On 2012-02-13 20:35, Jan Kiszka wrote: > On 2012-02-13 16:27, Zhi Yong Wu wrote: >> On Mon, Feb 13, 2012 at 4:24 AM, Jan Kiszka <jan.kis...@web.de> wrote: >>> On 2012-02-12 19:34, Michael S. Tsirkin wrote: >>>> It seems somewhat easy to crash qemu with slirp if we queue multiple >>>> packets. >>>> I didn't investigate further yet so I don't know if this >>>> is a regression. Anyone knowledgeable about slirp wants to take a look? >>>> >>>> /home/mst/qemu-test/bin/qemu-system-x86_64 -enable-kvm -m 1G -drive >>>> file=/home/mst/rhel6.qcow2 -netdev user,id=bar -net >>>> nic,netdev=bar,model=e1000,macaddr=52:54:00:12:34:57 -redir >>>> tcp:8022::22 -vnc :1 -monitor stdio >>>> >>>> While guest is booting, quickly do this >>>> >>>> ssh localhost -p 8022 >>>> CTRL-C >>>> ssh localhost -p 8022 >>>> CTRL-C >>>> ssh localhost -p 8022 >>>> CTRL-C >>>> ssh localhost -p 8022 >>>> CTRL-C >>> >>> Confirmed. A single canceled connection prior the interface setup is >>> enough. Possibly something is not properly removed / cleaned up here. >>> Will see if I find some time to debug, can't promise. >> Interesting thing, pls give me some time, and i am trying to debug this >> issue. > > I had a look today, but haven't found a fix yet. The problem is related > to our requeuing of packets if the target MAC is not yet known. > Something goes terribly wrong once it gets resolved (mbuf use after > release?). Maybe it was always wrong and the requeuing just surfaced the > bug, dunno. > > After starring at the code for a while, I got the bad feeling of > "unfixable with reasonable effort". The queuing code is horrible (well, > like most of slirp), and the requeuing just made it worse. But maybe I'm > just missing some trick now - yet another one that would make the code > even more unreadable... > > I'm inclined to suggest a slirp rewrite (base support, not all features > at once) as a GSOC project. QEMU really deserves something better. >
Despite my grumbling, I would welcome any patch that fixes the bug, of course! Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
