This patch adds a new netbe_peek_recvlen() function to the net
backend API. The new function allows the virtio-net receive code
to know in advance how many virtio descriptors chains will be
needed to receive the next packet. As a result, the implementation
of the virtio-net mergeable rx buffers feature becomes efficient,
so that we can enable it also with the tap(4) backend. For the
tap(4) backend, a bounce buffer is introduced to implement the
peeck_recvlen() callback, which implies an additional packet copy
on the receive datapath. In the future, it should be possible to
remove the bounce buffer (and so the additional copy), by
obtaining the length of the next packet from kevent data.
Reviewed by: grehan, aleksandr.fedorov@itglobal.com
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D23472
- buf_to_iov() does not use buflen parameter, allowing out of bound read.
- buf_to_iov() leaks memory if seek argument > 0.
- iov_to_buf() doesn't need to reallocate buffer for every segment.
- there is no point to use size_t for iov counts, int is more then enough.
- some iov function arguments can be constified.
- pci_vtscsi_request_handle() used truncate_iov() incorrectly, allowing
getting out of buffer and possibly corrupting data.
- pci_vtscsi_controlq_notify() written returned status at wrong offset.
- pci_vtscsi_controlq_notify() leaked one buffer per event.
Reported by: wg
Reviewed by: araujo
MFC after: 1 week
Sponsored by: iXsystems, Inc.
Differential Revision: https://reviews.freebsd.org/D18465
