-----邮件原件----- 发件人: Toke Høiland-Jørgensen [mailto:toke@xxxxxxxxxx] 发送时间: 2022年6月1日 17:25 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 v4,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. > > Signed-off-by: Zhengchao Shao <shaozhengchao@xxxxxxxxxx> The logic looks good now, just spotted one issue with the use of 'return errno' (which I just realised I suggested on the last version, sorry about that). > samples/bpf/xdp_fwd_user.c | 62 > ++++++++++++++++++++++++++++++++------ > 1 file changed, 53 insertions(+), 9 deletions(-) > > diff --git a/samples/bpf/xdp_fwd_user.c b/samples/bpf/xdp_fwd_user.c > index 1828487bae9a..a4ba53891653 100644 > --- a/samples/bpf/xdp_fwd_user.c > +++ b/samples/bpf/xdp_fwd_user.c > @@ -47,17 +47,61 @@ static int do_attach(int idx, int prog_fd, int map_fd, const char *name) > return err; > } > > -static int do_detach(int idx, const char *name) > +static int do_detach(int ifindex, const char *ifname, const char > +*app_name) > { > - int err; > + LIBBPF_OPTS(bpf_xdp_attach_opts, opts); > + struct bpf_prog_info prog_info = {}; > + char prog_name[BPF_OBJ_NAME_LEN]; > + __u32 info_len, curr_prog_id; > + int prog_fd; > + int err = 1; > + > + if (bpf_xdp_query_id(ifindex, xdp_flags, &curr_prog_id)) { > + printf("ERROR: bpf_xdp_query_id failed (%s)\n", > + strerror(errno)); > + return -errno; The printf above may override errno, so this could return 0; the actual return value is not really used by the caller, so you could just always 'return -1' or 'return err'. > + } > + > + if (!curr_prog_id) { > + printf("ERROR: flags(0x%x) xdp prog is not attached to %s\n", > + xdp_flags, ifname); > + goto err_out; Doesn't really need a label, just do a direct return here as well. > + } > > - err = bpf_xdp_detach(idx, xdp_flags, NULL); > - if (err < 0) > - printf("ERROR: failed to detach program from %s\n", name); > + info_len = sizeof(prog_info); > + prog_fd = bpf_prog_get_fd_by_id(curr_prog_id); > + if (prog_fd < 0) { > + printf("ERROR: bpf_prog_get_fd_by_id failed (%s)\n", > + strerror(errno)); > + return -errno; Same issue as above with errno being overwritten. > + } > + > + err = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &info_len); > + if (err) { > + printf("ERROR: bpf_obj_get_info_by_fd failed (%s)\n", > + strerror(errno)); > + goto close_out; > + } > + snprintf(prog_name, sizeof(prog_name), "%s_prog", app_name); > + prog_name[BPF_OBJ_NAME_LEN - 1] = '\0'; > + > + if (strcmp(prog_info.name, prog_name)) { > + printf("ERROR: %s isn't attached to %s\n", app_name, ifname); > + err = 1; > + } else { You can save a level of indentation by adding a 'goto close_out' after 'err=1' instead of using an 'else' block. > + opts.old_prog_fd = prog_fd; > + err = bpf_xdp_detach(ifindex, xdp_flags, &opts); > + if (err < 0) > + printf("ERROR: failed to detach program from %s (%s)\n", > + ifname, strerror(errno)); > + /* TODO: Remember to cleanup map, when adding use of shared map > + * bpf_map_delete_elem((map_fd, &idx); > + */ > + } > > - /* TODO: Remember to cleanup map, when adding use of shared map > - * bpf_map_delete_elem((map_fd, &idx); > - */ > +close_out: > + close(prog_fd); > +err_out: don't need the err_out label, see above. -Toke Hi Toke: Thank you for your reply. I will fix it in next patch. Zhengchao Shao
