On Wed, Apr 21, 2010 at 01:46:33PM +0200, Jan Kiszka wrote: > Michael S. Tsirkin wrote: > > On Tue, Apr 13, 2010 at 05:59:44PM +0300, Michael S. Tsirkin wrote: > >> The following situation was observed in the field: > >> tap1 sends packets, tap2 does not consume them, as a result > >> tap1 can not be closed. This happens because > >> tun/tap devices can hang on to skbs undefinitely. > >> > >> As noted by Herbert, possible solutions include a timeout followed by a > >> copy/change of ownership of the skb, or always copying/changing > >> ownership if we're going into a hostile device. > >> > >> This patch implements the second approach. > >> > >> Note: one issue still remaining is that since skbs > >> keep reference to tun socket and tun socket has a > >> reference to tun device, we won't flush backlog, > >> instead simply waiting for all skbs to get transmitted. > >> At least this is not user-triggerable, and > >> this was not reported in practice, my assumption is > >> other devices besides tap complete an skb > >> within finite time after it has been queued. > >> > >> A possible solution for the second issue > >> would not to have socket reference the device, > >> instead, implement dev->destructor for tun, and > >> wait for all skbs to complete there, but this > >> needs some thought, probably too risky for 2.6.34. > >> > >> Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > >> Tested-by: Yan Vugenfirer <yvuge...@redhat.com> > >> > >> --- > >> > >> Please review the below, and consider for 2.6.34, > >> and stable trees. > >> > >> drivers/net/tun.c | 4 ++++ > >> 1 files changed, 4 insertions(+), 0 deletions(-) > >> > >> diff --git a/drivers/net/tun.c b/drivers/net/tun.c > >> index 96c39bd..4326520 100644 > >> --- a/drivers/net/tun.c > >> +++ b/drivers/net/tun.c > >> @@ -387,6 +387,10 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, > >> struct net_device *dev) > >> } > >> } > >> > >> + /* Orphan the skb - required as we might hang on to it > >> + * for indefinite time. */ > >> + skb_orphan(skb); > >> + > >> /* Enqueue packet */ > >> skb_queue_tail(&tun->socket.sk->sk_receive_queue, skb); > >> dev->trans_start = jiffies; > >> -- > >> 1.7.0.2.280.gc6f05 > > > > This is commit 0110d6f22f392f976e84ab49da1b42f85b64a3c5 in net-2.6 > > Please cherry-pick this fix in stable kernels (2.6.32 and 2.6.33). > > > > Thanks! > > > > Before I forget again: > > Tested-by: Jan Kiszka <jan.kis...@siemens.com> > (namely the field test of our customer) > > Jan
Cool, thanks! > -- > Siemens AG, Corporate Technology, CT T DE IT 1 > Corporate Competence Center Embedded Linux
