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.

Set the error code and make xskq_prod_reserve_addr()/xskq_prod_reserve()
return values more meaningful when the queue is full.

Signed-off-by: Wang Liang <[email protected]>
Signed-off-by: NipaLocal <nipa@local>

Author: Wang Liang

net/xdp/xsk.c

@@ -805,7 +805,8 @@ 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)
 			goto out;
 
 		skb = xsk_build_skb(xs, &desc);

net/xdp/xsk_queue.h

@@ -371,7 +371,7 @@ static inline void xskq_prod_cancel_n(struct xsk_queue *q, u32 cnt)
 static inline int xskq_prod_reserve(struct xsk_queue *q)
 {
 	if (xskq_prod_is_full(q))
-		return -ENOSPC;
+		return -ENOBUFS;
 
 	/* A, matches D */
 	q->cached_prod++;
@@ -383,7 +383,7 @@ static inline int xskq_prod_reserve_addr(struct xsk_queue *q, u64 addr)
 	struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
 
 	if (xskq_prod_is_full(q))
-		return -ENOSPC;
+		return -ENOBUFS;
 
 	/* A, matches D */
 	ring->desc[q->cached_prod++ & q->ring_mask] = addr;