meta: Introduce new conditions 'time', 'day' and 'hour'

These keywords introduce new checks for a timestamp, an absolute date (which is converted to a timestamp),
an hour in the day (which is converted to the number of seconds since midnight) and a day of week.

When converting an ISO date (eg. 2019-06-06 17:00) to a timestamp,
we need to substract it the GMT difference in seconds, that is, the value
of the 'tm_gmtoff' field in the tm structure. This is because the kernel
doesn't know about time zones. And hence the kernel manages different timestamps
than those that are advertised in userspace when running, for instance, date +%s.

The same conversion needs to be done when converting hours (e.g 17:00) to seconds since midnight
as well.

The result needs to be computed modulo 86400 in case GMT offset (difference in seconds from UTC)
is negative.

We also introduce a new command line option (-t, --seconds) to show the actual
timestamps when printing the values, rather than the ISO dates, or the hour.

Some usage examples:

	time < "2019-06-06 17:00" drop;
	time < "2019-06-06 17:20:20" drop;
	time < 12341234 drop;
	day "Saturday" drop;
	day 6 drop;
	hour >= 17:00 drop;
	hour >= "17:00:01" drop;
	hour >= 63000 drop;

We need to convert an ISO date to a timestamp
without taking into account the time zone offset, since comparison will
be done in kernel space and there is no time zone information there.

Overwriting TZ is portable, but will cause problems when parsing a
ruleset that has 'time' and 'hour' rules. Parsing an 'hour' type must
not do time zone conversion, but that will be automatically done if TZ has
been overwritten to UTC.

Hence, we use timegm() to parse the 'time' type, even though it's not portable.
Overwriting TZ seems to be a much worse solution.

Finally, be aware that timestamps are converted to nanoseconds when
transferring to the kernel (as comparison is done with nanosecond
precision), and back to seconds when retrieving them for printing.

We swap left and right values in a range to properly handle
cross-day hour ranges (e.g. 23:15-03:22).

Signed-off-by: Ander Juaristi <a@juaristi.eus>
Reviewed-by: Florian Westphal <fw@strlen.de>

1 files changed, 261 insertions, 0 deletions

diff --git a/src/meta.c b/src/meta.c
index 0cd7eeea..f54b818e 100644
--- a/src/meta.c
+++ b/src/meta.c
@@ -37,6 +37,10 @@
 #include <iface.h>
 #include <json.h>
 
+#define _XOPEN_SOURCE
+#define __USE_XOPEN
+#include <time.h>
+
 static void tchandle_type_print(const struct expr *expr,
 				struct output_ctx *octx)
 {
@@ -375,6 +379,254 @@ const struct datatype ifname_type = {
 	.basetype	= &string_type,
 };
 
