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Implement Jitter #81

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Implement Jitter #81

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d2b0465
Implement Jitter
Mar 10, 2022
e026e84
Document Jitter Setting in Manpage
Mar 10, 2022
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3 changes: 3 additions & 0 deletions endlessh.1
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
.Nm endless
.Op Fl 46chsvV
.Op Fl d Ar delay
.Op Fl j Ar jitter
.Op Fl f Ar config
.Op Fl l Ar max banner length
.Op Fl m Ar max clients
Expand Down Expand Up @@ -40,6 +41,8 @@ Forces
to use IPv6 addresses only.
.It Fl d Ar delay
Message milliseconds delay. Default: 10000
.It Fl j Ar jitter
Randomizes the delay by j% (0-100). Default: 0 (no jitter)
.It Fl f Ar config
Set and load config file.
By default
Expand Down
45 changes: 42 additions & 3 deletions endlessh.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@

#define DEFAULT_PORT 2222
#define DEFAULT_DELAY 10000 /* milliseconds */
#define DEFAULT_DELAY_JITTER 0 /* Percent; for backward compatibility */
#define DEFAULT_MAX_LINE_LENGTH 32
#define DEFAULT_MAX_CLIENTS 4096

Expand Down Expand Up @@ -105,6 +106,14 @@ logsyslog(enum loglevel level, const char *format, ...)
}
}

static long long random_delay(int delay, uint16_t jitter) {
if(!jitter)
return delay;

long long max_difference = delay*jitter/100;
return delay+(rand()%(2*max_difference))-max_difference; //insecure rand() was used on purpose to avoid potential performance bottleneck
}

static struct {
long long connects;
long long milliseconds;
Expand Down Expand Up @@ -298,6 +307,7 @@ sigusr1_handler(int signal)
struct config {
int port;
int delay;
uint16_t jitter;
int max_line_length;
int max_clients;
int bind_family;
Expand All @@ -306,6 +316,7 @@ struct config {
#define CONFIG_DEFAULT { \
.port = DEFAULT_PORT, \
.delay = DEFAULT_DELAY, \
.jitter = DEFAULT_DELAY_JITTER, \
.max_line_length = DEFAULT_MAX_LINE_LENGTH, \
.max_clients = DEFAULT_MAX_CLIENTS, \
.bind_family = DEFAULT_BIND_FAMILY, \
Expand Down Expand Up @@ -341,6 +352,21 @@ config_set_delay(struct config *c, const char *s, int hardfail)
}
}

static void
config_set_jitter(struct config *c, const char *s, int hardfail) //TODO
{
errno = 0;
char *end;
long tmp = strtol(s, &end, 10);
if (errno || *end || tmp < 0 || tmp > 100) {
fprintf(stderr, "endlessh: Invalid jitter: %s (0 <= jitter <= 100)\n", s);
if (hardfail)
exit(EXIT_FAILURE);
} else {
c->jitter = (uint16_t)tmp;
}
}

static void
config_set_max_clients(struct config *c, const char *s, int hardfail)
{
Expand Down Expand Up @@ -396,6 +422,7 @@ enum config_key {
KEY_INVALID,
KEY_PORT,
KEY_DELAY,
KEY_JITTER,
KEY_MAX_LINE_LENGTH,
KEY_MAX_CLIENTS,
KEY_LOG_LEVEL,
Expand All @@ -408,6 +435,7 @@ config_key_parse(const char *tok)
static const char *const table[] = {
[KEY_PORT] = "Port",
[KEY_DELAY] = "Delay",
[KEY_JITTER] = "Jitter",
[KEY_MAX_LINE_LENGTH] = "MaxLineLength",
[KEY_MAX_CLIENTS] = "MaxClients",
[KEY_LOG_LEVEL] = "LogLevel",
Expand Down Expand Up @@ -472,6 +500,9 @@ config_load(struct config *c, const char *file, int hardfail)
case KEY_DELAY:
config_set_delay(c, tokens[1], hardfail);
break;
case KEY_JITTER:
config_set_jitter(c, tokens[1], hardfail);
break;
case KEY_MAX_LINE_LENGTH:
config_set_max_line_length(c, tokens[1], hardfail);
break;
Expand Down Expand Up @@ -505,6 +536,7 @@ config_log(const struct config *c)
{
logmsg(log_info, "Port %d", c->port);
logmsg(log_info, "Delay %d", c->delay);
logmsg(log_info, "Jitter %d", c->jitter);
logmsg(log_info, "MaxLineLength %d", c->max_line_length);
logmsg(log_info, "MaxClients %d", c->max_clients);
logmsg(log_info, "BindFamily %s",
Expand All @@ -522,6 +554,8 @@ usage(FILE *f)
fprintf(f, " -6 Bind to IPv6 only\n");
fprintf(f, " -d INT Message millisecond delay ["
XSTR(DEFAULT_DELAY) "]\n");
fprintf(f, " -j FLOAT Delay Jitter in Percent ["
XSTR(DEFAULT_DELAY_JITTER) "]\n");
fprintf(f, " -f Set and load config file ["
DEFAULT_CONFIG_FILE "]\n");
fprintf(f, " -h Print this help message and exit\n");
Expand Down Expand Up @@ -632,6 +666,8 @@ main(int argc, char **argv)
struct config config = CONFIG_DEFAULT;
const char *config_file = DEFAULT_CONFIG_FILE;

srand((unsigned int)time(NULL)); //insecure rand() was used on purpose to avoid potential performance bottleneck

#if defined(__OpenBSD__)
unveil(config_file, "r"); /* return ignored as the file may not exist */
if (pledge("inet stdio rpath unveil", 0) == -1)
Expand All @@ -641,7 +677,7 @@ main(int argc, char **argv)
config_load(&config, config_file, 1);

int option;
while ((option = getopt(argc, argv, "46d:f:hl:m:p:svV")) != -1) {
while ((option = getopt(argc, argv, "46d:j:f:hl:m:p:svV")) != -1) {
switch (option) {
case '4':
config_set_bind_family(&config, "4", 1);
Expand All @@ -652,6 +688,9 @@ main(int argc, char **argv)
case 'd':
config_set_delay(&config, optarg, 1);
break;
case 'j':
config_set_jitter(&config, optarg, 1);
break;
case 'f':
config_file = optarg;

Expand Down Expand Up @@ -765,7 +804,7 @@ main(int argc, char **argv)
if (fifo->head->send_next <= now) {
struct client *c = fifo_pop(fifo);
if (sendline(c, config.max_line_length, &rng)) {
c->send_next = now + config.delay;
c->send_next = now + random_delay(config.delay, config.jitter);
fifo_append(fifo, c);
}
} else {
Expand Down Expand Up @@ -818,7 +857,7 @@ main(int argc, char **argv)
exit(EXIT_FAILURE);
}
} else {
long long send_next = epochms() + config.delay;
long long send_next = epochms() + random_delay(config.delay, config.jitter);
struct client *client = client_new(fd, send_next);
int flags = fcntl(fd, F_GETFL, 0); /* cannot fail */
fcntl(fd, F_SETFL, flags | O_NONBLOCK); /* cannot fail */
Expand Down