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authorBjörn Töpel <bjorn.topel@intel.com>2020-11-23 20:56:00 +0300
committerDaniel Borkmann <daniel@iogearbox.net>2020-11-25 00:39:56 +0300
commit36ccdf85829a7dd6936dba5d02fa50138471f0d3 (patch)
tree9f0318f3a13070a94243d1058f6e2f32d9e29912 /include/linux
parent178648916e73e00de83150eb0c90c0d3a977a46a (diff)
downloadlinux-36ccdf85829a7dd6936dba5d02fa50138471f0d3.tar.xz
net, xsk: Avoid taking multiple skbuff references
Commit 642e450b6b59 ("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: 642e450b6b59 ("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
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/netdevice.h14
1 files changed, 13 insertions, 1 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 964b494b0e8d..76775abf259d 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -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);