xsk: support redirect to any socket bound to the same umem

Add support for directing a packet to any socket bound to the same
umem. This makes it possible to use the XDP program to select what
socket the packet should be received on. The user can populate the
XSKMAP with various sockets and as long as they share the same umem,
the XDP program can pick any one of them.
Suggested-by: Yuval El-Hanany <yuvale@radware.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240205123553.22180-2-magnus.karlsson@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

net/xdp/xsk.c

@@ -313,10 +313,13 @@ static bool xsk_is_bound(struct xdp_sock *xs)
 
 static int xsk_rcv_check(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
 {
+	struct net_device *dev = xdp->rxq->dev;
+	u32 qid = xdp->rxq->queue_index;
+
 	if (!xsk_is_bound(xs))
 		return -ENXIO;
 
-	if (xs->dev != xdp->rxq->dev || xs->queue_id != xdp->rxq->queue_index)
+	if (!dev->_rx[qid].pool || xs->umem != dev->_rx[qid].pool->umem)
 		return -EINVAL;
 
 	if (len > xsk_pool_get_rx_frame_size(xs->pool) && !xs->sg) {