On 08/26/2015 03:51 PM, Vladislav Yasevich wrote: > When rtl8139 card is running in standard mode, it is very easy > to overlflow and the receive buffer and get into a siutation > where all packets are dropped. Simply reproduction case is > to ping the guest from the host with 6500 byte packets. > > There are actually 2 problems here. > 1) When the rtl8129 buffer is overflow, the card emulation > returns the size of the packet back to queue transmission. > This signals successful reception even though the packet > has been dropped. The proper solution is to return 0, so > that the packet is re-queued and will be resubmitted later. > > 2) When packets are sized such that the fragments end up completely > filling the receive buffer without overflow, the device thinks > that the buffer is actually empty (instead of full). This causes > next packet to over-write the existing packets. With the above > ping reproducer, ever ICMP packet fills the buffer and thus keeps > overwriting the previous packet and never waking up the guest. > The solution here is track the number of unread bytes separately > so we would know if we have anything in buffer to read or not. > > V2: instead of tracking buffer_full condition, changed the code, as > suggested by Stefan Hajnoczi, to track the number of unread bytes > instead. We initialize it to 0 at the start, adjust it on every > receive from the network and read from the guest and can set > the number of unread of bytes to full buffer size when the buffer > full. > > Vladislav Yasevich (2): > rtl8139: Do not consume the packet during overflow in standard mode. > rtl8139: correctly track full receive buffer in standard mode >
Self nack. The second patch is wrong. Will resubmit when fixed. -vlad > hw/net/rtl8139.c | 44 +++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 39 insertions(+), 5 deletions(-) >
