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authorBjörn Töpel <bjorn.topel@intel.com>2020-11-23 18:56:00 +0100
committerDaniel Borkmann <daniel@iogearbox.net>2020-11-24 22:39:56 +0100
commit36ccdf85829a7dd6936dba5d02fa50138471f0d3 (patch)
tree9f0318f3a13070a94243d1058f6e2f32d9e29912 /net/core
parent178648916e73e00de83150eb0c90c0d3a977a46a (diff)
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 'net/core')
-rw-r--r--net/core/dev.c8
1 files changed, 2 insertions, 6 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index 82dc6b48e45f..8588ade790cb 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4180,7 +4180,7 @@ int dev_queue_xmit_accel(struct sk_buff *skb, struct net_device *sb_dev)
}
EXPORT_SYMBOL(dev_queue_xmit_accel);
-int dev_direct_xmit(struct sk_buff *skb, u16 queue_id)
+int __dev_direct_xmit(struct sk_buff *skb, u16 queue_id)
{
struct net_device *dev = skb->dev;
struct sk_buff *orig_skb = skb;
@@ -4210,17 +4210,13 @@ int dev_direct_xmit(struct sk_buff *skb, u16 queue_id)
dev_xmit_recursion_dec();
local_bh_enable();
-
- if (!dev_xmit_complete(ret))
- kfree_skb(skb);
-
return ret;
drop:
atomic_long_inc(&dev->tx_dropped);
kfree_skb_list(skb);
return NET_XMIT_DROP;
}
-EXPORT_SYMBOL(dev_direct_xmit);
+EXPORT_SYMBOL(__dev_direct_xmit);
/*************************************************************************
* Receiver routines