From 2c5ebd001d4f0c64a2dfda94eb1d9b31a8863c8d Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Fri, 26 Jun 2020 19:30:00 +0200 Subject: mptcp: refactor token container Replace the radix tree with a hash table allocated at boot time. The radix tree has some shortcoming: a single lock is contented by all the mptcp operation, the lookup currently use such lock, and traversing all the items would require a 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 a 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 a hash bucket with a long chain is considered a failed attempt - accept() no longer can fail to token management. - if token creation fails at connect() time, we do fallback to TCP (before the connection was closed) v1 -> v2: - fix "no newline at end of file" - Jakub Signed-off-by: Paolo Abeni Reviewed-by: Mat Martineau Signed-off-by: David S. Miller --- net/mptcp/token.c | 271 ++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 192 insertions(+), 79 deletions(-) (limited to 'net/mptcp/token.c') diff --git a/net/mptcp/token.c b/net/mptcp/token.c index 33352dd99d4d..9c0771774815 100644 --- a/net/mptcp/token.c +++ b/net/mptcp/token.c @@ -24,7 +24,7 @@ #include #include -#include +#include #include #include #include @@ -33,10 +33,55 @@ #include #include "protocol.h" -static RADIX_TREE(token_tree, GFP_ATOMIC); -static RADIX_TREE(token_req_tree, GFP_ATOMIC); -static DEFINE_SPINLOCK(token_tree_lock); -static int token_used __read_mostly; +#define TOKEN_MAX_RETRIES 4 +#define TOKEN_MAX_CHAIN_LEN 4 + +struct token_bucket { + spinlock_t lock; + int chain_len; + struct hlist_nulls_head req_chain; + struct hlist_nulls_head msk_chain; +}; + +static struct token_bucket *token_hash __read_mostly; +static unsigned int token_mask __read_mostly; + +static struct token_bucket *token_bucket(u32 token) +{ + return &token_hash[token & token_mask]; +} + +/* called with bucket lock held */ +static struct mptcp_subflow_request_sock * +__token_lookup_req(struct token_bucket *t, u32 token) +{ + struct mptcp_subflow_request_sock *req; + struct hlist_nulls_node *pos; + + hlist_nulls_for_each_entry_rcu(req, pos, &t->req_chain, token_node) + if (req->token == token) + return req; + return NULL; +} + +/* called with bucket lock held */ +static struct mptcp_sock * +__token_lookup_msk(struct token_bucket *t, u32 token) +{ + struct hlist_nulls_node *pos; + struct sock *sk; + + sk_nulls_for_each_rcu(sk, pos, &t->msk_chain) + if (mptcp_sk(sk)->token == token) + return mptcp_sk(sk); + return NULL; +} + +static bool __token_bucket_busy(struct token_bucket *t, u32 token) +{ + return !token || t->chain_len >= TOKEN_MAX_CHAIN_LEN || + __token_lookup_req(t, token) || __token_lookup_msk(t, token); +} /** * mptcp_token_new_request - create new key/idsn/token for subflow_request @@ -52,30 +97,32 @@ static int token_used __read_mostly; int mptcp_token_new_request(struct request_sock *req) { struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req); - int err; - - while (1) { - u32 token; - - mptcp_crypto_key_gen_sha(&subflow_req->local_key, - &subflow_req->token, - &subflow_req->idsn); - pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n", - req, subflow_req->local_key, subflow_req->token, - subflow_req->idsn); - - token = subflow_req->token; - spin_lock_bh(&token_tree_lock); - if (!radix_tree_lookup(&token_req_tree, token) && - !radix_tree_lookup(&token_tree, token)) - break; - spin_unlock_bh(&token_tree_lock); + int retries = TOKEN_MAX_RETRIES; + struct token_bucket *bucket; + u32 token; + +again: + mptcp_crypto_key_gen_sha(&subflow_req->local_key, + &subflow_req->token, + &subflow_req->idsn); + pr_debug("req=%p local_key=%llu, token=%u, idsn=%llu\n", + req, subflow_req->local_key, subflow_req->token, + subflow_req->idsn); + + token = subflow_req->token; + bucket = token_bucket(token); + spin_lock_bh(&bucket->lock); + if (__token_bucket_busy(bucket, token)) { + spin_unlock_bh(&bucket->lock); + if (!--retries) + return -EBUSY; + goto again; } - err = radix_tree_insert(&token_req_tree, - subflow_req->token, &token_used); - spin_unlock_bh(&token_tree_lock); - return err; + hlist_nulls_add_head_rcu(&subflow_req->token_node, &bucket->req_chain); + bucket->chain_len++; + spin_unlock_bh(&bucket->lock); + return 0; } /** @@ -97,48 +144,56 @@ int mptcp_token_new_request(struct request_sock *req) int mptcp_token_new_connect(struct sock *sk) { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); - struct sock *mptcp_sock = subflow->conn; - int err; - - while (1) { - u32 token; + struct mptcp_sock *msk = mptcp_sk(subflow->conn); + int retries = TOKEN_MAX_RETRIES; + struct token_bucket *bucket; - mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token, - &subflow->idsn); + pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n", + sk, subflow->local_key, subflow->token, subflow->idsn); - pr_debug("ssk=%p, local_key=%llu, token=%u, idsn=%llu\n", - sk, subflow->local_key, subflow->token, subflow->idsn); +again: + mptcp_crypto_key_gen_sha(&subflow->local_key, &subflow->token, + &subflow->idsn); - token = subflow->token; - spin_lock_bh(&token_tree_lock); - if (!radix_tree_lookup(&token_req_tree, token) && - !radix_tree_lookup(&token_tree, token)) - break; - spin_unlock_bh(&token_tree_lock); + bucket = token_bucket(subflow->token); + spin_lock_bh(&bucket->lock); + if (__token_bucket_busy(bucket, subflow->token)) { + spin_unlock_bh(&bucket->lock); + if (!