Subject: Re: [PATCH] libbpf: Don't error out if getsockopt() fails for XDP_OPTIONS

From: Toke Høiland-Jørgensen <[email-masked]>
Date: Tue, 10 Sep 2019 00:06:04 +0100

Yonghong Song <[email-masked]> writes:

> On 9/9/19 10:46 AM, Toke Høiland-Jørgensen wrote:
>> The xsk_socket__create() function fails and returns an error if it cannot
>> get the XDP_OPTIONS through getsockopt(). However, support for XDP_OPTIONS
>> was not added until kernel 5.3, so this means that creating XSK sockets
>> always fails on older kernels.
>> 
>> Since the option is just used to set the zero-copy flag in the xsk struct,
>> there really is no need to error out if the getsockopt() call fails.
>> 
>> Signed-off-by: Toke Høiland-Jørgensen <[email-masked]>
>> ---
>>   tools/lib/bpf/xsk.c | 8 ++------
>>   1 file changed, 2 insertions(+), 6 deletions(-)
>> 
>> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
>> index 680e63066cf3..598e487d9ce8 100644
>> --- a/tools/lib/bpf/xsk.c
>> +++ b/tools/lib/bpf/xsk.c
>> @@ -603,12 +603,8 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
>>   
>>   	optlen = sizeof(opts);
>>   	err = getsockopt(xsk->fd, SOL_XDP, XDP_OPTIONS, &opts, &optlen);
>> -	if (err) {
>> -		err = -errno;
>> -		goto out_mmap_tx;
>> -	}
>> -
>> -	xsk->zc = opts.flags & XDP_OPTIONS_ZEROCOPY;
>> +	if (!err)
>> +		xsk->zc = opts.flags & XDP_OPTIONS_ZEROCOPY;
>>   
>>   	if (!(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) {
>>   		err = xsk_setup_xdp_prog(xsk);
>
> Since 'zc' is not used by anybody, maybe all codes 'zc' related can be 
> removed? It can be added back back once there is an interface to use
> 'zc'?

Fine with me; up to the maintainers what they prefer, I guess? :)

-Toke