From 0fd365316a399ad57ae142697286e8ddc1938089 Mon Sep 17 00:00:00 2001 From: Nathaniel Wesley Filardo Date: Fri, 5 Jul 2019 12:01:30 +0100 Subject: [PATCH] Rewrite sntp in Lua with only a little C --- app/modules/sntppkt.c | 403 ++++++++++++++++++++++++++++++++++++++ docs/lua-modules/sntp.md | 239 ++++++++++++++++++++++ lua_modules/sntp/sntp.lua | 294 +++++++++++++++++++++++++++ mkdocs.yml | 2 + tools/luacheck_config.lua | 6 + 5 files changed, 944 insertions(+) create mode 100644 app/modules/sntppkt.c create mode 100644 docs/lua-modules/sntp.md create mode 100644 lua_modules/sntp/sntp.lua diff --git a/app/modules/sntppkt.c b/app/modules/sntppkt.c new file mode 100644 index 00000000..e6d6715e --- /dev/null +++ b/app/modules/sntppkt.c @@ -0,0 +1,403 @@ +/* + * Copyright 2015 Dius Computing Pty Ltd. All rights reserved. + * Copyright 2020 Nathaniel Wesley Filardo. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * - Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * - Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the + * distribution. + * - Neither the name of the copyright holders nor the names of + * its contributors may be used to endorse or promote products derived + * from this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL + * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, + * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR + * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, + * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED + * OF THE POSSIBILITY OF SUCH DAMAGE. + * + * @author Johny Mattsson + * @author Nathaniel Wesley Filardo + */ + +// Module for Simple Network Time Protocol (SNTP) packet processing; +// see lua_modules/sntp/sntp.lua for the user-friendly bits of this. + +#include "module.h" +#include "lauxlib.h" +#include "os_type.h" +#include "osapi.h" +#include "lwip/udp.h" +#include +#include "user_modules.h" +#include "lwip/dns.h" + +#define max(a,b) ((a < b) ? b : a) + +#define NTP_PORT 123 +#define NTP_ANYCAST_ADDR(dst) IP4_ADDR(dst, 224, 0, 1, 1) + +#if 0 +# define sntppkt_dbg(...) printf(__VA_ARGS__) +#else +# define sntppkt_dbg(...) +#endif + +typedef struct +{ + uint32_t sec; + uint32_t frac; +} ntp_timestamp_t; + +static const uint32_t NTP_TO_UNIX_EPOCH = 2208988800ul; + +typedef struct +{ + uint8_t mode : 3; + uint8_t ver : 3; + uint8_t LI : 2; + uint8_t stratum; + uint8_t poll; + uint8_t precision; + uint32_t delta_r; + uint32_t epsilon_r; + uint32_t refid; + ntp_timestamp_t ref; + ntp_timestamp_t origin; + ntp_timestamp_t recv; + ntp_timestamp_t xmit; +} __attribute__((packed)) ntp_frame_t; + +#define NTP_RESPONSE_METATABLE "sntppkt.resp" +typedef struct { + /* Copied from incoming packet */ + uint32_t delta_r; + uint32_t epsilon_r; + uint8_t LI; + uint8_t stratum; + + /* Computed as per RFC 5905; units are 2^(-32) seconds */ + int64_t theta; + int64_t delta; + + /* Local computation */ + uint64_t t_rx; + uint32_t score; +} ntp_response_t; + +static const uint32_t MICROSECONDS = 1000000; + +static uint64_t +sntppkt_div1m(uint64_t n) { + uint64_t q1 = (n >> 5) + (n >> 10); + uint64_t q2 = (n >> 12) + (q1 >> 1); + uint64_t q3 = (q2 >> 11) - (q2 >> 23); + + uint64_t q = n + q1 + q2 - q3; + + q = q >> 20; + + // Ignore the error term -- it is measured in pico seconds + return q; +} + +static uint32_t +sntppkt_us_to_frac(uint64_t us) { + return sntppkt_div1m(us << 32); +} + +static uint32_t +sntppkt_long_s(uint64_t time) { + return time >> 32; +} + +static uint32_t +sntppkt_long_us(uint64_t time) { + return ((time & 0xFFFFFFFF) * MICROSECONDS) >> 32; +} + +/* + * Convert sec/usec to a Lua string suitable for depositing into a SNTP packet + * buffer. This is a little gross, but it's not the worst thing a C + * programmer's ever done, I'm sure. + */ +static int +sntppkt_make_ts(lua_State *L) { + ntp_timestamp_t ts; + + ts.sec = htonl(luaL_checkinteger(L, 1) + NTP_TO_UNIX_EPOCH) ; + + uint32_t usec = luaL_checkinteger(L, 2) ; + ts.frac = htonl(sntppkt_us_to_frac(usec)); + + lua_pushlstring(L, (const char *)&ts, sizeof(ts)); + return 1; +} + +/* + * Convert ntp_timestamp_t to uint64_t + */ +static uint64_t +sntppkt_ts2uint64(ntp_timestamp_t ts) { + return (((uint64_t)(ts.sec)) << 32) + (uint64_t)(ts.frac); +} + +/* + * Process a SNTP packet as contained in a Lua string, given a cookie timestamp + * and local clock second*usecond pair. Generates a ntp_response_t userdata + * for later processing or a string if the server is telling us to go away. + * + * :: string (packet) + * -> string (cookie) + * -> int (local clock, sec component) + * -> int (local clock, usec component) + * -> sntppkt.resp + * + */ +static int +sntppkt_proc_pkt(lua_State *L) { + size_t pkts_len; + ntp_frame_t pktb; + const char *pkts = lua_tolstring(L, 1, &pkts_len); + + luaL_argcheck(L, pkts && pkts_len == sizeof(pktb), 1, "Bad packet"); + + // make sure we have an aligned copy to work from + memcpy (&pktb, pkts, sizeof(pktb)); + + uint32_t now_sec = luaL_checkinteger(L, 3); + uint32_t now_usec = luaL_checkinteger(L, 4); + + size_t cookie_len; + ntp_timestamp_t *cookie = (ntp_timestamp_t*) lua_tolstring(L, 2, &cookie_len); + + /* Bad *length* is clearly something bogus */ + luaL_argcheck(L, cookie && cookie_len == sizeof(*cookie), 2, "Bad cookie"); + + /* But mismatching value might just be a packet caught in the crossfire */ + if (memcmp((const char *)cookie, (const char *)&pktb.origin, sizeof (*cookie))) { + /* bad cookie; return nil */ + return 0; + } + + /* KOD? Do this test *after* checking the cookie */ + if (pktb.LI == 3) { + lua_pushlstring(L, (const char *)&pktb.refid, 4); + return 1; + } + + ntp_response_t *ntpr = lua_newuserdata(L, sizeof(ntp_response_t)); + luaL_getmetatable(L, NTP_RESPONSE_METATABLE); + lua_setmetatable(L, -2); + + ntpr->LI = pktb.LI; + ntpr->stratum = pktb.stratum; + + // NTP Short Format: 16 bit seconds, 16 bit fraction + ntpr->delta_r = ntohl(pktb.delta_r); + ntpr->epsilon_r = ntohl(pktb.epsilon_r); + + /* Heavy time lifting time */ + + // NTP Long Format: 32 bit seconds, 32 bit fraction + pktb.origin.sec = ntohl(pktb.origin.sec); + pktb.origin.frac = ntohl(pktb.origin.frac); + pktb.recv.sec = ntohl(pktb.recv.sec); + pktb.recv.frac = ntohl(pktb.recv.frac); + pktb.xmit.sec = ntohl(pktb.xmit.sec); + pktb.xmit.frac = ntohl(pktb.xmit.frac); + + uint64_t ntp_origin = sntppkt_ts2uint64(pktb.origin); // We sent it + uint64_t ntp_recv = sntppkt_ts2uint64(pktb.recv); // They got it + uint64_t ntp_xmit = sntppkt_ts2uint64(pktb.xmit); // They replied + + // When we got it back (our clock) + uint64_t ntp_dest = (((uint64_t) now_sec + NTP_TO_UNIX_EPOCH ) << 32) + + sntppkt_us_to_frac(now_usec); + + ntpr->t_rx = ntp_dest; + + // | outgoing offset | | incoming offset | + ntpr->theta = (int64_t)(ntp_recv - ntp_origin) / 2 + (int64_t)(ntp_xmit - ntp_dest) / 2; + + // | our clock delta | | their clock delta | + ntpr->delta = (int64_t)(ntp_dest - ntp_origin) / 2 + (int64_t)(ntp_xmit - ntp_recv) / 2; + + /* Used by sntppkt_resp_pick; bias towards closer clocks */ + ntpr->score = ntpr->delta_r * 2 + ntpr->delta; + + sntppkt_dbg("SNTPPKT n_o=%llx n_r=%llx n_x=%llx n_d=%llx th=%llx d=%llx\n", + ntp_origin, ntp_recv, ntp_xmit, ntp_dest, ntpr->theta, ntpr->delta); + + return 1; +} + +/* + * Left-biased selector of a "preferred" NTP response. Note that preference + * is rather subjective! + * + * Returns true iff we'd prefer the second response to the first. + * + * :: sntppkt.resp -> sntppkt.resp -> boolean + */ + +static int +sntppkt_resp_pick(lua_State *L) { + ntp_response_t *a = luaL_checkudata(L, 1, NTP_RESPONSE_METATABLE); + ntp_response_t *b = luaL_checkudata(L, 2, NTP_RESPONSE_METATABLE); + int biased = 0; + + biased = lua_toboolean(L, 3); + + /* + * If we're "biased", prefer the second structure if the score is less than + * 3/4ths of the score of the first. An unbiased comparison just uses the + * raw score values. + */ + if (biased) { + lua_pushboolean(L, a->score * 3 > b->score * 4); + } else { + lua_pushboolean(L, a->score > b->score ); + } + return 1; +} + +static void +field_from_integer(lua_State *L, const char * field_name, lua_Integer value) { + lua_pushinteger(L, value); + lua_setfield(L, -2, field_name); +} + +/* + * Inflate a NTP response into a Lua table + * + * :: sntppkt.resp -> { } + */ +static int +sntppkt_resp_totable(lua_State *L) { + ntp_response_t *r = luaL_checkudata(L, 1, NTP_RESPONSE_METATABLE); + + lua_createtable(L, 0, 6); + + sntppkt_dbg("SNTPPKT READ th=%llx\n", r->theta); + + /* + * The raw response ends up in here, too, so that we can pass the + * tabular view to user callbacks and still have the internal large integers + * for use in drift_compensate. + */ + lua_pushvalue(L, 1); + lua_setfield(L, -2, "raw"); + + field_from_integer(L, "theta_s", (int32_t)sntppkt_long_s (r->theta)); + field_from_integer(L, "theta_us", sntppkt_long_us(r->theta)); + + field_from_integer(L, "delta", r->delta >> 16); + field_from_integer(L, "delta_r", r->delta_r); + field_from_integer(L, "epsilon_r", r->epsilon_r); + + field_from_integer(L, "leapind", r->LI); + field_from_integer(L, "stratum", r->stratum); + field_from_integer(L, "rx_s" , sntppkt_long_s (r->t_rx) - NTP_TO_UNIX_EPOCH); + field_from_integer(L, "rx_us" , sntppkt_long_us(r->t_rx)); + + return 1; +} + +/* + * Compute local RTC drift rate given a SNTP response, previous sample time, + * and error integral value (i.e., this is a PI controller). Returns new rate + * and integral value. + * + * Likely only sensible if resp->theta is sufficiently small (so we require + * less than a quarter of a second) and the inter-sample duration must, of + * course, be positive. + * + * There's nothing magic about the constants of the PI loop here; someone with + * a better understanding of control theory is welcome to suggest improvements. + * + * :: sntppkt.resp (most recent sample) + * -> sntppkt.resp (prior sample) + * -> int (integral) + * -> int (rate), int (integral) + * + */ +static int +sntppkt_resp_drift_compensate(lua_State *L) { + ntp_response_t *resp = luaL_checkudata(L, 1, NTP_RESPONSE_METATABLE); + + int32_t tsec = sntppkt_long_s(resp->theta); + uint32_t tfrac = resp->theta & 0xFFFFFFFF; + if ((tsec != 0 && tsec != -1) || + ((tsec == 0) && (tfrac > 0x40000000UL)) || + ((tsec == -1) && (tfrac < 0xC0000000UL))) { + return luaL_error(L, "Large deviation"); + } + + int32_t dsec = sntppkt_long_s(resp->delta); + if (dsec != 0 && dsec != -1) { + return luaL_error(L, "Large estimated error"); + } + + ntp_response_t *prior_resp = luaL_checkudata(L, 2, NTP_RESPONSE_METATABLE); + + int64_t isdur = resp->t_rx - prior_resp->t_rx; + if (isdur <= 0) { + return luaL_error(L, "Negative time base"); + } + + int32_t err_int = luaL_checkinteger(L, 3); + + /* P: Compute drift over 2, in parts per 2^32 as expected by the RTC. */ + int32_t drift2 = (resp->theta << 31) / isdur; + + /* PI: rate is drift/4 + integral error */ + int32_t newrate = (drift2 >> 1) + err_int; + + /* I: Adjust integral by drift/32, with a little bit of wind-up protection */ + if ((newrate > ~0x40000) && (newrate < 0x40000)) { + err_int += (drift2 + 0xF) >> 4; + } + + sntppkt_dbg("SNTPPKT drift: isdur=%llx drift2=%lx -> newrate=%lx err_int=%lx\n", + isdur, drift2, newrate, err_int); + + lua_pushinteger(L, newrate); + lua_pushinteger(L, err_int); + return 2; +} + +LROT_BEGIN(sntppkt_resp, NULL, LROT_MASK_INDEX) + LROT_TABENTRY( __index, sntppkt_resp ) + LROT_FUNCENTRY( pick, sntppkt_resp_pick ) + LROT_FUNCENTRY( totable, sntppkt_resp_totable ) + LROT_FUNCENTRY( drift_compensate, sntppkt_resp_drift_compensate ) +LROT_END(sntppkt_resp, NULL, LROT_MASK_INDEX) + +static int +sntppkt_init(lua_State *L) +{ + luaL_rometatable(L, NTP_RESPONSE_METATABLE, LROT_TABLEREF(sntppkt_resp)); + return 0; +} + +// Module function map +LROT_BEGIN(sntppkt, NULL, 0) + LROT_FUNCENTRY( make_ts , sntppkt_make_ts ) + LROT_FUNCENTRY( proc_pkt , sntppkt_proc_pkt ) +LROT_END( sntppkt, NULL, 0 ) + +NODEMCU_MODULE(SNTPPKT, "sntppkt", sntppkt, sntppkt_init); diff --git a/docs/lua-modules/sntp.md b/docs/lua-modules/sntp.md new file mode 100644 index 00000000..00f3d413 --- /dev/null +++ b/docs/lua-modules/sntp.md @@ -0,0 +1,239 @@ +# SNTP Module +| Since | Origin / Contributor | Maintainer | Source | +| :----- | :-------------------- | :---------- | :------ | +| 2019-07-01 | [nwf](https://github.com/nwf) | [nwf](https://github.com/nwf) | [sntp.lua](../../lua_modules/sntp/sntp.lua) | + +This is a user-friendly, Lua wrapper around the `sntppkt` module to facilitate +the use of SNTP. + +!!! note + + This `sntp` module is expected to live in LFS, and so all the documentation + uses `node.flashindex()` to find the module. If the module is instead + loaded as a file, use, for example, `(require "sntp").go()` instead, but + note that this may consume a large amount of heap. + +## Default Constructor Wrapper + +The simplest use case is to use the `go` function with no arguments like this: + +```lua +node.flashindex("sntp")().go() +``` + +This will... + + * use `rtctime` to interface with the local clock; + + * use a default list of servers, including the server provided by the local + DHCP server, if any; + + * re-synchronize the clock every half-hour in the steady state; + + * attempt to discipline the local oscillator to improve timing accuracy (but + note that this may take a while to converge; advanced users may wish to + manually persist drift rate across reboots using the `rtctime` interface); + and + + * rapidly re-discipline the local oscillator when a large deviance is + observed (e.g., at cold boot) + +The sntp object encapsulating the state machine is returned, but this may be +safely ignored in simple use cases. (This object is augmented with `tmr`, the +timer used to manage resychronization, should you wish to dynamically start, +stop, or delay synchronization.) + +You can provide your own list of servers, too, overriding the default: + +```lua +node.flashindex("sntp")().go({ "ntp-server-1", "ntp-server-2" }) +``` + +Or, to just use the server provided by DHCP and no others, when one is certain +that the DHCP server will provide one, + +```lua +do + local ifi = net.ifinfo(0) + local srv = ifi and ifi.dhcp and ifi.dhcp.ntp_server + if srv then node.flashindex("sntp")().go({srv}) end +end +``` + +Similarly, the frequency of synchronization can be changed: + +```lua +-- use default servers and synchronize every ten minutes +node.flashindex("sntp")().go(nil, 600000) +``` + +Success and failure callbacks can be given as well, for advanced use or +increased reporting: + +```lua +node.flashindex("sntp")().go(nil, 1200000, + function(res, serv, self) + print("SNTP OK", serv, res.theta_s, res.theta_us, rtctime.get()) + end, + function(err, srv, rply) + if err == "all" then print("SNTP FAIL", srv) + elseif err == "kod" then print("SNTP server kiss of death", srv, rply) + elseif err == "goaway" then print("SNTP server rejected us", srv, rply) + else print("SNTP server unreachable", srv, err) + end + end) +``` + +Details of the parameters to the callbacks are given below. The remainder of +this document details increasingly internal details, and is likely of +decreasing interest to general