xsk: Fix __xsk_generic_xmit() error code when cq is full

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.

The bug was at the very early implementation of xsk, so the Fixes tag
targets the commit that introduced the changes in
xsk_cq_reserve_addr_locked where this fix depends on.

Fixes: e6c4047f5122 ("xsk: Use xsk_buff_pool directly for cq functions")
Suggested-by: Magnus Karlsson <magnus.karlsson@gmail.com>
Signed-off-by: Wang Liang <wangliang74@huawei.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250227081052.4096337-1-wangliang74@huawei.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index e5d104ce7b82f4072ed796fdb56eaabeec9ec99e..5696af45bcf711ce6b9df46a8783db0f4561e79a 100644 (file)
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -806,8 +806,11 @@ 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)) {