From 05cc2af50ba43431d6d50aff758e968833aab9c6 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Tue, 13 Sep 2022 07:35:10 +0200
Subject: tools/xenstore: add control command for setting and showing quota

Add a xenstore-control command "quota" to:
- show current quota settings
- change quota settings
- show current quota related values of a domain

Note that in the case the new quota is lower than existing one,
Xenstored may continue to handle requests from a domain exceeding the
new limit (depends on which one has been broken) and the amount of
resource used will not change. However the domain will not be able to
create more resource (associated to the quota) until it is back to below
the limit.

This is part of XSA-326.

Reported-by: Julien Grall <jgrall@amazon.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>

diff --git a/docs/misc/xenstore.txt b/docs/misc/xenstore.txt
index 334dc8b6fdf5..a7d006519ae8 100644
--- a/docs/misc/xenstore.txt
+++ b/docs/misc/xenstore.txt
@@ -366,6 +366,17 @@ CONTROL			<command>|[<parameters>|]
 	print|<string>
 		print <string> to syslog (xenstore runs as daemon) or
 		to console (xenstore runs as stubdom)
+	quota|[set <name> <val>|<domid>]
+		without parameters: print the current quota settings
+		with "set <name> <val>": set the quota <name> to new value
+		<val> (The admin should make sure all the domain usage is
+		below the quota. If it is not, then Xenstored may continue to
+		handle requests from the domain as long as the resource
+		violating the new quota setting isn't increased further)
+		with "<domid>": print quota related accounting data for
+		the domain <domid>
+	quota-soft|[set <name> <val>]
+		like the "quota" command, but for soft-quota.
 	help			<supported-commands>
 		return list of supported commands for CONTROL
 
diff --git a/tools/xenstore/xenstored_control.c b/tools/xenstore/xenstored_control.c
index adb8d51b043b..1031a81c3874 100644
--- a/tools/xenstore/xenstored_control.c
+++ b/tools/xenstore/xenstored_control.c
@@ -196,6 +196,115 @@ static int do_control_log(void *ctx, struct connection *conn,
 	return 0;
 }
 
+struct quota {
+	const char *name;
+	int *quota;
+	const char *descr;
+};
+
+static const struct quota hard_quotas[] = {
+	{ "nodes", &quota_nb_entry_per_domain, "Nodes per domain" },
+	{ "watches", &quota_nb_watch_per_domain, "Watches per domain" },
+	{ "transactions", &quota_max_transaction, "Transactions per domain" },
+	{ "outstanding", &quota_req_outstanding,
+		"Outstanding requests per domain" },
+	{ "transaction-nodes", &quota_trans_nodes,
+		"Max. number of accessed nodes per transaction" },
+	{ "memory", &quota_memory_per_domain_hard,
+		"Total Xenstore memory per domain (error level)" },
+	{ "node-size", &quota_max_entry_size, "Max. size of a node" },
+	{ "path-max", &quota_max_path_len, "Max. length of a node path" },
+	{ "permissions", &quota_nb_perms_per_node,
+		"Max. number of permissions per node" },
+	{ NULL, NULL, NULL }
+};
+
+static const struct quota soft_quotas[] = {
+	{ "memory", &quota_memory_per_domain_soft,
+		"Total Xenstore memory per domain (warning level)" },
+	{ NULL, NULL, NULL }
+};
+
+static int quota_show_current(const void *ctx, struct connection *conn,
+			      const struct quota *quotas)
+{
+	char *resp;
+	unsigned int i;
+
+	resp = talloc_strdup(ctx, "Quota settings:\n");
+	if (!resp)
+		return ENOMEM;
+
+	for (i = 0; quotas[i].quota; i++) {
+		resp = talloc_asprintf_append(resp, "%-17s: %8d %s\n",
+					      quotas[i].name, *quotas[i].quota,
+					      quotas[i].descr);
+		if (!resp)
+			return ENOMEM;
+	}
+
+	send_reply(conn, XS_CONTROL, resp, strlen(resp) + 1);
+
+	return 0;
+}
+
+static int quota_set(const void *ctx, struct connection *conn,
+		     char **vec, int num, const struct quota *quotas)
+{
+	unsigned int i;
+	int val;
+
+	if (num != 2)
+		return EINVAL;
+
+	val = atoi(vec[1]);
+	if (val < 1)
+		return EINVAL;
+
+	for (i = 0; quotas[i].quota; i++) {
+		if (!strcmp(vec[0], quotas[i].name)) {
+			*quotas[i].quota = val;
+			send_ack(conn, XS_CONTROL);
+			return 0;
+		}
+	}
+
+	return EINVAL;
+}
+
+static int quota_get(const void *ctx, struct connection *conn,
+		     char **vec, int num)
+{
+	if (num != 1)
+		return EINVAL;
+
+	return domain_get_quota(ctx, conn, atoi(vec[0]));
+}
+
+static int do_control_quota(void *ctx, struct connection *conn,
+			    char **vec, int num)
+{
+	if (num == 0)
+		return quota_show_current(ctx, conn, hard_quotas);
+
+	if (!strcmp(vec[0], "set"))
+		return quota_set(ctx, conn, vec + 1, num - 1, hard_quotas);
+
+	return quota_get(ctx, conn, vec, num);
+}
+
+static int do_control_quota_s(void *ctx, struct connection *conn,
+			      char **vec, int num)
+{
+	if (num == 0)
+		return quota_show_current(ctx, conn, soft_quotas);
+
+	if (!strcmp(vec[0], "set"))
+		return quota_set(ctx, conn, vec + 1, num - 1, soft_quotas);
+
+	return EINVAL;
+}
+
 #ifdef __MINIOS__
 static int do_control_memreport(void *ctx, struct connection *conn,
 				char **vec, int num)
@@ -847,6 +956,8 @@ static struct cmd_s cmds[] = {
 	{ "memreport", do_control_memreport, "[<file>]" },
 #endif
 	{ "print", do_control_print, "<string>" },
+	{ "quota", do_control_quota, "[set <name> <val>|<domid>]" },
+	{ "quota-soft", do_control_quota_s, "[set <name> <val>]" },
 	{ "help", do_control_help, "" },
 };
 
