Re: [PATCH iproute2-next 2/2] vdpa: Add vdpa tool

[David Ahern <dsahern@gmail.com>]

Looks fine. A few comments below around code re-use.

On 1/22/21 4:26 AM, Parav Pandit wrote:
> diff --git a/vdpa/vdpa.c b/vdpa/vdpa.c
> new file mode 100644
> index 00000000..942524b7
> --- /dev/null
> +++ b/vdpa/vdpa.c
> @@ -0,0 +1,828 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +
> +#include <stdio.h>
> +#include <getopt.h>
> +#include <errno.h>
> +#include <linux/genetlink.h>
> +#include <linux/vdpa.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/netlink.h>
> +#include <libmnl/libmnl.h>
> +#include "mnl_utils.h"
> +
> +#include "version.h"
> +#include "json_print.h"
> +#include "utils.h"
> +
> +static int g_indent_level;
> +
> +#define INDENT_STR_STEP 2
> +#define INDENT_STR_MAXLEN 32
> +static char g_indent_str[INDENT_STR_MAXLEN + 1] = "";

The indent code has a lot of parallels with devlink -- including helpers
below around indent_inc and _dec. Please take a look at how to refactor
and re-use.

> +
> +struct vdpa_socket {
> +	struct mnl_socket *nl;
> +	char *buf;
> +	uint32_t family;
> +	unsigned int seq;
> +};
> +
> +static int vdpa_socket_sndrcv(struct vdpa_socket *nlg, const struct nlmsghdr *nlh,
> +			      mnl_cb_t data_cb, void *data)
> +{
> +	int err;
> +
> +	err = mnl_socket_sendto(nlg->nl, nlh, nlh->nlmsg_len);
> +	if (err < 0) {
> +		perror("Failed to send data");
> +		return -errno;
> +	}
> +
> +	err = mnlu_socket_recv_run(nlg->nl, nlh->nlmsg_seq, nlg->buf, MNL_SOCKET_BUFFER_SIZE,
> +				   data_cb, data);
> +	if (err < 0) {
> +		fprintf(stderr, "vdpa answers: %s\n", strerror(errno));
> +		return -errno;
> +	}
> +	return 0;
> +}
> +
> +static int get_family_id_attr_cb(const struct nlattr *attr, void *data)
> +{
> +	int type = mnl_attr_get_type(attr);
> +	const struct nlattr **tb = data;
> +
> +	if (mnl_attr_type_valid(attr, CTRL_ATTR_MAX) < 0)
> +		return MNL_CB_ERROR;
> +
> +	if (type == CTRL_ATTR_FAMILY_ID &&
> +	    mnl_attr_validate(attr, MNL_TYPE_U16) < 0)
> +		return MNL_CB_ERROR;
> +	tb[type] = attr;
> +	return MNL_CB_OK;
> +}
> +
> +static int get_family_id_cb(const struct nlmsghdr *nlh, void *data)
> +{
> +	struct genlmsghdr *genl = mnl_nlmsg_get_payload(nlh);
> +	struct nlattr *tb[CTRL_ATTR_MAX + 1] = {};
> +	uint32_t *p_id = data;
> +
> +	mnl_attr_parse(nlh, sizeof(*genl), get_family_id_attr_cb, tb);
> +	if (!tb[CTRL_ATTR_FAMILY_ID])
> +		return MNL_CB_ERROR;
> +	*p_id = mnl_attr_get_u16(tb[CTRL_ATTR_FAMILY_ID]);
> +	return MNL_CB_OK;
> +}
> +
> +static int family_get(struct vdpa_socket *nlg)
> +{
> +	struct genlmsghdr hdr = {};
> +	struct nlmsghdr *nlh;
> +	int err;
> +
> +	hdr.cmd = CTRL_CMD_GETFAMILY;
> +	hdr.version = 0x1;
> +
> +	nlh = mnlu_msg_prepare(nlg->buf, GENL_ID_CTRL,
> +			       NLM_F_REQUEST | NLM_F_ACK,
> +			       &hdr, sizeof(hdr));
> +
> +	mnl_attr_put_strz(nlh, CTRL_ATTR_FAMILY_NAME, VDPA_GENL_NAME);
> +
> +	err = mnl_socket_sendto(nlg->nl, nlh, nlh->nlmsg_len);
> +	if (err < 0)
> +		return err;
> +
> +	err = mnlu_socket_recv_run(nlg->nl, nlh->nlmsg_seq, nlg->buf,
> +				   MNL_SOCKET_BUFFER_SIZE,
> +				   get_family_id_cb, &nlg->family);
> +	return err;
> +}
> +
> +static int vdpa_socket_open(struct vdpa_socket *nlg)
> +{
> +	int err;
> +
> +	nlg->buf = malloc(MNL_SOCKET_BUFFER_SIZE);
> +	if (!nlg->buf)
> +		goto err_buf_alloc;
> +
> +	nlg->nl = mnlu_socket_open(NETLINK_GENERIC);
> +	if (!nlg->nl)
> +		goto err_socket_open;
> +
> +	err = family_get(nlg);
> +	if (err)
> +		goto err_socket;
> +
> +	return 0;
> +
> +err_socket:
> +	mnl_socket_close(nlg->nl);
> +err_socket_open:
> +	free(nlg->buf);
> +err_buf_alloc:
> +	return -1;
> +}

The above 4 functions duplicate a lot of devlink functionality. Please
create a helper in lib/mnl_utils.c that can be used in both.

