A couple of notes from me. 1) I would use FromDevice(ethX, SNIFFER false), this ensures Linux kernel does not also handle the packets. See http://read.cs.ucla.edu/click/elements/fromdevice.u 2) Is your MyElementModify element recalculating IP and TCP/UDP checksums? 3) When you work with IP packets, ALWAYS put in a Classifier(12/0800, -) just after FromDevice to ensure you are not inadvertently working on non-IP packets like ARP etc. 4) Node B requires MarkIPHeader/CheckIPHeader before IPPrint.
Cant really comment any more without seeing how you modify the packet contents inside MyElementModify On Wed, Oct 6, 2010 at 11:56 AM, Ashok Anand <[email protected]> wrote: > I see. so the environment is emulab, > > the path is setup between, webserver to nodeA to nodeB to client > and for nodeA, click configuration looks like, > > FromDevice(eth6) > -> Strip(14) > -> CheckIPHeader(0, CHECKSUM true, VERBOSE true) > -> Print('Ok') > -> IPPrint(LENGTH true) > -> MyElementModify() > -> CheckIPHeader(0, CHECKSUM true, VERBOSE true) > -> Unstrip(14) > -> Queue(10) > -> ToDevice(eth8) > > and nodeB looks like, > > FromDevice(eth7) > -> Strip(14) > -> IPPrint(LENGTH true) > -> MyElementUnModify() > -> Unstrip(14) > -> Queue(10) > -> ToDevice(eth9) > > these interfaces are correct interfaces in the path. > > > > > On Wed, Oct 6, 2010 at 4:19 AM, Beyers Cronje <[email protected]> wrote: > >> Hi, >> >> You can modify packet data in userlevel Click, so that is not the problem. >> Maybe post an example of how you are changing the packet. >> >> On Wed, Oct 6, 2010 at 9:59 AM, Ashok Anand <[email protected]> wrote: >> >> > Hi, >> > >> > I am a new user to click. >> > I am trying to setup a simple testbed using click. >> > so there is a web server and a client, and there are two intermediate >> > nodes, >> > which runs click at userlevel. >> > First intermediate node, changes packet data, while second intermediate >> > undo >> > the changes. >> > >> > The problem that I am facing is that, the second intermediate node does >> not >> > find any changes in the packet. >> > Is it because, the click is running at userlevel, and modification at >> > userlevel, does not appear when sent to network.. >> > (I am using simple configuration, which just reads packet from an >> > interface, >> > changes it, and then sends to another interface). >> > >> > Please let me know. >> > >> > Thanks, >> > Ashish >> > _______________________________________________ >> > click mailing list >> > [email protected] >> > https://amsterdam.lcs.mit.edu/mailman/listinfo/click >> > >> _______________________________________________ >> click mailing list >> [email protected] >> https://amsterdam.lcs.mit.edu/mailman/listinfo/click >> > > _______________________________________________ click mailing list [email protected] https://amsterdam.lcs.mit.edu/mailman/listinfo/click
