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RangeIPLookup

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Tom Barbette edited this page Oct 3, 2018 · 2 revisions

RangeIPLookup Element Documentation

NAME

RangeIPLookup — Click element; IP routing lookup through binary search in a very compact table

SYNOPSIS

RangeIPLookup(ADDR1/MASK1 [GW1] OUT1, ADDR2/MASK2 [GW2] OUT2, ...)

Ports: 1 input, any number of outputs
Processing: push
Drivers: userlevel, bsdmodule

DESCRIPTION

Expects a destination IP address annotation with each packet. Looks up that address in its routing table, using longest-prefix-match, sets the destination annotation to the corresponding GW (if specified), and emits the packet on the indicated OUTput port.

Each argument is a route, specifying a destination and mask, an optional gateway IP address, and an output port. No destination-mask pair should occur more than once.

RangeIPLookup aims at achieving high lookup speeds through exploiting the CPU cache locality. The routing table is expanded into a very small lookup structure, typically occupying less then 4 bytes per IP prefix. As an example, a lookup structure corresponding to a routing table with 167000 entries (a realistic snapshot taken from a core Internet router) occupies only around 512 KBytes of RAM. Depending on how sucessfully the CPU cache affinity can be maintained, worst-case lookup rates exceeding 20 million lookups per second can be achieved using modern commodity CPUs.

RangeIPLookup maintains a large DirectIPLookup table as well as its own tables. Although this subsidiary table is only accessed during route updates, it significantly adds to RangeIPLookup's total memory footprint.

ELEMENT HANDLERS

  • table (read-only) — Outputs a human-readable version of the current routing table.
  • lookup (read-only) — Reports the OUTput port and GW corresponding to an address.
  • add (write-only) — Adds a route to the table. Format should be `ADDR/MASK [GW] OUT'. Fails if a route for ADDR/MASK already exists.
  • set (write-only) — Sets a route, whether or not a route for the same prefix already exists.
  • remove (write-only) — Removes a route from the table. Format should be `ADDR/MASK'.
  • ctrl (write-only) — Adds or removes a group of routes. Write `add/set ADDR/MASK [GW] OUT' to add a route, and `remove ADDR/MASK' to remove a route. You can supply multiple commands, one per line; all commands are executed as one atomic operation.
  • flush (write-only) — Clears the entire routing table in a single atomic operation.

NOTES

See IPRouteTable for a performance comparison of the various IP routing elements.

SEE ALSO

IPRouteTable, RadixIPLookup, DirectIPLookup, LinearIPLookup, SortedIPLookup, StaticIPLookup, LinuxIPLookup

Generated by click-elem2man from ../elements/ip/rangeiplookup.hh:8 on 2018/10/03.

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