package bart provides a Balanced-Routing-Table (BART).
BART is balanced in terms of memory usage and lookup time for the longest-prefix match.
BART is a multibit-trie with fixed stride length of 8 bits, using the baseIndex function from the ART algorithm to build the complete-binary-tree (CBT) of prefixes for each stride.
The CBT is implemented as a bit-vector, backtracking is just a matter of fast cache friendly bitmask operations.
The Table is implemented with popcount compressed sparse arrays together with path compression. This reduces storage consumption by almost two orders of magnitude in comparison to ART with comparable or even better lookup times for longest prefix match.
The algorithm is also excellent for determining whether two tables contain overlapping IP addresses.
func ExampleTable_Contains() {
// Create a new routing table
table := new(bart.Table[struct{}])
// Insert some prefixes
prefixes := []string{
"192.168.0.0/16", // corporate
"192.168.1.0/24", // department
"2001:7c0:3100::/40", // corporate
"2001:7c0:3100:1::/64", // department
"fc00::/7", // unique local
}
for _, s := range prefixes {
pfx := netip.MustParsePrefix(s)
table.Insert(pfx, struct{}{})
}
// Test some IP addresses for black/whitelist containment
ips := []string{
"192.168.1.100", // must match, department
"192.168.2.1", // must match, corporate
"2001:7c0:3100:1::1", // must match, department
"2001:7c0:3100:2::1", // must match, corporate
"fc00::1", // must match, unique local
//
"172.16.0.1", // must NOT match
"2003:dead:beef::1", // must NOT match
}
for _, s := range ips {
ip := netip.MustParseAddr(s)
fmt.Printf("%-20s is contained: %t\n", ip, table.Contains(ip))
}
// Output:
// 192.168.1.100 is contained: true
// 192.168.2.1 is contained: true
// 2001:7c0:3100:1::1 is contained: true
// 2001:7c0:3100:2::1 is contained: true
// fc00::1 is contained: true
// 172.16.0.1 is contained: false
// 2003:dead:beef::1 is contained: false
}Release v0.18 requires at least go1.23 and we use the iter.Seq2[netip.Prefix, V] types for iterators.
The lock-free versions of insert, update and delete are added, but still experimentell.
import "github.com/gaissmai/bart"
type Table[V any] struct {
// Has unexported fields.
}
Table is an IPv4 and IPv6 routing table with payload V. The zero value is
ready to use.
The Table is safe for concurrent readers but not for concurrent readers
and/or writers. Either the update operations must be protected by an
external lock mechanism or the various ...Persist functions must be used
which return a modified routing table by leaving the original unchanged
A Table must not be copied by value, see Table.Clone.
func (t *Table[V]) Insert(pfx netip.Prefix, val V)
func (t *Table[V]) Delete(pfx netip.Prefix)
func (t *Table[V]) Update(pfx netip.Prefix, cb func(val V, ok bool) V) (newVal V)
func (t *Table[V]) InsertPersist(pfx netip.Prefix, val V) *Table[V]
func (t *Table[V]) DeletePersist(pfx netip.Prefix) *Table[V]
func (t *Table[V]) UpdatePersist(pfx netip.Prefix, cb func(val V, ok bool) V) (pt *Table[V], newVal V)
func (t *Table[V]) Get(pfx netip.Prefix) (val V, ok bool)
func (t *Table[V]) GetAndDelete(pfx netip.Prefix) (val V, ok bool)
func (t *Table[V]) GetAndDeletePersist(pfx netip.Prefix) (pt *Table[V], val V, ok bool)
func (t *Table[V]) Union(o *Table[V])
func (t *Table[V]) Clone() *Table[V]
func (t *Table[V]) Contains(ip netip.Addr) bool
func (t *Table[V]) Lookup(ip netip.Addr) (val V, ok bool)
func (t *Table[V]) LookupPrefix(pfx netip.Prefix) (val V, ok bool)
func (t *Table[V]) LookupPrefixLPM(pfx netip.Prefix) (lpm netip.Prefix, val V, ok bool)
func (t *Table[V]) OverlapsPrefix(pfx netip.Prefix) bool
func (t *Table[V]) Overlaps(o *Table[V]) bool
func (t *Table[V]) Overlaps4(o *Table[V]) bool
func (t *Table[V]) Overlaps6(o *Table[V]) bool
func (t *Table[V]) Subnets(pfx netip.Prefix) iter.Seq2[netip.Prefix, V]
func (t *Table[V]) Supernets(pfx netip.Prefix) iter.Seq2[netip.Prefix, V]
func (t *Table[V]) All() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) All4() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) All6() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) AllSorted() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) AllSorted4() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) AllSorted6() iter.Seq2[netip.Prefix, V]
func (t *Table[V]) Size() int
func (t *Table[V]) Size4() int
func (t *Table[V]) Size6() int
func (t *Table[V]) String() string
func (t *Table[V]) Fprint(w io.Writer) error
func (t *Table[V]) MarshalText() ([]byte, error)
func (t *Table[V]) MarshalJSON() ([]byte, error)
func (t *Table[V]) DumpList4() []DumpListNode[V]
func (t *Table[V]) DumpList6() []DumpListNode[V]Please see the extensive benchmarks comparing bart with other IP routing table implementations.
Just a teaser, Contains and Lookups against the full Internet routing table with random IP address probes:
goos: linux
goarch: amd64
pkg: github.com/gaissmai/bart
cpu: Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
BenchmarkFullMatchV4/Contains 55906228 21.39 ns/op 0 B/op 0 allocs/op
BenchmarkFullMatchV6/Contains 100000000 11.38 ns/op 0 B/op 0 allocs/op
BenchmarkFullMissV4/Contains 52927538 22.69 ns/op 0 B/op 0 allocs/op
BenchmarkFullMissV6/Contains 250386540 4.883 ns/op 0 B/op 0 allocs/op
PASS
ok github.com/gaissmai/bart 11.291s
goos: linux
goarch: amd64
pkg: github.com/gaissmai/bart
cpu: Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
BenchmarkFullMatchV4/Lookup 53578766 21.77 ns/op 0 B/op 0 allocs/op
BenchmarkFullMatchV6/Lookup 57054618 21.07 ns/op 0 B/op 0 allocs/op
BenchmarkFullMissV4/Lookup 48289306 25.60 ns/op 0 B/op 0 allocs/op
BenchmarkFullMissV6/Lookup 142917571 8.387 ns/op 0 B/op 0 allocs/op
PASS
ok github.com/gaissmai/bart 10.455s
The package is currently released as a pre-v1 version, which gives the author the freedom to break backward compatibility to help improve the API as he learns which initial design decisions would need to be revisited to better support the use cases that the library solves for.
These occurrences are expected to be rare in frequency and the API is already quite stable.
Please open an issue for discussion before sending a pull request.
Standing on the shoulders of giants.
Credits for many inspirations go to
- the clever guys at tailscale,
- to Daniel Lemire for his inspiring blog,
- to Donald E. Knuth for the ART routing algorithm and
- to Yoichi Hariguchi who deciphered it for us mere mortals
And last but not least to the Go team who do a wonderful job!
MIT