Fix for getting dispersion instead of jitter on older servers (like xntpd on Solaris).

[monitoring-plugins.git] / plugins / check_ntp.c

/******************************************************************************
*
* Nagios check_ntp plugin
*
* License: GPL
* Copyright (c) 2006 sean finney <seanius@seanius.net>
* Copyright (c) 2006 nagios-plugins team
*
* Last Modified: $Date$
*
* Description:
*
* This file contains the check_ntp plugin
*
*  This plugin to check ntp servers independant of any commandline
*  programs or external libraries.
*
*
* License Information:
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 $Id$
 
*****************************************************************************/

const char *progname = "check_ntp";
const char *revision = "$Revision$";
const char *copyright = "2006";
const char *email = "nagiosplug-devel@lists.sourceforge.net";

#include "common.h"
#include "netutils.h"
#include "utils.h"

static char *server_address=NULL;
static int verbose=0;
static double owarn=60;
static double ocrit=120;
static short do_jitter=0;
static double jwarn=5000;
static double jcrit=10000;

int process_arguments (int, char **);
void print_help (void);
void print_usage (void);

/* number of times to perform each request to get a good average. */
#define AVG_NUM 4

/* max size of control message data */
#define MAX_CM_SIZE 468

/* this structure holds everything in an ntp request/response as per rfc1305 */
typedef struct {
        uint8_t flags;       /* byte with leapindicator,vers,mode. see macros */
        uint8_t stratum;     /* clock stratum */
        int8_t poll;         /* polling interval */
        int8_t precision;    /* precision of the local clock */
        int32_t rtdelay;     /* total rt delay, as a fixed point num. see macros */
        uint32_t rtdisp;     /* like above, but for max err to primary src */
        uint32_t refid;      /* ref clock identifier */
        uint64_t refts;      /* reference timestamp.  local time local clock */
        uint64_t origts;     /* time at which request departed client */
        uint64_t rxts;       /* time at which request arrived at server */
        uint64_t txts;       /* time at which request departed server */
} ntp_message;

/* this structure holds data about results from querying offset from a peer */
typedef struct {
        time_t waiting;         /* ts set when we started waiting for a response */ 
        int num_responses;      /* number of successfully recieved responses */
        uint8_t stratum;        /* copied verbatim from the ntp_message */
        double rtdelay;         /* converted from the ntp_message */
        double rtdisp;          /* converted from the ntp_message */
        double offset[AVG_NUM]; /* offsets from each response */
} ntp_server_results;

/* this structure holds everything in an ntp control message as per rfc1305 */
typedef struct {
        uint8_t flags;       /* byte with leapindicator,vers,mode. see macros */
        uint8_t op;          /* R,E,M bits and Opcode */
        uint16_t seq;        /* Packet sequence */
        uint16_t status;     /* Clock status */
        uint16_t assoc;      /* Association */
        uint16_t offset;     /* Similar to TCP sequence # */
        uint16_t count;      /* # bytes of data */
        char data[MAX_CM_SIZE]; /* ASCII data of the request */
                                /* NB: not necessarily NULL terminated! */
} ntp_control_message;

/* this is an association/status-word pair found in control packet reponses */
typedef struct {
        uint16_t assoc;
        uint16_t status;
} ntp_assoc_status_pair;

/* bits 1,2 are the leap indicator */
#define LI_MASK 0xc0
#define LI(x) ((x&LI_MASK)>>6)
#define LI_SET(x,y) do{ x |= ((y<<6)&LI_MASK); }while(0)
/* and these are the values of the leap indicator */
#define LI_NOWARNING 0x00
#define LI_EXTRASEC 0x01
#define LI_MISSINGSEC 0x02
#define LI_ALARM 0x03
/* bits 3,4,5 are the ntp version */
#define VN_MASK 0x38
#define VN(x)   ((x&VN_MASK)>>3)
#define VN_SET(x,y)     do{ x |= ((y<<3)&VN_MASK); }while(0)
#define VN_RESERVED 0x02
/* bits 6,7,8 are the ntp mode */
#define MODE_MASK 0x07
#define MODE(x) (x&MODE_MASK)
#define MODE_SET(x,y)   do{ x |= (y&MODE_MASK); }while(0)
/* here are some values */
#define MODE_CLIENT 0x03
#define MODE_CONTROLMSG 0x06
/* In control message, bits 8-10 are R,E,M bits */
#define REM_MASK 0xe0
#define REM_RESP 0x80
#define REM_ERROR 0x40
#define REM_MORE 0x20
/* In control message, bits 11 - 15 are opcode */
#define OP_MASK 0x1f
#define OP_SET(x,y)   do{ x |= (y&OP_MASK); }while(0)
#define OP_READSTAT 0x01
#define OP_READVAR  0x02
/* In peer status bytes, bits 6,7,8 determine clock selection status */
#define PEER_SEL(x) ((ntohs(x)>>8)&0x07)
#define PEER_INCLUDED 0x04
#define PEER_SYNCSOURCE 0x06

