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mptcp: refactor token container
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Replace the radix tree with an hash table allocated
at boot time. The radix tree has some short coming:
a single lock is contented by all the mptcp operation,
the lookup currently use such lock, and traversing
all the items would require lock, too.

With hash table instead we trade a little memory to
address all the above - a per bucket lock is used.

To hash the MPTCP sockets, we re-use the msk' sk_node
entry: the MPTCP sockets are never hashed by the stack.
Replace the existing hash proto callbacks with dummy
implementation, annotating the above constraint.

Additionally refactor the token creation to code to:

- limit the number of consecutive attempts to a fixed
maximum. Hitting an hash bucket with long chain is
considered a failed attempt

- accept() no longer can fail to to token management.

- if token creation fails at connect() time, we do
fallback to TCP (before the connection was closed)

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Paolo Abeni authored and jenkins-tessares committed Jun 16, 2020
1 parent 1dd5359 commit 7a138a0
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Showing 4 changed files with 236 additions and 113 deletions.
45 changes: 26 additions & 19 deletions net/mptcp/protocol.c
Original file line number Diff line number Diff line change
Expand Up @@ -1448,20 +1448,6 @@ struct sock *mptcp_sk_clone(const struct sock *sk,
msk->token = subflow_req->token;
msk->subflow = NULL;

if (unlikely(mptcp_token_new_accept(subflow_req->token, nsk))) {
nsk->sk_state = TCP_CLOSE;
bh_unlock_sock(nsk);

/* we can't call into mptcp_close() here - possible BH context
* free the sock directly.
* sk_clone_lock() sets nsk refcnt to two, hence call sk_free()
* too.
*/
sk_common_release(nsk);
sk_free(nsk);
return NULL;
}

msk->write_seq = subflow_req->idsn + 1;
atomic64_set(&msk->snd_una, msk->write_seq);
if (mp_opt->mp_capable) {
Expand Down Expand Up @@ -1547,7 +1533,7 @@ static void mptcp_destroy(struct sock *sk)
{
struct mptcp_sock *msk = mptcp_sk(sk);

mptcp_token_destroy(msk->token);
mptcp_token_destroy(msk);
if (msk->cached_ext)
__skb_ext_put(msk->cached_ext);

Expand Down Expand Up @@ -1636,6 +1622,20 @@ static void mptcp_release_cb(struct sock *sk)
}
}

static int mptcp_hash(struct sock *sk)
{
/* should never be called,
* we hash the TCP subflows not the master socket
*/
WARN_ON_ONCE(1);
return 0;
}

static void mptcp_unhash(struct sock *sk)
{
/* called from sk_common_release(), but nothing to do here */
}

static int mptcp_get_port(struct sock *sk, unsigned short snum)
{
struct mptcp_sock *msk = mptcp_sk(sk);
Expand Down Expand Up @@ -1679,7 +1679,6 @@ void mptcp_finish_connect(struct sock *ssk)
*/
WRITE_ONCE(msk->remote_key, subflow->remote_key);
WRITE_ONCE(msk->local_key, subflow->local_key);
WRITE_ONCE(msk->token, subflow->token);
WRITE_ONCE(msk->write_seq, subflow->idsn + 1);
WRITE_ONCE(msk->ack_seq, ack_seq);
WRITE_ONCE(msk->can_ack, 1);
Expand Down Expand Up @@ -1761,8 +1760,8 @@ static struct proto mptcp_prot = {
.sendmsg = mptcp_sendmsg,
.recvmsg = mptcp_recvmsg,
.release_cb = mptcp_release_cb,
.hash = inet_hash,
.unhash = inet_unhash,
.hash = mptcp_hash,
.unhash = mptcp_unhash,
.get_port = mptcp_get_port,
.sockets_allocated = &mptcp_sockets_allocated,
.memory_allocated = &tcp_memory_allocated,
Expand All @@ -1771,6 +1770,7 @@ static struct proto mptcp_prot = {
.sysctl_wmem_offset = offsetof(struct net, ipv4.sysctl_tcp_wmem),
.sysctl_mem = sysctl_tcp_mem,
.obj_size = sizeof(struct mptcp_sock),
.slab_flags = SLAB_TYPESAFE_BY_RCU,
.no_autobind = true,
};

Expand Down Expand Up @@ -1800,6 +1800,7 @@ static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
int addr_len, int flags)
{
struct mptcp_sock *msk = mptcp_sk(sock->sk);
struct mptcp_subflow_context *subflow;
struct socket *ssock;
int err;

