/* ntpdsim.c
*
* The source code for the ntp discrete event simulator.
*
* Written By: Sachin Kamboj
* University of Delaware
* Newark, DE 19711
* Copyright (c) 2006
* (Some code shamelessly based on the original NTP discrete event simulator)
*/
void (*event_ptr[]) (Event *) = {
sim_event_beep, sim_update_clocks, sim_event_timer, sim_event_recv_packet
}; /* Function pointer to the events */
/*
* Define a function to compare two events to determine which one occurs
* first.
*/
int
determine_event_ordering(
const Event *e1,
const Event *e2
)
{
return (e1->time - e2->time);
}
/*
* Define a function to compare two received packets to determine which
* one is received first.
*/
int
determine_recv_buf_ordering(
const struct recvbuf *b1,
const struct recvbuf *b2
)
{
double recv_time1;
double recv_time2;
/* Simply convert the time received to double and subtract */
LFPTOD(&b1->recv_time, recv_time1);
LFPTOD(&b2->recv_time, recv_time2);
return (int)(recv_time1 - recv_time2);
}
/* Define a function to create the server associations */
void create_server_associations(void)
{
int i;
for (i = 0; i < simulation.num_of_servers; ++i) {
printf("%s\n", stoa(simulation.servers[i].addr));
if (peer_config(simulation.servers[i].addr,
NULL,
loopback_interface,
MODE_CLIENT,
-1,
NTP_VERSION,
NTP_MINDPOLL,
NTP_MAXDPOLL,
0, /* peerflags */
0, /* ttl */
0, /* peerkey */
NULL /* group ident */) == 0) {
fprintf(stderr,
"ERROR!! Could not create association for: %s\n",
stoa(simulation.servers[i].addr));
}
}
}
/* Main Simulator Code */
int
ntpsim(
int argc,
char * argv[]
)
{
Event * curr_event;
struct timeval seed;
/* Initialize the local Clock */
simclock.local_time = 0;
simclock.adj = 0;
simclock.slew = 500e-6;
/* Call getconfig to parse the configuration file */
getconfig(argc, argv);
loop_config(LOOP_DRIFTINIT, 0);
initializing = FALSE;
/*
* Watch out here, we want the real time, not the silly stuff.
*/
gettimeofday(&seed, NULL);
ntp_srandom(seed.tv_usec);
/* Initialize the event queue */
event_queue = create_priority_queue((q_order_func)
determine_event_ordering);
/* Initialize the receive queue */
recv_queue = create_priority_queue((q_order_func)
determine_recv_buf_ordering);
/* Push a beep and a timer on the event queue */
enqueue(event_queue, event(0, BEEP));
enqueue(event_queue, event(simulation.sim_time + 1.0, TIMER));
/*
* Pop the queue until nothing is left or time is exceeded
*/
/* maxtime = simulation.sim_time + simulation.end_time;*/
while (simulation.sim_time <= simulation.end_time &&
(!empty(event_queue))) {
curr_event = dequeue(event_queue);
/* Update all the clocks to the time on the event */
sim_update_clocks(curr_event);
/* Execute the function associated with the event */
(*event_ptr[curr_event->function])(curr_event);
free_node(curr_event);
}
printf("sys_received: %lu\n", sys_received);
printf("sys_badlength: %lu\n", sys_badlength);
printf("sys_declined: %lu\n", sys_declined);
printf("sys_restricted: %lu\n", sys_restricted);
printf("sys_newversion: %lu\n", sys_newversion);
printf("sys_oldversion: %lu\n", sys_oldversion);
printf("sys_limitrejected: %lu\n", sys_limitrejected);
printf("sys_badauth: %lu\n", sys_badauth);
/* Define a function to create an return an Event */
Event *event(double t, funcTkn f)
{
Event *e;
if ((e = get_node(sizeof(*e))) == NULL)
abortsim("get_node failed in event");
e->time = t;
e->function = f;
return (e);
}
/* NTP SIMULATION FUNCTIONS */
/* Define a function for processing a timer interrupt.
* On every timer interrupt, call the NTP timer to send packets and process
* the clock and then call the receive function to receive packets.
*/
void sim_event_timer(Event *e)
{
struct recvbuf *rbuf;
/* Call the NTP timer.
* This will be responsible for actually "sending the packets."
* Since this is a simulation, the packets sent over the network
* will be processed by the simulate_server routine below.
*/
timer();
/* Process received buffers */
while (!empty(recv_queue)) {
rbuf = (struct recvbuf *)dequeue(recv_queue);
(*rbuf->receiver)(rbuf);
free_node(rbuf);
}
/* Arm the next timer interrupt. */
enqueue(event_queue,
event(simulation.sim_time + (1 << EVENT_TIMEOUT), TIMER));
}
/* Define a function to simulate a server.