/**
 ** a note about the 32-bit "fixed point" numbers:
 **
 they are divided into halves, each being a 16-bit int in network byte order:
 - the first 16 bits are an int on the left side of a decimal point.
 - the second 16 bits represent a fraction n/(2^16)
 likewise for the 64-bit "fixed point" numbers with everything doubled :) 
 **/

/* macros to access the left/right 16 bits of a 32-bit ntp "fixed point"
   number.  note that these can be used as lvalues too */
#define L16(x) (((uint16_t*)&x)[0])
#define R16(x) (((uint16_t*)&x)[1])
/* macros to access the left/right 32 bits of a 64-bit ntp "fixed point"
   number.  these too can be used as lvalues */
#define L32(x) (((uint32_t*)&x)[0])
#define R32(x) (((uint32_t*)&x)[1])

/* ntp wants seconds since 1/1/00, epoch is 1/1/70.  this is the difference */
#define EPOCHDIFF 0x83aa7e80UL

/* extract a 32-bit ntp fixed point number into a double */
#define NTP32asDOUBLE(x) (ntohs(L16(x)) + (double)ntohs(R16(x))/65536.0)

/* likewise for a 64-bit ntp fp number */
#define NTP64asDOUBLE(n) (double)(((uint64_t)n)?\
                         (ntohl(L32(n))-EPOCHDIFF) + \
                         (.00000001*(0.5+(double)(ntohl(R32(n))/42.94967296))):\
                         0)

/* convert a struct timeval to a double */
#define TVasDOUBLE(x) (double)(x.tv_sec+(0.000001*x.tv_usec))

/* convert an ntp 64-bit fp number to a struct timeval */
#define NTP64toTV(n,t) \
        do{ if(!n) t.tv_sec = t.tv_usec = 0; \
            else { \
                        t.tv_sec=ntohl(L32(n))-EPOCHDIFF; \
                        t.tv_usec=(int)(0.5+(double)(ntohl(R32(n))/4294.967296)); \
                } \
        }while(0)

/* convert a struct timeval to an ntp 64-bit fp number */
#define TVtoNTP64(t,n) \
        do{ if(!t.tv_usec && !t.tv_sec) n=0x0UL; \
                else { \
                        L32(n)=htonl(t.tv_sec + EPOCHDIFF); \
                        R32(n)=htonl((uint64_t)((4294.967296*t.tv_usec)+.5)); \
                } \
        } while(0)

/* NTP control message header is 12 bytes, plus any data in the data
 * field, plus null padding to the nearest 32-bit boundary per rfc.
 */
#define SIZEOF_NTPCM(m) (12+ntohs(m.count)+((m.count)?4-(ntohs(m.count)%4):0))

/* finally, a little helper or two for debugging: */
#define DBG(x) do{if(verbose>1){ x; }}while(0);
#define PRINTSOCKADDR(x) \
        do{ \
                printf("%u.%u.%u.%u", (x>>24)&0xff, (x>>16)&0xff, (x>>8)&0xff, x&0xff);\
        }while(0);

/* calculate the offset of the local clock */
static inline double calc_offset(const ntp_message *m, const struct timeval *t){
        double client_tx, peer_rx, peer_tx, client_rx;
        client_tx = NTP64asDOUBLE(m->origts);
        peer_rx = NTP64asDOUBLE(m->rxts);
        peer_tx = NTP64asDOUBLE(m->txts);
        client_rx=TVasDOUBLE((*t));
        return (.5*((peer_tx-client_rx)+(peer_rx-client_tx)));
}

