datapath-windows: return netlink error for read operation

The kernel datapath returns a NL error message upon any errors
during read operations, and returns STATUS_SUCCESS as the return
code. We reply on the input NL request to get the family ID, and the
PID. However, when the request is of type OVS_CTRL_CMD_EVENT_NOTIFY
and OVS_CTRL_CMD_READ_NOTIFY, there's no input buffer associated
with the request. So, we use a temporary input buffer to be able to
call the Netlink APIs for constructing the output NL error message.

Signed-off-by: Nithin Raju <nithin@vmware.com>
Acked-by: Sairam Venugopal <vsairam@vmware.com>
Acked-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/datapath-windows/ovsext/Datapath.c b/datapath-windows/ovsext/Datapath.c
index 1e166041d..b3dbd7164 100644
--- a/datapath-windows/ovsext/Datapath.c
+++ b/datapath-windows/ovsext/Datapath.c
@@ -1020,10 +1020,24 @@ InvokeNetlinkCmdHandler(POVS_USER_PARAMS_CONTEXT usrParamsCtx,
     if (status != STATUS_SUCCESS && status != STATUS_PENDING) {
         if (usrParamsCtx->devOp != OVS_WRITE_DEV_OP && *replyLen == 0) {
             NL_ERROR nlError = NlMapStatusToNlErr(status);
-            POVS_MESSAGE msgIn = (POVS_MESSAGE)usrParamsCtx->inputBuffer;
+            OVS_MESSAGE msgInTmp = { 0 };
+            POVS_MESSAGE msgIn = NULL;
             POVS_MESSAGE_ERROR msgError = (POVS_MESSAGE_ERROR)
                 usrParamsCtx->outputBuffer;
 
+            if (usrParamsCtx->ovsMsg->genlMsg.cmd == OVS_CTRL_CMD_EVENT_NOTIFY ||
+                usrParamsCtx->ovsMsg->genlMsg.cmd == OVS_CTRL_CMD_READ_NOTIFY) {
+                /* There's no input buffer associated with such requests. */
+                NL_BUFFER nlBuffer;
+                msgIn = &msgInTmp;
+                NlBufInit(&nlBuffer, (PCHAR)msgIn, sizeof *msgIn);
+                NlFillNlHdr(&nlBuffer, nlFamilyOps->id, 0, 0,
+                            usrParamsCtx->ovsInstance->pid);
+            } else {
+                msgIn = (POVS_MESSAGE)usrParamsCtx->inputBuffer;
+            }
+
+            ASSERT(msgIn);
             ASSERT(msgError);
             NlBuildErrorMsg(msgIn, msgError, nlError);
             *replyLen = msgError->nlMsg.nlmsgLen;