[PATCH v2 bpf-next 01/14] xsk: improve xdp_do_redirect() error codes

Maciej Fijalkowski
2022-04-13T15:30:35Z

From: Björn Töpel <bjorn@kernel.org>

The error codes returned by xdp_do_redirect() when redirecting a frame
to an AF_XDP socket has not been very useful. A driver could not
distinguish between different errors. Prior this change the following
codes where used:

Socket not bound or incorrect queue/netdev: EINVAL
XDP frame/AF_XDP buffer size mismatch: ENOSPC
Could not allocate buffer (copy mode): ENOSPC
AF_XDP Rx buffer full: ENOSPC

After this change:

Socket not bound or incorrect queue/netdev: EINVAL
XDP frame/AF_XDP buffer size mismatch: ENOSPC
Could not allocate buffer (copy mode): ENOMEM
AF_XDP Rx buffer full: ENOBUFS

An AF_XDP zero-copy driver can now potentially determine if the
failure was due to a full Rx buffer, and if so stop processing more
frames, yielding to the userland AF_XDP application.

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Björn Töpel <bjorn@kernel.org>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
---
net/xdp/xsk.c | 2 +-
net/xdp/xsk_queue.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 2c34caee0fd1..f75e121073e7 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -184,7 +184,7 @@ static int __xsk_rcv(struct xdp_sock *xs, struct xdp_buff *xdp)
xsk_xdp = xsk_buff_alloc(xs->pool);
if (!xsk_xdp) {
xs->rx_dropped++;
- return -ENOSPC;
+ return -ENOMEM;
}

xsk_copy_xdp(xsk_xdp, xdp, len);
diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index 801cda5d1938..644479e65578 100644
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -382,7 +382,7 @@ static inline int xskq_prod_reserve_desc(struct xsk_queue *q,
u32 idx;

if (xskq_prod_is_full(q))
- return -ENOSPC;
+ return -ENOBUFS;

/* A, matches D */
idx = q->cached_prod++ & q->ring_mask;
--
2.33.1