From: Kuniyuki Iwashima kuniyu@amazon.com
[ Upstream commit b261eda84ec136240a9ca753389853a3a1bccca2 ]
Kazuho Oku reported that setsockopt(SO_INCOMING_CPU) does not work with setsockopt(SO_REUSEPORT) since v4.6.
With the combination of SO_REUSEPORT and SO_INCOMING_CPU, we could build a highly efficient server application.
setsockopt(SO_INCOMING_CPU) associates a CPU with a TCP listener or UDP socket, and then incoming packets processed on the CPU will likely be distributed to the socket. Technically, a socket could even receive packets handled on another CPU if no sockets in the reuseport group have the same CPU receiving the flow.
The logic exists in compute_score() so that a socket will get a higher score if it has the same CPU with the flow. However, the score gets ignored after the blamed two commits, which introduced a faster socket selection algorithm for SO_REUSEPORT.
This patch introduces a counter of sockets with SO_INCOMING_CPU in a reuseport group to check if we should iterate all sockets to find a proper one. We increment the counter when
* calling listen() if the socket has SO_INCOMING_CPU and SO_REUSEPORT
* enabling SO_INCOMING_CPU if the socket is in a reuseport group
Also, we decrement it when
* detaching a socket out of the group to apply SO_INCOMING_CPU to migrated TCP requests
* disabling SO_INCOMING_CPU if the socket is in a reuseport group
When the counter reaches 0, we can get back to the O(1) selection algorithm.
The overall changes are negligible for the non-SO_INCOMING_CPU case, and the only notable thing is that we have to update sk_incomnig_cpu under reuseport_lock. Otherwise, the race prevents transitioning to the O(n) algorithm and results in the wrong socket selection.
cpu1 (setsockopt) cpu2 (listen) +-----------------+ +-------------+
lock_sock(sk1) lock_sock(sk2)
reuseport_update_incoming_cpu(sk1, val) . | /* set CPU as 0 */ |- WRITE_ONCE(sk1->incoming_cpu, val) | | spin_lock_bh(&reuseport_lock) | reuseport_grow(sk2, reuse) | . | |- more_socks_size = reuse->max_socks * 2U; | |- if (more_socks_size > U16_MAX && | | reuse->num_closed_socks) | | . | | |- RCU_INIT_POINTER(sk1->sk_reuseport_cb, NULL); | | `- __reuseport_detach_closed_sock(sk1, reuse) | | . | | `- reuseport_put_incoming_cpu(sk1, reuse) | | . | | | /* Read shutdown()ed sk1's sk_incoming_cpu | | | * without lock_sock(). | | | */ | | `- if (sk1->sk_incoming_cpu >= 0) | | . | | | /* decrement not-yet-incremented | | | * count, which is never incremented. | | | */ | | `- __reuseport_put_incoming_cpu(reuse); | | | `- spin_lock_bh(&reuseport_lock) | |- spin_lock_bh(&reuseport_lock) | |- reuse = rcu_dereference_protected(sk1->sk_reuseport_cb, ...) |- if (!reuse) | . | | /* Cannot increment reuse->incoming_cpu. */ | `- goto out; | `- spin_unlock_bh(&reuseport_lock)
Fixes: e32ea7e74727 ("soreuseport: fast reuseport UDP socket selection") Fixes: c125e80b8868 ("soreuseport: fast reuseport TCP socket selection") Reported-by: Kazuho Oku kazuhooku@gmail.com Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/sock_reuseport.h | 2 + net/core/sock.c | 2 +- net/core/sock_reuseport.c | 94 ++++++++++++++++++++++++++++++++++-- 3 files changed, 92 insertions(+), 6 deletions(-)
diff --git a/include/net/sock_reuseport.h b/include/net/sock_reuseport.h index efc9085c6892..6ec140b0a61b 100644 --- a/include/net/sock_reuseport.h +++ b/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 */ diff --git a/net/core/sock.c b/net/core/sock.c index 788c1372663c..f0eaa5d406b3 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1400,7 +1400,7 @@ int sock_setsockopt(struct socket *sock, 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: diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c index fb90e1e00773..5a165286e4d8 100644 --- a/net/core/sock_reuseport.c +++ b/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; }
/**