[PATCH net 2/2] xsk: Fix zero-copy AF_XDP fragment drop
From: Nikhil P. Rao <hidden>
Date: 2026-02-05 00:20:02
Subsystem:
networking [general], the rest, xdp sockets (af_xdp) · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Magnus Karlsson, Maciej Fijalkowski
AF_XDP should ensure that only a complete packet is sent to application.
In the zero-copy case, if the Rx queue gets full as fragments are being
enqueued, the remaining fragments are dropped.
Add a check to ensure that the Rx queue has enough space for all
fragments of a packet before starting to enqueue them.
Fixes: 24ea50127ecf ("xsk: support mbuf on ZC RX")
Signed-off-by: Nikhil P. Rao <redacted>
---
net/xdp/xsk.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index f2ec4f78bbb6..deec5a1e2c97 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c@@ -166,15 +166,20 @@ static int xsk_rcv_zc(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len) u32 frags = xdp_buff_has_frags(xdp); struct xdp_buff_xsk *pos, *tmp; struct list_head *xskb_list; + u32 num_desc = 1; u32 contd = 0; - int err; - if (frags) + if (frags) { + num_desc = xdp_get_shared_info_from_buff(xdp)->nr_frags + 1; contd = XDP_PKT_CONTD; + } - err = __xsk_rcv_zc(xs, xskb, len, contd); - if (err) - goto err; + if (xskq_prod_nb_free(xs->rx, num_desc) < num_desc) { + xs->rx_queue_full++; + return -ENOBUFS; + } + + __xsk_rcv_zc(xs, xskb, len, contd); if (likely(!frags)) return 0;
@@ -183,16 +188,11 @@ static int xsk_rcv_zc(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len) if (list_is_singular(xskb_list)) contd = 0; len = pos->xdp.data_end - pos->xdp.data; - err = __xsk_rcv_zc(xs, pos, len, contd); - if (err) - goto err; + __xsk_rcv_zc(xs, pos, len, contd); list_del_init(&pos->list_node); } return 0; -err: - xsk_buff_free(xdp); - return err; } static void *xsk_copy_xdp_start(struct xdp_buff *from)
--
2.43.0