/* print out a ntp packet in human readable/debuggable format */
void print_ntp_message(const ntp_message *p){
        struct timeval ref, orig, rx, tx;

        NTP64toTV(p->refts,ref);
        NTP64toTV(p->origts,orig);
        NTP64toTV(p->rxts,rx);
        NTP64toTV(p->txts,tx);

        printf("packet contents:\n");
        printf("\tflags: 0x%.2x\n", p->flags);
        printf("\t  li=%d (0x%.2x)\n", LI(p->flags), p->flags&LI_MASK);
        printf("\t  vn=%d (0x%.2x)\n", VN(p->flags), p->flags&VN_MASK);
        printf("\t  mode=%d (0x%.2x)\n", MODE(p->flags), p->flags&MODE_MASK);
        printf("\tstratum = %d\n", p->stratum);
        printf("\tpoll = %g\n", pow(2, p->poll));
        printf("\tprecision = %g\n", pow(2, p->precision));
        printf("\trtdelay = %-.16g\n", NTP32asDOUBLE(p->rtdelay));
        printf("\trtdisp = %-.16g\n", NTP32asDOUBLE(p->rtdisp));
        printf("\trefid = %x\n", p->refid);
        printf("\trefts = %-.16g\n", NTP64asDOUBLE(p->refts));
        printf("\torigts = %-.16g\n", NTP64asDOUBLE(p->origts));
        printf("\trxts = %-.16g\n", NTP64asDOUBLE(p->rxts));
        printf("\ttxts = %-.16g\n", NTP64asDOUBLE(p->txts));
}

void print_ntp_control_message(const ntp_control_message *p){
        int i=0, numpeers=0;
        const ntp_assoc_status_pair *peer=NULL;

        printf("control packet contents:\n");
        printf("\tflags: 0x%.2x , 0x%.2x\n", p->flags, p->op);
        printf("\t  li=%d (0x%.2x)\n", LI(p->flags), p->flags&LI_MASK);
        printf("\t  vn=%d (0x%.2x)\n", VN(p->flags), p->flags&VN_MASK);
        printf("\t  mode=%d (0x%.2x)\n", MODE(p->flags), p->flags&MODE_MASK);
        printf("\t  response=%d (0x%.2x)\n", (p->op&REM_RESP)>0, p->op&REM_RESP);
        printf("\t  more=%d (0x%.2x)\n", (p->op&REM_MORE)>0, p->op&REM_MORE);
        printf("\t  error=%d (0x%.2x)\n", (p->op&REM_ERROR)>0, p->op&REM_ERROR);
        printf("\t  op=%d (0x%.2x)\n", p->op&OP_MASK, p->op&OP_MASK);
        printf("\tsequence: %d (0x%.2x)\n", ntohs(p->seq), ntohs(p->seq));
        printf("\tstatus: %d (0x%.2x)\n", ntohs(p->status), ntohs(p->status));
        printf("\tassoc: %d (0x%.2x)\n", ntohs(p->assoc), ntohs(p->assoc));
        printf("\toffset: %d (0x%.2x)\n", ntohs(p->offset), ntohs(p->offset));
        printf("\tcount: %d (0x%.2x)\n", ntohs(p->count), ntohs(p->count));
        numpeers=ntohs(p->count)/(sizeof(ntp_assoc_status_pair));
        if(p->op&REM_RESP && p->op&OP_READSTAT){
                peer=(ntp_assoc_status_pair*)p->data;
                for(i=0;i<numpeers;i++){
                        printf("\tpeer id %.2x status %.2x", 
                               ntohs(peer[i].assoc), ntohs(peer[i].status));
                        if (PEER_SEL(peer[i].status) >= PEER_INCLUDED){
                                if(PEER_SEL(peer[i].status) >= PEER_SYNCSOURCE){
                                        printf(" <-- current sync source");
                                } else {
                                        printf(" <-- current sync candidate");
                                }
                        }
                        printf("\n");
                }
        }
}