audiences. + +#### Syntax +`node.flashindex("sntp")().go([servers, [frequency, [success_cb, [failure_cb]]]])` + +### Notes + +#### Interaction with the Garbage Collector + +As our network stack does not capture the time of received packets (nor does +it know how to timestamp egressing NTP packets as dedicated hardware does), +there is a fair bit of local processing delay, as we have to come into Lua +to get the local timestamps. For higher-precision time keeping, if +possible, it may help to move the device to a (E)GC mode which has more slop +than the default, which prioritizes prompt reclaim of memory. Consider, for +example, something like `node.egc.setmode(node.egc.ON_MEM_LIMIT, -4096)` to +permit the SNTP logic to run (more often) without interference of the GC. +(The `go` function above defaults to collecting garbage before triggering +SNTP synchronization.) + +## SNTP Object Constructor +```lua +sntp = node.flashindex("sntp")().new(servers, success_cb, [failure_cb], [clock]) +``` + +where + +* `servers` specifies the name(s) of the (S)NTP server(s) to use; it may be... + + * a string, either a DNS name or an IPv4 address in dotted quad form, + * an array of the above + * `nil` to use any DHCP-provided NTP server and some default + `*.nodemcu.pool.ntp.org` servers. + +* `success_cb` is called back at the end of a synchronization when at least one + server replied to us. It will be given three arguments: + + * the preferred SNTP result converted to a a table; see `sntppkt.res.totable` below. + * the name of the server whence that result came + * the `sntp` object itself + +* `failure_cb` may be `nil` but, otherwise, is called back in two circumstances: + + * at the end of a pass during which no server could be reached. In this case, + the first argument will be the string "all", the second will be the + number of servers tried, and the third will be the `sntp` object itself. + + * an individual server has failed in some way. In this case, the first + argument will be one of: + + * "dns" (if name resolution failed), + * "timeout" (if the server failed to reply in time), + * "goaway" (if the server refused to answer), or + * "kod" ("kiss of death", if the server told us to stop contacting it entirely). + + In all cases, the name of the server is the second argument and the `sntp` + object itself is the third; in the "goaway" case, the fourth argument will + contain the refusal string (e.g., "RATE" for rate-limiting or "DENY" for + kiss-of-death warnings. + + In the case of kiss-of-death packets, the server will be removed from all + subsequent syncs. This may result in there eventually being no servers to + contact. Paranoid applications should therefore monitor failures! + +* `clock`, if given, should return two values describing the local clock in + seconds and microseconds (between 0 and 1000000). If not given, the module + will fall back on `rtctime.get`; if `rtctime` is not available, a clock must + be provided. Using `function() return 0, 0 end` will result in the "clock + offset" (`theta`) reported by the success callback being a direct estimate of + the true time. + +## Other module methods + +The module contains some other utility functions beyond the SNTP object +constructor and the `go` utility function detailed above. + +### update_rtc() +Given a result from a SNTP `sync` pass, update the local RTC through `rtctime`. +Attempting to use this function without `rtctime` support will raise an error. + +`sntpobj` is used to track state between syncs and should be the "sntp object" +given in the success and failure callbacks. (In principle, any Lua table will +do, but that is the most convenient one. All data is passed using fields whose +keys are strings with prefix `rtc_`.) + +#### Syntax +`node.flashindex("sntp")().update_rtc(res, sntpobj)` + +## SNTP