openwrt/target/linux/generic/backport-5.15/609-v5.18-veth-Allow-jumbo-frames-in-xdp-mode.patch

From 7cda76d858a4e71ac4a04066c093679a12e1312c Mon Sep 17 00:00:00 2001
From: Lorenzo Bianconi <[email protected]>
Date: Fri, 11 Mar 2022 10:14:20 +0100
Subject: [PATCH] veth: Allow jumbo frames in xdp mode
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Allow increasing the MTU over page boundaries on veth devices
if the attached xdp program declares to support xdp fragments.

Signed-off-by: Lorenzo Bianconi <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Toke Høiland-Jørgensen <[email protected]>
Acked-by: John Fastabend <[email protected]>
Link: https://lore.kernel.org/bpf/d5dc039c3d4123426e7023a488c449181a7bc57f.1646989407.git.lorenzo@kernel.org
---
 drivers/net/veth.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -1455,9 +1455,14 @@ static int veth_xdp_set(struct net_devic
 			goto err;
 		}
 
-		max_mtu = PAGE_SIZE - VETH_XDP_HEADROOM -
-			  peer->hard_header_len -
-			  SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+		max_mtu = SKB_WITH_OVERHEAD(PAGE_SIZE - VETH_XDP_HEADROOM) -
+			  peer->hard_header_len;
+		/* Allow increasing the max_mtu if the program supports
+		 * XDP fragments.
+		 */
+		//if (prog->aux->xdp_has_frags)
+		max_mtu += PAGE_SIZE * MAX_SKB_FRAGS;
+
 		if (peer->mtu > max_mtu) {
 			NL_SET_ERR_MSG_MOD(extack, "Peer MTU is too large to set XDP");
 			err = -ERANGE;