device: change logging interface to use functions

This commit overhauls wireguard-go's logging.

The primary, motivating change is to use a function instead
of a *log.Logger as the basic unit of logging.
Using functions provides a lot more flexibility for
people to bring their own logging system.

It also introduces logging helper methods on Device.
These reduce line noise at the call site.
They also allow for log functions to be nil;
when nil, instead of generating a log line and throwing it away,
we don't bother generating it at all.
This spares allocation and pointless work.

This is a breaking change, although the fix required
of clients is fairly straightforward.

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/device/noise-protocol.go b/device/noise-protocol.go
index e34da83..df520d0 100644
--- a/device/noise-protocol.go
+++ b/device/noise-protocol.go
@@ -319,11 +319,11 @@ func (device *Device) ConsumeMessageInitiation(msg *MessageInitiation) *Peer {
 	flood := time.Since(handshake.lastInitiationConsumption) <= HandshakeInitationRate
 	handshake.mutex.RUnlock()
 	if replay {
-		device.log.Debug.Printf("%v - ConsumeMessageInitiation: handshake replay @ %v\n", peer, timestamp)
+		device.debugf("%v - ConsumeMessageInitiation: handshake replay @ %v", peer, timestamp)
 		return nil
 	}
 	if flood {
-		device.log.Debug.Printf("%v - ConsumeMessageInitiation: handshake flood\n", peer)
+		device.debugf("%v - ConsumeMessageInitiation: handshake flood", peer)
 		return nil
 	}