Anthony Liguori wrote: > On 07/15/2010 03:22 PM, Miguel Di Ciurcio Filho wrote: >> Hello, >> >> This is a prototype suggestion. I mostly copied and pasted the code from >> net/dump.c into net.c and made some adjustments. There is no command line >> parsing involved yet, just the internals and small changes in >> net/tap.c and >> net/slirp.c do make the thing work. >> >> In my tests, using tap as backend, e1000 as a guest device and running >> iperf from >> guest to host, the overhead of dumping the traffic caused a loss of >> around 30% >> of performance. >> >> I opened the dumped files in wireshark and they looked fine. When >> using slirp >> all requests were dumped fine too. >> > > A less invasive way to do this would be to chain netdev devices. > > Basically: > > -netdev tap,fd=X,id=foo > -netdev dump,file=foo.pcap,netdev=foo,id=bar > -net nic,model=virtio,netdev=bar > > I think this has some clear advantages to this architecturally. From a > user perspective, the only loss is that you have to add the dump device > at startup (you can still enable/disable capture dynamically).
At least I tend to forget this, and then you already have a VM running without that chain. And it looks like dynamic reconfiguration of the backend (netdev_del/add) implies hot-removing/adding the frontend as well. So this is also no option if the guest does not support that. A bit unhandy. Jan
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