Expand All @@ -1812,19 +1813,23 @@ static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
goto do_connect;
}

mptcp_token_destroy(msk);
ssock = __mptcp_socket_create(msk, TCP_SYN_SENT);
if (IS_ERR(ssock)) {
err = PTR_ERR(ssock);
goto unlock;
}

subflow = mptcp_subflow_ctx(ssock->sk);
#ifdef CONFIG_TCP_MD5SIG
/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
* TCP option space.
*/
if (rcu_access_pointer(tcp_sk(ssock->sk)->md5sig_info))
mptcp_subflow_ctx(ssock->sk)->request_mptcp = 0;
subflow->request_mptcp = 0;
#endif
if (subflow->request_mptcp && mptcp_token_new_connect(ssock->sk))
subflow->request_mptcp = 0;

do_connect:
err = ssock->ops->connect(ssock, uaddr, addr_len, flags);
Expand Down Expand Up @@ -1888,6 +1893,7 @@ static int mptcp_listen(struct socket *sock, int backlog)
pr_debug("msk=%p", msk);

lock_sock(sock->sk);
mptcp_token_destroy(msk);
ssock = __mptcp_socket_create(msk, TCP_LISTEN);
if (IS_ERR(ssock)) {
err = PTR_ERR(ssock);
Expand Down Expand Up @@ -2086,6 +2092,7 @@ void __init mptcp_proto_init(void)

mptcp_subflow_init();
mptcp_pm_init();
mptcp_token_init();

if (proto_register(&mptcp_prot, 1) != 0)
panic("Failed to register MPTCP proto.\n");
Expand Down
14 changes: 11 additions & 3 deletions net/mptcp/protocol.h
Original file line number Diff line number Diff line change
Expand Up @@ -255,6 +255,7 @@ struct mptcp_subflow_request_sock {
u32 local_nonce;
u32 remote_nonce;
struct mptcp_sock *msk;
struct hlist_nulls_node token_node;
};

static inline struct mptcp_subflow_request_sock *
Expand Down Expand Up @@ -382,12 +383,19 @@ bool mptcp_finish_join(struct sock *sk);
void mptcp_data_acked(struct sock *sk);
void mptcp_subflow_eof(struct sock *sk);

void __init mptcp_token_init(void);
static inline void mptcp_token_init_request(struct request_sock *req)
{
mptcp_subflow_rsk(req)->token_node.pprev = NULL;
}

int mptcp_token_new_request(struct request_sock *req);
void mptcp_token_destroy_request(u32 token);
void mptcp_token_destroy_request(struct request_sock *req);
int mptcp_token_new_connect(struct sock *sk);
int mptcp_token_new_accept(u32 token, struct sock *conn);
void mptcp_token_accept(struct mptcp_subflow_request_sock *r,
struct mptcp_sock *msk);
struct mptcp_sock *mptcp_token_get_sock(u32 token);
void mptcp_token_destroy(u32 token);
void mptcp_token_destroy(struct mptcp_sock *msk);

void mptcp_crypto_key_sha(u64 key, u32 *token, u64 *idsn);
static inline void mptcp_crypto_key_gen_sha(u64 *key, u32 *token, u64 *idsn)
Expand Down
19 changes: 7 additions & 12 deletions net/mptcp/subflow.c
Original file line number Diff line number Diff line change
Expand Up @@ -32,12 +32,9 @@ static void SUBFLOW_REQ_INC_STATS(struct request_sock *req,
static int subflow_rebuild_header(struct sock *sk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
int local_id, err = 0;
int local_id;

if (subflow->request_mptcp && !subflow->token) {
pr_debug("subflow=%p", sk);
err = mptcp_token_new_connect(sk);
} else if (subflow->request_join && !subflow->local_nonce) {
if (subflow->request_join && !subflow->local_nonce) {
struct mptcp_sock *msk = (struct mptcp_sock *)subflow->conn;

pr_debug("subflow=%p", sk);
Expand All @@ -57,9 +54,6 @@ static int subflow_rebuild_header(struct sock *sk)
}

out:
if (err)
return err;

return subflow->icsk_af_ops->rebuild_header(sk);
}

Expand All @@ -72,8 +66,7 @@ static void subflow_req_destructor(struct request_sock *req)
if (subflow_req->msk)
sock_put((struct sock *)subflow_req->msk);

if (subflow_req->mp_capable)
mptcp_token_destroy_request(subflow_req->token);
mptcp_token_destroy_request(req);
tcp_request_sock_ops.destructor(req);
}

Expand Down Expand Up @@ -135,6 +128,7 @@ static void subflow_init_req(struct request_sock *req,
subflow_req->mp_capable = 0;
subflow_req->mp_join = 0;
subflow_req->msk = NULL;
mptcp_token_init_request(req);

#ifdef CONFIG_TCP_MD5SIG
/* no MPTCP if MD5SIG is enabled on this socket or we may run out of
Expand Down Expand Up @@ -250,7 +244,7 @@ static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
subflow->remote_nonce = mp_opt.nonce;
pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u", subflow,
subflow->thmac, subflow->remote_nonce);
} else if (subflow->request_mptcp) {
} else {
tp->is_mptcp = 0;
}

Expand Down Expand Up @@ -386,7 +380,7 @@ static void mptcp_sock_destruct(struct sock *sk)
sock_orphan(sk);
}

mptcp_token_destroy(mptcp_sk(sk)->token);
mptcp_token_destroy(mptcp_sk(sk));
inet_sock_destruct(sk);
}

Expand Down Expand Up @@ -505,6 +499,7 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk,
*/
new_msk->sk_destruct = mptcp_sock_destruct;
mptcp_pm_new_connection(mptcp_sk(new_msk), 1);
mptcp_token_accept(subflow_req, mptcp_sk(new_msk));
ctx->conn = new_msk;
new_msk = NULL;

Expand Down
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