Merge branch 'netdev-support-dumping-a-single-netdev-in-qstats'

Jakub Kicinski says:

====================
netdev: support dumping a single netdev in qstats

I was writing a test for page pool which depended on qstats,
and got tired of having to filter dumps in user space.
Add support for dumping stats for a single netdev.

To get there we first need to add full support for extack
in dumps (and fix a dump error handling bug in YNL, sent
separately to the net tree).
====================

Link: https://lore.kernel.org/r/20240420023543.3300306-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 110 insertions, 78 deletions

diff --git a/net/core/netdev-genl-gen.c b/net/core/netdev-genl-gen.c
index 8d8ace9ef87f..8350a0afa9ec 100644
--- a/net/core/netdev-genl-gen.c
+++ b/net/core/netdev-genl-gen.c
@@ -70,6 +70,7 @@ static const struct nla_policy netdev_napi_get_dump_nl_policy[NETDEV_A_NAPI_IFIN
 
 /* NETDEV_CMD_QSTATS_GET - dump */
 static const struct nla_policy netdev_qstats_get_nl_policy[NETDEV_A_QSTATS_SCOPE + 1] = {
+	[NETDEV_A_QSTATS_IFINDEX] = NLA_POLICY_MIN(NLA_U32, 1),
 	[NETDEV_A_QSTATS_SCOPE] = NLA_POLICY_MASK(NLA_UINT, 0x1),
 };
 
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 7004b3399c2b..dd6510f2c652 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -639,6 +639,24 @@ nla_put_failure:
 	return -EMSGSIZE;
 }
 
+static int
+netdev_nl_qstats_get_dump_one(struct net_device *netdev, unsigned int scope,
+			      struct sk_buff *skb, const struct genl_info *info,
+			      struct netdev_nl_dump_ctx *ctx)
+{
+	if (!netdev->stat_ops)
+		return 0;
+
+	switch (scope) {
+	case 0:
+		return netdev_nl_stats_by_netdev(netdev, skb, info);
+	case NETDEV_QSTATS_SCOPE_QUEUE:
+		return netdev_nl_stats_by_queue(netdev, skb, info, ctx);
+	}
+
+	return -EINVAL;	/* Should not happen, per netlink policy */
+}
+
 int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
 				struct netlink_callback *cb)
 {
@@ -646,6 +664,7 @@ int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
 	const struct genl_info *info = genl_info_dump(cb);
 	struct net *net = sock_net(skb->sk);
 	struct net_device *netdev;
+	unsigned int ifindex;
 	unsigned int scope;
 	int err = 0;
 
@@ -653,21 +672,28 @@ int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
 	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;
+	ifindex = 0;
+	if (info->attrs[NETDEV_A_QSTATS_IFINDEX])
+		ifindex = nla_get_u32(info->attrs[NETDEV_A_QSTATS_IFINDEX]);
 
-		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;
+	rtnl_lock();
+	if (ifindex) {
+		netdev = __dev_get_by_index(net, ifindex);
+		if (netdev && netdev->stat_ops) {
+			err = netdev_nl_qstats_get_dump_one(netdev, scope, skb,
+							    info, ctx);
+		} else {
+			NL_SET_BAD_ATTR(info->extack,
+					info->attrs[NETDEV_A_QSTATS_IFINDEX]);
+			err = netdev ? -EOPNOTSUPP : -ENODEV;
+		}
+	} else {
+		for_each_netdev_dump(net, netdev, ctx->ifindex) {
+			err = netdev_nl_qstats_get_dump_one(netdev, scope, skb,
+							    info, ctx);
+			if (err < 0)
+				break;
 		}
-		if (err < 0)
-			break;
 	}
 	rtnl_unlock();
 
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index dc8c3c01d51b..fa9c090cf629 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2165,6 +2165,69 @@ __nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int fla
 }
 EXPORT_SYMBOL(__nlmsg_put);
 
+static size_t
+netlink_ack_tlv_len(struct netlink_sock *nlk, int err,
+		    const struct netlink_ext_ack *extack)
+{
+	size_t tlvlen;
+
+	if (!extack || !test_bit(NETLINK_F_EXT_ACK, &nlk->flags))
+		return 0;
+
+	tlvlen = 0;
+	if (extack->_msg)
+		tlvlen += nla_total_size(strlen(extack->_msg) + 1);
+	if (extack->cookie_len)
+		tlvlen += nla_total_size(extack->cookie_len);
+
+	/* Following attributes are only reported as error (not warning) */
+	if (!err)
+		return tlvlen;
+
+	if (extack->bad_attr)
+		tlvlen += nla_total_size(sizeof(u32));
+	if (extack->policy)
+		tlvlen += netlink_policy_dump_attr_size_estimate(extack->policy);
+	if (extack->miss_type)
+		tlvlen += nla_total_size(sizeof(u32));
+	if (extack->miss_nest)
+		tlvlen += nla_total_size(sizeof(u32));
+
+	return tlvlen;
+}
+
+static void
+netlink_ack_tlv_fill(struct sk_buff *in_skb, struct sk_buff *skb,
+		     const struct nlmsghdr *nlh, int err,
+		     const struct netlink_ext_ack *extack)
+{
+	if (extack->_msg)
+		WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG, extack->_msg));
+	if (extack->cookie_len)
+		WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
+				extack->cookie_len, extack->cookie));
+
+	if (!err)
+		return;
+
+	if (extack->bad_attr &&
+	    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
+		     (u8 *)extack->bad_attr >= in_skb->data + in_skb->len))
+		WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
+				    (u8 *)extack->bad_attr - (const u8 *)nlh));
+	if (extack->policy)
+		netlink_policy_dump_write_attr(skb, extack->policy,
+					       NLMSGERR_ATTR_POLICY);
+	if (extack->miss_type)
+		WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_MISS_TYPE,
+				    extack->miss_type));
+	if (extack->miss_nest &&
+	    !WARN_ON((u8 *)extack->miss_nest < in_skb->data ||
+		     (u8 *)extack->miss_nest > in_skb->data + in_skb->len))
+		WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_MISS_NEST,
+				    (u8 *)extack->miss_nest - (const u8 *)nlh));
+}
+
 /*
  * It looks a bit ugly.
  * It would be better to create kernel thread.
@@ -2175,6 +2238,7 @@ static int netlink_dump_done(struct netlink_sock *nlk, struct sk_buff *skb,
 			     struct netlink_ext_ack *extack)
 {
 	struct nlmsghdr *nlh;
+	size_t extack_len;
 
