Re: [PATCH net-next] libbpf: add function to setup XDP

[Jakub Kicinski]

On Sat,  9 Dec 2017 15:43:15 +0100, Eric Leblond wrote:
> +	for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
> +	     nh = NLMSG_NEXT(nh, len)) {
> +		if (nh->nlmsg_pid != getpid()) {
> +			ret = -LIBBPF_ERRNO__WRNGPID;
> +			goto cleanup;
> +		}
> +		if (nh->nlmsg_seq != seq) {
> +			ret = -LIBBPF_ERRNO__INVSEQ;
> +			goto cleanup;
> +		}
> +		switch (nh->nlmsg_type) {
> +		case NLMSG_ERROR:
> +			err = (struct nlmsgerr *)NLMSG_DATA(nh);
> +			if (!err->error)
> +				continue;
> +			ret = err->error;
> +			goto cleanup;
> +		case NLMSG_DONE:
> +			break;
> +		default:
> +			break;
> +		}

Would it be possible to print out or preferably return to the caller
the ext ack error message?  A couple of drivers are using it for XDP
mis-configuration reporting instead of printks.  We should encourage
other to do the same and support it in all user space since ext ack 
msgs lead to much better user experience.