From: Ciara Loftus <ciara.loftus@intel.com>

Date: Wed, 31 Mar 2021 06:12:18 +0000

Subject: libbpf: Only create rx and tx XDP rings when necessary

Patch-mainline: v5.12-rc7

Git-commit: ca7a83e2487ad0bc9a3e0e7a8645354aa1782f13

References: bsc#1155518

Prior to this commit xsk_socket__create(_shared) always attempted to create

the rx and tx rings for the socket. However this causes an issue when the

socket being setup is that which shares the fd with the UMEM. If a

previous call to this function failed with this socket after the rings were

set up, a subsequent call would always fail because the rings are not torn

down after the first call and when we try to set them up again we encounter

an error because they already exist. Solve this by remembering whether the

rings were set up by introducing new bools to struct xsk_umem which

represent the ring setup status and using them to determine whether or

not to set up the rings.

Fixes: 1cad07884239 ("libbpf: add support for using AF_XDP sockets")

Signed-off-by: Ciara Loftus <ciara.loftus@intel.com>

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Link: https://lore.kernel.org/bpf/20210331061218.1647-4-ciara.loftus@intel.com

Acked-by: Gary Lin <glin@suse.com>

---

 tools/lib/bpf/xsk.c |   13 +++++++++++--

 1 file changed, 11 insertions(+), 2 deletions(-)

--- a/tools/lib/bpf/xsk.c

+++ b/tools/lib/bpf/xsk.c

@@ -51,6 +51,8 @@ struct xsk_umem {

 	struct xsk_umem_config config;

 	int fd;

 	int refcount;

+	bool rx_ring_setup_done;

+	bool tx_ring_setup_done;

 };

 struct xsk_socket {

@@ -561,6 +563,7 @@ int xsk_socket__create(struct xsk_socket

 	struct xdp_mmap_offsets off;

 	struct xsk_socket *xsk;

 	int err;

+	bool rx_setup_done = false, tx_setup_done = false;

 	if (!umem || !xsk_ptr || !rx || !tx)

 		return -EFAULT;

@@ -582,6 +585,8 @@ int xsk_socket__create(struct xsk_socket

 		}

 	} else {

 		xsk->fd = umem->fd;

+		rx_setup_done = umem->rx_ring_setup_done;

+		tx_setup_done = umem->tx_ring_setup_done;

 	}

 	xsk->outstanding_tx = 0;

@@ -599,7 +604,7 @@ int xsk_socket__create(struct xsk_socket

 	if (err)

 		goto out_socket;

-	if (rx) {

+	if (rx && !rx_setup_done) {

 		err = setsockopt(xsk->fd, SOL_XDP, XDP_RX_RING,

 				 &xsk->config.rx_size,

 				 sizeof(xsk->config.rx_size));

@@ -607,8 +612,10 @@ int xsk_socket__create(struct xsk_socket

 			err = -errno;

 			goto out_socket;

 		}

+		if (xsk->fd == umem->fd)

+			umem->rx_ring_setup_done = true;

 	}

-	if (tx) {

+	if (tx && !tx_setup_done) {

 		err = setsockopt(xsk->fd, SOL_XDP, XDP_TX_RING,

 				 &xsk->config.tx_size,

 				 sizeof(xsk->config.tx_size));

@@ -616,6 +623,8 @@ int xsk_socket__create(struct xsk_socket

 			err = -errno;

 			goto out_socket;

 		}

+		if (xsk->fd == umem->fd)

+			umem->rx_ring_setup_done = true;

 	}

 	err = xsk_get_mmap_offsets(xsk->fd, &off;;