netdev - [PATCH v4 bpf 09/11] xdp: reflect tail increase for MEM_TYPE_XSK_BUFF

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Date: Sat, 20 Jan 2024 00:30:35 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: bpf@...r.kernel.org,
	ast@...nel.org,
	daniel@...earbox.net,
	andrii@...nel.org
Cc: netdev@...r.kernel.org,
	magnus.karlsson@...el.com,
	bjorn@...nel.org,
	maciej.fijalkowski@...el.com,
	echaudro@...hat.com,
	lorenzo@...nel.org,
	martin.lau@...ux.dev,
	tirthendu.sarkar@...el.com,
	john.fastabend@...il.com
Subject: [PATCH v4 bpf 09/11] xdp: reflect tail increase for MEM_TYPE_XSK_BUFF_POOL

XSK ZC Rx path calculates the size of data that will be posted to XSK Rx
queue via subtracting xdp_buff::data_end from xdp_buff::data.

In bpf_xdp_frags_increase_tail(), when underlying memory type of
xdp_rxq_info is MEM_TYPE_XSK_BUFF_POOL, add offset to data_end in tail
fragment, so that later on user space will be able to take into account
the amount of bytes added by XDP program.

Fixes: 24ea50127ecf ("xsk: support mbuf on ZC RX")
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 net/core/filter.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index 8e0cd8ca461e..9270b4d7acee 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4093,6 +4093,8 @@ static int bpf_xdp_frags_increase_tail(struct xdp_buff *xdp, int offset)
 	memset(skb_frag_address(frag) + skb_frag_size(frag), 0, offset);
 	skb_frag_size_add(frag, offset);
 	sinfo->xdp_frags_size += offset;
+	if (rxq->mem.type == MEM_TYPE_XSK_BUFF_POOL)
+		xsk_buff_get_tail(xdp)->data_end += offset;
 
 	return 0;
 }
-- 
2.34.1