答复: [PATCH bpf-next] samples/bpf: check detach prog exist or not in xdp_fwd

[shaozhengchao]

-----邮件原件-----
发件人: Toke Høiland-Jørgensen [mailto:toke@xxxxxxxxxx] 
发送时间: 2022年5月9日 17:46
收件人: shaozhengchao <shaozhengchao@xxxxxxxxxx>; bpf@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; ast@xxxxxxxxxx; daniel@xxxxxxxxxxxxx; davem@xxxxxxxxxxxxx; kuba@xxxxxxxxxx; hawk@xxxxxxxxxx; john.fastabend@xxxxxxxxx; andrii@xxxxxxxxxx; kafai@xxxxxx; songliubraving@xxxxxx; yhs@xxxxxx; kpsingh@xxxxxxxxxx
抄送: weiyongjun (A) <weiyongjun1@xxxxxxxxxx>; shaozhengchao <shaozhengchao@xxxxxxxxxx>; yuehaibing <yuehaibing@xxxxxxxxxx>
主题: Re: [PATCH bpf-next] samples/bpf: check detach prog exist or not in xdp_fwd

Zhengchao Shao <shaozhengchao@xxxxxxxxxx> writes:

> Before detach the prog, we should check detach prog exist or not.

If we're adding such a check we should also check that it's the *right* program. I.e., query the ID for the program name and check that it matches what the program attached, then obtain an fd and pass that as XDP_EXPECTED_FD on detach to make sure it wasn't swapped out in the meantime...

-Toke

Thank you for your reply. When finish running xdp_fwd to attatch prog, the program will exit and can't store fd as XDP_EXPECTED_FD. 

I think the sample xdp_fwd -d is just detach prog and don't care if the fd is expected.

-zhengchao shao