object methods + +### sync() + +Run a pass through the specified servers and call back as described above. + +#### Syntax +`sntpobj:sync()` + +### stop() + +Abort any pass in progress; no more callbacks will be called. The current +preferred response and server name (i.e., the arguments to the success +callback, should the pass end now) are returned. + +#### Syntax +`sntpobj:stop()` + +### servers +The table of NTP servers currently being used. Please treat this as +read-only. This may be investigated to see if kiss-of-death processing +has removed any servers, but one is probably better off listening for +the failure callback notifications. + +## Internal Details: sntppkt response object methods + +### sntppkt.resp.totable() + +Expose a `sntppkt.resp` result as a Lua table with the following fields: + +* `theta_s`: Local clock offset, seconds component +* `theta_us`: Local clock offset, microseconds component + +* `delta`: An estimate of the error, in 65536ths of a second (i.e., approx 15.3 microseconds) +* `delta_r`: The server's estimate of its error, in 65536ths of a second +* `epsilon_r`: The server's estimate of its dispersion, in 65536ths of a second + +* `leapind`: The leap-second indicator +* `stratum`: The server's stratum + +* `rx_s`: Packet reception timestamp, seconds component +* `rx_us`: Packet reception timestamp, microseconds component + +* `raw`: The `sntppkt.resp` itself, so that we can pass this table around to + user Lua code and still retain access to the raw internals in, for example, + `drift_compensate`, below. See the use in `update_rtc`. + +Note that negative offsets will be represented with a negative `theta_s` and +a *positive* `theta_us`. For example, -200 microseconds would be -1 seconds +and 999800 microseconds. + +#### Syntax +`res:totable()` + +### sntppkt.resp.pick() + +Used internally to select among multiple responses; see source for usage. + +### sntppkt.resp.drift_compensate() + +Encapsulates a Proportional-Integral (PI) controller update step for use in +disciplining the local oscillator. Used internally to `update_rtc`; see source +for usage. diff --git a/lua_modules/sntp/sntp.lua b/lua_modules/sntp/sntp.lua new file mode 100644 index 00000000..bb45332c --- /dev/null +++ b/lua_modules/sntp/sntp.lua @@ -0,0 +1,294 @@ +-- Constructor +-- sc and fc are our Success and Failure Callbacks, resp. +local new = function(serv, sc, fc, now) + + if type(serv) == "string" then serv = {serv} + elseif serv == nil then serv = + { + nil, + "1.nodemcu.pool.ntp.org", + "2.nodemcu.pool.ntp.org", + } + local ni = net.ifinfo(0) + ni = ni and ni.dhcp + serv[1] = ni.ntp_server or "0.nodemcu.pool.ntp.org" + elseif type(serv) ~= "table" then error "Bad server table" + end + + if type(sc) ~= "function" then error "Bad success callback type" end + if fc ~= nil and type(fc) ~= "function" then error "Bad failure callback type" end + if now ~= nil and type(now) ~= "function" then error "Bad clock type" end + + now = now or (rtctime and rtctime.get) + if now == nil then error "Need clock function" end + + local _self = {servers = serv} + + local _tmr -- contains the currently running timer, if any + local _udp -- the socket we're using to talk to the world + + local _kod -- kiss of death flags accumulated accoss syncs + local _pbest -- best server from prior pass + + local _res -- the best result we've got so far this pass + local _best -- best server this pass, for updating _pbest + + local _six -- index of the server in serv to whom we are speaking + local _sat -- number of times we've tried to reach this server + + -- Shut down the state machine + -- + -- upvals: _tmr, _udp, _six, _sat, _res, _best + local function _stop() + -- stop any time-based callbacks and drop _tmr + _tmr = _tmr and _tmr:unregister() + + _six, _sat, _res, _best = nil, nil, nil, nil + + -- stop any UDP callbacks and drop the socket; to be safe against + -- knots tied in the registry, explicitly unregister callbacks first + if _udp then + _udp:on("receive", nil) + _udp:on("sent" , nil) + _udp:on("dns" , nil) + _udp:close() + _udp = nil + end + + -- Count down _kod entries + if _kod then + for k,v in pairs(_kod) do _kod[k] = (v > 0) and (v - 1) or nil end + if #_kod == 0 then _kod = nil end + end + end + + local nextServer + local doserver + + -- Try communicating with the current server + -- + -- upvals: now, _tmr, _udp, _best, _kod, _pbest, _res, _six + local function hail(ip) + _tmr:alarm(5000 --[[const param: SNTP_TIMEOUT]], tmr.ALARM_SINGLE, function() + _udp:on("sent", nil) + _udp:on("receive", nil) + return doserver("timeout") + end) + + local txts = sntppkt.make_ts(now()) + + _udp:on("receive", + -- upvals: now, ip, txts, _tmr, _best, _kod, _pbest, _res, _six + function(skt, d, port, rxip) + -- many things constitute bad packets; drop with tmr running + if rxip ~= ip and ip ~= "224.0.1.1" then return end -- wrong peer (unless multicast) + if port ~= 123 then return end -- wrong port + if #d < 48 then return end -- too short + + local pok, pkt = pcall(sntppkt.proc_pkt, d, txts, now()) + + if not pok or pkt == nil then + -- sntppkt can also reject the packet for having a bad cookie; + -- this is important to prevent processing spurious or delayed responses + return + end + + _tmr:unregister() + skt:on("receive", nil) -- skt == _udp + skt:on("sent", nil) + + if type(pkt) == "string" then + if pkt == "DENY" then -- KoD packet + + if _kod and _kod[rxip] then + -- There was already a strike against this IP address, and now + -- it's permanent. We can't directly remove the IP from rotation, + -- but we can remove the DNS that's resolving to it, which isn't + -- great, but isn't the worst either. + if fc then fc("kod", serv[_six], _self) end + _kod[rxip] = nil + table.remove(serv, _six) + _six = _six - 1 -- nextServer will add one + else + _kod = _kod or {} + _kod[rxip] = 2 + if fc then fc("goaway", serv[_six], _self, pkt) end + end + else + if fc then fc("goaway", serv[_six], _self, pkt) end + end + return nextServer() + end + + if _pbest == serv[_six] then + -- this was our favorite server last time; if we don't have a + -- result or if we'd rather this one than the result we have... + if not _res or not pkt:pick(_res, true) then + _res = pkt + _best = _pbest + end + else + -- this was not our favorite server; take this result if we have no + -- other option or if it compares favorably to the one we have, which + -- might be from our favorite from last pass. + if not _res or _res:pick(pkt, _pbest == _best) then + _res = pkt + _best = serv[_six] + end + end + + return nextServer() + end) + + return _udp:send(123, ip, + -- '#' == 0x23: version 4, mode 3 (client), no LI + "#\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0" + .. txts) + end + + -- upvals: _sat, _six, _udp, hail, _self + function doserver(err) + if _sat == 2 --[[const param: MAX_SERVER_ATTEMPTS]] then + if fc then fc(err, serv[_six], _self) end + return nextServer() + end + _sat = _sat + 1 + + return _udp:dns(serv[_six], function(skt, ip) + skt:on("dns", nil) -- skt == _udp + if ip == nil then return doserver("dns") else return hail(ip) end + end) + end + + -- Move on to the next server or finish a pass + -- + -- upvals: fc, serv, sc, _best, _pbest, _res, _sat, _six + function nextServer() + if _six >= #serv then + if _res then + _pbest = _best + local res = _res + local best = _best + _stop() + return sc(res:totable(), best, _self) + else + _stop() + if fc then return fc("all", #serv, _self) else return end + end + end + + _six = _six + 1 + _sat = 0 + return doserver() + end + + -- Poke