netdev - bpf redirect will loop the packets

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Date:   Mon, 1 Nov 2021 14:32:17 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Cong Wang <xiyou.wangcong@...il.com>, ast@...nel.org,
        andrii@...nel.org, songliubraving@...com, yhs@...com
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: bpf redirect will loop the packets

Hi
I found the issue,
if we use the bpf_redirect to the same netdevice in the ingress path.
the packet loop.
and now linux doesn't check that. In tx path,
softnet_data.xmit.recursion will limit the recursion.
I think we should check that in ingress. any thoughts?

tc.c:
...
return bpf_redirect(skb->ifindex /* same netdev */, 1);

$ tc filter add dev $NETDEV ingress bpf direct-action obj tc.o sec .text

-- 
Best regards, Tonghao