Commit | Line | Data |
---|---|---|
0e87506f ACM |
1 | /* |
2 | * NET Generic infrastructure for Network protocols. | |
3 | * | |
4 | * Authors: Arnaldo Carvalho de Melo <acme@conectiva.com.br> | |
5 | * | |
6 | * From code originally in include/net/tcp.h | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU General Public License | |
10 | * as published by the Free Software Foundation; either version | |
11 | * 2 of the License, or (at your option) any later version. | |
12 | */ | |
13 | ||
14 | #include <linux/module.h> | |
15 | #include <linux/random.h> | |
16 | #include <linux/slab.h> | |
17 | #include <linux/string.h> | |
8336886f | 18 | #include <linux/tcp.h> |
72a3effa | 19 | #include <linux/vmalloc.h> |
0e87506f ACM |
20 | |
21 | #include <net/request_sock.h> | |
22 | ||
e52c1f17 DM |
23 | /* |
24 | * Maximum number of SYN_RECV sockets in queue per LISTEN socket. | |
25 | * One SYN_RECV socket costs about 80bytes on a 32bit machine. | |
26 | * It would be better to replace it with a global counter for all sockets | |
27 | * but then some measure against one socket starving all other sockets | |
28 | * would be needed. | |
29 | * | |
99b53bdd | 30 | * The minimum value of it is 128. Experiments with real servers show that |
e52c1f17 | 31 | * it is absolutely not enough even at 100conn/sec. 256 cures most |
99b53bdd PP |
32 | * of problems. |
33 | * This value is adjusted to 128 for low memory machines, | |
34 | * and it will increase in proportion to the memory of machine. | |
72a3effa | 35 | * Note : Dont forget somaxconn that may limit backlog too. |
e52c1f17 DM |
36 | */ |
37 | int sysctl_max_syn_backlog = 256; | |
493f377d | 38 | EXPORT_SYMBOL(sysctl_max_syn_backlog); |
e52c1f17 | 39 | |
0e87506f | 40 | int reqsk_queue_alloc(struct request_sock_queue *queue, |
72a3effa | 41 | unsigned int nr_table_entries) |
0e87506f | 42 | { |
72a3effa | 43 | size_t lopt_size = sizeof(struct listen_sock); |
f6d8cb2e | 44 | struct listen_sock *lopt = NULL; |
72a3effa ED |
45 | |
46 | nr_table_entries = min_t(u32, nr_table_entries, sysctl_max_syn_backlog); | |
47 | nr_table_entries = max_t(u32, nr_table_entries, 8); | |
48 | nr_table_entries = roundup_pow_of_two(nr_table_entries + 1); | |
49 | lopt_size += nr_table_entries * sizeof(struct request_sock *); | |
f6d8cb2e ED |
50 | |
51 | if (lopt_size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) | |
52 | lopt = kzalloc(lopt_size, GFP_KERNEL | | |
53 | __GFP_NOWARN | | |
54 | __GFP_NORETRY); | |
55 | if (!lopt) | |
7a1c8e5a | 56 | lopt = vzalloc(lopt_size); |
f6d8cb2e | 57 | if (!lopt) |
0e87506f ACM |
58 | return -ENOMEM; |
59 | ||
0e87506f | 60 | get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd)); |
b2827053 | 61 | spin_lock_init(&queue->syn_wait_lock); |
3eb4801d | 62 | queue->rskq_accept_head = NULL; |
83e3609e | 63 | lopt->nr_table_entries = nr_table_entries; |
f6d8cb2e | 64 | lopt->max_qlen_log = ilog2(nr_table_entries); |
0e87506f | 65 | |
b2827053 | 66 | spin_lock_bh(&queue->syn_wait_lock); |
0e87506f | 67 | queue->listen_opt = lopt; |
b2827053 | 68 | spin_unlock_bh(&queue->syn_wait_lock); |
0e87506f ACM |
69 | |
70 | return 0; | |
71 | } | |
72 | ||
dab6ba36 PE |
73 | void __reqsk_queue_destroy(struct request_sock_queue *queue) |
74 | { | |
f6d8cb2e ED |
