diff options
| -rw-r--r-- | content.tex | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/content.tex b/content.tex index 51a00b2..ef28bdb 100644 --- a/content.tex +++ b/content.tex @@ -3561,10 +3561,13 @@ Processing incoming packets involves: this packet is spread over (including this one): this will always be 1 if VIRTIO_NET_F_MRG_RXBUF was not negotiated. This allows receipt of large packets without having to allocate large - buffers. In this case, there will be at least \field{num_buffers} in - the used ring, and the device chains them together to form a - single packet. The other buffers will not begin with a struct - virtio_net_hdr. + buffers: a packet that does not fit in a single buffer can flow + over to the next buffer, and so on. In this case, there will be + at least \field{num_buffers} in the used ring, and the device + chains them together to form a single packet in a way similar to + how it would store it in a single buffer spread over multiple + descriptors. + The other buffers will not begin with a struct virtio_net_hdr. \item If \field{num_buffers} is one, then the entire packet will be @@ -3605,10 +3608,15 @@ If VIRTIO_NET_F_MRG_RXBUF has not been negotiated, the device MUST set \field{num_buffers} to 1. If VIRTIO_NET_F_MRG_RXBUF has been negotiated, the device MUST set -\field{num_buffers} to indicate the number of descriptors +\field{num_buffers} to indicate the number of buffers the packet (including the header) is spread over. -The device MUST use all descriptors used by a single receive +If a receive packet is spread over multiple buffers, the device +MUST use all buffers but the last (i.e. the first $num_buffers - +1$ buffers) completely up to the full length of each buffer +supplied by the driver. + +The device MUST use all buffers used by a single receive packet together, by atomically incrementing \field{idx} in the used ring by the \field{num_buffers} value. |