Add the new checks as check_ntp copies to keep full plug-in history

git-svn-id: https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/trunk@1843 f882894a-f735-0410-b71e-b25c423dba1c

1 files changed, 877 insertions, 0 deletions

diff --git a/plugins/check_ntp_time.c b/plugins/check_ntp_time.c
new file mode 100644
index 0000000..164d519
--- /dev/null
+++ b/plugins/check_ntp_time.c
@@ -0,0 +1,877 @@
+/******************************************************************************
+*
+* Nagios check_ntp plugin
+*
+* License: GPL
+* Copyright (c) 2006 sean finney <seanius@seanius.net>
+* Copyright (c) 2007 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 = "2007";
+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 short do_offset=0;
+static char *owarn="60";
+static char *ocrit="120";
+static short do_jitter=0;
+static char *jwarn="5000";
+static char *jcrit="10000";
+
+int process_arguments (int, char **);
+thresholds *offset_thresholds = NULL;
+thresholds *jitter_thresholds = NULL;
+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 */
+        uint8_t flags;       /* byte with leapindicator,vers,mode. see macros */
+} 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++){
+                /* sort out servers with error flags */
+                if ( LI(slist[cserver].flags) != LI_NOWARNING ){
+                        if (verbose) printf("discarding peer id %d: flags=%d\n", cserver, LI(slist[cserver].flags));
+                        break;
+                }
+
+                /* 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[i].flags=req[i].flags;
+                                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_UNKNOWN;
+        } 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_UNKNOWN;
+                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_UNKNOWN;
+                                } 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':
+                        do_offset=1;
+                        owarn = optarg;
+                        break;
+                case 'c':
+                        do_offset=1;
+                        ocrit = optarg;
+                        break;
+                case 'j':
+                        do_jitter=1;
+                        jwarn = optarg;
+                        break;
+                case 'k':
+                        do_jitter=1;
+                        jcrit = 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(server_address == NULL){
+                usage4(_("Hostname was not supplied"));
+        }
+
+        return 0;
+}
+
+char *perfd_offset (double offset)
+{
+        return fperfdata ("offset", offset, "s",
+                TRUE, offset_thresholds->warning->end,
+                TRUE, offset_thresholds->critical->end,
+                FALSE, 0, FALSE, 0);
+}
+
+char *perfd_jitter (double jitter)
+{
+        return fperfdata ("jitter", jitter, "s",
+                do_jitter, jitter_thresholds->warning->end,
+                do_jitter, jitter_thresholds->critical->end,
+                TRUE, 0, FALSE, 0);
+}
+
+int main(int argc, char *argv[]){
+        int result, offset_result, jitter_result;
+        double offset=0, jitter=0;
+        char *result_line, *perfdata_line;
+
+        result = offset_result = jitter_result = STATE_OK;
+
+        if (process_arguments (argc, argv) == ERROR)
+                usage4 (_("Could not parse arguments"));
+
+        set_thresholds(&offset_thresholds, owarn, ocrit);
+        set_thresholds(&jitter_thresholds, jwarn, jcrit);
+
+        /* initialize alarm signal handling */
+        signal (SIGALRM, socket_timeout_alarm_handler);
+
+        /* set socket timeout */
+        alarm (socket_timeout);
+
+        offset = offset_request(server_address, &offset_result);
+        /* check_ntp used to always return CRITICAL if offset_result == STATE_UNKNOWN.
+         * Now we'll only do that is the offset thresholds were set */
+        if (do_offset && offset_result == STATE_UNKNOWN) {
+                result = STATE_CRITICAL;
+        } else {
+                result = get_status(fabs(offset), offset_thresholds);
+        }
+
+        /* 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);
+                result = max_state_alt(result, get_status(jitter, jitter_thresholds));
+                /* -1 indicates that we couldn't calculate the jitter
+                 * Only overrides STATE_OK from the offset */
+                if(jitter == -1.0 && result == STATE_OK)
+                        result = STATE_UNKNOWN;
+        }
+        result = max_state_alt(result, jitter_result);
+
+        switch (result) {
+                case STATE_CRITICAL :
+                        asprintf(&result_line, "NTP CRITICAL:");
+                        break;
+                case STATE_WARNING :
+                        asprintf(&result_line, "NTP WARNING:");
+                        break;
+                case STATE_OK :
+                        asprintf(&result_line, "NTP OK:");
+                        break;
+                default :
+                        asprintf(&result_line, "NTP UNKNOWN:");
+                        break;
+        }
+        if(offset_result == STATE_UNKNOWN){
+                asprintf(&result_line, "%s %s", result_line, _("Offset unknown"));
+                asprintf(&perfdata_line, "");
+        } else {
+                asprintf(&result_line, "%s Offset %.10g secs", result_line, offset);
+                asprintf(&perfdata_line, "%s", perfd_offset(offset));
+        }
+        if (do_jitter) {
+                asprintf(&result_line, "%s, jitter=%f", result_line, jitter);
+                asprintf(&perfdata_line, "%s %s", perfdata_line,  perfd_jitter(jitter));
+        }
+        printf("%s|%s\n", result_line, perfdata_line);
+
+        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 (" %s\n", "-w, --warning=THRESHOLD");
+        printf ("    %s\n", _("Offset to result in warning status (seconds)"));
+        printf (" %s\n", "-c, --critical=THRESHOLD");
+        printf ("    %s\n", _("Offset to result in critical status (seconds)"));
+        printf (" %s\n", "-j, --warning=THRESHOLD");
+        printf ("    %s\n", _("Warning threshold for jitter"));
+        printf (" %s\n", "-k, --critical=THRESHOLD");
+        printf ("    %s\n", _("Critical threshold for jitter"));
+        printf (_(UT_TIMEOUT), DEFAULT_SOCKET_TIMEOUT);
+        printf (_(UT_VERBOSE));
+
+        printf("\n");
+        printf("%s\n", _("Notes:"));
+        printf(" %s\n", _("See:"));
+        printf(" %s\n", ("http://nagiosplug.sourceforge.net/developer-guidelines.html#THRESHOLDFORMAT"));
+        printf(" %s\n", _("for THRESHOLD format and examples."));
+
+        printf("\n");
+        printf("%s\n", _("Examples:"));
+        printf(" %s\n", _("Normal offset check:"));
+        printf("  %s\n", ("./check_ntp -H ntpserv -w 0.5 -c 1"));
+        printf(" %s\n", _("Check jitter too, avoiding critical notifications if jitter isn't available"));
+        printf(" %s\n", _("(See Notes above for more details on thresholds formats):"));
+        printf("  %s\n", ("./check_ntp -H ntpserv -w 0.5 -c 1 -j -1:100 -k -1:200"));
+
+        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);
+}