Work on UAPI

Cross-platform API (get operation)
Handshake initiation creation process
Outbound packet flow
Fixes from code-review

src/constants.go

@@ -5,12 +5,17 @@ import (
 )
 
 const (
-	RekeyAfterMessage  = (1 << 64) - (1 << 16) - 1
-	RekeyAfterTime     = time.Second * 120
-	RekeyAttemptTime   = time.Second * 90
-	RekeyTimeout       = time.Second * 5
-	RejectAfterTime    = time.Second * 180
-	RejectAfterMessage = (1 << 64) - (1 << 4) - 1
-	KeepaliveTimeout   = time.Second * 10
-	CookieRefreshTime  = time.Second * 2
+	RekeyAfterMessage      = (1 << 64) - (1 << 16) - 1
+	RekeyAfterTime         = time.Second * 120
+	RekeyAttemptTime       = time.Second * 90
+	RekeyTimeout           = time.Second * 5 // TODO: Exponential backoff
+	RejectAfterTime        = time.Second * 180
+	RejectAfterMessage     = (1 << 64) - (1 << 4) - 1
+	KeepaliveTimeout       = time.Second * 10
+	CookieRefreshTime      = time.Second * 2
+	MaxHandshakeAttempTime = time.Second * 90
+)
+
+const (
+	QueueOutboundSize = 1024
 )