xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

net, xsk: Avoid taking multiple skbuff references

Browse Source 
Commit 642e450b6b ("xsk: Do not discard packet when NETDEV_TX_BUSY")
addressed the problem that packets were discarded from the Tx AF_XDP
ring, when the driver returned NETDEV_TX_BUSY. Part of the fix was
bumping the skbuff reference count, so that the buffer would not be
freed by dev_direct_xmit(). A reference count larger than one means
that the skbuff is "shared", which is not the case.

If the "shared" skbuff is sent to the generic XDP receive path,
netif_receive_generic_xdp(), and pskb_expand_head() is entered the
BUG_ON(skb_shared(skb)) will trigger.

This patch adds a variant to dev_direct_xmit(), __dev_direct_xmit(),
where a user can select the skbuff free policy. This allows AF_XDP to
avoid bumping the reference count, but still keep the NETDEV_TX_BUSY
behavior.

Fixes: 642e450b6b ("xsk: Do not discard packet when NETDEV_TX_BUSY")
Reported-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20201123175600.146255-1-bjorn.topel@gmail.com
This commit is contained in:
Björn Töpel
2020-11-23 18:56:00 +01:00
committed by Daniel Borkmann
parent 178648916e
commit 36ccdf8582
3 changed files with 16 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
include/linux/netdevice.h
View File

@@ -2813,9 +2813,21 @@ u16 dev_pick_tx_zero(struct net_device *dev, struct sk_buff *skb,
struct net_device *sb_dev);
u16 dev_pick_tx_cpu_id(struct net_device *dev, struct sk_buff *skb,
struct net_device *sb_dev);
int dev_queue_xmit(struct sk_buff *skb);
int dev_queue_xmit_accel(struct sk_buff *skb, struct net_device *sb_dev);
int dev_direct_xmit(struct sk_buff *skb, u16 queue_id);
int __dev_direct_xmit(struct sk_buff *skb, u16 queue_id);
static inline int dev_direct_xmit(struct sk_buff *skb, u16 queue_id)
{
int ret;
ret = __dev_direct_xmit(skb, queue_id);
if (!dev_xmit_complete(ret))
kfree_skb(skb);
return ret;
}
int register_netdevice(struct net_device *dev);
void unregister_netdevice_queue(struct net_device *dev, struct list_head *head);
void unregister_netdevice_many(struct list_head *head);