Merge branch 'bpf: Allow bpf tcp iter to do bpf_(get|set)sockopt'

Martin KaFai says:

====================

This set is to allow bpf tcp iter to call bpf_(get|set)sockopt.

With bpf-tcp-cc, new algo rollout happens more often.  Instead of
restarting the applications to pick up the new tcp-cc, this set
allows the bpf tcp iter to call bpf_(get|set)sockopt(TCP_CONGESTION).
It is not limited to TCP_CONGESTION, the bpf tcp iter can call
bpf_(get|set)sockopt() with other options.  The bpf tcp iter can read
into all the fields of a tcp_sock, so there is a lot of flexibility
to select the desired sk to do setsockopt(), e.g. it can test for
TCP_LISTEN only and leave the established connections untouched,
or check the addr/port, or check the current tcp-cc name, ...etc.

Patch 1-4 are some cleanup and prep work in the tcp and bpf seq_file.

Patch 5 is to have the tcp seq_file iterate on the
port+addr lhash2 instead of the port only listening_hash.

Patch 6 is to have the bpf tcp iter doing batching which
then allows lock_sock.  lock_sock is needed for setsockopt.

Patch 7 allows the bpf tcp iter to call bpf_(get|set)sockopt.

v2:
- Use __GFP_NOWARN in patch 6
- Add bpf_getsockopt() in patch 7 to give a symmetrical user experience.
  selftest in patch 8 is changed to also cover bpf_getsockopt().
- Remove CAP_NET_ADMIN check in patch 7. Tracing bpf prog has already
  required CAP_SYS_ADMIN or CAP_PERFMON.
- Move some def macros to bpf_tracing_net.h in patch 8
====================
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

include/linux/bpf.h

@@ -1442,6 +1442,9 @@ typedef void (*bpf_iter_show_fdinfo_t) (const struct bpf_iter_aux_info *aux,
 					struct seq_file *seq);
 typedef int (*bpf_iter_fill_link_info_t)(const struct bpf_iter_aux_info *aux,
 					 struct bpf_link_info *info);
+typedef const struct bpf_func_proto *
+(*bpf_iter_get_func_proto_t)(enum bpf_func_id func_id,
+			     const struct bpf_prog *prog);
 
 enum bpf_iter_feature {
 	BPF_ITER_RESCHED	= BIT(0),
@@ -1454,6 +1457,7 @@ struct bpf_iter_reg {
 	bpf_iter_detach_target_t detach_target;
 	bpf_iter_show_fdinfo_t show_fdinfo;
 	bpf_iter_fill_link_info_t fill_link_info;
+	bpf_iter_get_func_proto_t get_func_proto;
 	u32 ctx_arg_info_size;
 	u32 feature;
 	struct bpf_ctx_arg_aux ctx_arg_info[BPF_ITER_CTX_ARG_MAX];
@@ -1476,6 +1480,8 @@ struct bpf_iter__bpf_map_elem {
 int bpf_iter_reg_target(const struct bpf_iter_reg *reg_info);
 void bpf_iter_unreg_target(const struct bpf_iter_reg *reg_info);
 bool bpf_iter_prog_supported(struct bpf_prog *prog);
+const struct bpf_func_proto *
+bpf_iter_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog);
 int bpf_iter_link_attach(const union bpf_attr *attr, bpfptr_t uattr, struct bpf_prog *prog);
 int bpf_iter_new_fd(struct bpf_link *link);
 bool bpf_link_is_iter(struct bpf_link *link);
@@ -2050,6 +2056,8 @@ extern const struct bpf_func_proto bpf_task_storage_get_proto;
 extern const struct bpf_func_proto bpf_task_storage_delete_proto;
 extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
 extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
+extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
+extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
 
 const struct bpf_func_proto *bpf_tracing_func_proto(
 	enum bpf_func_id func_id, const struct bpf_prog *prog);

include/net/inet_hashtables.h

@@ -160,6 +160,12 @@ struct inet_hashinfo {
 					____cacheline_aligned_in_smp;
 };
 
