shaozhengchao <shaozhengchao@xxxxxxxxxx> writes: > -----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. So why are you adding the check? Either keep it the way it is, or add a proper check that examines the program type; you're right that it doesn't store the prog FD, but you can still check the program name and see if it matches to get some idea that it's not a totally separate program that's loaded. I think doing so would be an improvement to the sample, but just adding a check if a program is loaded is not, really... -Toke