diff --git a/tools/xenstore/xenstored_domain.c b/tools/xenstore/xenstored_domain.c
index 94fd561e9de4..e7c6886ccf47 100644
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -31,6 +31,7 @@
 #include "xenstored_domain.h"
 #include "xenstored_transaction.h"
 #include "xenstored_watch.h"
+#include "xenstored_control.h"
 
 #include <xenevtchn.h>
 #include <xenctrl.h>
@@ -345,6 +346,38 @@ static struct domain *find_domain_struct(unsigned int domid)
 	return NULL;
 }
 
+int domain_get_quota(const void *ctx, struct connection *conn,
+		     unsigned int domid)
+{
+	struct domain *d = find_domain_struct(domid);
+	char *resp;
+	int ta;
+
+	if (!d)
+		return ENOENT;
+
+	ta = d->conn ? d->conn->transaction_started : 0;
+	resp = talloc_asprintf(ctx, "Domain %u:\n", domid);
+	if (!resp)
+		return ENOMEM;
+
+#define ent(t, e) \
+	resp = talloc_asprintf_append(resp, "%-16s: %8d\n", #t, e); \
+	if (!resp) return ENOMEM
+
+	ent(nodes, d->nbentry);
+	ent(watches, d->nbwatch);
+	ent(transactions, ta);
+	ent(outstanding, d->nboutstanding);
+	ent(memory, d->memory);
+
+#undef ent
+
+	send_reply(conn, XS_CONTROL, resp, strlen(resp) + 1);
+
+	return 0;
+}
+
 static struct domain *alloc_domain(const void *context, unsigned int domid)
 {
 	struct domain *domain;
diff --git a/tools/xenstore/xenstored_domain.h b/tools/xenstore/xenstored_domain.h
index 633c9a0a0a1f..904faa923afb 100644
--- a/tools/xenstore/xenstored_domain.h
+++ b/tools/xenstore/xenstored_domain.h
@@ -87,6 +87,8 @@ int domain_watch(struct connection *conn);
 void domain_outstanding_inc(struct connection *conn);
 void domain_outstanding_dec(struct connection *conn);
 void domain_outstanding_domid_dec(unsigned int domid);
+int domain_get_quota(const void *ctx, struct connection *conn,
+		     unsigned int domid);
 
 /* Special node permission handling. */
 int set_perms_special(struct connection *conn, const char *name,