[PATCH net-next v2 12/18] xdp: add generic xdp_build_skb_from_buff()

Alexander Lobakin
2024-10-15T14:55:03Z

The code which builds an skb from an &xdp_buff keeps multiplying itself
around the drivers with almost no changes. Let's try to stop that by
adding a generic function.
There's __xdp_build_skb_from_frame() already, so just convert it to take
&xdp_buff instead, while making the original one a wrapper. The original
one always took an already allocated skb, allow both variants here -- if
no skb passed, which is expected when calling from a driver, pick one via
napi_build_skb().

Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
---
include/net/xdp.h | 1 +
net/core/xdp.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 56 insertions(+)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index 19d2b283b845..83e3f4648caa 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -330,6 +330,7 @@ xdp_update_skb_shared_info(struct sk_buff *skb, u8 nr_frags,
void xdp_warn(const char *msg, const char *func, const int line);
#define XDP_WARN(msg) xdp_warn(msg, __func__, __LINE__)

+struct sk_buff *xdp_build_skb_from_buff(const struct xdp_buff *xdp);
struct xdp_frame *xdp_convert_zc_to_xdp_frame(struct xdp_buff *xdp);
struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
struct sk_buff *skb,
diff --git a/net/core/xdp.c b/net/core/xdp.c
index b1b426a9b146..9dc103a09b5c 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -624,6 +624,61 @@ int xdp_alloc_skb_bulk(void **skbs, int n_skb, gfp_t gfp)
}
EXPORT_SYMBOL_GPL(xdp_alloc_skb_bulk);

+/**
+ * xdp_build_skb_from_buff - create an skb from an &xdp_buff
+ * @xdp: &xdp_buff to convert to an skb
+ *
+ * Perform common operations to create a new skb to pass up the stack from
+ * an &xdp_buff: allocate an skb head from the NAPI percpu cache, initialize
+ * skb data pointers and offsets, set the recycle bit if the buff is PP-backed,
+ * Rx queue index, protocol and update frags info.
+ *
+ * Return: new &sk_buff on success, %NULL on error.
+ */
+struct sk_buff *xdp_build_skb_from_buff(const struct xdp_buff *xdp)
+{
+ const struct xdp_rxq_info *rxq = xdp->rxq;
+ const struct skb_shared_info *sinfo;
+ struct sk_buff *skb;
+ u32 nr_frags = 0;
+ int metalen;
+
+ if (unlikely(xdp_buff_has_frags(xdp))) {
+ sinfo = xdp_get_shared_info_from_buff(xdp);
+ nr_frags = sinfo->nr_frags;
+ }
+
+ skb = napi_build_skb(xdp->data_hard_start, xdp->frame_sz);
+ if (unlikely(!skb))
+ return NULL;
+
+ skb_reserve(skb, xdp->data - xdp->data_hard_start);
+ __skb_put(skb, xdp->data_end - xdp->data);
+
+ metalen = xdp->data - xdp->data_meta;
+ if (metalen > 0)
+ skb_metadata_set(skb, metalen);
+
+ if (is_page_pool_compiled_in() && rxq->mem.type == MEM_TYPE_PAGE_POOL)
+ skb_mark_for_recycle(skb);
+
+ skb_record_rx_queue(skb, rxq->queue_index);
+
+ if (unlikely(nr_frags)) {
+ u32 ts;
+
+ ts = sinfo->xdp_frags_truesize ? : nr_frags * xdp->frame_sz;
+ xdp_update_skb_shared_info(skb, nr_frags,
+ sinfo->xdp_frags_size, ts,
+ xdp_buff_is_frag_pfmemalloc(xdp));
+ }
+
+ skb->protocol = eth_type_trans(skb, rxq->dev);
+
+ return skb;
+}
+EXPORT_SYMBOL_GPL(xdp_build_skb_from_buff);
+
struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
struct sk_buff *skb,
struct net_device *dev)
--
2.46.2