[bpf-next,v3,5/5] bpf/selftests: add selftest for bpf_smc_ops

Commit Message

D. Wythe Dec. 18, 2024, 2:44 a.m. UTC

This tests introduces a tiny smc_ops for filtering SMC connections based on
IP pairs, and also adds a realistic topology model to verify this ops.

Also, we can only use SMC loopback under CI test, so an
additional configuration needs to be enabled.

Follow the steps below to run this test.

make -C tools/testing/selftests/bpf
cd tools/testing/selftests/bpf
sudo ./test_progs -t smc

Results shows:
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: D. Wythe <[e-mail]>
---
 tools/testing/selftests/bpf/config            |   4 +
 .../selftests/bpf/prog_tests/test_bpf_smc.c   | 535 ++++++++++++++++++
 tools/testing/selftests/bpf/progs/bpf_smc.c   | 109 ++++
 3 files changed, 648 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/test_bpf_smc.c
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_smc.c

Comments

Martin KaFai Lau Dec. 19, 2024, 10:59 p.m. UTC | #1

On 12/17/24 6:44 PM, D. Wythe wrote:
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include "vmlinux.h"
> +
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +#include "bpf_tracing_net.h"
> +
> +char _license[] SEC("license") = "GPL";
> +
> +struct smc_sock {

I suspect this should be "smc_sock___local". Otherwise, it can't compile if the 
same type is found in vmlinux.h.

I only looked at the high level of prog_tests/test_bpf_smc.c. A few comments,

Try to reuse the helpers in network_helpers.c and test_progs.c, e.g. netns 
creation helpers, start_server, ...etc. There are many examples in 
selftests/bpf/prog_tests using them.

I see 1s timeout everywhere. BPF CI could be slow some time. Please consider how 
reliable the multi-thread test is. If the test is too flaky, it will be put in 
the selftests/bpf/DENYLIST.

> +	struct sock sk;
> +	struct smc_sock *listen_smc;
> +	bool use_fallback;
> +} __attribute__((preserve_access_index));
> +

D. Wythe Dec. 23, 2024, 2:03 a.m. UTC | #2

On Thu, Dec 19, 2024 at 02:59:15PM -0800, Martin KaFai Lau wrote:
> On 12/17/24 6:44 PM, D. Wythe wrote:
> >+// SPDX-License-Identifier: GPL-2.0
> >+
> >+#include "vmlinux.h"
> >+
> >+#include <bpf/bpf_helpers.h>
> >+#include <bpf/bpf_tracing.h>
> >+#include "bpf_tracing_net.h"
> >+
> >+char _license[] SEC("license") = "GPL";
> >+
> >+struct smc_sock {
> 
> I suspect this should be "smc_sock___local". Otherwise, it can't
> compile if the same type is found in vmlinux.h.
> 

Yes, it has been changed to ___local.

> I only looked at the high level of prog_tests/test_bpf_smc.c. A few comments,
> 
> Try to reuse the helpers in network_helpers.c and test_progs.c, e.g.
> netns creation helpers, start_server, ...etc. There are many
> examples in selftests/bpf/prog_tests using them.
> 
> I see 1s timeout everywhere. BPF CI could be slow some time. Please
> consider how reliable the multi-thread test is. If the test is too
> flaky, it will be put in the selftests/bpf/DENYLIST.
> 

Got it, I will remove those timeouts in the next version. I have tried
reusing these helpers, it is very convenient and makes code more
concise!

D. Wythe

> >+	struct sock sk;
> >+	struct smc_sock *listen_smc;
> >+	bool use_fallback;
> >+} __attribute__((preserve_access_index));
> >+

