linux-kernel - Re: 答复: [PATCH v5,bpf-next] samples/bpf: check detach prog exist or not in xdp

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Date:   Thu, 02 Jun 2022 12:16:16 +0200
From:   Toke Høiland-Jørgensen <toke@...nel.org>
To:     shaozhengchao <shaozhengchao@...wei.com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "hawk@...nel.org" <hawk@...nel.org>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "kafai@...com" <kafai@...com>,
        "songliubraving@...com" <songliubraving@...com>,
        "yhs@...com" <yhs@...com>,
        "kpsingh@...nel.org" <kpsingh@...nel.org>
Cc:     "weiyongjun (A)" <weiyongjun1@...wei.com>,
        yuehaibing <yuehaibing@...wei.com>
Subject: Re: 答复: [PATCH v5,bpf-next] samples/bpf: check
 detach prog exist or
 not in xdp_fwd

shaozhengchao <shaozhengchao@...wei.com> writes:

> -----邮件原件-----
> 发件人: Toke Høiland-Jørgensen [mailto:toke@...nel.org] 
> 发送时间: 2022年6月2日 16:55
> 收件人: shaozhengchao <shaozhengchao@...wei.com>; bpf@...r.kernel.org; netdev@...r.kernel.org; linux-kernel@...r.kernel.org; ast@...nel.org; daniel@...earbox.net; davem@...emloft.net; kuba@...nel.org; hawk@...nel.org; john.fastabend@...il.com; andrii@...nel.org; kafai@...com; songliubraving@...com; yhs@...com; kpsingh@...nel.org
> 抄送: weiyongjun (A) <weiyongjun1@...wei.com>; shaozhengchao <shaozhengchao@...wei.com>; yuehaibing <yuehaibing@...wei.com>
> 主题: Re: [PATCH v5,bpf-next] samples/bpf: check detach prog exist or not in xdp_fwd
>
> Zhengchao Shao <shaozhengchao@...wei.com> writes:
>
>> Before detach the prog, we should check detach prog exist or not.
>>
>> Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
>
> You missed one 'return errno', see below:
>
>> ---
>>  samples/bpf/xdp_fwd_user.c | 55 
>> +++++++++++++++++++++++++++++++++-----
>>  1 file changed, 49 insertions(+), 6 deletions(-)
>>
>> diff --git a/samples/bpf/xdp_fwd_user.c b/samples/bpf/xdp_fwd_user.c 
>> index 1828487bae9a..d321e6aa9364 100644
>> --- a/samples/bpf/xdp_fwd_user.c
>> +++ b/samples/bpf/xdp_fwd_user.c
>> @@ -47,17 +47,60 @@ 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 err;
>> +	}
>>  
>> -	err = bpf_xdp_detach(idx, xdp_flags, NULL);
>> -	if (err < 0)
>> -		printf("ERROR: failed to detach program from %s\n", name);
>> +	if (!curr_prog_id) {
>> +		printf("ERROR: flags(0x%x) xdp prog is not attached to %s\n",
>> +		       xdp_flags, ifname);
>> +		return err;
>> +	}
>>  
>> +	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;
>
> This should just be ' return prog_fd ' to propagate the error...
>
> -Toke
>
>
> Hi Toke:
> 	Use 'return prog_fd' instead of 'return errno' first. And Which
> position missed one 'return errno'?

Ah, no, that's the one I was talking about; I meant "missed one" as in
"missed removing one of them", not "a return errno was missing but
should be there"; so just changing that one to 'return prog_fd' should
and I think we should be good :)

-Toke