On Fri, Mar 08, 2024 at 09:18:48AM +0100, Laurent
Vivier wrote:
On 3/8/24 07:53, David Gibson wrote:
This series has a handful of small improvements
to the tap send path.
See individual commit messages for the details.
I expect this will conflict with Laurent's upcoming work. I hope the
conflicts won't be too bad, and indeed will set us up for less
duplication there in the end.
I'm working on patch that devides TCP buffers in several buffers pointed out
by an IOV arrays and then provided to tap_send_frames(). I'm going to base
my patch on this series.
The idea is:
A frame is made with 4 iovecs:
#define TCP_IOV_VNET 0
#define TCP_IOV_ETH 1
#define TCP_IOV_IP 2
#define TCP_IOV_PAYLOAD 3
#define TCP_IOV_NUM 4
typedef struct iovec tap_iovec_t[TCP_IOV_NUM];
General concept seems good. Unless you have a specific reason to do
so, I'd suggest keeping VNET and ETH - i.e. L2 and everything below it
- together. As well as just making one less buffer for each frame, I
think that will make life easier if we want to add an L2 interface
with non-Ethernet framing (e.g. "tun" instead of "tap").
In fact keeping vnet header separated from eth header makes easier to remove
it from the list to pass the iovec array to pcap functions and to pasta send
function (can use iovec[1] and iovcount - 1).