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First preview release.
This commit is contained in:
Poul-Henning Kamp
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ntp_filter.c
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192
ntp_filter.c
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/*-
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* Copyright (c) 2014 Poul-Henning Kamp
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* Filter incoming NTP packets
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* ===========================
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*/
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#include <math.h>
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#include <stdlib.h>
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#include "ntimed.h"
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#include "ntp.h"
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#define PARAM_NTP_FILTER PARAM_INSTANCE
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#define PARAM_TABLE_NAME ntp_filter_param_table
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#include "param_instance.h"
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#undef PARAM_TABLE_NAME
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#undef PARAM_NTP_FILTER
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struct ntp_filter {
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unsigned magic;
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#define NTP_FILTER_MAGIC 0xf7b7032d
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double lo, mid, hi;
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double alo, amid, ahi;
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double alolo, ahihi;
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double navg;
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double trust;
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};
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static void __match_proto__(ntp_filter_f)
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nf_filter(struct ocx *ocx, const struct ntp_peer *np)
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{
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struct ntp_filter *nf;
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struct ntp_packet *rxp;
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int branch, fail_hi, fail_lo;
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double lo_noise, hi_noise;
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double lo_lim, hi_lim;
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double r;
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char buf[256];
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CAST_OBJ_NOTNULL(nf, np->filter_priv, NTP_FILTER_MAGIC);
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rxp = np->rx_pkt;
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CHECK_OBJ_NOTNULL(rxp, NTP_PACKET_MAGIC);
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NTP_Tool_Format(buf, sizeof buf, rxp);
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Put(NULL, OCX_TRACE, "NTP_Packet %+f %s %s %s\n",
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np->hostname, np->ip, buf);
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if (rxp->ntp_leap == NTP_LEAP_UNKNOWN)
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return; // XXX diags
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// XXX: Check leap warnings in wrong months
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// XXX: Check leap warnings against other sources
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if (rxp->ntp_version < 3 || rxp->ntp_version > 4) {
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Put(ocx, OCX_TRACE, "NF Bad version %d\n", rxp->ntp_version);
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return;
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}
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if (rxp->ntp_mode != NTP_MODE_SERVER) {
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Put(ocx, OCX_TRACE, "NF Bad mode %d\n", rxp->ntp_mode);
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return;
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}
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if (rxp->ntp_stratum == 0 || rxp->ntp_stratum > 15) {
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Put(ocx, OCX_TRACE, "NF Bad stratum %d\n", rxp->ntp_stratum);
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return;
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}
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r = TS_Diff(&rxp->ntp_transmit, &rxp->ntp_receive);
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if (r <= 0.0) {
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Put(ocx, OCX_TRACE, "NF rx after tx %.3e\n", r);
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return;
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}
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r = TS_Diff(&rxp->ntp_transmit, &rxp->ntp_reference);
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if (r < -2e-9) {
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/* two nanoseconds to Finagle rounding errors */
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Put(ocx, OCX_TRACE, "NF ref after tx %.3e\n", r);
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return; // XXX diags
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}
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// This is almost never a good sign.
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if (r > 2048) {
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/* XXX: 2048 -> param */
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Put(ocx, OCX_TRACE, "NF ancient ref %.3e\n", r);
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return;
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}
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if (nf->navg < param_ntp_filter_average)
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nf->navg += 1;
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nf->lo = TS_Diff(&rxp->ntp_origin, &rxp->ntp_receive);
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nf->hi = TS_Diff(&rxp->ts_rx, &rxp->ntp_transmit);
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nf->mid = .5 * (nf->lo + nf->hi);
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if (nf->navg > 2) {
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lo_noise = sqrt(nf->alolo - nf->alo * nf->alo);
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hi_noise = sqrt(nf->ahihi - nf->ahi * nf->ahi);
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} else {
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lo_noise = 0.0;
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hi_noise = 0.0;
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}
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lo_lim = nf->alo - lo_noise * param_ntp_filter_threshold;
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hi_lim = nf->ahi + hi_noise * param_ntp_filter_threshold;
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fail_lo = nf->lo < lo_lim;
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fail_hi = nf->hi > hi_lim;
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if (fail_lo && fail_hi) {
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branch = 1;
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} else if (nf->navg > 3 && fail_lo) {
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nf->mid = nf->amid + (nf->hi - nf->ahi);
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branch = 2;
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} else if (nf->navg > 3 && fail_hi) {
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nf->mid = nf->amid + nf->lo - nf->alo;
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branch = 3;
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} else {
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branch = 4;
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}
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r = nf->navg;
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if (nf->navg > 2 && branch != 4)
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r *= r;
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nf->alo += (nf->lo - nf->alo) / r;
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nf->amid += (nf->mid - nf->amid) / r;
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nf->ahi += (nf->hi - nf->ahi) / r;
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nf->alolo += (nf->lo*nf->lo - nf->alolo) / r;
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nf->ahihi += (nf->hi*nf->hi - nf->ahihi) / r;
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if (rxp->ntp_stratum == 0)
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nf->trust = 0.0;
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else if (rxp->ntp_stratum == 15)
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nf->trust = 0.0;
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else
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nf->trust = 1.0 / rxp->ntp_stratum;
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Put(ocx, OCX_TRACE,
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"NTP_Filter %s %s %d %.3e %.3e %.3e %.3e %.3e %.3e\n",
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np->hostname, np->ip, branch,
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nf->lo, nf->mid, nf->hi,
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lo_lim, nf->amid, hi_lim);
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if (np->combiner->func != NULL)
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np->combiner->func(ocx, np->combiner,
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nf->trust, nf->lo, nf->mid, nf->hi);
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}
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void
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NF_New(struct ntp_peer *np)
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{
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struct ntp_filter *nf;
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ALLOC_OBJ(nf, NTP_FILTER_MAGIC);
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AN(nf);
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np->filter_func = nf_filter;
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np->filter_priv = nf;
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}
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void
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NF_Init(void)
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{
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Param_Register(ntp_filter_param_table);
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}
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