Re: Input flush action for userspace FromDevice?

Markku Savela <[email protected]> Fri, 19 Oct 2012 08:47:37 +0300
Newsgroups gmane.network.routing.click
Message-ID <[email protected]> 
On 10/17/2012 01:19 PM, Markku Savela wrote:

> I cannot find such function in FromDevice or is there? First
> that comes to mind is some kind of flush handler that
> would read and discard input, until none... (there is, of
> course, a small concern of reading forever and never seeing
> "no data" if new data for socket is generated faster than
> click can read).

Ok, here is my test for such handler. This is not anything
that could be incorporated as is: it is hard coded to assume
the linux method for reading -- I didn't have time to study
how to achieve same with PCAP or NETMAP...

I suppose I should have wrapped this in FROMDEVICE_ALLOW_LINUX
and check the selected _method too.

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flush.diff (text/x-patch, 1.1 KB) 
diff --git a/elements/userlevel/fromdevice.cc b/elements/userlevel/fromdevice.cc
index 3da8dab..924ab8f 100644
--- a/elements/userlevel/fromdevice.cc
+++ b/elements/userlevel/fromdevice.cc
@@ -626,10 +626,24 @@ FromDevice::read_handler(Element* e, void *thunk)
 }
 
 int
-FromDevice::write_handler(const String &, Element *e, void *, ErrorHandler *)
+FromDevice::write_handler(const String &, Element *e, void *data, ErrorHandler *)
 {
     FromDevice* fd = static_cast<FromDevice*>(e);
-    fd->_count = 0;
+    unsigned count = 0;
+    unsigned char buf[100];
+
+    switch ((int)data) {
+    case 0:
+	fd->_count = 0;
+	break;
+    case 1:
+	while (recv(fd->_fd, buf, sizeof(buf), MSG_DONTWAIT) > 0)
+	    ++count;
+	click_chatter("flushed %u", count);
+	break;
+    default:
+	break;
+    }
     return 0;
 }
 
@@ -640,6 +654,7 @@ FromDevice::add_handlers()
     add_read_handler("encap", read_handler, 1);
     add_read_handler("count", read_handler, 2);
     add_write_handler("reset_counts", write_handler, 0, Handler::BUTTON);
+    add_write_handler("flush", write_handler, 1, Handler::BUTTON);
 }
 
 CLICK_ENDDECLS