75 | /* This is an error recovery path only, no locking needed */ |
76 | kvfree(queue->listen_opt); | |
dab6ba36 PE |
77 | } |
78 | ||
dab6ba36 PE |
79 | static inline struct listen_sock *reqsk_queue_yank_listen_sk( |
80 | struct request_sock_queue *queue) | |
81 | { | |
82 | struct listen_sock *lopt; | |
83 | ||
b2827053 | 84 | spin_lock_bh(&queue->syn_wait_lock); |
dab6ba36 PE |
85 | lopt = queue->listen_opt; |
86 | queue->listen_opt = NULL; | |
b2827053 | 87 | spin_unlock_bh(&queue->syn_wait_lock); |
dab6ba36 PE |
88 | |
89 | return lopt; | |
90 | } | |
91 | ||
83e3609e ACM |
92 | void reqsk_queue_destroy(struct request_sock_queue *queue) |
93 | { | |
94 | /* make all the listen_opt local to us */ | |
95 | struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue); | |
96 | ||
fa76ce73 | 97 | if (listen_sock_qlen(lopt) != 0) { |
72a3effa | 98 | unsigned int i; |
83e3609e ACM |
99 | |
100 | for (i = 0; i < lopt->nr_table_entries; i++) { | |
101 | struct request_sock *req; | |
102 | ||
b2827053 | 103 | spin_lock_bh(&queue->syn_wait_lock); |
83e3609e ACM |
104 | while ((req = lopt->syn_table[i]) != NULL) { |
105 | lopt->syn_table[i] = req->dl_next; | |
2235f2ac ED |
106 | /* Because of following del_timer_sync(), |
107 | * we must release the spinlock here | |
108 | * or risk a dead lock. | |
109 | */ | |
110 | spin_unlock_bh(&queue->syn_wait_lock); | |
fa76ce73 | 111 | atomic_inc(&lopt->qlen_dec); |
2235f2ac | 112 | if (del_timer_sync(&req->rsk_timer)) |
fa76ce73 | 113 | reqsk_put(req); |
13854e5a | 114 | reqsk_put(req); |
2235f2ac | 115 | spin_lock_bh(&queue->syn_wait_lock); |
83e3609e | 116 | } |
b2827053 | 117 | spin_unlock_bh(&queue->syn_wait_lock); |
83e3609e ACM |
118 | } |
119 | } | |
120 | ||
fa76ce73 ED |
121 | if (WARN_ON(listen_sock_qlen(lopt) != 0)) |
122 | pr_err("qlen %u\n", listen_sock_qlen(lopt)); | |
f6d8cb2e | 123 | kvfree(lopt); |
83e3609e ACM |
124 | } |
125 | ||
8336886f JC |
126 | /* |
127 | * This function is called to set a Fast Open socket's "fastopen_rsk" field | |
128 | * to NULL when a TFO socket no longer needs to access the request_sock. | |
129 | * This happens only after 3WHS has been either completed or aborted (e.g., | |
130 | * RST is received). | |
131 | * | |
132 | * Before TFO, a child socket is created only after 3WHS is completed, | |
133 | * hence it never needs to access the request_sock. things get a lot more | |
134 | * complex with TFO. A child socket, accepted or not, has to access its | |
135 | * request_sock for 3WHS processing, e.g., to retransmit SYN-ACK pkts, | |
136 | * until 3WHS is either completed or aborted. Afterwards the req will stay | |
137 | * until either the child socket is accepted, or in the rare case when the | |
138 | * listener is closed before the child is accepted. | |
139 | * | |
140 | * In short, a request socket is only freed after BOTH 3WHS has completed | |
141 | * (or aborted) and the child socket has been accepted (or listener closed). | |
142 | * When a child socket is accepted, its corresponding req->sk is set to | |
143 | * NULL since it's no longer needed. More importantly, "req->sk == NULL" | |
144 | * will be used by the code below to determine if a child socket has been | |
145 | * accepted or not, and the check is protected by the fastopenq->lock | |
146 | * described below. | |