void setup_request(ntp_message *p){
        struct timeval t;

        memset(p, 0, sizeof(ntp_message));
        LI_SET(p->flags, LI_ALARM);
        VN_SET(p->flags, 4);
        MODE_SET(p->flags, MODE_CLIENT);
        p->poll=4;
        p->precision=(int8_t)0xfa;
        L16(p->rtdelay)=htons(1);
        L16(p->rtdisp)=htons(1);

        gettimeofday(&t, NULL);
        TVtoNTP64(t,p->txts);
}

/* select the "best" server from a list of servers, and return its index.
 * this is done by filtering servers based on stratum, dispersion, and
 * finally round-trip delay. */
int best_offset_server(const ntp_server_results *slist, int nservers){
        int i=0, j=0, cserver=0, candidates[5], csize=0;

        /* for each server */
        for(cserver=0; cserver<nservers; cserver++){
                /* compare it to each of the servers already in the candidate list */
                for(i=0; i<csize; i++){
                        /* does it have an equal or better stratum? */
                        if(slist[cserver].stratum <= slist[i].stratum){
                                /* does it have an equal or better dispersion? */
                                if(slist[cserver].rtdisp <= slist[i].rtdisp){
                                        /* does it have a better rtdelay? */
                                        if(slist[cserver].rtdelay < slist[i].rtdelay){
                                                break;
                                        }
                                }
                        }
                }

                /* if we haven't reached the current list's end, move everyone
                 * over one to the right, and insert the new candidate */
                if(i<csize){
                        for(j=5; j>i; j--){
                                candidates[j]=candidates[j-1];
                        }
                }
                /* regardless, if they should be on the list... */
                if(i<5) {
                        candidates[i]=cserver;
                        if(csize<5) csize++;
                /* otherwise discard the server */
                } else {
                        DBG(printf("discarding peer id %d\n", cserver));
                }
        }

        if(csize>0) {
                DBG(printf("best server selected: peer %d\n", candidates[0]));
                return candidates[0];
        } else {
                DBG(printf("no peers meeting synchronization criteria :(\n"));
                return -1;
        }
}

/* do everything we need to get the total average offset
 * - we use a certain amount of parallelization with poll() to ensure
 *   we don't waste time sitting around waiting for single packets. 
 * - we also "manually" handle resolving host names and connecting, because
 *   we have to do it in a way that our lazy macros don't handle currently :( */
double offset_request(const char *host, int *status){
        int i=0, j=0, ga_result=0, num_hosts=0, *socklist=NULL, respnum=0;
        int servers_completed=0, one_written=0, one_read=0, servers_readable=0, best_index=-1;
        time_t now_time=0, start_ts=0;
        ntp_message *req=NULL;
        double avg_offset=0.;
        struct timeval recv_time;
        struct addrinfo *ai=NULL, *ai_tmp=NULL, hints;
        struct pollfd *ufds=NULL;
        ntp_server_results *servers=NULL;

        /* setup hints to only return results from getaddrinfo that we'd like */
        memset(&hints, 0, sizeof(struct addrinfo));
        hints.ai_family = address_family;
        hints.ai_protocol = IPPROTO_UDP;
        hints.ai_socktype = SOCK_DGRAM;

        /* fill in ai with the list of hosts resolved by the host name */
        ga_result = getaddrinfo(host, "123", &hints, &ai);
        if(ga_result!=0){
                die(STATE_UNKNOWN, "error getting address for %s: %s\n",
                    host, gai_strerror(ga_result));
        }

        /* count the number of returned hosts, and allocate stuff accordingly */
        for(ai_tmp=ai; ai_tmp!=NULL; ai_tmp=ai_tmp->ai_next){ num_hosts++; }
        req=(ntp_message*)malloc(sizeof(ntp_message)*num_hosts);
        if(req==NULL) die(STATE_UNKNOWN, "can not allocate ntp message array");
        socklist=(int*)malloc(sizeof(int)*num_hosts);
        if(socklist==NULL) die(STATE_UNKNOWN, "can not allocate socket array");
        ufds=(struct pollfd*)malloc(sizeof(struct pollfd)*num_hosts);
        if(ufds==NULL) die(STATE_UNKNOWN, "can not allocate socket array");
        servers=(ntp_server_results*)malloc(sizeof(ntp_server_results)*num_hosts);
        if(servers==NULL) die(STATE_UNKNOWN, "can not allocate server array");
        memset(servers, 0, sizeof(ntp_server_results)*num_hosts);

