Re: [PATCH net-next 2/2] tools: psock_tpacket: verify that packet was received on lo before counting it
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: 2017-01-04 14:31:11
On Tue, Jan 3, 2017 at 6:27 PM, Sowmini Varadhan [off-list ref] wrote:
Packets from any/all interfaces may be queued up on the PF_PACKET socket before it is bound to the loopback interface by psock_tpacket, and when these are passed up by the kernel, they should not be counted toward the conditions needed to pass/fail the Rx tests.
The common and simpler solution to this problem is to open the socket with protocol 0 to reject all packets, add the BPF filter and only then bind with sll_ifindex set to lo. That way no false positives can arrive.