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clientlog: separate NTP timestamps from IP addresses

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Instead of keeping one pair of RX and TX timestamp for each address, add
a separate RX->TX map using an ordered circular buffer. Save the RX
timestamps as 64-bit integers and search them with a combined linear
interpolation and binary algorithm.

This enables the server to support multiple interleaved clients sharing
the same IP address (e.g. NAT) and it will allow other improvements to
be implemented later. A drawback is that a single broken client sending
interleaved requests at a high rate (without spoofing the source
address) can now prevent clients on other addresses from getting
interleaved responses.

The total number of saved timestamps does not change. It's still
determined by the clientloglimit directive. A new option may be added
later if needed. The whole buffer is allocated at once, but only on
first use to not waste memory on client-only configurations.
This commit is contained in:
Miroslav Lichvar
2021-10-11 13:27:35 +02:00
parent 5cb469b204
commit 14b8df3702
5 changed files with 519 additions and 40 deletions
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40
ntp_core.c
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@@ -2042,8 +2042,8 @@ NCR_ProcessRxUnknown(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_a
{
NTP_PacketInfo info;
NTP_Mode my_mode;
NTP_int64 *local_ntp_rx, *local_ntp_tx;
NTP_Local_Timestamp local_tx, *tx_ts;
NTP_int64 ntp_rx, *local_ntp_rx;
int log_index, interleaved, poll, version;
uint32_t kod;
@@ -2106,7 +2106,7 @@ NCR_ProcessRxUnknown(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_a
CLG_LogAuthNtpRequest();
}
local_ntp_rx = local_ntp_tx = NULL;
local_ntp_rx = NULL;
tx_ts = NULL;
interleaved = 0;
@@ -2115,18 +2115,15 @@ NCR_ProcessRxUnknown(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_a
in the interleaved mode. This means the third reply to a new client is
the earliest one that can be interleaved. We don't want to waste time
on clients that are not using the interleaved mode. */
if (kod == 0 && log_index >= 0) {
CLG_GetNtpTimestamps(log_index, &local_ntp_rx, &local_ntp_tx);
interleaved = !UTI_IsZeroNtp64(local_ntp_rx) &&
!UTI_CompareNtp64(&message->originate_ts, local_ntp_rx) &&
UTI_CompareNtp64(&message->receive_ts, &message->transmit_ts);
if (kod == 0 &&
UTI_CompareNtp64(&message->receive_ts, &message->transmit_ts) != 0) {
ntp_rx = message->originate_ts;
local_ntp_rx = &ntp_rx;
interleaved = CLG_GetNtpTxTimestamp(&ntp_rx, &local_tx.ts);
if (interleaved) {
UTI_Ntp64ToTimespec(local_ntp_tx, &local_tx.ts);
tx_ts = &local_tx;
} else {
UTI_ZeroNtp64(local_ntp_tx);
local_ntp_tx = NULL;
CLG_DisableNtpTimestamps(&ntp_rx);
}
}
@@ -2144,9 +2141,8 @@ NCR_ProcessRxUnknown(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_a
rx_ts, tx_ts, local_ntp_rx, NULL, remote_addr, local_addr,
message, &info);
/* Save the transmit timestamp */
if (tx_ts)
UTI_TimespecToNtp64(&tx_ts->ts, local_ntp_tx, NULL);
if (local_ntp_rx)
CLG_SaveNtpTimestamps(local_ntp_rx, tx_ts ? &tx_ts->ts : NULL);
}
/* ================================================== */
@@ -2208,10 +2204,9 @@ void
NCR_ProcessTxUnknown(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
NTP_Local_Timestamp *tx_ts, NTP_Packet *message, int length)
{
NTP_int64 *local_ntp_rx, *local_ntp_tx;
NTP_Local_Timestamp local_tx;
NTP_int64 *local_ntp_rx;
NTP_PacketInfo info;
int log_index;
if (!parse_packet(message, length, &info))
return;
@@ -2219,18 +2214,17 @@ NCR_ProcessTxUnknown(NTP_Remote_Address *remote_addr, NTP_Local_Address *local_a
if (info.mode == MODE_BROADCAST)
return;
log_index = CLG_GetClientIndex(&remote_addr->ip_addr);
if (log_index < 0)
return;
if (SMT_IsEnabled() && info.mode == MODE_SERVER)
UTI_AddDoubleToTimespec(&tx_ts->ts, SMT_GetOffset(&tx_ts->ts), &tx_ts->ts);
CLG_GetNtpTimestamps(log_index, &local_ntp_rx, &local_ntp_tx);
local_ntp_rx = &message->receive_ts;
if (!CLG_GetNtpTxTimestamp(local_ntp_rx, &local_tx.ts))
return;
UTI_Ntp64ToTimespec(local_ntp_tx, &local_tx.ts);
update_tx_timestamp(&local_tx, tx_ts, local_ntp_rx, NULL, message);
UTI_TimespecToNtp64(&local_tx.ts, local_ntp_tx, NULL);
CLG_UpdateNtpTxTimestamp(local_ntp_rx, &local_tx.ts);
}
/* ================================================== */