X-Git-Url: http://git.subgeniuskitty.com/icmpmonitor/.git/blobdiff_plain/fc361e474b55944ca0817df904904a1be77ccc20..a68b34a0f2c525bbe19d0aec981809af7debe9da:/icmpmonitor.c diff --git a/icmpmonitor.c b/icmpmonitor.c index cc141b5..6dede30 100644 --- a/icmpmonitor.c +++ b/icmpmonitor.c @@ -27,6 +27,7 @@ #include #include #include +#include #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? */ +/* 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. */ -struct monitor_host { +struct host_entry { /* From the config file */ char * name; int ping_interval; @@ -55,64 +65,42 @@ struct monitor_host { 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. */ - 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; /* - * 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; - 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); - 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) { @@ -151,7 +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; @@ -167,8 +155,7 @@ pinger(int ignore) 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)); @@ -183,11 +170,11 @@ pinger(int ignore) } signal(SIGALRM, pinger); /* restore handler */ - alarm(send_delay); + alarm(TIMER_RESOLUTION); } static void -read_icmp_data(struct monitor_host * p) +read_icmp_data(struct host_entry * p) { 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)); - 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; @@ -243,10 +230,10 @@ get_response(void) { fd_set rfds; int retval, maxd = -1; - struct monitor_host * p; + struct host_entry * p; while (1) { - p = hosts; + p = first_host_in_list; 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) { - 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; @@ -288,7 +275,7 @@ parse_config(const char * conf_file) 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)); @@ -296,7 +283,7 @@ parse_config(const char * conf_file) 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); @@ -333,8 +320,8 @@ parse_config(const char * conf_file) 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; @@ -346,62 +333,84 @@ parse_config(const char * conf_file) 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) { - 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); } -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) { - struct monitor_host * p = hosts; + struct host_entry * host; struct protoent * proto; - int ok = 0; 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; } } - if (hosts == NULL) { + if (first_host_in_list == NULL) { 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); - alarm(send_delay); + alarm(TIMER_RESOLUTION); get_response();