src: allow burst 0 for byte ratelimit and use it as default

Packet-based limit burst is set to 5, as in iptables. However,
byte-based limit burst adds to the rate to calculate the bucket size,
and this is also sets this to 5 (... bytes in this case). Update it to
use zero byte burst by default instead.

This patch also updates manpage to describe how the burst value
influences the kernel module's token bucket in each of the two modes.
This documentation update is based on original text by Phil Sutter.

Adjust tests/py to silence warnings due to mismatching byte burst.

Fixes: 285baccfea46 ("src: disallow burst 0 in ratelimits")
Acked-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/parser_json.c b/src/parser_json.c
index 9e93927a..2437b1ba 100644
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -1826,7 +1826,7 @@ static struct stmt *json_parse_limit_stmt(struct json_ctx *ctx,
 					  const char *key, json_t *value)
 {
 	struct stmt *stmt;
-	uint64_t rate, burst = 5;
+	uint64_t rate, burst = 0;
 	const char *rate_unit = "packets", *time, *burst_unit = "bytes";
 	int inv = 0;
 
@@ -1840,6 +1840,9 @@ static struct stmt *json_parse_limit_stmt(struct json_ctx *ctx,
 		stmt = limit_stmt_alloc(int_loc);
 
 		if (!strcmp(rate_unit, "packets")) {
+			if (burst == 0)
+				burst = 5;
+
 			stmt->limit.type = NFT_LIMIT_PKTS;
 			stmt->limit.rate = rate;
 			stmt->limit.burst = burst;