@@ -42,8 +42,9 @@ sk_so_peek_off
 socket
 so_incoming_cpu
 so_netns_cookie
-so_txtime
 so_rcv_listener
+so_rcvbuf
+so_txtime
 stress_reuseport_listen
 tap
 tcp_fastopen_backup_key

@@ -87,7 +87,7 @@ TEST_GEN_PROGS += sk_bind_sendto_listen
 TEST_GEN_PROGS += sk_connect_zero_addr
 TEST_GEN_PROGS += sk_so_peek_off
 TEST_PROGS += test_ingress_egress_chaining.sh
-TEST_GEN_PROGS += so_incoming_cpu
+TEST_GEN_PROGS += so_incoming_cpu so_rcvbuf
 TEST_PROGS += sctp_vrf.sh
 TEST_GEN_FILES += sctp_hello
 TEST_GEN_FILES += ip_local_port_range

@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates. */
+
+#include <limits.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "../kselftest_harness.h"
+
+static int udp_max_pages;
+
+static int udp_parse_pages(struct __test_metadata *_metadata,
+			   char *line, int *pages)
+{
+	int ret, unused;
+
+	if (strncmp(line, "UDP:", 4))
+		return -1;
+
+	ret = sscanf(line + 4, " inuse %d mem %d", &unused, pages);
+	ASSERT_EQ(2, ret);
+
+	return 0;
+}
+
+FIXTURE(so_rcvbuf)
+{
+	union {
+		struct sockaddr addr;
+		struct sockaddr_in addr4;
+		struct sockaddr_in6 addr6;
+	};
+	socklen_t addrlen;
+	int server;
+	int client;
+};
+
+FIXTURE_VARIANT(so_rcvbuf)
+{
+	int family;
+	int type;
+	int protocol;
+	int *max_pages;
+	int (*parse_pages)(struct __test_metadata *_metadata,
+			   char *line, int *pages);
+};
+
+FIXTURE_VARIANT_ADD(so_rcvbuf, udp_ipv4)
+{
+	.family = AF_INET,
+	.type = SOCK_DGRAM,
+	.protocol = 0,
+	.max_pages = &udp_max_pages,
+	.parse_pages = udp_parse_pages,
+};
+
+FIXTURE_VARIANT_ADD(so_rcvbuf, udp_ipv6)
+{
+	.family = AF_INET6,
+	.type = SOCK_DGRAM,
+	.protocol = 0,
+	.max_pages = &udp_max_pages,
+	.parse_pages = udp_parse_pages,
+};
+
+static int get_page_shift(void)
+{
+	int page_size = getpagesize();
+	int page_shift = 0;
+
+	while (page_size > 1) {
+		page_size >>= 1;
+		page_shift++;
+	}
+
+	return page_shift;
+}
+
+FIXTURE_SETUP(so_rcvbuf)
+{
+	self->addr.sa_family = variant->family;
+
+	if (variant->family == AF_INET)
+		self->addrlen = sizeof(struct sockaddr_in);
+	else
+		self->addrlen = sizeof(struct sockaddr_in6);
+
+	udp_max_pages = (INT_MAX + 1L) >> get_page_shift();
+}
+
+FIXTURE_TEARDOWN(so_rcvbuf)
+{
+}
+
+static void create_socketpair(struct __test_metadata *_metadata,
+			      FIXTURE_DATA(so_rcvbuf) *self,
+			      const FIXTURE_VARIANT(so_rcvbuf) *variant)
+{
+	int ret;
+
+	self->server = socket(variant->family, variant->type, variant->protocol);
+	ASSERT_NE(self->server, -1);
+
+	self->client = socket(variant->family, variant->type, variant->protocol);
+	ASSERT_NE(self->client, -1);
+
+	ret = bind(self->server, &self->addr, self->addrlen);
+	ASSERT_EQ(ret, 0);
+
+	ret = getsockname(self->server, &self->addr, &self->addrlen);
+	ASSERT_EQ(ret, 0);
+
+	ret = connect(self->client, &self->addr, self->addrlen);
+	ASSERT_EQ(ret, 0);
+}
+
+static int get_prot_pages(struct __test_metadata *_metadata,
+			  const FIXTURE_VARIANT(so_rcvbuf) *variant)
+{
+	char *line = NULL;
+	size_t unused;
+	int pages = 0;
+	FILE *f;
+
+	f = fopen("/proc/net/sockstat", "r");
+	ASSERT_NE(NULL, f);
+
+	while (getline(&line, &unused, f) != -1)
+		if (!variant->parse_pages(_metadata, line, &pages))
+			break;
+
+	free(line);
+	fclose(f);
+
+	return pages;
+}
+
+TEST_F(so_rcvbuf, rmem_max)
+{
+	int ret, i, pages;
+	char buf[16] = {};
+
+	create_socketpair(_metadata, self, variant);
+
+	ret = setsockopt(self->server, SOL_SOCKET, SO_RCVBUFFORCE,
+			 &(int){INT_MAX}, sizeof(int));
+	ASSERT_EQ(ret, 0);
+
+	pages = get_prot_pages(_metadata, variant);
+	ASSERT_EQ(pages, 0);
+
+	for (i = 1; ; i++) {
+		ret = send(self->client, buf, sizeof(buf), 0);
+		ASSERT_EQ(ret, sizeof(buf));
+
+		/* Make sure we don't stop at pages == (INT_MAX >> PAGE_SHIFT)
+		 * in case ASSERT_LE() should fail.
+		 */
+		if (i % 10000 == 0) {
+			pages = get_prot_pages(_metadata, variant);
+
+			/* sk_rmem_alloc wrapped around by >PAGE_SIZE ? */
+			ASSERT_LE(pages, *variant->max_pages);
+
+			if (pages == *variant->max_pages)
+				break;
+		}
+	}
+
+	TH_LOG("max_pages: %d", pages);
+
+	close(self->client);
+	close(self->server);
+
+	/* Give RCU a chance to call udp_destruct_common() */
+	for (i = 0; i < 30; i++) {
+		sleep(1);
+
+		pages = get_prot_pages(_metadata, variant);
+		if (!pages)
+			break;
+	}
+
+	ASSERT_EQ(pages, 0);
+}
+
+TEST_HARNESS_MAIN