+static void date_type_print(const struct expr *expr, struct output_ctx *octx)
+{
+	uint64_t tstamp = mpz_get_uint64(expr->value);
+	struct tm *tm, *cur_tm;
+	char timestr[21];
+
+	/* Convert from nanoseconds to seconds */
+	tstamp /= 1000000000L;
+
+	if (!nft_output_seconds(octx)) {
+		/* Obtain current tm, to add tm_gmtoff to the timestamp */
+		cur_tm = localtime((time_t *) &tstamp);
+
+		if (cur_tm)
+			tstamp += cur_tm->tm_gmtoff;
+
+		if ((tm = gmtime((time_t *) &tstamp)) != NULL &&
+			strftime(timestr, sizeof(timestr) - 1, "%F %T", tm))
+			nft_print(octx, "\"%s\"", timestr);
+		else
+			nft_print(octx, "Error converting timestamp to printed time");
+
+		return;
+	}
+
+	/*
+	 * Do our own printing. The default print function will print in
+	 * nanoseconds, which is ugly.
+	 */
+	nft_print(octx, "%lu", tstamp);
+}
+
+static time_t parse_iso_date(const char *sym)
+{
+	struct tm tm, *cur_tm;
+	time_t ts;
+
+	memset(&tm, 0, sizeof(struct tm));
+
+	if (strptime(sym, "%F %T", &tm))
+		goto success;
+	if (strptime(sym, "%F %R", &tm))
+		goto success;
+	if (strptime(sym, "%F", &tm))
+		goto success;
+
+	return -1;
+
+success:
+	/*
+	 * Overwriting TZ is problematic if we're parsing hour types in this same process,
+	 * hence I'd rather use timegm() which doesn't take into account the TZ env variable,
+	 * even though it's Linux-specific.
+	 */
+	ts = timegm(&tm);
+
+	/* Obtain current tm as well (at the specified time), so that we can substract tm_gmtoff */
+	cur_tm = localtime(&ts);
+
+	if (ts == (time_t) -1 || cur_tm == NULL)
+		return ts;
+
+	/* Substract tm_gmtoff to get the current time */
+	return ts - cur_tm->tm_gmtoff;
+}
+
+static struct error_record *date_type_parse(struct parse_ctx *ctx,
+					    const struct expr *sym,
+					    struct expr **res)
+{
+	const char *endptr = sym->identifier;
+	time_t tstamp;
+
+	if ((tstamp = parse_iso_date(sym->identifier)) != -1)
+		goto success;
+
+	tstamp = strtoul(sym->identifier, (char **) &endptr, 10);
+	if (*endptr == '\0' && endptr != sym->identifier)
+		goto success;
+
+	return error(&sym->location, "Cannot parse date");
+
+success:
+	/* Convert to nanoseconds */
+	tstamp *= 1000000000L;
+	*res = constant_expr_alloc(&sym->location, sym->dtype,
+				   BYTEORDER_HOST_ENDIAN,
+				   sizeof(uint64_t) * BITS_PER_BYTE,
+				   &tstamp);
+	return NULL;
+}
+
+static const struct symbol_table day_type_tbl = {
+	.base		= BASE_DECIMAL,
+	.symbols	= {
+		SYMBOL("Sunday", 0),
+		SYMBOL("Monday", 1),
+		SYMBOL("Tuesday", 2),
+		SYMBOL("Wednesday", 3),
+		SYMBOL("Thursday", 4),
+		SYMBOL("Friday", 5),
+		SYMBOL("Saturday", 6),
+		SYMBOL_LIST_END,
+	},
+};
+
+static void day_type_print(const struct expr *expr, struct output_ctx *octx)
+{
+	return symbolic_constant_print(&day_type_tbl, expr, true, octx);
+}
+
+static void __hour_type_print_r(int hours, int minutes, int seconds, char *out, size_t buflen)
+{
+	if (minutes == 60)
+		return __hour_type_print_r(++hours, 0, seconds, out, buflen);
+	else if (minutes > 60)
+		return __hour_type_print_r((int) (minutes / 60), minutes % 60, seconds, out, buflen);
+
+	if (seconds == 60)
+		return __hour_type_print_r(hours, ++minutes, 0, out, buflen);
+	else if (seconds > 60)
+		return __hour_type_print_r(hours, (int) (seconds / 60), seconds % 60, out, buflen);
+
+	if (seconds == 0)
+		snprintf(out, buflen, "%02d:%02d", hours, minutes);
+	else
+		snprintf(out, buflen, "%02d:%02d:%02d", hours, minutes, seconds);
+}
+
+static void hour_type_print(const struct expr *expr, struct output_ctx *octx)
+{
+	uint32_t seconds = mpz_get_uint32(expr->value);
+	struct tm *cur_tm;
+	char out[32];
