From 3cc236d3f62c015a95d3d6dc578ad7fcfa19607a 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.

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

--- a/docs/misc/xenstore.txt
+++ b/docs/misc/xenstore.txt
@@ -320,6 +320,17 @@ DEBUG			print|<string>|??	    sends <str
 DEBUG			print|<thing-with-no-nul>   EINVAL
 DEBUG			check|??		    checks xenstored innards
 DEBUG			<anything-else|>	    no-op (future extension)
+DEBUG			quota|[set <name> <val>|<domid>]
+DEBUG				without parameters: print the current quota settings
+DEBUG				with "set <name> <val>": set the quota <name> to new value
+DEBUG				<val> (The admin should make sure all the domain usage is
+DEBUG				below the quota. If it is not, then Xenstored may continue to
+DEBUG				handle requests from the domain as long as the resource
+DEBUG				violating the new quota setting isn't increased further)
+DEBUG				with "<domid>": print quota related accounting data for
+DEBUG				the domain <domid>
+DEBUG			quota-soft|[set <name> <val>]
+DEBUG				like the "quota" command, but for soft-quota.
 
 	These requests should not generally be used and may be
 	withdrawn in the future.
--- a/tools/xenstore/xenstored_control.c
+++ b/tools/xenstore/xenstored_control.c
@@ -19,6 +19,7 @@
 #include <errno.h>
 #include <stdarg.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
@@ -78,6 +79,114 @@ static int do_control_logfile(void *ctx,
 	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" },
+	{ "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;
+}
+
 static int do_control_memreport(void *ctx, struct connection *conn,
 				char **vec, int num)
 {
@@ -137,6 +246,8 @@ static struct cmd_s cmds[] = {
 	{ "logfile", do_control_logfile, "<file>" },
 	{ "memreport", do_control_memreport, "[<file>]" },
 	{ "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, "" },
 };
 
--- a/tools/xenstore/xenstored_domain.c
+++ b/tools/xenstore/xenstored_domain.c
@@ -33,6 +33,7 @@
 #include "xenstored_domain.h"
 #include "xenstored_transaction.h"
 #include "xenstored_watch.h"
+#include "xenstored_control.h"
 
 #include <xenctrl.h>
 #include <xen/grant_table.h>
@@ -361,6 +362,38 @@ static struct domain *find_domain_struct
 	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(void *context, unsigned int domid)
 {
 	struct domain *domain;
--- a/tools/xenstore/xenstored_domain.h
+++ b/tools/xenstore/xenstored_domain.h
@@ -93,6 +93,8 @@ 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,