+#define inet_lhash2_for_each_icsk_continue(__icsk) \
+	hlist_for_each_entry_continue(__icsk, icsk_listen_portaddr_node)
+
+#define inet_lhash2_for_each_icsk(__icsk, list) \
+	hlist_for_each_entry(__icsk, list, icsk_listen_portaddr_node)
+
 #define inet_lhash2_for_each_icsk_rcu(__icsk, list) \
 	hlist_for_each_entry_rcu(__icsk, list, icsk_listen_portaddr_node)
 

include/net/tcp.h

@@ -1959,7 +1959,6 @@ struct tcp_iter_state {
 	struct seq_net_private	p;
 	enum tcp_seq_states	state;
 	struct sock		*syn_wait_sk;
-	struct tcp_seq_afinfo	*bpf_seq_afinfo;
 	int			bucket, offset, sbucket, num;
 	loff_t			last_pos;
 };

kernel/bpf/bpf_iter.c

@@ -360,6 +360,28 @@ bool bpf_iter_prog_supported(struct bpf_prog *prog)
 	return supported;
 }
 
+const struct bpf_func_proto *
+bpf_iter_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	const struct bpf_iter_target_info *tinfo;
+	const struct bpf_func_proto *fn = NULL;
+
+	mutex_lock(&targets_mutex);
+	list_for_each_entry(tinfo, &targets, list) {
+		if (tinfo->btf_id == prog->aux->attach_btf_id) {
+			const struct bpf_iter_reg *reg_info;
+
+			reg_info = tinfo->reg_info;
+			if (reg_info->get_func_proto)
+				fn = reg_info->get_func_proto(func_id, prog);
+			break;
+		}
+	}
+	mutex_unlock(&targets_mutex);
+
+	return fn;
+}
+
 static void bpf_iter_link_release(struct bpf_link *link)
 {
 	struct bpf_iter_link *iter_link =

kernel/trace/bpf_trace.c

@@ -1461,6 +1461,8 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 const struct bpf_func_proto *
 tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
+	const struct bpf_func_proto *fn;
+
 	switch (func_id) {
 #ifdef CONFIG_NET
 	case BPF_FUNC_skb_output:
@@ -1501,7 +1503,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_d_path:
 		return &bpf_d_path_proto;
 	default:
-		return raw_tp_prog_func_proto(func_id, prog);
+		fn = raw_tp_prog_func_proto(func_id, prog);
+		if (!fn && prog->expected_attach_type == BPF_TRACE_ITER)
+			fn = bpf_iter_get_func_proto(func_id, prog);
+		return fn;
 	}
 }
 

net/core/filter.c

@@ -5016,6 +5016,40 @@ static int _bpf_getsockopt(struct sock *sk, int level, int optname,
 	return -EINVAL;
 }
 
+BPF_CALL_5(bpf_sk_setsockopt, struct sock *, sk, int, level,
+	   int, optname, char *, optval, int, optlen)
+{
+	return _bpf_setsockopt(sk, level, optname, optval, optlen);
+}
+
+const struct bpf_func_proto bpf_sk_setsockopt_proto = {
+	.func		= bpf_sk_setsockopt,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_BTF_ID_SOCK_COMMON,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_PTR_TO_MEM,
+	.arg5_type	= ARG_CONST_SIZE,
+};
+
+BPF_CALL_5(bpf_sk_getsockopt, struct sock *, sk, int, level,
+	   int, optname, char *, optval, int, optlen)
+{
+	return _bpf_getsockopt(sk, level, optname, optval, optlen);
+}
+
+const struct bpf_func_proto bpf_sk_getsockopt_proto = {
+	.func		= bpf_sk_getsockopt,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_BTF_ID_SOCK_COMMON,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+	.arg4_type	= ARG_PTR_TO_UNINIT_MEM,
+	.arg5_type	= ARG_CONST_SIZE,
+};
+
 BPF_CALL_5(bpf_sock_addr_setsockopt, struct bpf_sock_addr_kern *, ctx,
 	   int, level, int, optname, char *, optval, int, optlen)
 {

tools/testing/selftests/bpf/network_helpers.c

@@ -66,17 +66,13 @@ int settimeo(int fd, int timeout_ms)
 
 #define save_errno_close(fd) ({ int __save = errno; close(fd); errno = __save; })
 
-int start_server(int family, int type, const char *addr_str, __u16 port,
-		 int timeout_ms)
+static int __start_server(int type, const struct sockaddr *addr,
+			  socklen_t addrlen, int timeout_ms, bool reuseport)
 {
-	struct sockaddr_storage addr = {};
-	socklen_t len;
+	int on = 1;
 	int fd;
 