+	time_t ts;
+
+	if (!nft_output_seconds(octx)) {
+		/* Obtain current tm, so that we can add tm_gmtoff */
+		ts = time(NULL);
+		cur_tm = localtime(&ts);
+
+		if (cur_tm)
+			seconds = (seconds + cur_tm->tm_gmtoff) % 86400;
+
+		__hour_type_print_r(0, 0, seconds, out, sizeof(out));
+		nft_print(octx, "\"%s\"", out);
+
+		return;
+	}
+
+	expr_basetype(expr)->print(expr, octx);
+}
+
+static struct error_record *hour_type_parse(struct parse_ctx *ctx,
+					    const struct expr *sym,
+					    struct expr **res)
+{
+	struct error_record *er;
+	struct tm tm, *cur_tm;
+	uint64_t result = 0;
+	char *endptr;
+	time_t ts;
+
+	memset(&tm, 0, sizeof(struct tm));
+
+	/* First, try to parse it as a number */
+	result = strtoul(sym->identifier, (char **) &endptr, 10);
+	if (*endptr == '\0' && endptr != sym->identifier)
+		goto success;
+
+	result = 0;
+
+	/* Obtain current tm, so that we can substract tm_gmtoff */
+	ts = time(NULL);
+	cur_tm = localtime(&ts);
+
+	endptr = strptime(sym->identifier, "%T", &tm);
+	if (endptr && *endptr == '\0')
+		goto convert;
+
+	endptr = strptime(sym->identifier, "%R", &tm);
+	if (endptr && *endptr == '\0')
+		goto convert;
+
+	if (endptr && *endptr)
+		return error(&sym->location, "Can't parse trailing input: \"%s\"\n", endptr);
+
+	if ((er = time_parse(&sym->location, sym->identifier, &result)) == NULL) {
+		result /= 1000;
+		goto convert;
+	}
+
+	return er;
+
+convert:
+	/* Convert the hour to the number of seconds since midnight */
+	if (result == 0)
+		result = tm.tm_hour * 3600 + tm.tm_min * 60 + tm.tm_sec;
+
+	/* Substract tm_gmtoff to get the current time */
+	if (cur_tm) {
+		if ((long int) result >= cur_tm->tm_gmtoff)
+			result = (result - cur_tm->tm_gmtoff) % 86400;
+		else
+			result = 86400 - cur_tm->tm_gmtoff + result;
+	}
+
+success:
+	*res = constant_expr_alloc(&sym->location, sym->dtype,
+				   BYTEORDER_HOST_ENDIAN,
+				   sizeof(uint32_t) * BITS_PER_BYTE,
+				   &result);
+	return NULL;
+}
+
+const struct datatype date_type = {
+	.type = TYPE_TIME_DATE,
+	.name = "time",
+	.desc = "Relative time of packet reception",
+	.byteorder = BYTEORDER_HOST_ENDIAN,
+	.size = sizeof(uint64_t) * BITS_PER_BYTE,
+	.basetype = &integer_type,
+	.print = date_type_print,
+	.parse = date_type_parse,
+};
+
+const struct datatype day_type = {
+	.type = TYPE_TIME_DAY,
+	.name = "day",
+	.desc = "Day of week of packet reception",
+	.byteorder = BYTEORDER_HOST_ENDIAN,
+	.size = 1 * BITS_PER_BYTE,
+	.basetype = &integer_type,
+	.print = day_type_print,
+	.sym_tbl = &day_type_tbl,
+};
+
+const struct datatype hour_type = {
+	.type = TYPE_TIME_HOUR,
+	.name = "hour",
+	.desc = "Hour of day of packet reception",
+	.byteorder = BYTEORDER_HOST_ENDIAN,
+	.size = sizeof(uint64_t) * BITS_PER_BYTE,
+	.basetype = &integer_type,
+	.print = hour_type_print,
+	.parse = hour_type_parse,
+};
+
 const struct meta_template meta_templates[] = {
 	[NFT_META_LEN]		= META_TEMPLATE("length",    &integer_type,
 						4 * 8, BYTEORDER_HOST_ENDIAN),
@@ -448,6 +700,15 @@ const struct meta_template meta_templates[] = {
 	[NFT_META_BRI_IIFVPROTO] = META_TEMPLATE("ibrvproto",   &ethertype_type,
 						 2 * BITS_PER_BYTE,
 						 BYTEORDER_BIG_ENDIAN),
+	[NFT_META_TIME_NS]	= META_TEMPLATE("time",   &date_type,
+						8 * BITS_PER_BYTE,
+						BYTEORDER_HOST_ENDIAN),
+	[NFT_META_TIME_DAY]	= META_TEMPLATE("day", &day_type,
+						1 * BITS_PER_BYTE,
+						BYTEORDER_HOST_ENDIAN),
+	[NFT_META_TIME_HOUR]	= META_TEMPLATE("hour", &hour_type,
+						4 * BITS_PER_BYTE,
+						BYTEORDER_HOST_ENDIAN),
 };
 
 static bool meta_key_is_unqualified(enum nft_meta_keys key)