Patch

diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index c378d5d07e02..79248eb04ec4 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -113,3 +113,7 @@  CONFIG_XDP_SOCKETS=y
 CONFIG_XFRM_INTERFACE=y
 CONFIG_TCP_CONG_DCTCP=y
 CONFIG_TCP_CONG_BBR=y
+CONFIG_INFINIBAND=m
+CONFIG_SMC=m
+CONFIG_SMC_OPS=y
+CONFIG_SMC_LO=y
\ No newline at end of file
diff --git a/tools/testing/selftests/bpf/prog_tests/test_bpf_smc.c b/tools/testing/selftests/bpf/prog_tests/test_bpf_smc.c
new file mode 100644
index 000000000000..4b7c43badc06
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/test_bpf_smc.c
@@ -0,0 +1,535 @@ 
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <linux/genetlink.h>
+#include "bpf_smc.skel.h"
+
+#ifndef IPPROTO_SMC
+#define IPPROTO_SMC 256
+#endif
+
+#define CLIENT_IP			"127.0.0.1"
+#define SERVER_IP			"127.0.1.0"
+#define SERVER_IP_VIA_RISK_PATH	"127.0.2.0"
+
+#define SERVICE_1	11234
+#define SERVICE_2	22345
+#define SERVICE_3	33456
+
+enum {
+	SMC_NETLINK_ADD_UEID = 10,
+	SMC_NETLINK_REMOVE_UEID
+};
+
+enum {
+	SMC_NLA_EID_TABLE_UNSPEC,
+	SMC_NLA_EID_TABLE_ENTRY,    /* string */
+};
+
+struct smc_strat_ip_key {
+	__u32  sip;
+	__u32  dip;
+};
+
+struct smc_strat_ip_value {
+	__u8	mode;
+};
+
+struct msgtemplate {
+	struct nlmsghdr n;
+	struct genlmsghdr g;
+	char buf[1024];
+};
+
+#define GENLMSG_DATA(glh)	((void *)(NLMSG_DATA(glh) + GENL_HDRLEN))
+#define GENLMSG_PAYLOAD(glh)	(NLMSG_PAYLOAD(glh, 0) - GENL_HDRLEN)
+#define NLA_DATA(na)		((void *)((char *)(na) + NLA_HDRLEN))
+#define NLA_PAYLOAD(len)	((len) - NLA_HDRLEN)
+
+#define MAX_MSG_SIZE		1024
+
+#define SMC_GENL_FAMILY_NAME	"SMC_GEN_NETLINK"
+#define SMC_BPFTEST_UEID	"SMC-BPFTEST-UEID"
+
+static uint16_t smc_nl_family_id = -1;
+static bool running = true;
+
+static int send_cmd(int fd, __u16 nlmsg_type, __u32 nlmsg_pid, __u16 nlmsg_flags,
+			__u8 genl_cmd, __u16 nla_type,
+			void *nla_data, int nla_len)
+{
+	struct nlattr *na;
+	struct sockaddr_nl nladdr;
+	int r, buflen;
+	char *buf;
+
+	struct msgtemplate msg = {0};
+
+	msg.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
+	msg.n.nlmsg_type = nlmsg_type;
+	msg.n.nlmsg_flags = nlmsg_flags;
+	msg.n.nlmsg_seq = 0;
+	msg.n.nlmsg_pid = nlmsg_pid;
+	msg.g.cmd = genl_cmd;
+	msg.g.version = 1;
+	na = (struct nlattr *) GENLMSG_DATA(&msg);
+	na->nla_type = nla_type;
+	na->nla_len = nla_len + 1 + NLA_HDRLEN;
+	memcpy(NLA_DATA(na), nla_data, nla_len);
+	msg.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);
+
+	buf = (char *) &msg;
+	buflen = msg.n.nlmsg_len;
+	memset(&nladdr, 0, sizeof(nladdr));
+	nladdr.nl_family = AF_NETLINK;
+
+	while ((r = sendto(fd, buf, buflen, 0, (struct sockaddr *) &nladdr,
+			   sizeof(nladdr))) < buflen) {
+		if (r > 0) {
+			buf += r;
+			buflen -= r;
+		} else if (errno != EAGAIN)
+			return -1;
+		}
+	return 0;
+}
+
+static bool load_smc_module(void)
+{
+	int fd = socket(AF_INET, SOCK_STREAM, IPPROTO_SMC);
+
+	if (!ASSERT_GE(fd, 0, "create ipproto_smc"))
+		return false;
+	close(fd);
+	return true;
+}
+
+static bool create_netns(void)
+{
+	if (!ASSERT_OK(unshare(CLONE_NEWNET), "create netns"))
+		return false;
+
+	if (!ASSERT_OK(system("ip addr add 127.0.1.0/8 dev lo"), "add server node"))
+		return false;
+
+	if (!ASSERT_OK(system("ip addr add 127.0.2.0/8 dev lo"), "server via risk path"))