 	nlh = nlmsg_put_answer(skb, cb, NLMSG_DONE, sizeof(nlk->dump_done_errno),
 			       NLM_F_MULTI | cb->answer_flags);
@@ -2184,10 +2248,14 @@ static int netlink_dump_done(struct netlink_sock *nlk, struct sk_buff *skb,
 	nl_dump_check_consistent(cb, nlh);
 	memcpy(nlmsg_data(nlh), &nlk->dump_done_errno, sizeof(nlk->dump_done_errno));
 
-	if (extack->_msg && test_bit(NETLINK_F_EXT_ACK, &nlk->flags)) {
+	extack_len = netlink_ack_tlv_len(nlk, nlk->dump_done_errno, extack);
+	if (extack_len) {
 		nlh->nlmsg_flags |= NLM_F_ACK_TLVS;
-		if (!nla_put_string(skb, NLMSGERR_ATTR_MSG, extack->_msg))
+		if (skb_tailroom(skb) >= extack_len) {
+			netlink_ack_tlv_fill(cb->skb, skb, cb->nlh,
+					     nlk->dump_done_errno, extack);
 			nlmsg_end(skb, nlh);
+		}
 	}
 
 	return 0;
@@ -2406,69 +2474,6 @@ error_free:
 }
 EXPORT_SYMBOL(__netlink_dump_start);
 
-static size_t
-netlink_ack_tlv_len(struct netlink_sock *nlk, int err,
-		    const struct netlink_ext_ack *extack)
-{
-	size_t tlvlen;
-
-	if (!extack || !test_bit(NETLINK_F_EXT_ACK, &nlk->flags))
-		return 0;
-
-	tlvlen = 0;
-	if (extack->_msg)
-		tlvlen += nla_total_size(strlen(extack->_msg) + 1);
-	if (extack->cookie_len)
-		tlvlen += nla_total_size(extack->cookie_len);
-
-	/* Following attributes are only reported as error (not warning) */
-	if (!err)
-		return tlvlen;
-
-	if (extack->bad_attr)
-		tlvlen += nla_total_size(sizeof(u32));
-	if (extack->policy)
-		tlvlen += netlink_policy_dump_attr_size_estimate(extack->policy);
-	if (extack->miss_type)
-		tlvlen += nla_total_size(sizeof(u32));
-	if (extack->miss_nest)
-		tlvlen += nla_total_size(sizeof(u32));
-
-	return tlvlen;
-}
-
-static void
-netlink_ack_tlv_fill(struct sk_buff *in_skb, struct sk_buff *skb,
-		     struct nlmsghdr *nlh, int err,
-		     const struct netlink_ext_ack *extack)
-{
-	if (extack->_msg)
-		WARN_ON(nla_put_string(skb, NLMSGERR_ATTR_MSG, extack->_msg));
-	if (extack->cookie_len)
-		WARN_ON(nla_put(skb, NLMSGERR_ATTR_COOKIE,
-				extack->cookie_len, extack->cookie));
-
-	if (!err)
-		return;
-
-	if (extack->bad_attr &&
-	    !WARN_ON((u8 *)extack->bad_attr < in_skb->data ||
-		     (u8 *)extack->bad_attr >= in_skb->data + in_skb->len))
-		WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_OFFS,
-				    (u8 *)extack->bad_attr - (u8 *)nlh));
-	if (extack->policy)
-		netlink_policy_dump_write_attr(skb, extack->policy,
-					       NLMSGERR_ATTR_POLICY);
-	if (extack->miss_type)
-		WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_MISS_TYPE,
-				    extack->miss_type));
-	if (extack->miss_nest &&
-	    !WARN_ON((u8 *)extack->miss_nest < in_skb->data ||
-		     (u8 *)extack->miss_nest > in_skb->data + in_skb->len))
-		WARN_ON(nla_put_u32(skb, NLMSGERR_ATTR_MISS_NEST,
-				    (u8 *)extack->miss_nest - (u8 *)nlh));
-}
-
 void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err,
 		 const struct netlink_ext_ack *extack)
 {