[PATCH bpf 3/3] libbpf: ignore return values of setsockopt for XDP rings.
From: Ciara Loftus <hidden>
Date: 2021-03-24 14:45:47
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [library] (libbpf), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
During xsk_socket__create the XDP_RX_RING and XDP_TX_RING setsockopts
are called to create the rx and tx rings for the AF_XDP socket. If the ring
has already been set up, the setsockopt will return an error. However,
in the event of a failure during xsk_socket__create(_shared) after the
rings have been set up, the user may wish to retry the socket creation
using these pre-existing rings. In this case we can ignore the error
returned by the setsockopts. If there is a true error, the subsequent
call to mmap() will catch it.
Fixes: 1cad07884239 ("libbpf: add support for using AF_XDP sockets")
Signed-off-by: Ciara Loftus <redacted>
---
tools/lib/bpf/xsk.c | 34 ++++++++++++++++------------------
1 file changed, 16 insertions(+), 18 deletions(-)
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index ec3c23299329..1f1c4c11c292 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c@@ -904,24 +904,22 @@ int xsk_socket__create_shared(struct xsk_socket **xsk_ptr, } xsk->ctx = ctx; - if (rx) { - err = setsockopt(xsk->fd, SOL_XDP, XDP_RX_RING, - &xsk->config.rx_size, - sizeof(xsk->config.rx_size)); - if (err) { - err = -errno; - goto out_put_ctx; - } - } - if (tx) { - err = setsockopt(xsk->fd, SOL_XDP, XDP_TX_RING, - &xsk->config.tx_size, - sizeof(xsk->config.tx_size)); - if (err) { - err = -errno; - goto out_put_ctx; - } - } + /* The return values of these setsockopt calls are intentionally not checked. + * If the ring has already been set up setsockopt will return an error. However, + * this scenario is acceptable as the user may be retrying the socket creation + * with rings which were set up in a previous but ultimately unsuccessful call + * to xsk_socket__create(_shared). The call later to mmap() will fail if there + * is a real issue and we handle that return value appropriately there. + */ + if (rx) + setsockopt(xsk->fd, SOL_XDP, XDP_RX_RING, + &xsk->config.rx_size, + sizeof(xsk->config.rx_size)); + + if (tx) + setsockopt(xsk->fd, SOL_XDP, XDP_TX_RING, + &xsk->config.tx_size, + sizeof(xsk->config.tx_size)); err = xsk_get_mmap_offsets(xsk->fd, &off); if (err) {
--
2.17.1