+		return false;
+
+	if (!ASSERT_OK(system("ip link set dev lo up"), "bring up lo"))
+		return false;
+
+	return true;
+}
+
+static bool get_smc_nl_family_id(void)
+{
+	struct sockaddr_nl nl_src;
+	struct msgtemplate msg;
+	struct nlattr *nl;
+	int fd, ret;
+	pid_t pid;
+
+	fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC);
+	if (!ASSERT_GT(fd, 0, "nl_family socket"))
+		return false;
+
+	pid = getpid();
+
+	memset(&nl_src, 0, sizeof(nl_src));
+	nl_src.nl_family = AF_NETLINK;
+	nl_src.nl_pid = pid;
+
+	ret = bind(fd, (struct sockaddr *) &nl_src, sizeof(nl_src));
+	if (!ASSERT_GE(ret, 0, "nl_family bind"))
+		goto fail;
+
+	ret = send_cmd(fd, GENL_ID_CTRL, pid,
+		       NLM_F_REQUEST, CTRL_CMD_GETFAMILY,
+		       CTRL_ATTR_FAMILY_NAME, (void *)SMC_GENL_FAMILY_NAME,
+		       strlen(SMC_GENL_FAMILY_NAME));
+	if (!ASSERT_EQ(ret, 0, "nl_family query"))
+		goto fail;
+
+	ret = recv(fd, &msg, sizeof(msg), 0);
+	if (!ASSERT_FALSE(msg.n.nlmsg_type == NLMSG_ERROR || (ret < 0) ||
+			  !NLMSG_OK((&msg.n), ret), "nl_family response"))
+		goto fail;
+
+	nl = (struct nlattr *) GENLMSG_DATA(&msg);
+	nl = (struct nlattr *) ((char *) nl + NLA_ALIGN(nl->nla_len));
+	if (!ASSERT_EQ(nl->nla_type, CTRL_ATTR_FAMILY_ID, "nl_family nla type"))
+		goto fail;
+
+	smc_nl_family_id = *(uint16_t *) NLA_DATA(nl);
+	close(fd);
+	return true;
+fail:
+	close(fd);
+	return false;
+}
+
+static bool smc_ueid(int op)
+{
+	struct sockaddr_nl nl_src;
+	struct msgtemplate msg;
+	struct nlmsgerr *err;
+	char test_ueid[32];
+	int fd, ret;
+	pid_t pid;
+
+	/* UEID required */
+	memset(test_ueid, '\x20', sizeof(test_ueid));
+	memcpy(test_ueid, SMC_BPFTEST_UEID, strlen(SMC_BPFTEST_UEID));
+	fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC);
+	if (!ASSERT_GT(fd, 0, "ueid socket"))
+		return false;
+
+	pid = getpid();
+	memset(&nl_src, 0, sizeof(nl_src));
+	nl_src.nl_family = AF_NETLINK;
+	nl_src.nl_pid = pid;
+
+	ret = bind(fd, (struct sockaddr *) &nl_src, sizeof(nl_src));
+	if (!ASSERT_GE(ret, 0, "ueid bind"))
+		goto fail;
+
+	ret = send_cmd(fd, smc_nl_family_id, pid,
+		       NLM_F_REQUEST | NLM_F_ACK, op, SMC_NLA_EID_TABLE_ENTRY,
+	(void *)test_ueid, sizeof(test_ueid));
+	if (!ASSERT_EQ(ret, 0, "ueid cmd"))
+		goto fail;
+
+	ret = recv(fd, &msg, sizeof(msg), 0);
+	if (!ASSERT_FALSE((ret < 0) || !NLMSG_OK((&msg.n), ret), "ueid response"))
+		goto fail;
+
+	if (msg.n.nlmsg_type == NLMSG_ERROR) {
+		err = NLMSG_DATA(&msg);
+		switch (op) {
+		case SMC_NETLINK_REMOVE_UEID:
+			if (!ASSERT_FALSE((err->error && err->error != -ENOENT), "ueid remove"))
+				goto fail;
+			break;
+		case SMC_NETLINK_ADD_UEID:
+			if (!ASSERT_EQ(err->error, 0, "ueid add"))
+				goto fail;
+			break;
+		default:
+			break;
+		}
+	}
+	close(fd);
+	return true;
+fail:
+	close(fd);
+	return false;
+}
+
+static bool setup_smc(void)
+{
+	/* required smc module was loaded */
+	if (!load_smc_module())
+		return false;
+
+	/* setup new netns to avoid make impact on other tests */
+	if (!create_netns())
+		return false;
+
+	/* get smc nl id */
+	if (!get_smc_nl_family_id())
+		return false;
+
+	/* clear and add ueid for bpftest */
+	(void) smc_ueid(SMC_NETLINK_REMOVE_UEID);
+	/* smc-loopback required ueid */
+	if (!smc_ueid(SMC_NETLINK_ADD_UEID))
+		return false;
+
+	return true;
