Merge branch 'soreuseport-fix-broken-so_incoming_cpu'

Kuniyuki Iwashima says:

====================
soreuseport: Fix broken SO_INCOMING_CPU.

setsockopt(SO_INCOMING_CPU) for UDP/TCP is broken since 4.5/4.6 due to
these commits:

  * e32ea7e ("soreuseport: fast reuseport UDP socket selection")
  * c125e80 ("soreuseport: fast reuseport TCP socket selection")

These commits introduced the O(1) socket selection algorithm and removed
O(n) iteration over the list, but it ignores the score calculated by
compute_score().  As a result, it caused two misbehaviours:

  * Unconnected sockets receive packets sent to connected sockets
  * SO_INCOMING_CPU does not work

The former is fixed by commit acdcecc ("udp: correct reuseport
selection with connected sockets").  This series fixes the latter and
adds some tests for SO_INCOMING_CPU.
====================

Link: https://lore.kernel.org/r/20221021204435.4259-1-kuniyu@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: Paolo Abeni

include/net/sock_reuseport.h

@@ -16,6 +16,7 @@ struct sock_reuseport {
 	u16			max_socks;		/* length of socks */
 	u16			num_socks;		/* elements in socks */
 	u16			num_closed_socks;	/* closed elements in socks */
+	u16			incoming_cpu;
 	/* The last synq overflow event timestamp of this
 	 * reuse->socks[] group.
 	 */
@@ -58,5 +59,6 @@ static inline bool reuseport_has_conns(struct sock *sk)
 }
 
 void reuseport_has_conns_set(struct sock *sk);
+void reuseport_update_incoming_cpu(struct sock *sk, int val);
 
 #endif  /* _SOCK_REUSEPORT_H */

net/core/sock.c

@@ -1436,7 +1436,7 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
 		break;
 		}
 	case SO_INCOMING_CPU:
-		WRITE_ONCE(sk->sk_incoming_cpu, val);
+		reuseport_update_incoming_cpu(sk, val);
 		break;
 
 	case SO_CNX_ADVICE:

net/core/sock_reuseport.c

@@ -37,6 +37,70 @@ void reuseport_has_conns_set(struct sock *sk)
 }
 EXPORT_SYMBOL(reuseport_has_conns_set);
 
+static void __reuseport_get_incoming_cpu(struct sock_reuseport *reuse)
+{
+	/* Paired with READ_ONCE() in reuseport_select_sock_by_hash(). */
+	WRITE_ONCE(reuse->incoming_cpu, reuse->incoming_cpu + 1);
+}
+
+static void __reuseport_put_incoming_cpu(struct sock_reuseport *reuse)
+{
+	/* Paired with READ_ONCE() in reuseport_select_sock_by_hash(). */
+	WRITE_ONCE(reuse->incoming_cpu, reuse->incoming_cpu - 1);
+}
+
+static void reuseport_get_incoming_cpu(struct sock *sk, struct sock_reuseport *reuse)
+{
+	if (sk->sk_incoming_cpu >= 0)
+		__reuseport_get_incoming_cpu(reuse);
+}
+
+static void reuseport_put_incoming_cpu(struct sock *sk, struct sock_reuseport *reuse)
+{
+	if (sk->sk_incoming_cpu >= 0)
+		__reuseport_put_incoming_cpu(reuse);
+}
+
+void reuseport_update_incoming_cpu(struct sock *sk, int val)
+{
+	struct sock_reuseport *reuse;
+	int old_sk_incoming_cpu;
+
+	if (unlikely(!rcu_access_pointer(sk->sk_reuseport_cb))) {
+		/* Paired with REAE_ONCE() in sk_incoming_cpu_update()
+		 * and compute_score().
+		 */
+		WRITE_ONCE(sk->sk_incoming_cpu, val);
+		return;
+	}
+
+	spin_lock_bh(&reuseport_lock);
+
+	/* This must be done under reuseport_lock to avoid a race with
+	 * reuseport_grow(), which accesses sk->sk_incoming_cpu without
+	 * lock_sock() when detaching a shutdown()ed sk.
+	 *
+	 * Paired with READ_ONCE() in reuseport_select_sock_by_hash().
+	 */
+	old_sk_incoming_cpu = sk->sk_incoming_cpu;
+	WRITE_ONCE(sk->sk_incoming_cpu, val);
+
+	reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
+					  lockdep_is_held(&reuseport_lock));
+
+	/* reuseport_grow() has detached a closed sk. */
+	if (!reuse)
+		goto out;
+
+	if (old_sk_incoming_cpu < 0 && val >= 0)
+		__reuseport_get_incoming_cpu(reuse);
+	else if (old_sk_incoming_cpu >= 0 && val < 0)
+		__reuseport_put_incoming_cpu(reuse);
+
+out:
+	spin_unlock_bh(&reuseport_lock);
+}
+
 static int reuseport_sock_index(struct sock *sk,
 				const struct sock_reuseport *reuse,
 				bool closed)
@@ -64,6 +128,7 @@ static void __reuseport_add_sock(struct sock *sk,
 	/* paired with smp_rmb() in reuseport_(select|migrate)_sock() */
 	smp_wmb();
 	reuse->num_socks++;
+	reuseport_get_incoming_cpu(sk, reuse);
 }
 
