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 -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