        /* setup each socket for writing, and the corresponding struct pollfd */
        ai_tmp=ai;
        for(i=0;ai_tmp;i++){
                socklist[i]=socket(ai_tmp->ai_family, SOCK_DGRAM, IPPROTO_UDP);
                if(socklist[i] == -1) {
                        perror(NULL);
                        die(STATE_UNKNOWN, "can not create new socket");
                }
                if(connect(socklist[i], ai_tmp->ai_addr, ai_tmp->ai_addrlen)){
                        die(STATE_UNKNOWN, "can't create socket connection");
                } else {
                        ufds[i].fd=socklist[i];
                        ufds[i].events=POLLIN;
                        ufds[i].revents=0;
                }
                ai_tmp = ai_tmp->ai_next;
        }

        /* now do AVG_NUM checks to each host.  we stop before timeout/2 seconds
         * have passed in order to ensure post-processing and jitter time. */
        now_time=start_ts=time(NULL);
        while(servers_completed<num_hosts && now_time-start_ts <= socket_timeout/2){
                /* loop through each server and find each one which hasn't
                 * been touched in the past second or so and is still lacking
                 * some responses.  for each of these servers, send a new request,
                 * and update the "waiting" timestamp with the current time. */
                one_written=0;
                now_time=time(NULL);

                for(i=0; i<num_hosts; i++){
                        if(servers[i].waiting<now_time && servers[i].num_responses<AVG_NUM){
                                if(verbose && servers[i].waiting != 0) printf("re-");
                                if(verbose) printf("sending request to peer %d\n", i);
                                setup_request(&req[i]);
                                write(socklist[i], &req[i], sizeof(ntp_message));
                                servers[i].waiting=now_time;
                                one_written=1;
                                break;
                        }
                }

                /* quickly poll for any sockets with pending data */
                servers_readable=poll(ufds, num_hosts, 100);
                if(servers_readable==-1){
                        perror("polling ntp sockets");
                        die(STATE_UNKNOWN, "communication errors");
                }

                /* read from any sockets with pending data */
                for(i=0; servers_readable && i<num_hosts; i++){
                        if(ufds[i].revents&POLLIN && servers[i].num_responses < AVG_NUM){
                                if(verbose) {
                                        printf("response from peer %d: ", i);
                                }

                                read(ufds[i].fd, &req[i], sizeof(ntp_message));
                                gettimeofday(&recv_time, NULL);
                                DBG(print_ntp_message(&req[i]));
                                respnum=servers[i].num_responses++;
                                servers[i].offset[respnum]=calc_offset(&req[i], &recv_time);
                                if(verbose) {
                                        printf("offset %.10g\n", servers[i].offset[respnum]);
                                }
                                servers[i].stratum=req[i].stratum;
                                servers[i].rtdisp=NTP32asDOUBLE(req[i].rtdisp);
                                servers[i].rtdelay=NTP32asDOUBLE(req[i].rtdelay);
                                servers[i].waiting=0;
                                servers_readable--;
                                one_read = 1;
                                if(servers[i].num_responses==AVG_NUM) servers_completed++;
                        }
                }
                /* lather, rinse, repeat. */
        }

        if (one_read == 0) {
                die(STATE_CRITICAL, "NTP CRITICAL: No response from NTP server\n");
        }

        /* now, pick the best server from the list */
        best_index=best_offset_server(servers, num_hosts);
        if(best_index < 0){
                *status=STATE_CRITICAL;
        } else {
                /* finally, calculate the average offset */
                for(i=0; i<servers[best_index].num_responses;i++){
                        avg_offset+=servers[best_index].offset[j];
                }
                avg_offset/=servers[best_index].num_responses;
        }

