1 files changed, 247 insertions, 22 deletions

diff --git a/plugins/check_ntp.c b/plugins/check_ntp.c
index 5037786..2954aa8 100644
--- a/plugins/check_ntp.c
+++ b/plugins/check_ntp.c
@@ -43,6 +43,12 @@ 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 */
@@ -58,6 +64,25 @@ typedef struct {
         uint64_t txts;       /* time at which request departed server */
 } ntp_message;
 
+/* 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)
@@ -71,12 +96,28 @@ typedef struct {
 #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, bytes 6,7,8 determine clock selection status */
+#define PEER_SEL(x) (x&0x07)
+#define PEER_INCLUDED 0x04
+#define PEER_SYNCSOURCE 0x06
 
 /**
  ** a note about the 32-bit "fixed point" numbers:
@@ -116,7 +157,7 @@ typedef struct {
         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)); \
+                        t.tv_usec=(int)(0.5+(double)(ntohl(R32(n))/4294.967296)); \
                 } \
         }while(0)
 
@@ -129,6 +170,17 @@ typedef struct {
                 } \
         } 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){
@@ -142,7 +194,7 @@ static inline double calc_offset(const ntp_message *m, const struct timeval *t){
 }
 
 /* print out a ntp packet in human readable/debuggable format */
-void print_packet(const ntp_message *p){
+void print_ntp_message(const ntp_message *p){
         struct timeval ref, orig, rx, tx;
 
         NTP64toTV(p->refts,ref);
@@ -167,6 +219,42 @@ void print_packet(const ntp_message *p){
         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;
 
@@ -189,7 +277,8 @@ double offset_request(const char *host){
         double next_offset=0., avg_offset=0.;
         struct timeval recv_time;
 
-        for(i=0; i<4; i++){
+        for(i=0; i<AVG_NUM; i++){
+                if(verbose) printf("offset run: %d/%d\n", i+1, AVG_NUM);
                 setup_request(&req);
                 my_udp_connect(server_address, 123, &conn);
                 write(conn, &req, sizeof(ntp_message));
@@ -201,12 +290,134 @@ double offset_request(const char *host){
                 if(verbose) printf("offset: %g\n", next_offset);
                 avg_offset+=next_offset;
         }
-        return avg_offset/4.;
+        avg_offset/=AVG_NUM;
+        if(verbose) printf("average offset: %g\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 */
 }
 
-/* not yet implemented yet */
+/* XXX handle responses with the error bit set */
 double jitter_request(const char *host){
-        return 0.;
+        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;
+        ntp_assoc_status_pair *peers;
+        ntp_control_message req;
+        double rval = 0.0, jitter = -1.0;
+        char *startofvalue=NULL, *nptr=NULL;
+
+        /* 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);
+        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
+         * Is it possible for an NTP server to have more than 117 synchronization
+         * sources?  If so, we will receive a second datagram with additional
+         * peers listed, since 117 is the maximum number that can fit in a
+         * single NTP control datagram.  This code doesn't handle that case */
+        /* XXX check the REM_MORE bit */
+        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.
+         */
+        npeers=ntohs(req.count)/sizeof(ntp_assoc_status_pair);
+        peers=(ntp_assoc_status_pair*)malloc(sizeof(ntp_assoc_status_pair)*npeers);
+        memcpy((void*)peers, (void*)req.data, sizeof(ntp_assoc_status_pair)*npeers);
+        /* 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");
+        /* XXX if ! syncsource_found set status to warning */
+
+        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){
+                                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
+                                 */
+                                strncpy(req.data, "jitter", 6);
+                                req.count = htons(6);
+                                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));
+
+                                /* get to the float value */
+                                if(verbose) {
+                                        printf("parsing jitter from peer %.2x: ", peers[i].assoc);
+                                }
+                                startofvalue = strchr(req.data, '=') + 1;
+                                jitter = strtod(startofvalue, &nptr);
+                                num_selected++;
+                                if(jitter == 0 && startofvalue==nptr){
+                                        printf("warning: unable to parse server response.\n");
+                                        /* XXX errors value ... */
+                                } else {
+                                        if(verbose) printf("%g\n", jitter);
+                                        num_valid++;
+                                        rval += jitter;
+                                }
+                        }
+                }
+                if(verbose){
+                        printf("jitter parsed from %d/%d peers\n", num_selected, num_valid);
+                }
+        }
+
+        rval /= num_valid;
+
+        close(conn);
+        free(peers);
+        /* If we return -1.0, it means no synchronization source was found */
+        return rval;
 }
 
 int process_arguments(int argc, char **argv){
@@ -247,7 +458,7 @@ int process_arguments(int argc, char **argv){
                         exit(STATE_OK);
                         break;
                 case 'v':
-                        verbose = 1;
+                        verbose++;
                         break;
                 case 'w':
                         owarn = atof(optarg);
@@ -321,35 +532,49 @@ int main(int argc, char *argv[]){
 
         offset = offset_request(server_address);
         if(offset > ocrit){
-                printf("NTP CRITICAL: ");
                 result = STATE_CRITICAL;
         } else if(offset > owarn) {
-                printf("NTP WARNING: ");
                 result = STATE_WARNING;
         } else {
-                printf("NTP OK: ");
                 result = STATE_OK;
         }
 
-        /* not implemented yet: */
-        jitter=jitter_request(server_address);
-
-        /* not implemented yet:
+        /* 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);
                 if(jitter > jcrit){
-                        printf("NTP CRITICAL: ");
-                        result = STATE_CRITICAL;
+                        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;
+                }
+        }
+
+        switch (result) {
+                case STATE_CRITICAL :
+                        printf("NTP CRITICAL: ");
+                        break;
+                case STATE_WARNING :
                         printf("NTP WARNING: ");
-                        result = STATE_WARNING;
-                } else {
+                        break;
+                case STATE_OK :
                         printf("NTP OK: ");
-                        result = STATE_OK;
-                }
+                        break;
+                default :
+                        printf("NTP UNKNOWN: ");
+                        break;
         }
-        */
 
-        printf("Offset %g secs|offset=%g\n", offset, offset);
+        printf("Offset %g secs|offset=%g", offset, offset);
+        if (do_jitter) printf("|jitter=%f", jitter);
+        printf("\n");
 
         if(server_address!=NULL) free(server_address);
         return result;