[PATCH net v2] xsk: fix __xsk_generic_xmit() error code when cq is full

[Wang Liang <wangliang74@huawei.com>]

When the cq reservation is failed, the error code is not set which is
initialized to zero in __xsk_generic_xmit(). That means the packet is not
send successfully but sendto() return ok.

Considering the impact on uapi, return -EAGAIN is a good idea. The cq is
full usually because it is not released in time, try to send msg again is
appropriate.

Suggested-by: Magnus Karlsson <magnus.karlsson@gmail.com>
Signed-off-by: Wang Liang <wangliang74@huawei.com>
---
 net/xdp/xsk.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 89d2bef96469..e04809a4c5d3 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -802,8 +802,11 @@ static int __xsk_generic_xmit(struct sock *sk)
 		 * if there is space in it. This avoids having to implement
 		 * any buffering in the Tx path.
 		 */
-		if (xsk_cq_reserve_addr_locked(xs->pool, desc.addr))
+		err = xsk_cq_reserve_addr_locked(xs->pool, desc.addr);
+		if (err) {
+			err = -EAGAIN;
 			goto out;
+		}
 
 		skb = xsk_build_skb(xs, &desc);
 		if (IS_ERR(skb)) {
-- 
2.34.1