        /* cleanup */
        /* FIXME: Not closing the socket to avoid re-use of the local port
         * which can cause old NTP packets to be read instead of NTP control
         * pactets in jitter_request(). THERE MUST BE ANOTHER WAY...
         * for(j=0; j<num_hosts; j++){ close(socklist[j]); } */
        free(socklist);
        free(ufds);
        free(servers);
        free(req);
        freeaddrinfo(ai);

        if(verbose) printf("overall average offset: %.10g\n", avg_offset);
        return avg_offset;
}

void
setup_control_request(ntp_control_message *p, uint8_t opcode, uint16_t seq){
        memset(p, 0, sizeof(ntp_control_message));
        LI_SET(p->flags, LI_NOWARNING);
        VN_SET(p->flags, VN_RESERVED);
        MODE_SET(p->flags, MODE_CONTROLMSG);
        OP_SET(p->op, opcode);
        p->seq = htons(seq);
        /* Remaining fields are zero for requests */
}

/* XXX handle responses with the error bit set */
double jitter_request(const char *host, int *status){
        int conn=-1, i, npeers=0, num_candidates=0, syncsource_found=0;
        int run=0, min_peer_sel=PEER_INCLUDED, num_selected=0, num_valid=0;
        int peers_size=0, peer_offset=0;
        ntp_assoc_status_pair *peers=NULL;
        ntp_control_message req;
        const char *getvar = "jitter";
        double rval = 0.0, jitter = -1.0;
        char *startofvalue=NULL, *nptr=NULL;
        void *tmp;

        /* Long-winded explanation:
         * Getting the jitter requires a number of steps:
         * 1) Send a READSTAT request.
         * 2) Interpret the READSTAT reply
         *  a) The data section contains a list of peer identifiers (16 bits)
         *     and associated status words (16 bits)
         *  b) We want the value of 0x06 in the SEL (peer selection) value,
         *     which means "current synchronizatin source".  If that's missing,
         *     we take anything better than 0x04 (see the rfc for details) but
         *     set a minimum of warning.
         * 3) Send a READVAR request for information on each peer identified
         *    in 2b greater than the minimum selection value.
         * 4) Extract the jitter value from the data[] (it's ASCII)
         */
        my_udp_connect(server_address, 123, &conn);

        /* keep sending requests until the server stops setting the
         * REM_MORE bit, though usually this is only 1 packet. */
        do{
                setup_control_request(&req, OP_READSTAT, 1);
                DBG(printf("sending READSTAT request"));
                write(conn, &req, SIZEOF_NTPCM(req));
                DBG(print_ntp_control_message(&req));
                /* Attempt to read the largest size packet possible */
                req.count=htons(MAX_CM_SIZE);
                DBG(printf("recieving READSTAT response"))
                read(conn, &req, SIZEOF_NTPCM(req));
                DBG(print_ntp_control_message(&req));
                /* Each peer identifier is 4 bytes in the data section, which
                 * we represent as a ntp_assoc_status_pair datatype.
                 */
                peers_size+=ntohs(req.count);
                if((tmp=realloc(peers, peers_size)) == NULL)
                        free(peers), die(STATE_UNKNOWN, "can not (re)allocate 'peers' buffer\n");
                peers=tmp;
                memcpy((void*)((ptrdiff_t)peers+peer_offset), (void*)req.data, ntohs(req.count));
                npeers=peers_size/sizeof(ntp_assoc_status_pair);
                peer_offset+=ntohs(req.count);
        } while(req.op&REM_MORE);

        /* first, let's find out if we have a sync source, or if there are
         * at least some candidates.  in the case of the latter we'll issue
         * a warning but go ahead with the check on them. */
        for (i = 0; i < npeers; i++){
                if (PEER_SEL(peers[i].status) >= PEER_INCLUDED){
                        num_candidates++;
                        if(PEER_SEL(peers[i].status) >= PEER_SYNCSOURCE){
                                syncsource_found=1;
                                min_peer_sel=PEER_SYNCSOURCE;
                        }
                }
        }
        if(verbose) printf("%d candiate peers available\n", num_candidates);
        if(verbose && syncsource_found) printf("synchronization source found\n");
        if(! syncsource_found){
                *status = STATE_WARNING;
                if(verbose) printf("warning: no synchronization source found\n");
        }


