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Date: Mon, 05 Feb 2018 10:17:49 -0800
From: John Fastabend <john.fastabend@...il.com>
To: ast@...nel.org, daniel@...earbox.net, davejwatson@...com
Cc: netdev@...r.kernel.org
Subject: [bpf PATCH v4 2/3] bpf: sockmap,
add sock close() hook to remove socks
The selftests test_maps program was leaving dangling BPF sockmap
programs around because not all psock elements were removed from
the map. The elements in turn hold a reference on the BPF program
they are attached to causing BPF programs to stay open even after
test_maps has completed.
The original intent was that sk_state_change() would be called
when TCP socks went through TCP_CLOSE state. However, because
socks may be in SOCK_DEAD state or the sock may be a listening
socket the event is not always triggered.
To resolve this use the ULP infrastructure and register our own
proto close() handler. This fixes the above case.
Fixes: 174a79ff9515 ("bpf: sockmap with sk redirect support")
Reported-by: Prashant Bhole <bhole_prashant_q7@....ntt.co.jp>
Signed-off-by: John Fastabend <john.fastabend@...il.com>
---
include/net/tcp.h | 2 +
kernel/bpf/sockmap.c | 168 ++++++++++++++++++++++++++++++--------------------
2 files changed, 103 insertions(+), 67 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index a58292d..e3fc667 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1985,6 +1985,7 @@ static inline void tcp_listendrop(const struct sock *sk)
enum {
TCP_ULP_TLS,
+ TCP_ULP_BPF,
};
struct tcp_ulp_ops {
@@ -2003,6 +2004,7 @@ struct tcp_ulp_ops {
int tcp_register_ulp(struct tcp_ulp_ops *type);
void tcp_unregister_ulp(struct tcp_ulp_ops *type);
int tcp_set_ulp(struct sock *sk, const char *name);
+int tcp_set_ulp_id(struct sock *sk, const int ulp);
void tcp_get_available_ulp(char *buf, size_t len);
void tcp_cleanup_ulp(struct sock *sk);
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 0314d17..bd4a6d9 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -86,9 +86,10 @@ struct smap_psock {
struct work_struct tx_work;
struct work_struct gc_work;
+ struct proto *sk_proto;
+ void (*save_close)(struct sock *sk, long timeout);
void (*save_data_ready)(struct sock *sk);
void (*save_write_space)(struct sock *sk);
- void (*save_state_change)(struct sock *sk);
};
static inline struct smap_psock *smap_psock_sk(const struct sock *sk)
@@ -96,12 +97,102 @@ static inline struct smap_psock *smap_psock_sk(const struct sock *sk)
return rcu_dereference_sk_user_data(sk);
}
+static struct proto tcp_bpf_proto;
+static int bpf_tcp_init(struct sock *sk)
+{
+ struct smap_psock *psock;
+
+ rcu_read_lock();
+ psock = smap_psock_sk(sk);
+ if (unlikely(!psock)) {
+ rcu_read_unlock();
+ return -EINVAL;
+ }
+
+ if (unlikely(psock->sk_proto)) {
+ rcu_read_unlock();
+ return -EBUSY;
+ }
+
+ psock->save_close = sk->sk_prot->close;
+ psock->sk_proto = sk->sk_prot;
+ sk->sk_prot = &tcp_bpf_proto;
+ rcu_read_unlock();
+ return 0;
+}
+
+static void bpf_tcp_release(struct sock *sk)
+{
+ struct smap_psock *psock;
+
+ rcu_read_lock();
+ psock = smap_psock_sk(sk);
+
+ if (likely(psock)) {
+ sk->sk_prot = psock->sk_proto;
+ psock->sk_proto = NULL;
+ }
+ rcu_read_unlock();
+}
+
+static void smap_release_sock(struct smap_psock *psock, struct sock *sock);
+
+static void bpf_tcp_close(struct sock *sk, long timeout)
+{
+ void (*close_fun)(struct sock *sk, long timeout);
+ struct smap_psock_map_entry *e, *tmp;
+ struct smap_psock *psock;
+ struct sock *osk;
+
+ rcu_read_lock();
+ psock = smap_psock_sk(sk);
+ if (unlikely(!psock)) {
+ rcu_read_unlock();
+ return sk->sk_prot->close(sk, timeout);
+ }
+
+ /* The psock may be destroyed anytime after exiting the RCU critial
+ * section so by the time we use close_fun the psock may no longer
+ * be valid. However, bpf_tcp_close is called with the sock lock
+ * held so the close hook and sk are still valid.
