[PATCH net-next] xsk: Enable shared umem support.

[William Tu <u9012063@gmail.com>]

Currently the shared umem feature is not supported in libbpf.
The patch removes the refcount check in libbpf to enable use of
shared umem.  Also, a umem can be shared by multiple netdevs,
so remove the checking at xsk_bind.

Tested using OVS at:
https://mail.openvswitch.org/pipermail/ovs-dev/2019-November/364392.html

Signed-off-by: William Tu <u9012063@gmail.com>
---
 net/xdp/xsk.c       |  5 -----
 tools/lib/bpf/xsk.c | 10 +++++-----
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 6040bc2b0088..0f2b16e275e3 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -697,11 +697,6 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 			sockfd_put(sock);
 			goto out_unlock;
 		}
-		if (umem_xs->dev != dev || umem_xs->queue_id != qid) {
-			err = -EINVAL;
-			sockfd_put(sock);
-			goto out_unlock;
-		}
 
 		xdp_get_umem(umem_xs->umem);
 		WRITE_ONCE(xs->umem, umem_xs->umem);
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index 74d84f36a5b2..e6c4eb077dcd 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -579,16 +579,13 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
 	struct sockaddr_xdp sxdp = {};
 	struct xdp_mmap_offsets off;
 	struct xsk_socket *xsk;
+	bool shared;
 	int err;
 
 	if (!umem || !xsk_ptr || !rx || !tx)
 		return -EFAULT;
 
-	if (umem->refcount) {
-		pr_warn("Error: shared umems not supported by libbpf.\n");
-		return -EBUSY;
-	}
-
+	shared = !!(usr_config->bind_flags & XDP_SHARED_UMEM);
 	xsk = calloc(1, sizeof(*xsk));
 	if (!xsk)
 		return -ENOMEM;
@@ -687,6 +684,9 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
 	sxdp.sxdp_queue_id = xsk->queue_id;
 	sxdp.sxdp_flags = xsk->config.bind_flags;
 
+	if (shared)
+		sxdp.sxdp_shared_umem_fd = umem->fd;
+
 	err = bind(xsk->fd, (struct sockaddr *)&sxdp, sizeof(sxdp));
 	if (err) {
 		err = -errno;
-- 
2.7.4