netdev: add per-queue statistics

The ethtool-nl family does a good job exposing various protocol
related and IEEE/IETF statistics which used to get dumped under
ethtool -S, with creative names. Queue stats don't have a netlink
API, yet, and remain a lion's share of ethtool -S output for new
drivers. Not only is that bad because the names differ driver to
driver but it's also bug-prone. Intuitively drivers try to report
only the stats for active queues, but querying ethtool stats
involves multiple system calls, and the number of stats is
read separately from the stats themselves. Worse still when user
space asks for values of the stats, it doesn't inform the kernel
how big the buffer is. If number of stats increases in the meantime
kernel will overflow user buffer.

Add a netlink API for dumping queue stats. Queue information is
exposed via the netdev-genl family, so add the stats there.
Support per-queue and sum-for-device dumps. Latter will be useful
when subsequent patches add more interesting common stats than
just bytes and packets.

The API does not currently distinguish between HW and SW stats.
The expectation is that the source of the stats will either not
matter much (good packets) or be obvious (skb alloc errors).

Acked-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Amritha Nambiar <amritha.nambiar@intel.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240306195509.1502746-2-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 227 insertions, 0 deletions

diff --git a/net/core/netdev-genl-gen.c b/net/core/netdev-genl-gen.c
index be7f2ebd61b2..8d8ace9ef87f 100644
--- a/net/core/netdev-genl-gen.c
+++ b/net/core/netdev-genl-gen.c
@@ -68,6 +68,11 @@ static const struct nla_policy netdev_napi_get_dump_nl_policy[NETDEV_A_NAPI_IFIN
 	[NETDEV_A_NAPI_IFINDEX] = NLA_POLICY_MIN(NLA_U32, 1),
 };
 
+/* NETDEV_CMD_QSTATS_GET - dump */
+static const struct nla_policy netdev_qstats_get_nl_policy[NETDEV_A_QSTATS_SCOPE + 1] = {
+	[NETDEV_A_QSTATS_SCOPE] = NLA_POLICY_MASK(NLA_UINT, 0x1),
+};
+
 /* Ops table for netdev */
 static const struct genl_split_ops netdev_nl_ops[] = {
 	{
@@ -138,6 +143,13 @@ static const struct genl_split_ops netdev_nl_ops[] = {
 		.maxattr	= NETDEV_A_NAPI_IFINDEX,
 		.flags		= GENL_CMD_CAP_DUMP,
 	},
+	{
+		.cmd		= NETDEV_CMD_QSTATS_GET,
+		.dumpit		= netdev_nl_qstats_get_dumpit,
+		.policy		= netdev_qstats_get_nl_policy,
+		.maxattr	= NETDEV_A_QSTATS_SCOPE,
+		.flags		= GENL_CMD_CAP_DUMP,
+	},
 };
 
 static const struct genl_multicast_group netdev_nl_mcgrps[] = {
diff --git a/net/core/netdev-genl-gen.h b/net/core/netdev-genl-gen.h
index a47f2bcbe4fa..4db40fd5b4a9 100644
--- a/net/core/netdev-genl-gen.h
+++ b/net/core/netdev-genl-gen.h
@@ -28,6 +28,8 @@ int netdev_nl_queue_get_dumpit(struct sk_buff *skb,
 			       struct netlink_callback *cb);
 int netdev_nl_napi_get_doit(struct sk_buff *skb, struct genl_info *info);
 int netdev_nl_napi_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
+int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
+				struct netlink_callback *cb);
 
 enum {
 	NETDEV_NLGRP_MGMT,
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 918b109e0cf4..7fa75e13dc6d 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -8,6 +8,7 @@
 #include <net/xdp.h>
 #include <net/xdp_sock.h>
 #include <net/netdev_rx_queue.h>
+#include <net/netdev_queues.h>
 #include <net/busy_poll.h>
 
 #include "netdev-genl-gen.h"
@@ -460,6 +461,218 @@ int netdev_nl_queue_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 	return err;
 }
 