-	if (make_sockaddr(family, addr_str, port, &addr, &len))
-		return -1;
-
-	fd = socket(family, type, 0);
+	fd = socket(addr->sa_family, type, 0);
 	if (fd < 0) {
 		log_err("Failed to create server socket");
 		return -1;
@@ -85,7 +81,13 @@ int start_server(int family, int type, const char *addr_str, __u16 port,
 	if (settimeo(fd, timeout_ms))
 		goto error_close;
 
-	if (bind(fd, (const struct sockaddr *)&addr, len) < 0) {
+	if (reuseport &&
+	    setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &on, sizeof(on))) {
+		log_err("Failed to set SO_REUSEPORT");
+		return -1;
+	}
+
+	if (bind(fd, addr, addrlen) < 0) {
 		log_err("Failed to bind socket");
 		goto error_close;
 	}
@@ -104,6 +106,69 @@ int start_server(int family, int type, const char *addr_str, __u16 port,
 	return -1;
 }
 
+int start_server(int family, int type, const char *addr_str, __u16 port,
+		 int timeout_ms)
+{
+	struct sockaddr_storage addr;
+	socklen_t addrlen;
+
+	if (make_sockaddr(family, addr_str, port, &addr, &addrlen))
+		return -1;
+
+	return __start_server(type, (struct sockaddr *)&addr,
+			      addrlen, timeout_ms, false);
+}
+
+int *start_reuseport_server(int family, int type, const char *addr_str,
+			    __u16 port, int timeout_ms, unsigned int nr_listens)
+{
+	struct sockaddr_storage addr;
+	unsigned int nr_fds = 0;
+	socklen_t addrlen;
+	int *fds;
+
+	if (!nr_listens)
+		return NULL;
+
+	if (make_sockaddr(family, addr_str, port, &addr, &addrlen))
+		return NULL;
+
+	fds = malloc(sizeof(*fds) * nr_listens);
+	if (!fds)
+		return NULL;
+
+	fds[0] = __start_server(type, (struct sockaddr *)&addr, addrlen,
+				timeout_ms, true);
+	if (fds[0] == -1)
+		goto close_fds;
+	nr_fds = 1;
+
+	if (getsockname(fds[0], (struct sockaddr *)&addr, &addrlen))
+		goto close_fds;
+
+	for (; nr_fds < nr_listens; nr_fds++) {
+		fds[nr_fds] = __start_server(type, (struct sockaddr *)&addr,
+					     addrlen, timeout_ms, true);
+		if (fds[nr_fds] == -1)
+			goto close_fds;
+	}
+
+	return fds;
+
+close_fds:
+	free_fds(fds, nr_fds);
+	return NULL;
+}
+
+void free_fds(int *fds, unsigned int nr_close_fds)
+{
+	if (fds) {
+		while (nr_close_fds)
+			close(fds[--nr_close_fds]);
+		free(fds);
+	}
+}
+
 int fastopen_connect(int server_fd, const char *data, unsigned int data_len,
 		     int timeout_ms)
 {
@@ -217,6 +282,7 @@ int make_sockaddr(int family, const char *addr_str, __u16 port,
 	if (family == AF_INET) {
 		struct sockaddr_in *sin = (void *)addr;
 
+		memset(addr, 0, sizeof(*sin));
 		sin->sin_family = AF_INET;
 		sin->sin_port = htons(port);
 		if (addr_str &&
@@ -230,6 +296,7 @@ int make_sockaddr(int family, const char *addr_str, __u16 port,
 	} else if (family == AF_INET6) {
 		struct sockaddr_in6 *sin6 = (void *)addr;
 