        for (run=0; run<AVG_NUM; run++){
                if(verbose) printf("jitter run %d of %d\n", run+1, AVG_NUM);
                for (i = 0; i < npeers; i++){
                        /* Only query this server if it is the current sync source */
                        if (PEER_SEL(peers[i].status) >= min_peer_sel){
                                num_selected++;
                                setup_control_request(&req, OP_READVAR, 2);
                                req.assoc = peers[i].assoc;
                                /* By spec, putting the variable name "jitter"  in the request
                                 * should cause the server to provide _only_ the jitter value.
                                 * thus reducing net traffic, guaranteeing us only a single
                                 * datagram in reply, and making intepretation much simpler
                                 */
                                /* Older servers doesn't know what jitter is, so if we get an
                                 * error on the first pass we redo it with "dispersion" */
                                strncpy(req.data, getvar, MAX_CM_SIZE-1);
                                req.count = htons(strlen(getvar));
                                DBG(printf("sending READVAR request...\n"));
                                write(conn, &req, SIZEOF_NTPCM(req));
                                DBG(print_ntp_control_message(&req));

                                req.count = htons(MAX_CM_SIZE);
                                DBG(printf("recieving READVAR response...\n"));
                                read(conn, &req, SIZEOF_NTPCM(req));
                                DBG(print_ntp_control_message(&req));

                                if(req.op&REM_ERROR && strstr(getvar, "jitter")) {
                                        if(verbose) printf("The 'jitter' command failed (old ntp server?)\nRestarting with 'dispersion'...\n");
                                        getvar = "dispersion";
                                        num_selected--;
                                        i--;
                                        continue;
                                }

                                /* get to the float value */
                                if(verbose) {
                                        printf("parsing jitter from peer %.2x: ", ntohs(peers[i].assoc));
                                }
                                startofvalue = strchr(req.data, '=');
                                if(startofvalue != NULL) {
                                        startofvalue++;
                                        jitter = strtod(startofvalue, &nptr);
                                }
                                if(startofvalue == NULL || startofvalue==nptr){
                                        printf("warning: unable to read server jitter response.\n");
                                        *status = STATE_WARNING;
                                } else {
                                        if(verbose) printf("%g\n", jitter);
                                        num_valid++;
                                        rval += jitter;
                                }
                        }
                }
                if(verbose){
                        printf("jitter parsed from %d/%d peers\n", num_valid, num_selected);
                }
        }

        rval = num_valid ? rval / num_valid : -1.0;

        close(conn);
        if(peers!=NULL) free(peers);
        /* If we return -1.0, it means no synchronization source was found */
        return rval;
}

int process_arguments(int argc, char **argv){
        int c;
        int option=0;
        static struct option longopts[] = {
                {"version", no_argument, 0, 'V'},
                {"help", no_argument, 0, 'h'},
                {"verbose", no_argument, 0, 'v'},
                {"use-ipv4", no_argument, 0, '4'},
                {"use-ipv6", no_argument, 0, '6'},
                {"warning", required_argument, 0, 'w'},
                {"critical", required_argument, 0, 'c'},
                {"jwarn", required_argument, 0, 'j'},
                {"jcrit", required_argument, 0, 'k'},
                {"timeout", required_argument, 0, 't'},
                {"hostname", required_argument, 0, 'H'},
                {0, 0, 0, 0}
        };

        
        if (argc < 2)
                usage ("\n");

        while (1) {
                c = getopt_long (argc, argv, "Vhv46w:c:j:k:t:H:", longopts, &option);
                if (c == -1 || c == EOF || c == 1)
                        break;

                switch (c) {
                case 'h':
                        print_help();
                        exit(STATE_OK);
                        break;
                case 'V':
                        print_revision(progname, revision);
                        exit(STATE_OK);
                        break;
                case 'v':
                        verbose++;
                        break;
                case 'w':
                        owarn = atof(optarg);
                        break;
                case 'c':
                        ocrit = atof(optarg);
                        break;
                case 'j':
                        do_jitter=1;
                        jwarn = atof(optarg);
                        break;
                case 'k':
                        do_jitter=1;
                        jcrit = atof(optarg);
                        break;
                case 'H':
                        if(is_host(optarg) == FALSE)
                                usage2(_("Invalid hostname/address"), optarg);
                        server_address = strdup(optarg);
                        break;
                case 't':
                        socket_timeout=atoi(optarg);
                        break;
                case '4':
                        address_family = AF_INET;
                        break;
                case '6':
#ifdef USE_IPV6
                        address_family = AF_INET6;
#else
                        usage4 (_("IPv6 support not available"));
#endif
                        break;
                case '?':
                        /* print short usage statement if args not parsable */
                        usage5 ();
                        break;
                }
        }