all the servers and invoke the user's callbacks + -- + -- upvals: _stop, _udp, _ENV, _tmr, _six, nextServer + function _self.sync() + _stop() + _udp = net.createUDPSocket() + _tmr = tmr.create() + _udp:listen() -- on random port + _six = 0 + nextServer() + end + + function _self.stop() + local res, best = _res, _best + _stop() + return res and res:totable(), best + end + + return _self + +end + +-- A utility function which applies a result to the rtc +local update_rtc = function(res, obj) + local rate = nil + if obj.rtc_last ~= nil then + -- adjust drift compensation. We have three pieces of information: + -- + -- our idea of time at rx (res.rx_*), + -- our idea of time at the last sync (obj.rtc_last.rx_*) + -- the measured theta now (res.theta_us) + -- + -- We're going to integrate the theta signal over time and use + -- that to mediate the rate we set, making this a PI controller, + -- but we might take big steps if theta gets too bad. + local ok, err_int + local raw = res.raw + ok, rate, err_int = pcall(raw.drift_compensate, raw, obj.rtc_last, + obj.rtc_err_int or 0) + if not ok then + rate = nil -- don't set the rate this time + obj.rtc_last = nil -- or next time + else + obj.rtc_last = res.raw + obj.rtc_err_int = err_int + end + else + obj.rtc_last = res.raw + end + + if rate == nil then + -- update time (and cut rate, in case it's gotten out of hand) + local now_s, now_us, now_r = rtctime.get() + local new_s, new_us = now_s + res.theta_s, now_us + res.theta_us + if new_us > 1000000 then + new_s = new_s + 1 + new_us = new_us - 1000000 + end + rtctime.set(new_s, new_us, now_r / 2) + else + -- just change the rate + rtctime.set(nil, nil, rate) + end + + return rate ~= nil +end + +-- Default operation +-- +-- upvals: new, update_rtc +local go = function(servs, period, sc, fc) + local sntpobj = new(servs, + -- wrap the success callback with a utility function for managing the rtc + -- and polling frequency + function(res, serv, self) + local ok = update_rtc(res, self) + + -- if the rate estimator thinks it has this under control, only poll + -- the server occasionally. Otherwise, bother it more frequently, + -- in a "bursty" way + if ok and ((self.rtc_burst or 0) == 0) + then self.tmr:interval(period or 1800000) + self.rtc_burst = nil + else self.tmr:interval(30000) + self.rtc_burst = (ok and self.rtc_burst or 40) - 1 + end + + -- invoke the user's callback + if sc then return sc(res, serv, self) end + end, + fc) + + local t = tmr.create() + sntpobj.tmr = t + t:alarm(60000, tmr.ALARM_AUTO, function() collectgarbage() sntpobj.sync() end) + sntpobj.sync() + + return sntpobj +end + +-- from sntppkt +-- luacheck: ignore +local _lfs_strings = "theta_s", "theta_us", "delta", "delta_r", "epsilon_r", + "leapind", "stratum", "rx_s", "rx_us" + +return { +update_rtc = update_rtc, +new = new, +go = go, +} diff --git a/mkdocs.yml b/mkdocs.yml index 964b8b5d..421e5fff 100644 --- a/mkdocs.yml +++ b/mkdocs.yml @@ -67,6 +67,7 @@ pages: - 'mcp23008': 'lua-modules/mcp23008.md' - 'mcp23017': 'lua-modules/mcp23017.md' - 'redis': 'lua-modules/redis.md' + - 'sntp' : 'lua-modules/sntp.md' - 'telnet': 'lua-modules/telnet.md' - 'yeelink': 'lua-modules/yeelink.md' - C Modules: @@ -120,6 +121,7 @@ pages: - 'sigma delta': 'modules/sigma-delta.md' - 'sjson': 'modules/sjson.md' - 'sntp': 'modules/sntp.md' + # sntppkt deliberately not documented - 'softuart': 'modules/softuart.md' - 'somfy': 'modules/somfy.md' - 'spi': 'modules/spi.md' diff --git a/tools/luacheck_config.lua b/tools/luacheck_config.lua index 4857c24e..e07a5d02 100644 --- a/tools/luacheck_config.lua +++ b/tools/luacheck_config.lua @@ -619,6 +619,12 @@ stds.nodemcu_libs = { sync = empty } }, + sntppkt = { + fields = { + make_ts = empty, + proc_pkt = empty, + } + }, somfy = { fields = { DOWN = empty,