On 25/11/2020 11:48, kfm@xxxxxxxxxxxxx wrote:
On 24/11/2020 22:37, ѽ҉ᶬḳ℠ wrote:On 24/11/2020 23:08, kfm@xxxxxxxxxxxxx wrote:On 14/11/2020 12:29, ѽ҉ᶬḳ℠ wrote:host: armv7l GNU/Linux kernel: 5.10.0-rc3-next-20201113 nftables: v0.9.6 ______ this rule in a > inet filter prerouting chain:icmp type 8 add @b_sa4_lan_pinger { ip saddr limit rate over 2/day } log flags all prefix "ping_ip4 from LAN > rate_limit_d DROP: " drop;Having tried different values, e.g. limit rate over 2/day limit rate over 44/day limit rate over 300/dayframes # 1 -5 are always passing through but as of frame count # 6 the frames always being dropped, no matter the x/day value.That's probably because the default burst value is 5, not that anyone would know this by reading the nft documentation. The terse explanation of the limit module in iptables-extensions(8) applies but there is a better explanation to be found here:https://www.netfilter.org/documentation/HOWTO/packet-filtering-HOWTO-7.htmlGiven 2/day, the initial five tokens are being taken from the bucket, following which no token is added until 12 hours have elapsed. Try repeating your experiments with the burst value specified as 1.Documentation aside, it doesn't help that both iptables/xt_limit and nft/limit fail to report the burst value unless it was explicitly defined.Thank you for your valuable thoughts. I am not sure however that the default bust limit is the cause here, for two reasons:It explains the cause of the initial five packets being permitted before running up against any limit. Given 2 as a numerator, try with lower burst values.Take "2/min burst 1 packets" as an example. The bucket will have a capacity of just one token and will be initialised with one upon loading the ruleset. The bucket will be topped up with one token every 30 seconds, but never beyond its capacity. The result should be that one packet is allowed to pass at rigid 30 second intervals.Specifying "2/min burst 2 packets" will result in the bucket being initialised with - and having a capacity of - two tokens. Within the first 30 second delta, it will be possible for two packets to pass before the limit applies. Still, the bucket is topped up at the same rate of one token every 30 seconds.the outcome is the same with: limit rate over 44/dayOn average, this should allow for 44 a day by recharging the bucket at a rate of one token every 24/44*60 = 32.73 minutes.limit rate over 300/dayIn this case, by recharging the bucket at a rate of one token every 4.8 minutes. You would need to run your test case for at least that long to observe a difference and for at least 24 hours to prove whether or not the overall rate is maintained.
Thank you for the extensive explanation(s). To test your theory I removed the default burst of 5 packets from the equation with:
limit rate over 300/day burst 0 packetsIn which case I would expect the bucket credit of 300 to be burned prior rejecting frame #301 from the source, however the frames are being dropped as of frame count #6:
# ping -6 -n 20 fd30:d64c:1eed:4c3a::12 Pinging fd30:d64c:1eed:4c3a::12 with 32 bytes of data: Reply from fd30:d64c:1eed:4c3a::12: time=1ms Reply from fd30:d64c:1eed:4c3a::12: time=2ms Reply from fd30:d64c:1eed:4c3a::12: time=1ms Reply from fd30:d64c:1eed:4c3a::12: time=1ms Reply from fd30:d64c:1eed:4c3a::12: time=1ms Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Ping statistics for fd30:d64c:1eed:4c3a::12: Packets: Sent = 20, Received = 5, Lost = 15 (75% loss), Approximate round trip times in milli-seconds: Minimum = 1ms, Maximum = 2ms, Average = 1ms --------------- Then adjusted to: limit rate over 300/day burst 10 packets: # ping -6 -n 20 fd30:d64c:1eed:4c3a::12 Pinging fd30:d64c:1eed:4c3a::12 with 32 bytes of data: Reply from fd30:d64c:1eed:4c3a::12: time=4ms Reply from fd30:d64c:1eed:4c3a::12: time=1ms Reply from fd30:d64c:1eed:4c3a::12: time=1ms Reply from fd30:d64c:1eed:4c3a::12: time=2ms Reply from fd30:d64c:1eed:4c3a::12: time=2ms Reply from fd30:d64c:1eed:4c3a::12: time=1ms Reply from fd30:d64c:1eed:4c3a::12: time=1ms Reply from fd30:d64c:1eed:4c3a::12: time=3ms Reply from fd30:d64c:1eed:4c3a::12: time=2ms Reply from fd30:d64c:1eed:4c3a::12: time=2ms Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Request timed out. Ping statistics for fd30:d64c:1eed:4c3a::12: Packets: Sent = 20, Received = 10, Lost = 10 (50% loss), Approximate round trip times in milli-seconds: Minimum = 1ms, Maximum = 4ms, Average = 1msNow 10 frames being passed through (matching the burst value) but as of count # 11 being dropped.
This seems to be indicative of: * burst value below the default (of 5) being disregarded entirely * limit rate over X/day being disregarded and only the burst token applied.
and should not be however. The other reason is that it should be the same outcome with limit rate over X/minute but it is notFor the benefit of anyone investigating, could you define a test case that concretely demonstrates the problem?
see below
A somewhat inconsistent behaviour with x/minute value, e.g.icmp type 8 add @b_sa4_lan_pinger { ip saddr limit rate over 13/minute } log flags all prefix "ping_ip4 from LAN > rate_limit_d DROP: " drop;produces on the client side: ping -4 -n 20 google.com Pinging google.com [216.58.208.110] with 32 bytes of data: Reply from 216.58.208.110: bytes=32 time=14ms TTL=114 Reply from 216.58.208.110: bytes=32 time=15ms TTL=114 Reply from 216.58.208.110: bytes=32 time=14ms TTL=114 Reply from 216.58.208.110: bytes=32 time=18ms TTL=114 Reply from 216.58.208.110: bytes=32 time=18ms TTL=114 Reply from 216.58.208.110: bytes=32 time=13ms TTL=114 Request timed out. Reply from 216.58.208.110: bytes=32 time=14ms TTL=114 Request timed out. Reply from 216.58.208.110: bytes=32 time=16ms TTL=114 Request timed out. Reply from 216.58.208.110: bytes=32 time=16ms TTL=114 Reply from 216.58.208.110: bytes=32 time=13ms TTL=114 Request timed out. Reply from 216.58.208.110: bytes=32 time=154ms TTL=114 Request timed out. Reply from 216.58.208.110: bytes=32 time=32ms TTL=114 Reply from 216.58.208.110: bytes=32 time=13ms TTL=114 Request timed out. Reply from 216.58.208.110: bytes=32 time=14ms TTL=114 Ping statistics for 216.58.208.110: Packets: Sent = 20, Received = 14, Lost = 6 (30% loss), Approximate round trip times in milli-seconds: Minimum = 13ms, Maximum = 154ms, Average = 26msWhilst the count is matching the rule it is not clear why not all 13 initial frames are passing through consistently and the excess being dropped consistently but instead the first being dropped is earlier?
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