        if (ocrit < owarn){
                usage4(_("Critical offset should be larger than warning offset"));
        }

        if (ocrit < owarn){
                usage4(_("Critical jitter should be larger than warning jitter"));
        }

        if(server_address == NULL){
                usage4(_("Hostname was not supplied"));
        }

        return 0;
}

int main(int argc, char *argv[]){
        int result, offset_result, jitter_result;
        double offset=0, jitter=0;

        result=offset_result=jitter_result=STATE_UNKNOWN;

        if (process_arguments (argc, argv) == ERROR)
                usage4 (_("Could not parse arguments"));

        /* initialize alarm signal handling */
        signal (SIGALRM, socket_timeout_alarm_handler);

        /* set socket timeout */
        alarm (socket_timeout);

        offset = offset_request(server_address, &offset_result);
        if(fabs(offset) > ocrit){
                result = STATE_CRITICAL;
        } else if(fabs(offset) > owarn) {
                result = STATE_WARNING;
        } else {
                result = STATE_OK;
        }
        result=max_state(result, offset_result);

        /* If not told to check the jitter, we don't even send packets.
         * jitter is checked using NTP control packets, which not all
         * servers recognize.  Trying to check the jitter on OpenNTPD
         * (for example) will result in an error
         */
        if(do_jitter){
                jitter=jitter_request(server_address, &jitter_result);
                if(jitter > jcrit){
                        result = max_state(result, STATE_CRITICAL);
                } else if(jitter > jwarn) {
                        result = max_state(result, STATE_WARNING);
                } else if(jitter == -1.0 && result == STATE_OK){
                        /* -1 indicates that we couldn't calculate the jitter
                         * Only overrides STATE_OK from the offset */
                        result = STATE_UNKNOWN;
                }
        }
        result=max_state(result, jitter_result);

        switch (result) {
                case STATE_CRITICAL :
                        printf("NTP CRITICAL: ");
                        break;
                case STATE_WARNING :
                        printf("NTP WARNING: ");
                        break;
                case STATE_OK :
                        printf("NTP OK: ");
                        break;
                default :
                        printf("NTP UNKNOWN: ");
                        break;
        }
        if(offset_result==STATE_CRITICAL){
                printf("Offset unknown|offset=unknown");
        } else {
                if(offset_result==STATE_WARNING){
                        printf("Unable to fully sample sync server. ");
                }
                printf("Offset %.10g secs|offset=%.10g", offset, offset);
        }
        if (do_jitter) printf(" jitter=%f", jitter);
        printf("\n");

        if(server_address!=NULL) free(server_address);
        return result;
}



void print_help(void){
        print_revision(progname, revision);

        printf ("Copyright (c) 2006 Sean Finney\n");
        printf (COPYRIGHT, copyright, email);
  
  printf ("%s\n", _("This plugin checks the selected ntp server"));

  printf ("\n\n");
  
        print_usage();
        printf (_(UT_HELP_VRSN));
        printf (_(UT_HOST_PORT), 'p', "123");
        printf (_(UT_WARN_CRIT));
        printf (" %s\n", "-j, --warning=DOUBLE");
        printf ("    %s\n", _("warning value for jitter"));
        printf (" %s\n", "-k, --critical=DOUBLE");
        printf ("    %s\n", _("critical value for jitter"));
        printf (_(UT_TIMEOUT), DEFAULT_SOCKET_TIMEOUT);
        printf (_(UT_VERBOSE));
        printf (_(UT_SUPPORT));
}

void
print_usage(void)
{
  printf (_("Usage:"));
  printf("%s -H <host> [-w <warn>] [-c <crit>] [-j <warn>] [-k <crit>] [-v verbose]\n", progname);
}