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);