+}
+
+static void cleanup_smc(void)
+{
+	(void) smc_ueid(SMC_NETLINK_REMOVE_UEID);
+}
+
+static pthread_t create_service(const char *ip, int port, void *(*handler) (void *))
+{
+	struct sockaddr_in servaddr;
+	pthread_t th;
+	int server, rc;
+
+	server = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (!server)
+		return (pthread_t)0;
+
+	servaddr.sin_family = AF_INET;
+	servaddr.sin_port = htons(port);
+	servaddr.sin_addr.s_addr = inet_addr(ip);
+
+	rc = bind(server, &servaddr, sizeof(servaddr));
+	if (!ASSERT_EQ(rc, 0, "server bind"))
+		goto fail;
+
+	rc = listen(server, 1024);
+	if (!ASSERT_EQ(rc, 0, "server listen"))
+		goto fail;
+
+	rc = pthread_create(&th, NULL, handler, (void *)(intptr_t)server);
+	if (!ASSERT_EQ(rc, 0, "pthread_create"))
+		goto fail;
+
+	return th;
+fail:
+	close(server);
+	return (pthread_t)0;
+}
+
+static bool set_sock_timeout(int fd, int timeout_sec)
+{
+	struct timeval timeout = { .tv_sec = timeout_sec, };
+	int rc;
+
+	rc = setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &timeout, sizeof(timeout));
+	if (rc != 0)
+		return false;
+
+	rc = setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout));
+	if (rc != 0)
+		return false;
+
+	return true;
+}
+
+static void req_once(const char *local, const char *remote, int port)
+{
+	struct sockaddr_in localaddr, servaddr;
+	int client, rc, dummy = 0;
+
+	client = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+	if (!client)
+		return;
+
+	/* 1 sec timeout for rcv and snd(connect) */
+	if (!ASSERT_TRUE(set_sock_timeout(client, 1), "client sockopt"))
+		goto fail;
+
+	localaddr.sin_family = AF_INET;
+	localaddr.sin_port = htons(0);
+	localaddr.sin_addr.s_addr = inet_addr(local);
+
+	rc = bind(client, &localaddr, sizeof(localaddr));
+	if (!ASSERT_EQ(rc, 0, "client bind"))
+		goto fail;
+
+	servaddr.sin_family = AF_INET;
+	servaddr.sin_port = htons(port);
+	servaddr.sin_addr.s_addr = inet_addr(remote);
+
+	rc = connect(client, &servaddr, sizeof(servaddr));
+	if (!ASSERT_EQ(rc, 0, "client connect"))
+		goto fail;
+
+	rc = send(client, &dummy, sizeof(dummy), 0);
+	if (!ASSERT_EQ(rc, sizeof(dummy), "client query"))
+		goto fail;
+
+	rc = recv(client, &dummy, sizeof(dummy), 0);
+	if (!ASSERT_EQ(rc, sizeof(dummy), "client response"))
+		goto fail;
+
+	close(client);
+	return;
+fail:
+	close(client);
+}
+
+static void *service1(void *ctx)
+{
+	int fd = (int)(intptr_t)ctx;
+	int cli, rc, dummy;
+
+	/* 1 sec for accept timeout */
+	if (!set_sock_timeout(fd, 1))
+		goto finish;
+
+	while (running) {
+		cli = accept(fd, NULL, NULL);
+		if (cli < 0)
+			continue;
+
+		if (!set_sock_timeout(cli, 1))
+			goto skip;
+
+		rc = recv(cli, &dummy, sizeof(dummy), 0);
+		if (rc != sizeof(dummy))
+			goto skip;
+
+		/* service1 send a request to service2 */
+		req_once(SERVER_IP, SERVER_IP, SERVICE_2);
+
+		/* then echo dummy back to cli */
+		rc = send(cli, &dummy, sizeof(dummy), 0);
+		if (rc != sizeof(dummy))
+			goto skip;
+skip:
+		close(cli);
+	}
+finish:
+	close(fd);
+	return NULL;
+}
+
+static void *service2(void *ctx)
+{
+	int fd = (int)(intptr_t)ctx;
+	int cli, rc, dummy;
+
+	/* 1 sec for accept timeout */
+	if (!set_sock_timeout(fd, 1))
+		goto finish;
+
+	while (running) {
+		cli = accept(fd, NULL, NULL);
+		if (cli < 0)
+			continue;
+