+		memset(addr, 0, sizeof(*sin6));
 		sin6->sin6_family = AF_INET6;
 		sin6->sin6_port = htons(port);
 		if (addr_str &&

tools/testing/selftests/bpf/network_helpers.h

@@ -36,6 +36,10 @@ extern struct ipv6_packet pkt_v6;
 int settimeo(int fd, int timeout_ms);
 int start_server(int family, int type, const char *addr, __u16 port,
 		 int timeout_ms);
+int *start_reuseport_server(int family, int type, const char *addr_str,
+			    __u16 port, int timeout_ms,
+			    unsigned int nr_listens);
+void free_fds(int *fds, unsigned int nr_close_fds);
 int connect_to_fd(int server_fd, int timeout_ms);
 int connect_fd_to_fd(int client_fd, int server_fd, int timeout_ms);
 int fastopen_connect(int server_fd, const char *data, unsigned int data_len,

tools/testing/selftests/bpf/prog_tests/bpf_iter_setsockopt.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#define _GNU_SOURCE
+#include <sched.h>
+#include <test_progs.h>
+#include "network_helpers.h"
+#include "bpf_dctcp.skel.h"
+#include "bpf_cubic.skel.h"
+#include "bpf_iter_setsockopt.skel.h"
+
+static int create_netns(void)
+{
+	if (!ASSERT_OK(unshare(CLONE_NEWNET), "create netns"))
+		return -1;
+
+	if (!ASSERT_OK(system("ip link set dev lo up"), "bring up lo"))
+		return -1;
+
+	return 0;
+}
+
+static unsigned int set_bpf_cubic(int *fds, unsigned int nr_fds)
+{
+	unsigned int i;
+
+	for (i = 0; i < nr_fds; i++) {
+		if (setsockopt(fds[i], SOL_TCP, TCP_CONGESTION, "bpf_cubic",
+			       sizeof("bpf_cubic")))
+			return i;
+	}
+
+	return nr_fds;
+}
+
+static unsigned int check_bpf_dctcp(int *fds, unsigned int nr_fds)
+{
+	char tcp_cc[16];
+	socklen_t optlen = sizeof(tcp_cc);
+	unsigned int i;
+
+	for (i = 0; i < nr_fds; i++) {
+		if (getsockopt(fds[i], SOL_TCP, TCP_CONGESTION,
+			       tcp_cc, &optlen) ||
+		    strcmp(tcp_cc, "bpf_dctcp"))
+			return i;
+	}
+
+	return nr_fds;
+}
+
+static int *make_established(int listen_fd, unsigned int nr_est,
+			     int **paccepted_fds)
+{
+	int *est_fds, *accepted_fds;
+	unsigned int i;
+
+	est_fds = malloc(sizeof(*est_fds) * nr_est);
+	if (!est_fds)
+		return NULL;
+
+	accepted_fds = malloc(sizeof(*accepted_fds) * nr_est);
+	if (!accepted_fds) {
+		free(est_fds);
+		return NULL;
+	}
+
+	for (i = 0; i < nr_est; i++) {
+		est_fds[i] = connect_to_fd(listen_fd, 0);
+		if (est_fds[i] == -1)
+			break;
+		if (set_bpf_cubic(&est_fds[i], 1) != 1) {
+			close(est_fds[i]);
+			break;
+		}
+
+		accepted_fds[i] = accept(listen_fd, NULL, 0);
+		if (accepted_fds[i] == -1) {
+			close(est_fds[i]);
+			break;
+		}
+	}
+
+	if (!ASSERT_EQ(i, nr_est, "create established fds")) {
+		free_fds(accepted_fds, i);
+		free_fds(est_fds, i);
+		return NULL;
+	}
+
+	*paccepted_fds = accepted_fds;
+	return est_fds;
+}
+
+static unsigned short get_local_port(int fd)
+{
+	struct sockaddr_in6 addr;
+	socklen_t addrlen = sizeof(addr);
+
+	if (!getsockname(fd, &addr, &addrlen))
+		return ntohs(addr.sin6_port);
+
+	return 0;
+}
+
+static void do_bpf_iter_setsockopt(struct bpf_iter_setsockopt *iter_skel,
+				   bool random_retry)
+{
+	int *reuse_listen_fds = NULL, *accepted_fds = NULL, *est_fds = NULL;
+	unsigned int nr_reuse_listens = 256, nr_est = 256;
+	int err, iter_fd = -1, listen_fd = -1;
+	char buf;
+
+	/* Prepare non-reuseport listen_fd */
+	listen_fd = start_server(AF_INET6, SOCK_STREAM, "::1", 0, 0);
+	if (!ASSERT_GE(listen_fd, 0, "start_server"))
+		return;
+	if (!ASSERT_EQ(set_bpf_cubic(&listen_fd, 1), 1,
+		       "set listen_fd to cubic"))
