From: =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= <bjorn@kernel.org>
Date: Wed, 13 Apr 2022 17:30:02 +0200
Subject: xsk: Improve xdp_do_redirect() error codes
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Patch-mainline: v5.19-rc1
Git-commit: c6c1f11b691e619802474f886355cb3bc9034021
References: jsc#PED-1377

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.

Signed-off-by: Björn Töpel <bjorn@kernel.org>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Link: https://lore.kernel.org/bpf/20220413153015.453864-2-maciej.fijalkowski@intel.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 net/xdp/xsk.c       |    2 +-
 net/xdp/xsk_queue.h |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -184,7 +184,7 @@ static int __xsk_rcv(struct xdp_sock *xs
 	xsk_xdp = xsk_buff_alloc(xs->pool);
 	if (!xsk_xdp) {
 		xs->rx_dropped++;
-		return -ENOSPC;
+		return -ENOMEM;
 	}
 
 	xsk_copy_xdp(xsk_xdp, xdp, len);
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -382,7 +382,7 @@ static inline int xskq_prod_reserve_desc
 	u32 idx;
 
 	if (xskq_prod_is_full(q))
-		return -ENOSPC;
+		return -ENOBUFS;
 
 	/* A, matches D */
 	idx = q->cached_prod++ & q->ring_mask;