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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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7
clientlog.h
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@@ -43,9 +43,14 @@ extern int CLG_GetClientIndex(IPAddr *client);
extern int CLG_LogServiceAccess(CLG_Service service, IPAddr *client, struct timespec *now);
extern int CLG_LimitServiceRate(CLG_Service service, int index);
extern void CLG_LogAuthNtpRequest(void);
extern void CLG_GetNtpTimestamps(int index, NTP_int64 **rx_ts, NTP_int64 **tx_ts);
extern int CLG_GetNtpMinPoll(void);
/* Functions to save and retrieve timestamps for server interleaved mode */
extern void CLG_SaveNtpTimestamps(NTP_int64 *rx_ts, struct timespec *tx_ts);
extern void CLG_UpdateNtpTxTimestamp(NTP_int64 *rx_ts, struct timespec *tx_ts);
extern int CLG_GetNtpTxTimestamp(NTP_int64 *rx_ts, struct timespec *tx_ts);
extern void CLG_DisableNtpTimestamps(NTP_int64 *rx_ts);
/* And some reporting functions, for use by chronyc. */
extern int CLG_GetNumberOfIndices(void);