[OSSTEST PATCH] ms-queuedaemon: Do not spin if client input is delayed/truncated

[OSSTEST PATCH] ms-queuedaemon: Do not spin if client input is delayed/truncated

[Ian Jackson]

chan-read-data would spin if `read' returns early because of
nonblocking mode.

Check whether the return value is the empty string (which can only
happen on eof or nonblocking lack of data, and we checked eof just
before), and if so, simply return.  The fileevent remains set up so we
will be called again when more data arrives.

(Deployment/testing note: this change is currently live in Cambridge,
as I cowboyed it directly into ~osstest/daemons-testing.git, on
observing this misbehaviour.)

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 tcl/daemonlib.tcl |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/tcl/daemonlib.tcl b/tcl/daemonlib.tcl
index 55bc385..972b5e2 100644
--- a/tcl/daemonlib.tcl
+++ b/tcl/daemonlib.tcl
@@ -166,6 +166,9 @@ proc chan-read-data {chan} {
 		chan-destroy $chan
 		return
 	    }
+            if {![string length $got]} {
+		return
+	    }
 	    append data $got
 	    incr len -[string length $got]
 	}
-- 
1.7.10.4

Re: [OSSTEST PATCH] ms-queuedaemon: Do not spin if client input is delayed/truncated

[Ian Campbell]

On Tue, 2015-10-20 at 18:26 +0100, Ian Jackson wrote:
> chan-read-data would spin if `read' returns early because of
> nonblocking mode.
> 
> Check whether the return value is the empty string (which can only
> happen on eof or nonblocking lack of data, and we checked eof just
> before), and if so, simply return.  The fileevent remains set up so we
> will be called again when more data arrives.
> 
> (Deployment/testing note: this change is currently live in Cambridge,
> as I cowboyed it directly into ~osstest/daemons-testing.git, on
> observing this misbehaviour.)
> 
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>

Acked-by: Ian Campbell <ian.campbell@citrix.com>