Jun Hu <hujun.work@xxxxxxxxx> writes: > On Tue, Oct 26, 2021 at 4:08 AM Konrad Zemek <konrad@xxxxxxxx> wrote: >> >> On Monday, October 25th, 2021 at 8:26 PM, Jun Hu <hujun.work@xxxxxxxxx> wrote: >> >> > On Mon, Oct 25, 2021 at 3:48 AM Toke Høiland-Jørgensen toke@xxxxxxxxxx wrote: >> > >> > > Jun Hu hujun.work@xxxxxxxxx writes: >> > > >> > > > Hi, >> > > > >> > > > I want to put a timestamp in the egress packets, and I want to use >> > > > >> > > > AF_XDP socket for both sending and receiving packets; since a XDP >> > > > >> > > > kernel program only work in ingress direction, I wonder if I could use >> > > > >> > > > a tc kernel program to change a packet sent out via an AF_XDP socket? >> > > > >> > > > I searched around, but couldn't find any direct answer... >> > > >> > > Nope, AF_XDP bypasses the stack completely, so TC won't see the packet >> > > >> > > on egress... >> > > >> > > -Toke >> > >> > Ok, thanks for the clarification, I guess I have to wait for the XDP >> > >> > egress support ... >> >> You can also directly modify the packet that you send out through an >> AF_XDP socket, before putting it on the outgoing queue. Is there >> anything specific that you would want to do in an egress-attached BPF >> program that you would not be able to do in the userspace program >> that manages your AF_XDP socket? >> >> Konrad > > Yes, that's what I am doing right now, however ideally I want to add a > timestamp to the packet as close as it egress the NIC; since AF_XDP > doesn't have access to hardware timestamp, that's why I was searching > for an alternative solution. Cc. Jesper, as I believe timestamps is one of his initial use cases for xdp-hints (hardware metadata). -Toke
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