--retries) + return -EBUSY; + goto again; } - err = radix_tree_insert(&token_tree, subflow->token, mptcp_sock); - spin_unlock_bh(&token_tree_lock); - return err; + WRITE_ONCE(msk->token, subflow->token); + __sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain); + bucket->chain_len++; + spin_unlock_bh(&bucket->lock); + return 0; } /** - * mptcp_token_new_accept - insert token for later processing - * @token: the token to insert to the tree - * @conn: the just cloned socket linked to the new connection + * mptcp_token_accept - replace a req sk with full sock in token hash + * @req: the request socket to be removed + * @msk: the just cloned socket linked to the new connection * * Called when a SYN packet creates a new logical connection, i.e. * is not a join request. */ -int mptcp_token_new_accept(u32 token, struct sock *conn) +void mptcp_token_accept(struct mptcp_subflow_request_sock *req, + struct mptcp_sock *msk) { - int err; + struct mptcp_subflow_request_sock *pos; + struct token_bucket *bucket; - spin_lock_bh(&token_tree_lock); - err = radix_tree_insert(&token_tree, token, conn); - spin_unlock_bh(&token_tree_lock); + bucket = token_bucket(req->token); + spin_lock_bh(&bucket->lock); - return err; + /* pedantic lookup check for the moved token */ + pos = __token_lookup_req(bucket, req->token); + if (!WARN_ON_ONCE(pos != req)) + hlist_nulls_del_init_rcu(&req->token_node); + __sk_nulls_add_node_rcu((struct sock *)msk, &bucket->msk_chain); + spin_unlock_bh(&bucket->lock); } /** @@ -152,45 +207,103 @@ int mptcp_token_new_accept(u32 token, struct sock *conn) */ struct mptcp_sock *mptcp_token_get_sock(u32 token) { - struct sock *conn; - - spin_lock_bh(&token_tree_lock); - conn = radix_tree_lookup(&token_tree, token); - if (conn) { - /* token still reserved? */ - if (conn == (struct sock *)&token_used) - conn = NULL; - else - sock_hold(conn); + struct hlist_nulls_node *pos; + struct token_bucket *bucket; + struct mptcp_sock *msk; + struct sock *sk; + + rcu_read_lock(); + bucket = token_bucket(token); + +again: + sk_nulls_for_each_rcu(sk, pos, &bucket->msk_chain) { + msk = mptcp_sk(sk); + if (READ_ONCE(msk->token) != token) + continue; + if (!refcount_inc_not_zero(&sk->sk_refcnt)) + goto not_found; + if (READ_ONCE(msk->token) != token) { + sock_put(sk); + goto again; + } + goto found; } - spin_unlock_bh(&token_tree_lock); + if (get_nulls_value(pos) != (token & token_mask)) + goto again; + +not_found: + msk = NULL; - return mptcp_sk(conn); +found: + rcu_read_unlock(); + return msk; } /** * mptcp_token_destroy_request - remove mptcp connection/token - * @token: token of mptcp connection to remove + * @req: mptcp request socket dropping the token * - * Remove not-yet-fully-established incoming connection identified - * by @token. + * Remove the token associated to @req. */ -void mptcp_token_destroy_request(u32 token) +void mptcp_token_destroy_request(struct request_sock *req) { - spin_lock_bh(&token_tree_lock); - radix_tree_delete(&token_req_tree, token); - spin_unlock_bh(&token_tree_lock); + struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req); + struct mptcp_subflow_request_sock *pos; + struct token_bucket *bucket; + + if (hlist_nulls_unhashed(&subflow_req->token_node)) + return; + + bucket = token_bucket(subflow_req->token); + spin_lock_bh(&bucket->lock); + pos = __token_lookup_req(bucket, subflow_req->token); + if (!WARN_ON_ONCE(pos != subflow_req)) { + hlist_nulls_del_init_rcu(&pos->token_node); + bucket->chain_len--; + } + spin_unlock_bh(&bucket->lock); } /** * mptcp_token_destroy - remove mptcp connection/token - * @token: token of mptcp connection to remove + * @msk: mptcp connection dropping the token * - * Remove the connection identified by @token. + * Remove the token associated to @msk */ -void mptcp_token_destroy(u32 token) +void mptcp_token_destroy(struct mptcp_sock *msk) { - spin_lock_bh(&token_tree_lock); - radix_tree_delete(&token_tree, token); - spin_unlock_bh(&token_tree_lock); + struct token_bucket *bucket; + struct mptcp_sock *pos; + + if (sk_unhashed((struct sock *)msk)) + return; + + bucket = token_bucket(msk->token); + spin_lock_bh(&bucket->lock); + pos = __token_lookup_msk(bucket, msk->token); + if (!WARN_ON_ONCE(pos != msk)) { + __sk_nulls_del_node_init_rcu((struct sock *)pos); + bucket->chain_len--; + } + spin_unlock_bh(&bucket->lock); +} + +void __init mptcp_token_init(void) +{ + int i; + + token_hash = alloc_large_system_hash("MPTCP token", + sizeof(struct token_bucket), + 0, + 20,/* one slot per 1MB of memory */ + 0, + NULL, + &token_mask, + 0, + 64 * 1024); + for (i = 0; i < token_mask + 1; ++i) { + INIT_HLIST_NULLS_HEAD(&token_hash[i].req_chain, i); + INIT_HLIST_NULLS_HEAD(&token_hash[i].msk_chain, i); + spin_lock_init(&token_hash[i].lock); + } } -- cgit v1.2.3