xsk: introduce helper to determine rxq->frag_size

rxq->frag_size is basically a step between consecutive strictly aligned
frames. In ZC mode, chunk size fits exactly, but if chunks are unaligned,
there is no safe way to determine accessible space to grow tailroom.

Report frag_size to be zero, if chunks are unaligned, chunk_size otherwise.

Fixes: 24ea50127ecf ("xsk: support mbuf on ZC RX")
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Link: https://patch.msgid.link/20260305111253.2317394-3-larysa.zaremba@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index aefc368449d590a7b5a8316d4a968fd24403cabd..6b9ebae2dc952e69ff6b685846f1ca8f593de69d 100644 (file)
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -51,6 +51,11 @@ static inline u32 xsk_pool_get_rx_frame_size(struct xsk_buff_pool *pool)
        return xsk_pool_get_chunk_size(pool) - xsk_pool_get_headroom(pool);
 }
 
+static inline u32 xsk_pool_get_rx_frag_step(struct xsk_buff_pool *pool)
+{
+       return pool->unaligned ? 0 : xsk_pool_get_chunk_size(pool);
+}
+
 static inline void xsk_pool_set_rxq_info(struct xsk_buff_pool *pool,
                                         struct xdp_rxq_info *rxq)
 {
@@ -337,6 +342,11 @@ static inline u32 xsk_pool_get_rx_frame_size(struct xsk_buff_pool *pool)
        return 0;
 }
 
+static inline u32 xsk_pool_get_rx_frag_step(struct xsk_buff_pool *pool)
+{
+       return 0;
+}
+
 static inline void xsk_pool_set_rxq_info(struct xsk_buff_pool *pool,
                                         struct xdp_rxq_info *rxq)
 {