+#define NETDEV_STAT_NOT_SET		(~0ULL)
+
+static void netdev_nl_stats_add(void *_sum, const void *_add, size_t size)
+{
+	const u64 *add = _add;
+	u64 *sum = _sum;
+
+	while (size) {
+		if (*add != NETDEV_STAT_NOT_SET && *sum != NETDEV_STAT_NOT_SET)
+			*sum += *add;
+		sum++;
+		add++;
+		size -= 8;
+	}
+}
+
+static int netdev_stat_put(struct sk_buff *rsp, unsigned int attr_id, u64 value)
+{
+	if (value == NETDEV_STAT_NOT_SET)
+		return 0;
+	return nla_put_uint(rsp, attr_id, value);
+}
+
+static int
+netdev_nl_stats_write_rx(struct sk_buff *rsp, struct netdev_queue_stats_rx *rx)
+{
+	if (netdev_stat_put(rsp, NETDEV_A_QSTATS_RX_PACKETS, rx->packets) ||
+	    netdev_stat_put(rsp, NETDEV_A_QSTATS_RX_BYTES, rx->bytes))
+		return -EMSGSIZE;
+	return 0;
+}
+
+static int
+netdev_nl_stats_write_tx(struct sk_buff *rsp, struct netdev_queue_stats_tx *tx)
+{
+	if (netdev_stat_put(rsp, NETDEV_A_QSTATS_TX_PACKETS, tx->packets) ||
+	    netdev_stat_put(rsp, NETDEV_A_QSTATS_TX_BYTES, tx->bytes))
+		return -EMSGSIZE;
+	return 0;
+}
+
+static int
+netdev_nl_stats_queue(struct net_device *netdev, struct sk_buff *rsp,
+		      u32 q_type, int i, const struct genl_info *info)
+{
+	const struct netdev_stat_ops *ops = netdev->stat_ops;
+	struct netdev_queue_stats_rx rx;
+	struct netdev_queue_stats_tx tx;
+	void *hdr;
+
+	hdr = genlmsg_iput(rsp, info);
+	if (!hdr)
+		return -EMSGSIZE;
+	if (nla_put_u32(rsp, NETDEV_A_QSTATS_IFINDEX, netdev->ifindex) ||
+	    nla_put_u32(rsp, NETDEV_A_QSTATS_QUEUE_TYPE, q_type) ||
+	    nla_put_u32(rsp, NETDEV_A_QSTATS_QUEUE_ID, i))
+		goto nla_put_failure;
+
+	switch (q_type) {
+	case NETDEV_QUEUE_TYPE_RX:
+		memset(&rx, 0xff, sizeof(rx));
+		ops->get_queue_stats_rx(netdev, i, &rx);
+		if (!memchr_inv(&rx, 0xff, sizeof(rx)))
+			goto nla_cancel;
+		if (netdev_nl_stats_write_rx(rsp, &rx))
+			goto nla_put_failure;
+		break;
+	case NETDEV_QUEUE_TYPE_TX:
+		memset(&tx, 0xff, sizeof(tx));
+		ops->get_queue_stats_tx(netdev, i, &tx);
+		if (!memchr_inv(&tx, 0xff, sizeof(tx)))
+			goto nla_cancel;
+		if (netdev_nl_stats_write_tx(rsp, &tx))
+			goto nla_put_failure;
+		break;
+	}
+
+	genlmsg_end(rsp, hdr);
+	return 0;
+
+nla_cancel:
+	genlmsg_cancel(rsp, hdr);
+	return 0;
+nla_put_failure:
+	genlmsg_cancel(rsp, hdr);
+	return -EMSGSIZE;
+}
+
+static int
+netdev_nl_stats_by_queue(struct net_device *netdev, struct sk_buff *rsp,
+			 const struct genl_info *info,
+			 struct netdev_nl_dump_ctx *ctx)
+{
+	const struct netdev_stat_ops *ops = netdev->stat_ops;
+	int i, err;
+
+	if (!(netdev->flags & IFF_UP))
+		return 0;
+
+	i = ctx->rxq_idx;
+	while (ops->get_queue_stats_rx && i < netdev->real_num_rx_queues) {
+		err = netdev_nl_stats_queue(netdev, rsp, NETDEV_QUEUE_TYPE_RX,
+					    i, info);
+		if (err)
+			return err;