* This function processes the sent packet according to the server script,
* creates a reply packet and pushes the reply packet onto the event queue
*/
int simulate_server(
sockaddr_u *serv_addr, /* Address of the server */
endpt * inter, /* Interface on which the reply should
be inserted */
struct pkt *rpkt /* Packet sent to the server that
needs to be processed. */
)
{
struct pkt xpkt; /* Packet to be transmitted back
to the client */
struct recvbuf rbuf; /* Buffer for the received packet */
Event *e; /* Packet receive event */
server_info *server; /* Pointer to the server being simulated */
script_info *curr_script; /* Current script being processed */
int i;
double d1, d2, d3; /* Delays while the packet is enroute */
double t1, t2, t3, t4; /* The four timestamps in the packet */
l_fp lfp_host; /* host-order l_fp */
ZERO(xpkt);
ZERO(rbuf);
/* Search for the server with the desired address */
server = NULL;
for (i = 0; i < simulation.num_of_servers; ++i) {
if (memcmp(simulation.servers[i].addr, serv_addr,
sizeof(*serv_addr)) == 0) {
server = &simulation.servers[i];
break;
}
}
fprintf(stderr, "Received packet from %s on %s\n",
stoa(serv_addr), latoa(inter));
if (server == NULL)
abortsim("Server with specified address not found!!!");
/* Get the current script for the server */
curr_script = server->curr_script;
/* Create a server reply packet.
* Masquerade the reply as a stratum-1 server with a GPS clock
*/
xpkt.li_vn_mode = PKT_LI_VN_MODE(LEAP_NOWARNING, NTP_VERSION,
MODE_SERVER);
xpkt.stratum = STRATUM_TO_PKT(((u_char)1));
memcpy(&xpkt.refid, "GPS", 4);
xpkt.ppoll = rpkt->ppoll;
xpkt.precision = rpkt->precision;
xpkt.rootdelay = 0;
xpkt.rootdisp = 0;
/* Note: In the transmitted packet:
* 1. t1 and t4 are times in the client according to the local clock.
* 2. t2 and t3 are server times according to the simulated server.
* Compute t1, t2, t3 and t4
* Note: This function is called at time t1.
*/
/* Save the timestamps */
xpkt.org = rpkt->xmt;
DTOLFP(t2, &lfp_host);
HTONL_FP(&lfp_host, &xpkt.rec);
DTOLFP(t3, &lfp_host);
HTONL_FP(&lfp_host, &xpkt.xmt);
xpkt.reftime = xpkt.xmt;
/*
* Ok, we are done with the packet. Now initialize the receive
* buffer for the packet.
*/
rbuf.used = 1;
rbuf.receiver = &receive; /* callback to process the packet */
rbuf.recv_length = LEN_PKT_NOMAC;
rbuf.recv_pkt = xpkt;
rbuf.dstadr = inter;
rbuf.fd = inter->fd;
memcpy(&rbuf.srcadr, serv_addr, sizeof(rbuf.srcadr));
memcpy(&rbuf.recv_srcadr, serv_addr, sizeof(rbuf.recv_srcadr));
/*
* Create a packet event and insert it onto the event_queue at the
* arrival time (t4) of the packet at the client
*/
e = event(t4, PACKET);
e->rcv_buf = rbuf;
enqueue(event_queue, e);
/*
* Check if the time of the script has expired. If yes, delete it.
*/
if (curr_script->duration > simulation.sim_time &&
NULL == HEAD_PFIFO(server->script)) {
printf("Hello\n");
/*
* For some reason freeing up the curr_script memory kills the
* simulation. Further debugging is needed to determine why.
* free(curr_script);
*/
UNLINK_FIFO(curr_script, *server->script, link);
}
return (0);
}
/* Define a function to update all the clocks
* Most of the code is modified from the systime.c file by Prof. Mills
*/
void sim_update_clocks(Event *e)
{
double time_gap;
double adj;
int i;
/* Compute the time between the last update event and this update */
time_gap = e->time - simulation.sim_time;
if (time_gap < 0)
printf("WARNING: e->time %.6g comes before sim_time %.6g (gap %+.6g)\n",
e->time, simulation.sim_time, time_gap);
/* Advance the client clock */
if (e->time + time_gap < simclock.local_time)
printf("WARNING: e->time + gap %.6g comes before local_time %.6g\n",
e->time + time_gap, simclock.local_time);
simclock.local_time = e->time + time_gap;
/* Advance the simulation time */
simulation.sim_time = e->time;
/* Advance the server clocks adjusted for systematic and random frequency
* errors. The random error is a random walk computed as the
* integral of samples from a Gaussian distribution.