147 | * | |
148 | * Note that fastopen_rsk is only accessed from the child socket's context | |
149 | * with its socket lock held. But a request_sock (req) can be accessed by | |
150 | * both its child socket through fastopen_rsk, and a listener socket through | |
151 | * icsk_accept_queue.rskq_accept_head. To protect the access a simple spin | |
152 | * lock per listener "icsk->icsk_accept_queue.fastopenq->lock" is created. | |
153 | * only in the rare case when both the listener and the child locks are held, | |
154 | * e.g., in inet_csk_listen_stop() do we not need to acquire the lock. | |
155 | * The lock also protects other fields such as fastopenq->qlen, which is | |
156 | * decremented by this function when fastopen_rsk is no longer needed. | |
157 | * | |
158 | * Note that another solution was to simply use the existing socket lock | |
159 | * from the listener. But first socket lock is difficult to use. It is not | |
160 | * a simple spin lock - one must consider sock_owned_by_user() and arrange | |
161 | * to use sk_add_backlog() stuff. But what really makes it infeasible is the | |
162 | * locking hierarchy violation. E.g., inet_csk_listen_stop() may try to | |
163 | * acquire a child's lock while holding listener's socket lock. A corner | |
164 | * case might also exist in tcp_v4_hnd_req() that will trigger this locking | |
165 | * order. | |
166 | * | |
9439ce00 ED |
167 | * This function also sets "treq->tfo_listener" to false. |
168 | * treq->tfo_listener is used by the listener so it is protected by the | |
8336886f JC |
169 | * fastopenq->lock in this function. |
170 | */ | |
171 | void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, | |
172 | bool reset) | |
173 | { | |
9439ce00 ED |
174 | struct sock *lsk = req->rsk_listener; |
175 | struct fastopen_queue *fastopenq; | |
176 | ||
177 | fastopenq = inet_csk(lsk)->icsk_accept_queue.fastopenq; | |
8336886f | 178 | |
8336886f JC |
179 | tcp_sk(sk)->fastopen_rsk = NULL; |
180 | spin_lock_bh(&fastopenq->lock); | |
181 | fastopenq->qlen--; | |
9439ce00 | 182 | tcp_rsk(req)->tfo_listener = false; |
8336886f JC |
183 | if (req->sk) /* the child socket hasn't been accepted yet */ |
184 | goto out; | |
185 | ||
186 | if (!reset || lsk->sk_state != TCP_LISTEN) { | |
187 | /* If the listener has been closed don't bother with the | |
188 | * special RST handling below. | |
189 | */ | |
190 | spin_unlock_bh(&fastopenq->lock); | |
13854e5a | 191 | reqsk_put(req); |
8336886f JC |
192 | return; |
193 | } | |
194 | /* Wait for 60secs before removing a req that has triggered RST. | |
195 | * This is a simple defense against TFO spoofing attack - by | |
196 | * counting the req against fastopen.max_qlen, and disabling | |
197 | * TFO when the qlen exceeds max_qlen. | |
198 | * | |
199 | * For more details see CoNext'11 "TCP Fast Open" paper. | |
200 | */ | |
fa76ce73 | 201 | req->rsk_timer.expires = jiffies + 60*HZ; |
8336886f JC |
202 | if (fastopenq->rskq_rst_head == NULL) |
203 | fastopenq->rskq_rst_head = req; | |
204 | else | |
205 | fastopenq->rskq_rst_tail->dl_next = req; | |
206 | ||
207 | req->dl_next = NULL; | |
208 | fastopenq->rskq_rst_tail = req; | |
209 | fastopenq->qlen++; | |
210 | out: | |
211 | spin_unlock_bh(&fastopenq->lock); | |
8336886f | 212 | } |