Le 16/05/2017 à 16:11, Ido Schimmel a écrit : > On Tue, May 16, 2017 at 02:57:47PM +0200, Nicolas Dichtel wrote: >>>> I suspect that there can be scenarii where some packets of a flow are >>>> forwarded >>>> by the driver and some other are forwarded by the kernel. >>> >>> Can you elaborate? The kernel only sees specific packets, which were >>> trapped to the CPU. See: >>> https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/tree/drivers/net/ethernet/mellanox/mlxsw/spectrum.c#n2996 >> Ok, this part was not clear for me, thank you for the pointer. >> >> So, when an arp resolution is needed, the packets are not trapped to the CPU, >> the device manages the queue itself? > > There are two cases here. If you need an ARP resolution following a hit > of a directly connected route and this neighbour isn't in the device's > table, then packet is trapped (HOST_MISS_IPV4 in above list) to the CPU > and triggers ARP resolution in the kernel. Eventually a NETEVENT will be > sent and the neighbour will be programmed to the device. > > If you need an ARP resolution of a nexthop, then this is a bit > different. If you have an ECMP group with several nexthops, then once > one of them is resolved, packets will be forwarded using it. To make > sure other nexthops will also be resolved we try to periodically refresh > them. Otherwise packets will always be forwarded using a single nexthop, > as the kernel won't have motivation to resolve the others. > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c#n987 > > In case no nexthops can be resolved, then packets will be trapped to the > CPU (RTR_INGRESS0 in above list) and forwarded by the kernel. > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c#n1896 > Ok, thank you for the details.
Regards, Nicolas
