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ntp: add server support for experimental extension field

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Maintain a server monotonic timescale needed for the experimental
extension field. It follows the best estimate of frequency without
time corrections. Implement it as an offset relative to the NTP time,
starting at zero, using a slew handler to cancel time corrections of the
NTP clock. The 32-bit epoch ID is set to a random value on start and
every step of the system clock.
This commit is contained in:
Miroslav Lichvar 2021-11-10 14:56:31 +01:00
parent 2e126ed2b5
commit 0bf39c0ab9
1 changed files with 61 additions and 0 deletions
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61
ntp_core.c
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@ -294,6 +294,11 @@ static int server_sock_fd6;
static ADF_AuthTable access_auth_table; static ADF_AuthTable access_auth_table;
/* Current offset between monotonic and cooked time, and its epoch ID
which is reset on clock steps */
static double server_mono_offset;
static uint32_t server_mono_epoch;
/* Characters for printing synchronisation status and timestamping source */ /* Characters for printing synchronisation status and timestamping source */
static const char leap_chars[4] = {'N', '+', '-', '?'}; static const char leap_chars[4] = {'N', '+', '-', '?'};
static const char tss_chars[3] = {'D', 'K', 'H'}; static const char tss_chars[3] = {'D', 'K', 'H'};
@ -380,6 +385,20 @@ zero_local_timestamp(NTP_Local_Timestamp *ts)
/* ================================================== */ /* ================================================== */
static void
handle_slew(struct timespec *raw, struct timespec *cooked, double dfreq,
double doffset, LCL_ChangeType change_type, void *anything)
{
if (change_type == LCL_ChangeAdjust) {
server_mono_offset += doffset;
} else {
UTI_GetRandomBytes(&server_mono_epoch, sizeof (server_mono_epoch));
server_mono_offset = 0.0;
}
}
/* ================================================== */
void void
NCR_Initialise(void) NCR_Initialise(void)
{ {
@ -396,6 +415,9 @@ NCR_Initialise(void)
/* Server socket will be opened when access is allowed */ /* Server socket will be opened when access is allowed */
server_sock_fd4 = INVALID_SOCK_FD; server_sock_fd4 = INVALID_SOCK_FD;
server_sock_fd6 = INVALID_SOCK_FD; server_sock_fd6 = INVALID_SOCK_FD;
LCL_AddParameterChangeHandler(handle_slew, NULL);
handle_slew(NULL, NULL, 0.0, 0.0, LCL_ChangeUnknownStep, NULL);
} }
/* ================================================== */ /* ================================================== */
@ -405,6 +427,8 @@ NCR_Finalise(void)
{ {
unsigned int i; unsigned int i;
LCL_RemoveParameterChangeHandler(handle_slew, NULL);
if (server_sock_fd4 != INVALID_SOCK_FD) if (server_sock_fd4 != INVALID_SOCK_FD)
NIO_CloseServerSocket(server_sock_fd4); NIO_CloseServerSocket(server_sock_fd4);
if (server_sock_fd6 != INVALID_SOCK_FD) if (server_sock_fd6 != INVALID_SOCK_FD)
@ -925,6 +949,38 @@ receive_timeout(void *arg)
/* ================================================== */ /* ================================================== */
static int
add_ext_exp1(NTP_Packet *message, NTP_PacketInfo *info, struct timespec *rx,
double root_delay, double root_dispersion)
{
struct timespec mono_rx;
NTP_ExtFieldExp1 exp1;
NTP_int64 ts_fuzz;
memset(&exp1, 0, sizeof (exp1));
exp1.magic = htonl(NTP_EF_EXP1_MAGIC);
if (info->mode != MODE_CLIENT) {
exp1.root_delay = UTI_DoubleToNtp32f28(root_delay);
exp1.root_dispersion = UTI_DoubleToNtp32f28(root_dispersion);
UTI_AddDoubleToTimespec(rx, server_mono_offset, &mono_rx);
UTI_GetNtp64Fuzz(&ts_fuzz, message->precision);
UTI_TimespecToNtp64(&mono_rx, &exp1.mono_receive_ts, &ts_fuzz);
exp1.mono_epoch = htonl(server_mono_epoch);
}
if (!NEF_AddField(message, info, NTP_EF_EXP1, &exp1, sizeof (exp1))) {
DEBUG_LOG("Could not add EF");
return 0;
}
info->ext_field_flags |= NTP_EF_FLAG_EXP1;
return 1;
}
/* ================================================== */
static int static int
transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
int interleaved, /* Flag enabling interleaved mode */ int interleaved, /* Flag enabling interleaved mode */
@ -1070,6 +1126,11 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
return 0; return 0;
if (ext_field_flags) { if (ext_field_flags) {
if (ext_field_flags & NTP_EF_FLAG_EXP1) {
if (!add_ext_exp1(&message, &info, &local_receive,
our_root_delay, our_root_dispersion))
return 0;
}
} }
do { do {