+		if (!set_sock_timeout(cli, 1))
+			goto skip;
+
+		rc = recv(cli, &dummy, sizeof(dummy), 0);
+		if (rc != sizeof(dummy))
+			goto skip;
+
+		/* then echo dummy back to cli */
+		rc = send(cli, &dummy, sizeof(dummy), 0);
+		if (rc != sizeof(dummy))
+			goto skip;
+skip:
+		close(cli);
+	}
+finish:
+	close(fd);
+	return NULL;
+}
+
+static void *service3(void *ctx)
+{
+	return service2(ctx);
+}
+
+static void block_link(int map_fd, const char *src, const char *dst)
+{
+	struct smc_strat_ip_value val = { .mode = /* block */ 0 };
+	struct smc_strat_ip_key key = {
+		.sip = inet_addr(src),
+		.dip = inet_addr(dst),
+	};
+
+	bpf_map_update_elem(map_fd, &key, &val, BPF_ANY);
+}
+
+/*
+ * This test describes a real-life service topology as follows:
+ *
+ *                             +-------------> service_1
+ *            link1            |                     |
+ *   +--------------------> server                   |  link 2
+ *   |                         |                     V
+ *   |                         +-------------> service_2
+ *   |        link 3
+ *  client -------------------> server_via_unsafe_path -> service_3
+ *
+ * Among them，
+ * 1. link-1 is very suitable for using SMC.
+ * 2. link-2 is not suitable for using SMC, because the mode of this link is kind of
+ *     short-link services.
+ * 3. link-3 is also not suitable for using SMC, because the RDMA link is unavailable and
+ *     needs to go through a long timeout before it can fallback to TCP.
+ *
+ * To achieve this goal, we use a customized SMC ip strategy via smc_ops.
+ */
+static void test_topo(void)
+{
+	pthread_t service_1, service_2, service_3;
+	struct bpf_smc *skel;
+	int rc, map_fd;
+
+	skel = bpf_smc__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "bpf_smc__open_and_load"))
+		return;
+
+	rc = bpf_smc__attach(skel);
+	if (!ASSERT_EQ(rc, 0, "bpf_smc__attach"))
+		goto fail;
+
+	map_fd = bpf_map__fd(skel->maps.smc_strats_ip);
+	if (!ASSERT_GT(map_fd, 0, "bpf_map__fd"))
+		goto fail;
+
+	/* Mock the process of transparent replacement, since we will modify protocol
+	 * to ipproto_smc accropding to it via fmod_ret/update_socket_protocol.
+	 */
+	system("sysctl -w net.smc.ops=linkcheck");
+
+	/* Configure ip strat */
+	block_link(map_fd, CLIENT_IP, SERVER_IP_VIA_RISK_PATH);
+	block_link(map_fd, SERVER_IP, SERVER_IP);
+	close(map_fd);
+
+	/* Load service */
+	service_1 = create_service(SERVER_IP, SERVICE_1, service1);
+	if (!ASSERT_NEQ(service_1, (pthread_t)0, "create service_1"))
+		goto fail;
+
+	service_2 = create_service(SERVER_IP, SERVICE_2, service2);
+	if (!ASSERT_NEQ(service_2, (pthread_t)0, "create service_2")) {
+		running = false;
+		goto fail_service2;
+	}
+
+	service_3 = create_service(SERVER_IP_VIA_RISK_PATH, SERVICE_3, service3);
+	if (!ASSERT_NEQ(service_3, (pthread_t)0, "create service_3")) {
+		running = false;
+		goto fail_service3;
+	}
+
+	/* Run client*/
+	req_once(CLIENT_IP, SERVER_IP, SERVICE_1);
+
+	ASSERT_EQ(skel->bss->smc_cnt, 2, "smc count");
+	ASSERT_EQ(skel->bss->fallback_cnt, 1, "fallback count");
+
+	req_once(CLIENT_IP, SERVER_IP, SERVICE_2);
+
+	ASSERT_EQ(skel->bss->smc_cnt, 3, "smc count");
+	ASSERT_EQ(skel->bss->fallback_cnt, 1, "fallback count");
+
+	req_once(CLIENT_IP, SERVER_IP_VIA_RISK_PATH, SERVICE_3);
+
