From e814b958ad8857d6f7354d3a189776eb604d86dd Mon Sep 17 00:00:00 2001 From: Heng Qi Date: Sat, 14 Jan 2023 16:22:21 +0800 Subject: [PATCH] virtio-net: fix calculation of MTU for single-buffer xdp When single-buffer xdp is loaded, the size of the buffer filled each time is 'sz = (PAGE_SIZE - headroom - tailroom)', which is the maximum packet length that the driver allows the device to pass in. Otherwise, the packet with a length greater than sz will come in, so num_buf will be greater than or equal to 2, and xdp_linearize_page() will be performed and the packet will be dropped because the total length is greater than PAGE_SIZE. So the maximum value of MTU for single-buffer xdp is 'max_sz = sz - ETH_HLEN'. Signed-off-by: Heng Qi Reviewed-by: Xuan Zhuo Acked-by: Jason Wang Signed-off-by: David S. Miller --- drivers/net/virtio_net.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index a3271d2c7c022..81d92978cc92f 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3081,7 +3081,9 @@ static int virtnet_restore_guest_offloads(struct virtnet_info *vi) static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, struct netlink_ext_ack *extack) { - unsigned long int max_sz = PAGE_SIZE - sizeof(struct padded_vnet_hdr); + unsigned int room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM + + sizeof(struct skb_shared_info)); + unsigned int max_sz = PAGE_SIZE - room - ETH_HLEN; struct virtnet_info *vi = netdev_priv(dev); struct bpf_prog *old_prog; u16 xdp_qp = 0, curr_qp; @@ -3106,7 +3108,7 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, if (dev->mtu > max_sz) { NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP"); - netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz); + netdev_warn(dev, "XDP requires MTU less than %u\n", max_sz); return -EINVAL; } -- 2.30.2