On Mon, Dec 17, 2012 at 7:36 PM, Steffen Dettmer
<steffen.dett...@gmail.com> wrote:
> the larger values I use for -l in UDP mode, the lower bandwidth
> is reported by iperf, incorrectly I think. With tcpdump I found
> that it really seems like iperf would calculate only with one IP
> fragement instead of the whole UDP packet.
I took a look to the sources and found issues with buffer handling.
1. usage tells:
-l, --len #[KM] length of buffer to read or write (default 8 KB)
but code tells:
main->mBufLen = 128 * 1024; // -l, 8 Kbyte
mExtSettings->mBufLen = kDefault_UDPBufLen;
with const int kDefault_UDPBufLen = 1470
For the first one it could be that a bug entry already exists
in a tracker.
2. recv is used with a buffer of that size, which is too small to
take UDP packets in general (they can be up to almost 64KB),
see man recv:
If a message is too long to fit in the supplied buffer,
excess bytes may be discarded depending on the type of
socket the message is received from.
[...]
MSG_TRUNC
Return the real length of the packet, even when it was longer
than the passed buffer. Only valid for packet sockets.
But MSG_TRUNC is not given.
3. patch idea
diff -Nur iperf-2.0.5.dist/src/Server.cpp iperf-2.0.5/src/Server.cpp
--- iperf-2.0.5.dist/src/Server.cpp 2012-12-17 20:03:54.000000000 +0100
+++ iperf-2.0.5/src/Server.cpp 2012-12-17 20:06:18.000000000 +0100
@@ -109,7 +109,7 @@
mSettings->reporthdr = InitReport( mSettings );
do {
// perform read
- currLen = recv( mSettings->mSock, mBuf, mSettings->mBufLen, 0 );
+ currLen = recv( mSettings->mSock, mBuf,
mSettings->mBufLen, MSG_TRUNC );
if ( isUDP( mSettings ) ) {
// read the datagram ID and sentTime out of the buffer
(there are "trailing whitespace" issues in the sources
and thus in the patch, hope they remain correctly in this mail)
What do you think?
oki,
Steffen
------------------------------------------------------------------------------
LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial
Remotely access PCs and mobile devices and provide instant support
Improve your efficiency, and focus on delivering more value-add services
Discover what IT Professionals Know. Rescue delivers
http://p.sf.net/sfu/logmein_12329d2d
_______________________________________________
Iperf-users mailing list
Iperf-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/iperf-users
