netdev - [PATCH RFC bpf-next 29/52] net, xdp: try to fill skb fields when converting from an &xdp

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Date:   Tue, 28 Jun 2022 21:47:49 +0200
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        Larysa Zaremba <larysa.zaremba@...el.com>,
        Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Toke Hoiland-Jorgensen <toke@...hat.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        John Fastabend <john.fastabend@...il.com>,
        Yajun Deng <yajun.deng@...ux.dev>,
        Willem de Bruijn <willemb@...gle.com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        xdp-hints@...-project.net
Subject: [PATCH RFC bpf-next 29/52] net, xdp: try to fill skb fields when converting from an &xdp_frame

In __xdp_build_skb_from_frame(), if there's a metadata in front of
the data, check if it's a generic-compatible metadata and try to
populate the HW-originated skb fields: checksum status, hash etc.
As xdp_populate_skb_meta_generic() requires the skb->mac_header
to be set and valid, call the skb_reset_mac_header() first, as
skb->data at this point is pointing (sic!) to the MAC header.
The two most obvious users are cpumap and veth.

Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
---
 net/bpf/core.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/net/bpf/core.c b/net/bpf/core.c
index 775f9648e8cf..d2d01b8e6441 100644
--- a/net/bpf/core.c
+++ b/net/bpf/core.c
@@ -659,8 +659,11 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
 
 	skb_reserve(skb, headroom);
 	__skb_put(skb, xdpf->len);
-	if (metasize)
+	if (metasize) {
+		skb_reset_mac_header(skb);
 		skb_metadata_set(skb, metasize);
+		xdp_populate_skb_meta_generic(skb);
+	}
 
 	if (unlikely(xdp_frame_has_frags(xdpf)))
 		xdp_update_skb_shared_info(skb, nr_frags,
@@ -671,12 +674,6 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
 	/* Essential SKB info: protocol and skb->dev */
 	skb->protocol = eth_type_trans(skb, dev);
 
-	/* Optional SKB info, currently missing:
-	 * - HW checksum info		(skb->ip_summed)
-	 * - HW RX hash			(skb_set_hash)
-	 * - RX ring dev queue index	(skb_record_rx_queue)
-	 */
-
 	/* Until page_pool get SKB return path, release DMA here */
 	xdp_release_frame(xdpf);
 
-- 
2.36.1