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https://github.com/logicog/RTLPlayground.git
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DrDoof
de431c6d84
Storm control used meters 0 to 39, the same meters the ACL hands out, so a storm limit and an acl meter could overwrite each other. It now uses 24 + port * 4 + type, meters 24 to 63. parse_storm() is no longer reentrant and uses plain locals, looks the type up in a while loop and returns straight from the one-line cases. storm_show() uses plain locals too. The documentation says how IGMP decides between mcast and umcast, how to get from a meter index to its limit, where the IFG bit of a meter is, and what an ingress bandwidth limit on the same port does to the storm limit.
55 lines
2.9 KiB
Markdown
55 lines
2.9 KiB
Markdown
# Storm Control
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Storm control limits the rate at which a port admits broadcast, multicast,
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unknown unicast and unknown multicast frames. Frames of a type above its limit
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are dropped at ingress, so a loop or a misbehaving host cannot flood the rest
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of the network through that port. Known unicast traffic is not affected.
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## Commands
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```
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storm <port> bcast|mcast|ucast|umcast <rate> pps
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storm <port> bcast|mcast|ucast|umcast <rate> kbps
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storm <port> bcast|mcast|ucast|umcast off
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storm
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```
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`ucast` is unicast to a MAC address the switch has not learned yet, and
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`umcast` is multicast without an entry in the address table. Multicast groups
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get their entries from IGMP snooping, so without `igmp on` all multicast is
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unknown and only the `umcast` limit applies to it; `mcast` covers the groups
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IGMP has learned. A limit in
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packets per second goes from 1 to 1048575, a limit in kbit/s from 1 to
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10000000. `storm` without arguments prints the limits of every port. The
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limits are kept in the configuration like any other setting, and the Bandwidth
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page of the web interface has a Storm control card to set them.
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## Registers
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Each port and type has an enable bit and a meter index, and each limit uses
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one of the 64 shared meters of the switch. RTLPlayground gives every port and
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type its own meter, index `24 + port * 4 + type`, so one port's storm does not
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eat into the limit of another. Storm control uses meters 24 to 63 and leaves
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0 to 23 to the ACL. The limit of a meter is in `RTL837X_METER_RATE + 4 *
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meter`, and bit `meter % 32` of `RTL837X_METER_MODE + 4 * (meter / 32)`
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selects pps instead of kbit/s.
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```
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#define RTL837X_STORM_CTRL 0x54e4 /* + 4 * type, bit = port */
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#define RTL837X_STORM_MIDX 0x54f4 /* + 8 * type + 4 * (port / 5), 6 bits per port */
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#define RTL837X_METER_RATE 0x5cf0 /* + 4 * meter, 24 bits, kbit/s or pps */
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#define RTL837X_METER_MODE 0x5ef0 /* + 4 * (meter / 32), bit set = pps */
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```
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In kbit/s mode one step of the rate is 1 kbit/s. Measured with 100 and 1000 byte
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frames, the meter counts a frame with its FCS, but without preamble and
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interframe gap. Every meter has a bit that adds them, in `0x5f08 + 4 * (meter
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/ 32)`, which storm control leaves cleared. `IGBW_INC_IFG` and `EGBW_INC_IFG`
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are the matching bits of the bandwidth control.
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An ingress bandwidth limit on the same port works on the same arriving frames
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as the storm limit rather than after it, and the two together pass far less
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than either one: a 1 Mbit/s `umcast` limit with a 10 Mbit/s ingress limit let
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0.12 to 0.16 Mbit/s of a 1.4 Gbit/s stream through, where each alone passed
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1.17 and 10.2 Mbit/s.
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The type is 0 for broadcast, 1 for multicast, 2 for unknown unicast and 3 for
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unknown multicast. The burst size of a meter (0x5df0 + 4 * meter) counts packets
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in pps mode; its default of 0x2000 lets 8192 frames through before a pps limit
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bites, so a pps limit sets the burst to one second of traffic. A kbit/s limit
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puts back the default.
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