+		goto done;
+	iter_skel->bss->listen_hport = get_local_port(listen_fd);
+	if (!ASSERT_NEQ(iter_skel->bss->listen_hport, 0,
+			"get_local_port(listen_fd)"))
+		goto done;
+
+	/* Connect to non-reuseport listen_fd */
+	est_fds = make_established(listen_fd, nr_est, &accepted_fds);
+	if (!ASSERT_OK_PTR(est_fds, "create established"))
+		goto done;
+
+	/* Prepare reuseport listen fds */
+	reuse_listen_fds = start_reuseport_server(AF_INET6, SOCK_STREAM,
+						  "::1", 0, 0,
+						  nr_reuse_listens);
+	if (!ASSERT_OK_PTR(reuse_listen_fds, "start_reuseport_server"))
+		goto done;
+	if (!ASSERT_EQ(set_bpf_cubic(reuse_listen_fds, nr_reuse_listens),
+		       nr_reuse_listens, "set reuse_listen_fds to cubic"))
+		goto done;
+	iter_skel->bss->reuse_listen_hport = get_local_port(reuse_listen_fds[0]);
+	if (!ASSERT_NEQ(iter_skel->bss->reuse_listen_hport, 0,
+			"get_local_port(reuse_listen_fds[0])"))
+		goto done;
+
+	/* Run bpf tcp iter to switch from bpf_cubic to bpf_dctcp */
+	iter_skel->bss->random_retry = random_retry;
+	iter_fd = bpf_iter_create(bpf_link__fd(iter_skel->links.change_tcp_cc));
+	if (!ASSERT_GE(iter_fd, 0, "create iter_fd"))
+		goto done;
+
+	while ((err = read(iter_fd, &buf, sizeof(buf))) == -1 &&
+	       errno == EAGAIN)
+		;
+	if (!ASSERT_OK(err, "read iter error"))
+		goto done;
+
+	/* Check reuseport listen fds for dctcp */
+	ASSERT_EQ(check_bpf_dctcp(reuse_listen_fds, nr_reuse_listens),
+		  nr_reuse_listens,
+		  "check reuse_listen_fds dctcp");
+
+	/* Check non reuseport listen fd for dctcp */
+	ASSERT_EQ(check_bpf_dctcp(&listen_fd, 1), 1,
+		  "check listen_fd dctcp");
+
+	/* Check established fds for dctcp */
+	ASSERT_EQ(check_bpf_dctcp(est_fds, nr_est), nr_est,
+		  "check est_fds dctcp");
+
+	/* Check accepted fds for dctcp */
+	ASSERT_EQ(check_bpf_dctcp(accepted_fds, nr_est), nr_est,
+		  "check accepted_fds dctcp");
+
+done:
+	if (iter_fd != -1)
+		close(iter_fd);
+	if (listen_fd != -1)
+		close(listen_fd);
+	free_fds(reuse_listen_fds, nr_reuse_listens);
+	free_fds(accepted_fds, nr_est);
+	free_fds(est_fds, nr_est);
+}
+
+void test_bpf_iter_setsockopt(void)
+{
+	struct bpf_iter_setsockopt *iter_skel = NULL;
+	struct bpf_cubic *cubic_skel = NULL;
+	struct bpf_dctcp *dctcp_skel = NULL;
+	struct bpf_link *cubic_link = NULL;
+	struct bpf_link *dctcp_link = NULL;
+
+	if (create_netns())
+		return;
+
+	/* Load iter_skel */
+	iter_skel = bpf_iter_setsockopt__open_and_load();
+	if (!ASSERT_OK_PTR(iter_skel, "iter_skel"))
+		return;
+	iter_skel->links.change_tcp_cc = bpf_program__attach_iter(iter_skel->progs.change_tcp_cc, NULL);
+	if (!ASSERT_OK_PTR(iter_skel->links.change_tcp_cc, "attach iter"))
+		goto done;
+
+	/* Load bpf_cubic */
+	cubic_skel = bpf_cubic__open_and_load();
+	if (!ASSERT_OK_PTR(cubic_skel, "cubic_skel"))
+		goto done;
+	cubic_link = bpf_map__attach_struct_ops(cubic_skel->maps.cubic);
+	if (!ASSERT_OK_PTR(cubic_link, "cubic_link"))
+		goto done;
+
+	/* Load bpf_dctcp */
+	dctcp_skel = bpf_dctcp__open_and_load();
+	if (!ASSERT_OK_PTR(dctcp_skel, "dctcp_skel"))
+		goto done;
+	dctcp_link = bpf_map__attach_struct_ops(dctcp_skel->maps.dctcp);
+	if (!ASSERT_OK_PTR(dctcp_link, "dctcp_link"))
+		goto done;
+
+	do_bpf_iter_setsockopt(iter_skel, true);
+	do_bpf_iter_setsockopt(iter_skel, false);
+
+done:
+	bpf_link__destroy(cubic_link);
+	bpf_link__destroy(dctcp_link);
+	bpf_cubic__destroy(cubic_skel);
+	bpf_dctcp__destroy(dctcp_skel);
+	bpf_iter_setsockopt__destroy(iter_skel);
+}

