device: use linked list for per-peer allowed-ip traversal

This makes the IpcGet method much faster.

We also refactor the traversal API to use a callback so that we don't
need to allocate at all. Avoiding allocations we do self-masking on
insertion, which in turn means that split intermediate nodes require a
copy of the bits.

benchmark               old ns/op     new ns/op     delta
BenchmarkUAPIGet-16     3243          2659          -18.01%

benchmark               old allocs     new allocs     delta
BenchmarkUAPIGet-16     35             30             -14.29%

benchmark               old bytes     new bytes     delta
BenchmarkUAPIGet-16     1218          737           -39.49%

This benchmark is good, though it's only for a pair of peers, each with
only one allowedips. As this grows, the delta expands considerably.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/device/uapi.go b/device/uapi.go
index 148a7a2..cbfe25e 100644
--- a/device/uapi.go
+++ b/device/uapi.go
@@ -108,9 +108,10 @@ func (device *Device) IpcGetOperation(w io.Writer) error {
 			sendf("rx_bytes=%d", atomic.LoadUint64(&peer.stats.rxBytes))
 			sendf("persistent_keepalive_interval=%d", atomic.LoadUint32(&peer.persistentKeepaliveInterval))
 
-			for _, ip := range device.allowedips.EntriesForPeer(peer) {
-				sendf("allowed_ip=%s", ip.String())
-			}
+			device.allowedips.EntriesForPeer(peer, func(ip net.IP, cidr uint) bool {
+				sendf("allowed_ip=%s/%d", ip.String(), cidr)
+				return true
+			})
 		}
 	}()