X-Git-Url: http://git.subgeniuskitty.com/icmpmonitor/.git/blobdiff_plain/a68b34a0f2c525bbe19d0aec981809af7debe9da..22e9f47e32f5905d2bd9ae5ee35020ace9091428:/icmpmonitor.c diff --git a/icmpmonitor.c b/icmpmonitor.c index 6dede30..462c920 100644 --- a/icmpmonitor.c +++ b/icmpmonitor.c @@ -11,6 +11,12 @@ * See LICENSE file for copyright and license details. */ +/* Wishlist */ +/* TODO: Add IPv6 support. */ +/* TODO: Turn the global '-r' functionality into per-host config file option. */ +/* TODO: Add 'auto' keyword to 'start_condition', testing host on startup. */ +/* TODO: Double-check the network code when interrupted while receiving a packet. */ + #include #include #include @@ -94,173 +100,158 @@ 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) { - 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; } /* - * 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); } -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]; - - gettimeofday(&tv, (struct timezone *) NULL); + struct timeval now; + gettimeofday(&now, 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; } - /* 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; } - 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()) { - system(p->up_cmd); + system(host->up_cmd); exit(EXIT_SUCCESS); - } else { - wait(NULL); } } } 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) { - 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); - 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); @@ -279,38 +270,37 @@ 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)); - 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'; - 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'; - 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'; - 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'; - 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'; - 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'; - /* 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);