tools/testing/selftests/bpf/progs/bpf_iter_setsockopt.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include "bpf_iter.h"
+#include "bpf_tracing_net.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+#define bpf_tcp_sk(skc)	({				\
+	struct sock_common *_skc = skc;			\
+	sk = NULL;					\
+	tp = NULL;					\
+	if (_skc) {					\
+		tp = bpf_skc_to_tcp_sock(_skc);		\
+		sk = (struct sock *)tp;			\
+	}						\
+	tp;						\
+})
+
+unsigned short reuse_listen_hport = 0;
+unsigned short listen_hport = 0;
+char cubic_cc[TCP_CA_NAME_MAX] = "bpf_cubic";
+char dctcp_cc[TCP_CA_NAME_MAX] = "bpf_dctcp";
+bool random_retry = false;
+
+static bool tcp_cc_eq(const char *a, const char *b)
+{
+	int i;
+
+	for (i = 0; i < TCP_CA_NAME_MAX; i++) {
+		if (a[i] != b[i])
+			return false;
+		if (!a[i])
+			break;
+	}
+
+	return true;
+}
+
+SEC("iter/tcp")
+int change_tcp_cc(struct bpf_iter__tcp *ctx)
+{
+	char cur_cc[TCP_CA_NAME_MAX];
+	struct tcp_sock *tp;
+	struct sock *sk;
+	int ret;
+
+	if (!bpf_tcp_sk(ctx->sk_common))
+		return 0;
+
+	if (sk->sk_family != AF_INET6 ||
+	    (sk->sk_state != TCP_LISTEN &&
+	     sk->sk_state != TCP_ESTABLISHED) ||
+	    (sk->sk_num != reuse_listen_hport &&
+	     sk->sk_num != listen_hport &&
+	     bpf_ntohs(sk->sk_dport) != listen_hport))
+		return 0;
+
+	if (bpf_getsockopt(tp, SOL_TCP, TCP_CONGESTION,
+			   cur_cc, sizeof(cur_cc)))
+		return 0;
+
+	if (!tcp_cc_eq(cur_cc, cubic_cc))
+		return 0;
+
+	if (random_retry && bpf_get_prandom_u32() % 4 == 1)
+		return 1;
+
+	bpf_setsockopt(tp, SOL_TCP, TCP_CONGESTION, dctcp_cc, sizeof(dctcp_cc));
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/bpf_tracing_net.h

@@ -5,6 +5,10 @@
 #define AF_INET			2
 #define AF_INET6		10
 
+#define SOL_TCP			6
+#define TCP_CONGESTION		13
+#define TCP_CA_NAME_MAX		16
+
 #define ICSK_TIME_RETRANS	1
 #define ICSK_TIME_PROBE0	3
 #define ICSK_TIME_LOSS_PROBE	5
@@ -32,6 +36,8 @@
 #define ir_v6_rmt_addr		req.__req_common.skc_v6_daddr
 #define ir_v6_loc_addr		req.__req_common.skc_v6_rcv_saddr
 
+#define sk_num			__sk_common.skc_num
+#define sk_dport		__sk_common.skc_dport
 #define sk_family		__sk_common.skc_family
 #define sk_rmem_alloc		sk_backlog.rmem_alloc
 #define sk_refcnt		__sk_common.skc_refcnt