Merge branch 'mptcp-cleanups'

Matthieu Baerts says:

====================
mptcp: a couple of cleanups and improvements

Patch 1 removes an unneeded address copy in subflow_syn_recv_sock().

Patch 2 simplifies subflow_syn_recv_sock() to postpone some actions and
to avoid a bunch of conditionals.

Patch 3 stops reporting limits that are not taken into account when the
userspace PM is used.

Patch 4 adds a new test to validate that the 'subflows' field reported
by the kernel is correct. Such info can be retrieved via Netlink (e.g.
with ss) or getsockopt(SOL_MPTCP, MPTCP_INFO).

---
Changes in v2:
- Patch 3/4's commit message has been updated to use the correct SHA
- Rebased on latest net-next
- Link to v1: https://lore.kernel.org/r/20230324-upstream-net-next-20230324-misc-features-v1-0-5a29154592bd@tessares.net
====================
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/mptcp/sockopt.c

@@ -885,7 +885,6 @@ static int mptcp_getsockopt_first_sf_only(struct mptcp_sock *msk, int level, int
 void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
 {
 	u32 flags = 0;
-	u8 val;
 
 	memset(info, 0, sizeof(*info));
 
@@ -893,12 +892,19 @@ void mptcp_diag_fill_info(struct mptcp_sock *msk, struct mptcp_info *info)
 	info->mptcpi_add_addr_signal = READ_ONCE(msk->pm.add_addr_signaled);
 	info->mptcpi_add_addr_accepted = READ_ONCE(msk->pm.add_addr_accepted);
 	info->mptcpi_local_addr_used = READ_ONCE(msk->pm.local_addr_used);
-	info->mptcpi_subflows_max = mptcp_pm_get_subflows_max(msk);
-	val = mptcp_pm_get_add_addr_signal_max(msk);
-	info->mptcpi_add_addr_signal_max = val;
-	val = mptcp_pm_get_add_addr_accept_max(msk);
-	info->mptcpi_add_addr_accepted_max = val;
-	info->mptcpi_local_addr_max = mptcp_pm_get_local_addr_max(msk);
+
+	/* The following limits only make sense for the in-kernel PM */
+	if (mptcp_pm_is_kernel(msk)) {
+		info->mptcpi_subflows_max =
+			mptcp_pm_get_subflows_max(msk);
+		info->mptcpi_add_addr_signal_max =
+			mptcp_pm_get_add_addr_signal_max(msk);
+		info->mptcpi_add_addr_accepted_max =
+			mptcp_pm_get_add_addr_accept_max(msk);
+		info->mptcpi_local_addr_max =
+			mptcp_pm_get_local_addr_max(msk);
+	}
+
 	if (test_bit(MPTCP_FALLBACK_DONE, &msk->flags))
 		flags |= MPTCP_INFO_FLAG_FALLBACK;
 	if (READ_ONCE(msk->can_ack))

net/mptcp/subflow.c

@@ -696,14 +696,6 @@ static bool subflow_hmac_valid(const struct request_sock *req,
 	return !crypto_memneq(hmac, mp_opt->hmac, MPTCPOPT_HMAC_LEN);
 }
 
-static void mptcp_force_close(struct sock *sk)
-{
-	/* the msk is not yet exposed to user-space, and refcount is 2 */
-	inet_sk_state_store(sk, TCP_CLOSE);
-	sk_common_release(sk);
-	sock_put(sk);
-}
-
 static void subflow_ulp_fallback(struct sock *sk,
 				 struct mptcp_subflow_context *old_ctx)
 {
@@ -755,7 +747,6 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 	struct mptcp_subflow_request_sock *subflow_req;
 	struct mptcp_options_received mp_opt;
 	bool fallback, fallback_is_fatal;
-	struct sock *new_msk = NULL;
 	struct mptcp_sock *owner;
 	struct sock *child;
 
@@ -784,14 +775,9 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 		 * options.
 		 */
 		mptcp_get_options(skb, &mp_opt);
-		if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPC)) {
+		if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPC))
 			fallback = true;
-			goto create_child;
-		}
 
-		new_msk = mptcp_sk_clone(listener->conn, &mp_opt, req);
-		if (!new_msk)
-			fallback = true;
 	} else if (subflow_req->mp_join) {
 		mptcp_get_options(skb, &mp_opt);
 		if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPJ) ||
@@ -820,23 +806,23 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 				subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
 				goto dispose_child;
 			}
-
-			if (new_msk)
-				mptcp_copy_inaddrs(new_msk, child);
-			mptcp_subflow_drop_ctx(child);
-			goto out;
+			goto fallback;
 		}
 