*/
for (i = 0; i < simulation.num_of_servers; ++i) {
simulation.servers[i].curr_script->freq_offset +=
gauss(0, time_gap * simulation.servers[i].curr_script->wander);
/* Perform the adjtime() function. If the adjustment completed
* in the previous interval, amortize the entire amount; if not,
* carry the leftover to the next interval.
*/
/* Allocate a receive buffer and copy the packet to it */
if ((rbuf = get_node(sizeof(*rbuf))) == NULL)
abortsim("get_node failed in sim_event_recv_packet");
memcpy(rbuf, &e->rcv_buf, sizeof(*rbuf));
/* Store the local time in the received packet */
DTOLFP(simclock.local_time, &rbuf->recv_time);
/* Insert the packet received onto the receive queue */
enqueue(recv_queue, rbuf);
}
/* Define a function to output simulation statistics on a beep event
*/
/*** TODO: Need to decide on how to output for multiple servers ***/
void sim_event_beep(Event *e)
{
#if 0
static int first_time = 1;
char *dash = "-----------------";
#endif
/* CODE ORIGINALLY IN libntp/systime.c
* -----------------------------------
* This code was a part of the original NTP simulator and originally
* had its home in the libntp/systime.c file.
*
* It has been shamelessly moved to here and has been modified for the
* purposes of the current simulator.
*/
/*
* get_systime - return the system time in NTP timestamp format
*/
void
get_systime(
l_fp *now /* current system time in l_fp */ )
{
/*
* To fool the code that determines the local clock precision,
* we advance the clock a minimum of 200 nanoseconds on every
* clock read. This is appropriate for a typical modern machine
* with nanosecond clocks. Note we make no attempt here to
* simulate reading error, since the error is so small. This may
* change when the need comes to implement picosecond clocks.
*/
if (simclock.local_time == simclock.last_read_time)
simclock.local_time += 200e-9;
/*
* adj_systime - advance or retard the system clock exactly like the
* real thng.
*/
int /* always succeeds */
adj_systime(
double now /* time adjustment (s) */
)
{
struct timeval adjtv; /* new adjustment */
double dtemp;
long ticks;
int isneg = 0;
/*
* Most Unix adjtime() implementations adjust the system clock
* in microsecond quanta, but some adjust in 10-ms quanta. We
* carefully round the adjustment to the nearest quantum, then
* adjust in quanta and keep the residue for later.
*/
dtemp = now + sys_residual;
if (dtemp < 0) {
isneg = 1;
dtemp = -dtemp;
}
adjtv.tv_sec = (long)dtemp;
dtemp -= adjtv.tv_sec;
ticks = (long)(dtemp / sys_tick + .5);
adjtv.tv_usec = (long)(ticks * sys_tick * 1e6);
dtemp -= adjtv.tv_usec / 1e6;
sys_residual = dtemp;
/*
* Convert to signed seconds and microseconds for the Unix
* adjtime() system call. Note we purposely lose the adjtime()
* leftover.
*/
if (isneg) {
adjtv.tv_sec = -adjtv.tv_sec;
adjtv.tv_usec = -adjtv.tv_usec;
sys_residual = -sys_residual;
}
simclock.adj = now;
/* ntp_node.adj = now; */
return (1);
}
/*
* step_systime - step the system clock. We are religious here.
*/
int /* always succeeds */
step_systime(
double now /* step adjustment (s) */
)
{
#ifdef DEBUG
if (debug)
printf("step_systime: time %.6f adj %.6f\n",
simclock.local_time, now);
#endif
simclock.local_time += now;
return (1);
}
/*
* gauss() - returns samples from a gaussion distribution
*/
double /* Gaussian sample */
gauss(
double m, /* sample mean */
double s /* sample standard deviation (sigma) */
)
{
double q1, q2;
/*
* Roll a sample from a Gaussian distribution with mean m and
* standard deviation s. For m = 0, s = 1, mean(y) = 0,
* std(y) = 1.
*/
if (s == 0)
return (m);
while ((q1 = drand48()) == 0)
/* empty statement */;
q2 = drand48();
return (m + s * sqrt(-2. * log(q1)) * cos(2. * PI * q2));
}
/*
* poisson() - returns samples from a network delay distribution
*/
double /* delay sample (s) */
poisson(
double m, /* fixed propagation delay (s) */
double s /* exponential parameter (mu) */
)
{
double q1;
/*
* Roll a sample from a composite distribution with propagation
* delay m and exponential distribution time with parameter s.
* For m = 0, s = 1, mean(y) = std(y) = 1.
*/
if (s == 0)
return (m);
while ((q1 = drand48()) == 0)
/* empty statement */;
return (m - s * log(q1 * s));
}