 static bool __reuseport_detach_sock(struct sock *sk,
@@ -76,6 +141,7 @@ static bool __reuseport_detach_sock(struct sock *sk,
 
 	reuse->socks[i] = reuse->socks[reuse->num_socks - 1];
 	reuse->num_socks--;
+	reuseport_put_incoming_cpu(sk, reuse);
 
 	return true;
 }
@@ -86,6 +152,7 @@ static void __reuseport_add_closed_sock(struct sock *sk,
 	reuse->socks[reuse->max_socks - reuse->num_closed_socks - 1] = sk;
 	/* paired with READ_ONCE() in inet_csk_bind_conflict() */
 	WRITE_ONCE(reuse->num_closed_socks, reuse->num_closed_socks + 1);
+	reuseport_get_incoming_cpu(sk, reuse);
 }
 
 static bool __reuseport_detach_closed_sock(struct sock *sk,
@@ -99,6 +166,7 @@ static bool __reuseport_detach_closed_sock(struct sock *sk,
 	reuse->socks[i] = reuse->socks[reuse->max_socks - reuse->num_closed_socks];
 	/* paired with READ_ONCE() in inet_csk_bind_conflict() */
 	WRITE_ONCE(reuse->num_closed_socks, reuse->num_closed_socks - 1);
+	reuseport_put_incoming_cpu(sk, reuse);
 
 	return true;
 }
@@ -166,6 +234,7 @@ int reuseport_alloc(struct sock *sk, bool bind_inany)
 	reuse->bind_inany = bind_inany;
 	reuse->socks[0] = sk;
 	reuse->num_socks = 1;
+	reuseport_get_incoming_cpu(sk, reuse);
 	rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
 
 out:
@@ -209,6 +278,7 @@ static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
 	more_reuse->reuseport_id = reuse->reuseport_id;
 	more_reuse->bind_inany = reuse->bind_inany;
 	more_reuse->has_conns = reuse->has_conns;
+	more_reuse->incoming_cpu = reuse->incoming_cpu;
 
 	memcpy(more_reuse->socks, reuse->socks,
 	       reuse->num_socks * sizeof(struct sock *));
@@ -458,18 +528,32 @@ static struct sock *run_bpf_filter(struct sock_reuseport *reuse, u16 socks,
 static struct sock *reuseport_select_sock_by_hash(struct sock_reuseport *reuse,
 						  u32 hash, u16 num_socks)
 {
+	struct sock *first_valid_sk = NULL;
 	int i, j;
 
 	i = j = reciprocal_scale(hash, num_socks);
-	while (reuse->socks[i]->sk_state == TCP_ESTABLISHED) {
+	do {
+		struct sock *sk = reuse->socks[i];
+
+		if (sk->sk_state != TCP_ESTABLISHED) {
+			/* Paired with WRITE_ONCE() in __reuseport_(get|put)_incoming_cpu(). */
+			if (!READ_ONCE(reuse->incoming_cpu))
+				return sk;
+
+			/* Paired with WRITE_ONCE() in reuseport_update_incoming_cpu(). */
+			if (READ_ONCE(sk->sk_incoming_cpu) == raw_smp_processor_id())
+				return sk;
+
+			if (!first_valid_sk)
+				first_valid_sk = sk;
+		}
+
 		i++;
 		if (i >= num_socks)
 			i = 0;
-		if (i == j)
-			return NULL;
-	}
+	} while (i != j);
 
-	return reuse->socks[i];
+	return first_valid_sk;
 }
 
 /**

tools/testing/selftests/net/.gitignore

@@ -25,6 +25,7 @@ rxtimestamp
 sk_bind_sendto_listen
 sk_connect_zero_addr
 socket
+so_incoming_cpu
 so_netns_cookie
 so_txtime
 stress_reuseport_listen

tools/testing/selftests/net/Makefile

@@ -71,6 +71,7 @@ TEST_GEN_FILES += bind_bhash
 TEST_GEN_PROGS += sk_bind_sendto_listen
 TEST_GEN_PROGS += sk_connect_zero_addr
 TEST_PROGS += test_ingress_egress_chaining.sh
+TEST_GEN_PROGS += so_incoming_cpu
 
 TEST_FILES := settings