Add description of IO_CSQ algorithms

Remove this file when this is done.

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

csq_psuedo_description.c

@@ -0,0 +1,173 @@
+typedef struct _PACKET_QUEUE {
+	KSPIN_LOCK Lock;
+	NET_BUFFER_LIST *FirstNbl, *LastNbl;
+	volatile NET_BUFFER_LIST *FirstToFree;
+	NET_BUFFER *NextNb;
+	UINT NumNbl;
+} PACKET_QUEUE, *PPACKET_QUEUE;
+
+// Annotation: requires Queue->Lock
+void AddToFreeList(PACKET_QUEUE *Queue, NET_BUFFER_LIST *Nbl)
+{
+	if (!Queue->FirstToFree)
+		Queue->FirstToFree = Nbl;
+	else {
+		NET_BUFFER_LIST_NEXT_NBL(Nbl) = Queue->FirstToFree;
+		Queue->FirstToFree = Nbl;
+	}
+	--Queue->NumNbl;
+}
+
+// Annotation: requires Queue->Lock
+void FreeFreeList(PACKET_QUEUE *Queue)
+{
+	NET_BUFFER_LIST *Next;
+
+	while (Queue->FirstToFree) {
+		Next = NET_BUFFER_LIST_NEXT_NBL(Queue->FirstToFree);
+		FreeNbl(Queue->FirstToFree);
+		Queue->FirstToFree = Next;
+	}
+}
+
+// Annotation: requires Queue->Lock
+NET_BUFFER *RemoveFromQueue(PACKET_QUEUE *Queue, NET_BUFFER_LIST **DetachedNbl)
+{
+	NET_BUFFER_LIST *Top;
+	NET_BUFFER *Ret;
+
+	Top = Queue->FirstNbl;
+	if (!Top)
+		return NULL;
+	if (!Queue->NextNb)
+		Queue->NextNb = NET_BUFFER_LIST_FIRST_NB(Top);
+	Ret = Queue->NextNb;
+	Queue->NextNb = NET_BUFFER_NEXT_NB(Ret);
+	if (!Queue->NextNb) {
+		Queue->FirstNbl = NET_BUFFER_LIST_NEXT_NBL(Top);
+		if (!Queue->FirstNbl)
+			Queue->LastNbl = NULL;
+		NET_BUFFER_LIST_NEXT_NBL(Top) = NULL;
+		AddToFreeList(Queue, Top);
+		if (DetachedNbl)
+			*DetachedNbl = Top;
+	}
+	return Ret;
+}
+
+// Annotation: requires Queue->Lock
+void AppendToQueue(PACKET_QUEUE *Queue, NET_BUFFER_LIST *Nbl)
+{
+	NET_BUFFER_LIST *Next;
+
+	for (; Nbl; Nbl = Next) {
+		Next = NET_BUFFER_LIST_NEXT_NBL(Nbl);
+		if (!NET_BUFFER_LIST_FIRST_NB(Nbl->FirstNb)) {
+			FreeNbl(Nbl);
+			continue;
+		}
+		if (!Queue->FirstNbl)
+			Queue->FirstNbl = Queue->LastNbl = Nbl;
+		else {
+			NET_BUFFER_LIST_NEXT_NBL(Queue->LastNbl) = Nbl;
+			Queue->LastNbl = Nbl;
+		}
+		++Queue->NumNbl;
+	}
+}
+
+// Annotation: requires Queue->Lock
+// Note: Must be called immediately after RemoveFromQueue without dropping Queue->Lock.
+void PrependToQueue(PACKET_QUEUE *Queue, NET_BUFFER *Nb, NET_BUFFER_LIST *DetachedNbl)
+{
+	Queue->NextNb = Nb;
+
+	if (!DetachedNbl)
+		return;
+
+	if (DetachedNbl == Queue->FirstToFree)
+		Queue->FirstToFree = NET_BUFFER_LIST_NEXT_NBL(DetachedNbl);
+
+	if (!Queue->FirstNbl)
+		Queue->FirstNbl = Queue->LastNbl = DetachedNbl;
+	else {
+		NET_BUFFER_LIST_NEXT_NBL(DetachedNbl) = Queue->FirstNbl;
+		Queue->FirstNbl = DetachedNbl;
+	}
+	++Queue->NumNbl;
+}
+
+// Annotation: requires Queue->Lock
+void TrimQueueToNItems(PACKET_QUEUE *Queue, UINT MaxNbls)
+{
+	NET_BUFFER_LIST *Next;
+
+	while (Queue->NumNbl > MaxNbls) {
+		if (!Queue->FirstNbl)
+			return;
+		Next = NET_BUFFER_LIST_NEXT_NBL(Queue->FirstNbl);
+		AddToFreeList(Queue->FirstNbl);
+		Queue->NextNb = NULL;
+		Queue->FirstNbl = Next;
+		if (!Queue->FirstNbl)
+			Queue->LastNbl = NULL;
+	}
+	FreeFreeList(Queue);
+}
+
+void TunDispatchRead(IRP *Irp)
+{
+	IoCsqInsertIrpEx(IoCsq, Irp, NULL, NULL);
+	ProcessQueuedPackets();
+}
+
+void ProcessQueuedPackets(void)
+{
+	IRP *Irp;
+	NET_BUFFER *Nb;
+	KLOCK_QUEUE_HANDLE LockHandle;
+
+	for (;;) {
+		if (!Irp) {
+			NET_BUFFER_LIST *DetachedNbl = NULL;
+
+			KeAcquireInStackQueuedSpinLock(Queue->Lock, &LockHandle);
+			Nb = RemoveFromQueue(Queue, &DetachedNbl);
+			if (!Nb) {
+				KeReleaseInStackQueuedSpinLock(Queue->Lock, &LockHandle);
+				return;
+			}
+			Irp = IoCsqRemoveNextIrp(IoCsq, NULL);
+			if (!Irp) {
+				PrependToQueue(Queue, Nb, DetachedNbl);
+				KeReleaseInStackQueuedSpinLock(Queue, &LockHandle);
+				return;
+			}
+			KeReleaseInStackQueuedSpinLock(Queue->Lock, &LockHandle);
+		} else {
+			KeAcquireInStackQueuedSpinLock(Queue->Lock, &LockHandle);
+			Nb = RemoveFromQueue(Queue, NULL);
+			KeReleaseInStackQueuedSpinLock(Queue->Lock, &LockHandle);
+		}
+		if (!Nb || WriteIntoIrp(Irp, Nb) == IRP_HAD_NO_ROOM_FOR_IT) {
+			TunCompleteRequest(Irp, 0, STATUS_SUCCESS);
+			Irp = NULL;
+		}
+		if (Queue->FirstToFree) {
+			KeAcquireInStackQueuedSpinLock(Queue->Lock, &LockHandle);
+			FreeFreeList(Queue);
+			KeReleaseInStackQueuedSpinLock(Queue->Lock, &LockHandle);
+		}
+	}
+}
+
+void TunSendNetBufferLists(NET_BUFFER_LIST *Nbl)
+{
+	KLOCK_QUEUE_HANDLE LockHandle;
+
+	KeAcquireInStackQueuedSpinLock(Queue->Lock, &LockHandle);
+	AppendToQueue(Queue, Nbl);
+	TrimQueueToNItems(Queue, 1000);
+	KeReleaseInStackQueuedSpinLock(Queue->Lock, &LockHandle);
+	ProcessQueuedPackets();
+}