULL) {
+            first_host_in_list = cur_host;

             host_list_end = cur_host;
         } else {
             host_list_end->next = cur_host;
             host_list_end = cur_host;
         } else {
             host_list_end->next = cur_host;


@@ -346,62 +333,84 @@ parse_config(const char * conf_file)
     iniparser_freedict(conf);
 }
 
     iniparser_freedict(conf);
 }
 

-static int
+/*
+ * Parse string (IP or hostname) to Internet address.
+ *
+ * Returns 0 if host can't be resolved, otherwise returns an Internet address.
+ */
+uint32_t

 get_host_addr(const char * name)
 {
 get_host_addr(const char * name)
 {

-    static int res;
-    struct hostent * host_ent;
-
-    if ((res = inet_addr(name)) < 0) {
-        host_ent = gethostbyname(name);
-        if (!host_ent) return -1;
-        memcpy(&res, host_ent->h_addr, host_ent->h_length);
-    }
-    return(res);
+    struct addrinfo hints;
+    memset(&hints, 0, sizeof(hints));
+    hints.ai_family = AF_INET;
+
+    int rv;
+    struct addrinfo * address;
+    if ((rv = getaddrinfo(name, NULL, &hints, &address)) != 0) return 0;
+    uint32_t result = ((struct sockaddr_in *)(address->ai_addr))->sin_addr.s_addr;
+    freeaddrinfo(address);
+    return result;

 }
 
 }
 

-static int
-gcd(int x, int y)
+size_t
+gcd(const size_t x, const size_t y)

 {
 {

-    int remainder = x % y;
+    size_t remainder = x % y;

     if (remainder == 0) return y;
     return gcd(y, remainder);
 }
 
     if (remainder == 0) return y;
     return gcd(y, remainder);
 }
 

-static void
+void
+remove_host_from_list(struct host_entry * host)
+{
+    assert(first_host_in_list);
+    assert(host);
+
+    if (host == first_host_in_list) {
+        first_host_in_list = host->next;
+    } else {
+        struct host_entry * temp = first_host_in_list;
+        while (temp->next != host && temp->next != NULL) temp = temp->next;
+        if (temp->next == NULL) return;
+        temp->next = temp->next->next;
+    }
+    free(host);
+}
+
+void

 init_hosts(void)
 {
 init_hosts(void)
 {

-    struct monitor_host * p = hosts;
+    struct host_entry * host;

     struct protoent * proto;
     struct protoent * proto;

-    int ok = 0;

 
     if ((proto = getprotobyname("icmp")) == NULL) {
         fprintf(stderr, "ERROR: Unknown protocol: icmp.\n");
         exit(EXIT_FAILURE);
     }
 
 
     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 = get_host_addr(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++;
-            }
+    assert(first_host_in_list);
+    host = first_host_in_list;
+    while (host) {
+        struct host_entry * next_host = host->next;
+        bzero(&host->dest, sizeof(host->dest));
+        host->dest.sin_family = AF_INET;
+        if (!(host->dest.sin_addr.s_addr = get_host_addr(host->name))) {
+            fprintf(stderr, "WARN: Removing unresolvable host %s from list.\n", host->name);
+            remove_host_from_list(host);

         }
         }

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

     }
 
     }
 

-    if (!ok) {
-        fprintf(stderr, "ERROR: No hosts left to process.\n");
-        exit(EXIT_FAILURE);
+    assert(first_host_in_list);
+    host = first_host_in_list;
+    while (host) {
+        struct host_entry * next_host = host->next;
+        if ((host->socket = socket(AF_INET, SOCK_RAW, proto->p_proto)) < 0) {
+            fprintf(stderr, "WARN: Failed creating socket. Removing host %s from list.\n", host->name);
+            remove_host_from_list(host);
+        }
+        host = next_host;

     }
 }
 
     }
 }
 


@@ -440,7 +449,7 @@ parse_params(int argc, char ** argv)
                 break;
         }
     }
                 break;
         }
     }

-    if (hosts == NULL) {
+    if (first_host_in_list == NULL) {

         fprintf(stderr, "ERROR: Unable to parse a config file.\n");
         exit(EXIT_FAILURE);
     }
         fprintf(stderr, "ERROR: Unable to parse a config file.\n");
         exit(EXIT_FAILURE);
     }


@@ -454,7 +463,7 @@ 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();