+ */
+ close_fun = psock->save_close;
+
+ write_lock_bh(&sk->sk_callback_lock);
+ list_for_each_entry_safe(e, tmp, &psock->maps, list) {
+ osk = cmpxchg(e->entry, sk, NULL);
+ if (osk == sk) {
+ list_del(&e->list);
+ smap_release_sock(psock, sk);
+ }
+ }
+ write_unlock_bh(&sk->sk_callback_lock);
+ rcu_read_unlock();
+ close_fun(sk, timeout);
+}
+
enum __sk_action {
__SK_DROP = 0,
__SK_PASS,
__SK_REDIRECT,
};
+static struct tcp_ulp_ops bpf_tcp_ulp_ops __read_mostly = {
+ .name = "bpf_tcp",
+ .uid = TCP_ULP_BPF,
+ .user_visible = false,
+ .owner = NULL,
+ .init = bpf_tcp_init,
+ .release = bpf_tcp_release,
+};
+
+static int bpf_tcp_ulp_register(void)
+{
+ tcp_bpf_proto = tcp_prot;
+ tcp_bpf_proto.close = bpf_tcp_close;
+ return tcp_register_ulp(&bpf_tcp_ulp_ops);
+}
+
static int smap_verdict_func(struct smap_psock *psock, struct sk_buff *skb)
{
struct bpf_prog *prog = READ_ONCE(psock->bpf_verdict);
@@ -166,68 +257,6 @@ static void smap_report_sk_error(struct smap_psock *psock, int err)
sk->sk_error_report(sk);
}
-static void smap_release_sock(struct smap_psock *psock, struct sock *sock);
-
-/* Called with lock_sock(sk) held */
-static void smap_state_change(struct sock *sk)
-{
- struct smap_psock_map_entry *e, *tmp;
- struct smap_psock *psock;
- struct socket_wq *wq;
- struct sock *osk;
-
- rcu_read_lock();
-
- /* Allowing transitions into an established syn_recv states allows
- * for early binding sockets to a smap object before the connection
- * is established.
- */
- switch (sk->sk_state) {
- case TCP_SYN_SENT:
- case TCP_SYN_RECV:
- case TCP_ESTABLISHED:
- break;
- case TCP_CLOSE_WAIT:
- case TCP_CLOSING:
- case TCP_LAST_ACK:
- case TCP_FIN_WAIT1:
- case TCP_FIN_WAIT2:
- case TCP_LISTEN:
- break;
- case TCP_CLOSE:
- /* Only release if the map entry is in fact the sock in
- * question. There is a case where the operator deletes
- * the sock from the map, but the TCP sock is closed before
- * the psock is detached. Use cmpxchg to verify correct
- * sock is removed.
- */
- psock = smap_psock_sk(sk);
- if (unlikely(!psock))
- break;
- write_lock_bh(&sk->sk_callback_lock);
- list_for_each_entry_safe(e, tmp, &psock->maps, list) {
- osk = cmpxchg(e->entry, sk, NULL);
- if (osk == sk) {
- list_del(&e->list);
- smap_release_sock(psock, sk);
- }
- }
- write_unlock_bh(&sk->sk_callback_lock);
- break;
- default:
- psock = smap_psock_sk(sk);
- if (unlikely(!psock))
- break;
- smap_report_sk_error(psock, EPIPE);
- break;
- }
-
- wq = rcu_dereference(sk->sk_wq);
- if (skwq_has_sleeper(wq))
- wake_up_interruptible_all(&wq->wait);
- rcu_read_unlock();
-}
-
static void smap_read_sock_strparser(struct strparser *strp,
struct sk_buff *skb)
{
@@ -322,10 +351,8 @@ static void smap_stop_sock(struct smap_psock *psock, struct sock *sk)
return;
sk->sk_data_ready = psock->save_data_ready;
sk->sk_write_space = psock->save_write_space;
- sk->sk_state_change = psock->save_state_change;
psock->save_data_ready = NULL;
psock->save_write_space = NULL;
- psock->save_state_change = NULL;
strp_stop(&psock->strp);
psock->strp_enabled = false;
}
@@ -350,6 +377,7 @@ static void smap_release_sock(struct smap_psock *psock, struct sock *sock)
if (psock->refcnt)
return;
+ tcp_cleanup_ulp(sock);
smap_stop_sock(psock, sock);
clear_bit(SMAP_TX_RUNNING, &psock->state);
rcu_assign_sk_user_data(sock, NULL);
@@ -427,10 +455,8 @@ static void smap_start_sock(struct smap_psock *psock, struct sock *sk)
return;
psock->save_data_ready = sk->sk_data_ready;
psock->save_write_space = sk->sk_write_space;
- psock->save_state_change = sk->sk_state_change;
sk->sk_data_ready = smap_data_ready;
sk->sk_write_space = smap_write_space;
- sk->sk_state_change = smap_state_change;
psock->strp_enabled = true;
}
@@ -509,6 +535,10 @@ static struct bpf_map *sock_map_alloc(union bpf_attr *attr)
if (attr->value_size > KMALLOC_MAX_SIZE)
return ERR_PTR(-E2BIG);
+ err = bpf_tcp_ulp_register();
+ if (err && err != -EEXIST)
+ return ERR_PTR(err);
+
stab = kzalloc(sizeof(*stab), GFP_USER);
if (!stab)
return ERR_PTR(-ENOMEM);
@@ -754,6 +784,10 @@ static int sock_map_ctx_update_elem(struct bpf_sock_ops_kern *skops,
goto out_progs;
}
+ err = tcp_set_ulp_id(sock, TCP_ULP_BPF);
+ if (err)
+ goto out_progs;
+
set_bit(SMAP_TX_RUNNING, &psock->state);
}
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