 		/* ssk inherits options of listener sk */
 		ctx->setsockopt_seq = listener->setsockopt_seq;
 
 		if (ctx->mp_capable) {
-			owner = mptcp_sk(new_msk);
+			ctx->conn = mptcp_sk_clone(listener->conn, &mp_opt, req);
+			if (!ctx->conn)
+				goto fallback;
+
+			owner = mptcp_sk(ctx->conn);
 
 			/* this can't race with mptcp_close(), as the msk is
 			 * not yet exposted to user-space
 			 */
-			inet_sk_state_store((void *)new_msk, TCP_ESTABLISHED);
+			inet_sk_state_store(ctx->conn, TCP_ESTABLISHED);
 
 			/* record the newly created socket as the first msk
 			 * subflow, but don't link it yet into conn_list
@@ -846,11 +832,9 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 			/* new mpc subflow takes ownership of the newly
 			 * created mptcp socket
 			 */
-			mptcp_sk(new_msk)->setsockopt_seq = ctx->setsockopt_seq;
+			owner->setsockopt_seq = ctx->setsockopt_seq;
 			mptcp_pm_new_connection(owner, child, 1);
 			mptcp_token_accept(subflow_req, owner);
-			ctx->conn = new_msk;
-			new_msk = NULL;
 
 			/* set msk addresses early to ensure mptcp_pm_get_local_id()
 			 * uses the correct data
@@ -900,11 +884,6 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 		}
 	}
 
-out:
-	/* dispose of the left over mptcp master, if any */
-	if (unlikely(new_msk))
-		mptcp_force_close(new_msk);
-
 	/* check for expected invariant - should never trigger, just help
 	 * catching eariler subtle bugs
 	 */
@@ -922,6 +901,10 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
 
 	/* The last child reference will be released by the caller */
 	return child;
+
+fallback:
+	mptcp_subflow_drop_ctx(child);
+	return child;
 }
 
 static struct inet_connection_sock_af_ops subflow_specific __ro_after_init;

tools/testing/selftests/net/mptcp/mptcp_join.sh

@@ -1719,6 +1719,46 @@ chk_subflow_nr()
 	fi
 }
 
+chk_mptcp_info()
+{
+	local nr_info=$1
+	local info
+	local cnt1
+	local cnt2
+	local dump_stats
+
+	if [[ $nr_info = "subflows_"* ]]; then
+		info="subflows"
+		nr_info=${nr_info:9}
+	else
+		echo "[fail] unsupported argument: $nr_info"
+		fail_test
+		return 1
+	fi
+
+	printf "%-${nr_blank}s %-30s" " " "mptcp_info $info=$nr_info"
+
+	cnt1=$(ss -N $ns1 -inmHM | grep "$info:" |
+		sed -n 's/.*\('"$info"':\)\([[:digit:]]*\).*$/\2/p;q')
+	[ -z "$cnt1" ] && cnt1=0
+	cnt2=$(ss -N $ns2 -inmHM | grep "$info:" |
+		sed -n 's/.*\('"$info"':\)\([[:digit:]]*\).*$/\2/p;q')
+	[ -z "$cnt2" ] && cnt2=0
+	if [ "$cnt1" != "$nr_info" ] || [ "$cnt2" != "$nr_info" ]; then
+		echo "[fail] got $cnt1:$cnt2 $info expected $nr_info"
+		fail_test
+		dump_stats=1
+	else
+		echo "[ ok ]"
+	fi
+
+	if [ "$dump_stats" = 1 ]; then
+		ss -N $ns1 -inmHM
+		ss -N $ns2 -inmHM
+		dump_stats
+	fi
+}
+
 chk_link_usage()
 {
 	local ns=$1
@@ -3118,13 +3158,18 @@ endpoint_tests()
 		run_tests $ns1 $ns2 10.0.1.1 4 0 0 speed_20 2>/dev/null &
 
 		wait_mpj $ns2
+		chk_subflow_nr needtitle "before delete" 2
+		chk_mptcp_info subflows_1
+
 		pm_nl_del_endpoint $ns2 2 10.0.2.2
 		sleep 0.5
-		chk_subflow_nr needtitle "after delete" 1
+		chk_subflow_nr "" "after delete" 1
+		chk_mptcp_info subflows_0
 
 		pm_nl_add_endpoint $ns2 10.0.2.2 dev ns2eth2 flags subflow
 		wait_mpj $ns2
 		chk_subflow_nr "" "after re-add" 2
+		chk_mptcp_info subflows_1
 		kill_tests_wait
 	fi
 }