+	ASSERT_EQ(skel->bss->smc_cnt, 4, "smc count");
+	ASSERT_EQ(skel->bss->fallback_cnt, 2, "fallback count");
+
+	/* We have set a timeout of 1 second for each accept */
+	running = false;
+	pthread_join(service_3, NULL);
+fail_service3:
+	pthread_join(service_2, NULL);
+fail_service2:
+	pthread_join(service_1, NULL);
+fail:
+	bpf_smc__destroy(skel);
+}
+
+void test_bpf_smc(void)
+{
+	if (!setup_smc()) {
+		printf("setup for smc test failed, test SKIP:\n");
+		test__skip();
+		return;
+	}
+
+	if (test__start_subtest("topo"))
+		test_topo();
+
+	cleanup_smc();
+}
diff --git a/tools/testing/selftests/bpf/progs/bpf_smc.c b/tools/testing/selftests/bpf/progs/bpf_smc.c
new file mode 100644
index 000000000000..3ef99da662a1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_smc.c
@@ -0,0 +1,109 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_tracing_net.h"
+
+char _license[] SEC("license") = "GPL";
+
+struct smc_sock {
+	struct sock sk;
+	struct smc_sock *listen_smc;
+	bool use_fallback;
+} __attribute__((preserve_access_index));
+
+int smc_cnt = 0;
+int fallback_cnt = 0;
+
+SEC("fentry/smc_listen_work")
+int BPF_PROG(bpf_smc_listen_work)
+{
+	smc_cnt++;
+	return 0;
+}
+
+SEC("fentry/smc_switch_to_fallback")
+int BPF_PROG(bpf_smc_switch_to_fallback, struct smc_sock *smc)
+{
+	/* only count from one side (client) */
+	if (smc && !smc->listen_smc)
+		fallback_cnt++;
+	return 0;
+}
+
+/* go with default value if no strat was found */
+bool default_ip_strat_value = true;
+
+struct smc_strat_ip_key {
+	__u32	sip;
+	__u32	dip;
+};
+
+struct smc_strat_ip_value {
+	__u8	mode;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(struct smc_strat_ip_key));
+	__uint(value_size, sizeof(struct smc_strat_ip_value));
+	__uint(max_entries, 128);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+} smc_strats_ip SEC(".maps");
+
+static bool smc_check_ip(__u32 src, __u32 dst)
+{
+	struct smc_strat_ip_value *value;
+	struct smc_strat_ip_key key = {
+		.sip = src,
+		.dip = dst,
+	};
+
+	value = bpf_map_lookup_elem(&smc_strats_ip, &key);
+	return value ? value->mode : default_ip_strat_value;
+}
+
+SEC("fmod_ret/update_socket_protocol")
+int BPF_PROG(smc_run, int family, int type, int protocol)
+{
+	struct task_struct *task;
+
+	if (family != AF_INET && family != AF_INET6)
+		return protocol;
+
+	if ((type & 0xf) != SOCK_STREAM)
+		return protocol;
+
+	if (protocol != 0 && protocol != IPPROTO_TCP)
+		return protocol;
+
+	task = bpf_get_current_task_btf();
+	/* Prevent from affecting other tests */
+	if (!task || !task->nsproxy->net_ns->smc.ops)
+		return protocol;
+
+	return IPPROTO_SMC;
+}
+
+SEC("struct_ops/bpf_smc_set_tcp_option_cond")
+int BPF_PROG(bpf_smc_set_tcp_option_cond, const struct tcp_sock *tp, struct inet_request_sock *ireq)
+{
+	return smc_check_ip(ireq->req.__req_common.skc_daddr,
+			    ireq->req.__req_common.skc_rcv_saddr);
+}
+
+SEC("struct_ops/bpf_smc_set_tcp_option")
+int BPF_PROG(bpf_smc_set_tcp_option, struct tcp_sock *tp)
+{
+	return smc_check_ip(tp->inet_conn.icsk_inet.sk.__sk_common.skc_rcv_saddr,
+			    tp->inet_conn.icsk_inet.sk.__sk_common.skc_daddr);
+}
+
+SEC(".struct_ops.link")
+struct smc_ops  linkcheck = {
+	.name			= "linkcheck",
+	.set_option		= (void *) bpf_smc_set_tcp_option,
+	.set_option_cond	= (void *) bpf_smc_set_tcp_option_cond,
+};