> +
> +static void vdpa_socket_close(struct vdpa_socket *nlg)
> +{
> +	mnl_socket_close(nlg->nl);
> +	free(nlg->buf);
> +}
> +
> +#define VDPA_OPT_MGMTDEV_HANDLE		BIT(0)
> +#define VDPA_OPT_VDEV_MGMTDEV_HANDLE	BIT(1)
> +#define VDPA_OPT_VDEV_NAME 		BIT(2)
> +#define VDPA_OPT_VDEV_HANDLE 		BIT(3)
> +
> +struct vdpa_opts {
> +	uint64_t present; /* flags of present items */
> +	const char *mdev_bus_name;
> +	const char *mdev_name;
> +	const char *vdev_name;
> +	unsigned int device_id;
> +};
> +
> +struct vdpa {
> +	struct vdpa_socket nlg;
> +	struct vdpa_opts opts;
> +	bool json_output;
> +};
> +
> +static void indent_inc(void)
> +{
> +	if (g_indent_level + INDENT_STR_STEP > INDENT_STR_MAXLEN)
> +		return;
> +	g_indent_level += INDENT_STR_STEP;
> +	memset(g_indent_str, ' ', sizeof(g_indent_str));
> +	g_indent_str[g_indent_level] = '\0';
> +}
> +
> +static void indent_dec(void)
> +{
> +	if (g_indent_level - INDENT_STR_STEP < 0)
> +		return;
> +	g_indent_level -= INDENT_STR_STEP;
> +	g_indent_str[g_indent_level] = '\0';
> +}
> +
> +static void indent_print(void)
> +{
> +	if (g_indent_level)
> +		printf("%s", g_indent_str);
> +}
> +
> +static void pr_out_section_start(struct vdpa *vdpa, const char *name)
> +{
> +	open_json_object(NULL);
> +	open_json_object(name);
> +}
> +
> +static void pr_out_section_end(struct vdpa *vdpa)
> +{
> +	close_json_object();
> +	close_json_object();
> +}
> +
> +static void pr_out_array_start(struct vdpa *vdpa, const char *name)
> +{
> +	if (!vdpa->json_output) {
> +		print_nl();
> +		indent_inc();
> +		indent_print();
> +	}
> +	open_json_array(PRINT_ANY, name);
> +}
> +
> +static void pr_out_array_end(struct vdpa *vdpa)
> +{
> +	close_json_array(PRINT_JSON, NULL);
> +	if (!vdpa->json_output)
> +		indent_dec();
> +}
> +
> +static const enum mnl_attr_data_type vdpa_policy[VDPA_ATTR_MAX + 1] = {
> +	[VDPA_ATTR_MGMTDEV_BUS_NAME] = MNL_TYPE_NUL_STRING,
> +	[VDPA_ATTR_MGMTDEV_DEV_NAME] = MNL_TYPE_NUL_STRING,
> +	[VDPA_ATTR_DEV_NAME] = MNL_TYPE_STRING,
> +	[VDPA_ATTR_DEV_ID] = MNL_TYPE_U32,
> +	[VDPA_ATTR_DEV_VENDOR_ID] = MNL_TYPE_U32,
> +	[VDPA_ATTR_DEV_MAX_VQS] = MNL_TYPE_U32,
> +	[VDPA_ATTR_DEV_MAX_VQ_SIZE] = MNL_TYPE_U16,
> +};
> +
> +static int attr_cb(const struct nlattr *attr, void *data)
> +{
> +	const struct nlattr **tb = data;
> +	int type;
> +
> +	if (mnl_attr_type_valid(attr, VDPA_ATTR_MAX) < 0)
> +		return MNL_CB_OK;
> +
> +	type = mnl_attr_get_type(attr);
> +	if (mnl_attr_validate(attr, vdpa_policy[type]) < 0)
> +		return MNL_CB_ERROR;
> +
> +	tb[type] = attr;
> +	return MNL_CB_OK;
> +}
> +
> +static unsigned int strslashcount(char *str)
> +{
> +	unsigned int count = 0;
> +	char *pos = str;
> +
> +	while ((pos = strchr(pos, '/'))) {
> +		count++;
> +		pos++;
> +	}
> +	return count;
> +}

you could make that a generic function (e.g., str_char_count) by passing
'/' as an input.

> +
> +static int strslashrsplit(char *str, const char **before, const char **after)
> +{
> +	char *slash;
> +
> +	slash = strrchr(str, '/');
> +	if (!slash)
> +		return -EINVAL;
> +	*slash = '\0';
> +	*before = str;
> +	*after = slash + 1;
> +	return 0;
> +}

similarly here. If you start with things like this in lib/utils you make
it easier for follow on users to find.