X-Git-Url: http://git.subgeniuskitty.com/icmpmonitor/.git/blobdiff_plain/d1e434e73890522c37c0f81f6ab8da0ccc1d9f0c..3900fd4332290428dea7ffaa693887e5f23f1a89:/icmpmonitor.c diff --git a/icmpmonitor.c b/icmpmonitor.c index bf5ab9b..f2bf43e 100644 --- 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 * © 1999 Vadim Zaliva * © 1989 The Regents of the University of California & Mike Muuss + * * See LICENSE file for copyright and license details. */ @@ -24,6 +27,8 @@ #include #include #include +#include + #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? */ +/* 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 @@ -49,70 +63,44 @@ struct monitor_host { 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. */ - static struct monitor_host ** hosts = NULL; + static struct monitor_host * hosts = NULL; /* 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) { - int cc, i; + int i; 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); - 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) { @@ -152,7 +139,7 @@ pinger(int ignore) } 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; @@ -166,10 +153,9 @@ pinger(int ignore) 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)); @@ -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); } - p->sent_packets++; } } p = p->next; } signal(SIGALRM, pinger); /* restore handler */ - alarm(send_delay); + alarm(TIMER_RESOLUTION); } 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) { - p->recvd_packets++; 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; @@ -249,7 +233,7 @@ get_response(void) struct monitor_host * p; while (1) { - p = hosts[0]; + p = hosts; 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) { - p = hosts[0]; + p = hosts; 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); } - 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)); @@ -299,45 +283,52 @@ parse_config(const char * conf_file) 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); - 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); - 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); - 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); - 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); - 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. */ - hosts[i]->host_up = true; + cur_host->host_up = true; /* 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); } - 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); } @@ -367,7 +358,7 @@ gcd(int x, int y) static void init_hosts(void) { - struct monitor_host * p = hosts[0]; + struct monitor_host * p = hosts; 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 { - 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++; } } @@ -450,7 +441,7 @@ main(int argc, char ** argv) init_hosts(); signal(SIGALRM, pinger); - alarm(send_delay); + alarm(TIMER_RESOLUTION); get_response();