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.
2.9 KiB
Storm Control
Storm control limits the rate at which a port admits broadcast, multicast, unknown unicast and unknown multicast frames. Frames of a type above its limit are dropped at ingress, so a loop or a misbehaving host cannot flood the rest of the network through that port. Known unicast traffic is not affected.
Commands
storm <port> bcast|mcast|ucast|umcast <rate> pps
storm <port> bcast|mcast|ucast|umcast <rate> kbps
storm <port> bcast|mcast|ucast|umcast off
storm
ucast is unicast to a MAC address the switch has not learned yet, and
umcast is multicast without an entry in the address table. Multicast groups
get their entries from IGMP snooping, so without igmp on all multicast is
unknown and only the umcast limit applies to it; mcast covers the groups
IGMP has learned. A limit in
packets per second goes from 1 to 1048575, a limit in kbit/s from 1 to
10000000. storm without arguments prints the limits of every port. The
limits are kept in the configuration like any other setting, and the Bandwidth
page of the web interface has a Storm control card to set them.
Registers
Each port and type has an enable bit and a meter index, and each limit uses
one of the 64 shared meters of the switch. RTLPlayground gives every port and
type its own meter, index 24 + port * 4 + type, so one port's storm does not
eat into the limit of another. Storm control uses meters 24 to 63 and leaves
0 to 23 to the ACL. The limit of a meter is in RTL837X_METER_RATE + 4 * meter, and bit meter % 32 of RTL837X_METER_MODE + 4 * (meter / 32)
selects pps instead of kbit/s.
#define RTL837X_STORM_CTRL 0x54e4 /* + 4 * type, bit = port */
#define RTL837X_STORM_MIDX 0x54f4 /* + 8 * type + 4 * (port / 5), 6 bits per port */
#define RTL837X_METER_RATE 0x5cf0 /* + 4 * meter, 24 bits, kbit/s or pps */
#define RTL837X_METER_MODE 0x5ef0 /* + 4 * (meter / 32), bit set = pps */
In kbit/s mode one step of the rate is 1 kbit/s. Measured with 100 and 1000 byte
frames, the meter counts a frame with its FCS, but without preamble and
interframe gap. Every meter has a bit that adds them, in 0x5f08 + 4 * (meter / 32), which storm control leaves cleared. IGBW_INC_IFG and EGBW_INC_IFG
are the matching bits of the bandwidth control.
An ingress bandwidth limit on the same port works on the same arriving frames
as the storm limit rather than after it, and the two together pass far less
than either one: a 1 Mbit/s umcast limit with a 10 Mbit/s ingress limit let
0.12 to 0.16 Mbit/s of a 1.4 Gbit/s stream through, where each alone passed
1.17 and 10.2 Mbit/s.
The type is 0 for broadcast, 1 for multicast, 2 for unknown unicast and 3 for unknown multicast. The burst size of a meter (0x5df0 + 4 * meter) counts packets in pps mode; its default of 0x2000 lets 8192 frames through before a pps limit bites, so a pps limit sets the burst to one second of traffic. A kbit/s limit puts back the default.