+		ctx->rxq_idx = i++;
+	}
+	i = ctx->txq_idx;
+	while (ops->get_queue_stats_tx && i < netdev->real_num_tx_queues) {
+		err = netdev_nl_stats_queue(netdev, rsp, NETDEV_QUEUE_TYPE_TX,
+					    i, info);
+		if (err)
+			return err;
+		ctx->txq_idx = i++;
+	}
+
+	ctx->rxq_idx = 0;
+	ctx->txq_idx = 0;
+	return 0;
+}
+
+static int
+netdev_nl_stats_by_netdev(struct net_device *netdev, struct sk_buff *rsp,
+			  const struct genl_info *info)
+{
+	struct netdev_queue_stats_rx rx_sum, rx;
+	struct netdev_queue_stats_tx tx_sum, tx;
+	const struct netdev_stat_ops *ops;
+	void *hdr;
+	int i;
+
+	ops = netdev->stat_ops;
+	/* Netdev can't guarantee any complete counters */
+	if (!ops->get_base_stats)
+		return 0;
+
+	memset(&rx_sum, 0xff, sizeof(rx_sum));
+	memset(&tx_sum, 0xff, sizeof(tx_sum));
+
+	ops->get_base_stats(netdev, &rx_sum, &tx_sum);
+
+	/* The op was there, but nothing reported, don't bother */
+	if (!memchr_inv(&rx_sum, 0xff, sizeof(rx_sum)) &&
+	    !memchr_inv(&tx_sum, 0xff, sizeof(tx_sum)))
+		return 0;
+
+	hdr = genlmsg_iput(rsp, info);
+	if (!hdr)
+		return -EMSGSIZE;
+	if (nla_put_u32(rsp, NETDEV_A_QSTATS_IFINDEX, netdev->ifindex))
+		goto nla_put_failure;
+
+	for (i = 0; i < netdev->real_num_rx_queues; i++) {
+		memset(&rx, 0xff, sizeof(rx));
+		if (ops->get_queue_stats_rx)
+			ops->get_queue_stats_rx(netdev, i, &rx);
+		netdev_nl_stats_add(&rx_sum, &rx, sizeof(rx));
+	}
+	for (i = 0; i < netdev->real_num_tx_queues; i++) {
+		memset(&tx, 0xff, sizeof(tx));
+		if (ops->get_queue_stats_tx)
+			ops->get_queue_stats_tx(netdev, i, &tx);
+		netdev_nl_stats_add(&tx_sum, &tx, sizeof(tx));
+	}
+
+	if (netdev_nl_stats_write_rx(rsp, &rx_sum) ||
+	    netdev_nl_stats_write_tx(rsp, &tx_sum))
+		goto nla_put_failure;
+
+	genlmsg_end(rsp, hdr);
+	return 0;
+
+nla_put_failure:
+	genlmsg_cancel(rsp, hdr);
+	return -EMSGSIZE;
+}
+
+int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
+				struct netlink_callback *cb)
+{
+	struct netdev_nl_dump_ctx *ctx = netdev_dump_ctx(cb);
+	const struct genl_info *info = genl_info_dump(cb);
+	struct net *net = sock_net(skb->sk);
+	struct net_device *netdev;
+	unsigned int scope;
+	int err = 0;
+
+	scope = 0;
+	if (info->attrs[NETDEV_A_QSTATS_SCOPE])
+		scope = nla_get_uint(info->attrs[NETDEV_A_QSTATS_SCOPE]);
+
+	rtnl_lock();
+	for_each_netdev_dump(net, netdev, ctx->ifindex) {
+		if (!netdev->stat_ops)
+			continue;
+
+		switch (scope) {
+		case 0:
+			err = netdev_nl_stats_by_netdev(netdev, skb, info);
+			break;
+		case NETDEV_QSTATS_SCOPE_QUEUE:
+			err = netdev_nl_stats_by_queue(netdev, skb, info, ctx);
+			break;
+		}
+		if (err < 0)
+			break;
+	}
+	rtnl_unlock();
+
+	return err;
+}
+
 static int netdev_genl_netdevice_event(struct notifier_block *nb,
 				       unsigned long event, void *ptr)
 {