]>
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 ED |
43 | size_t lopt_size = sizeof(struct listen_sock); |
44 | struct listen_sock *lopt; | |
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 *); | |
50 | if (lopt_size > PAGE_SIZE) | |
7a1c8e5a | 51 | lopt = vzalloc(lopt_size); |
72a3effa ED |
52 | else |
53 | lopt = kzalloc(lopt_size, GFP_KERNEL); | |
0e87506f ACM |
54 | if (lopt == NULL) |
55 | return -ENOMEM; | |
56 | ||
72a3effa ED |
57 | for (lopt->max_qlen_log = 3; |
58 | (1 << lopt->max_qlen_log) < nr_table_entries; | |
0e87506f ACM |
59 | lopt->max_qlen_log++); |
60 | ||
61 | get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd)); | |
62 | rwlock_init(&queue->syn_wait_lock); | |
3eb4801d | 63 | queue->rskq_accept_head = NULL; |
83e3609e | 64 | lopt->nr_table_entries = nr_table_entries; |
0e87506f ACM |
65 | |
66 | write_lock_bh(&queue->syn_wait_lock); | |
67 | queue->listen_opt = lopt; | |
68 | write_unlock_bh(&queue->syn_wait_lock); | |
69 | ||
70 | return 0; | |
71 | } | |
72 | ||
dab6ba36 PE |
73 | void __reqsk_queue_destroy(struct request_sock_queue *queue) |
74 | { | |
75 | struct listen_sock *lopt; | |
76 | size_t lopt_size; | |
77 | ||
78 | /* | |
79 | * this is an error recovery path only | |
80 | * no locking needed and the lopt is not NULL | |
81 | */ | |
82 | ||
83 | lopt = queue->listen_opt; | |
84 | lopt_size = sizeof(struct listen_sock) + | |
85 | lopt->nr_table_entries * sizeof(struct request_sock *); | |
86 | ||
87 | if (lopt_size > PAGE_SIZE) | |
88 | vfree(lopt); | |
89 | else | |
90 | kfree(lopt); | |
91 | } | |
92 | ||
dab6ba36 PE |
93 | static inline struct listen_sock *reqsk_queue_yank_listen_sk( |
94 | struct request_sock_queue *queue) | |
95 | { | |
96 | struct listen_sock *lopt; | |
97 | ||
98 | write_lock_bh(&queue->syn_wait_lock); | |
99 | lopt = queue->listen_opt; | |
100 | queue->listen_opt = NULL; | |
101 | write_unlock_bh(&queue->syn_wait_lock); | |
102 | ||
103 | return lopt; | |
104 | } | |
105 | ||
83e3609e ACM |
106 | void reqsk_queue_destroy(struct request_sock_queue *queue) |
107 | { | |
108 | /* make all the listen_opt local to us */ | |
109 | struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue); | |
72a3effa ED |
110 | size_t lopt_size = sizeof(struct listen_sock) + |
111 | lopt->nr_table_entries * sizeof(struct request_sock *); | |
83e3609e ACM |
112 | |
113 | if (lopt->qlen != 0) { | |
72a3effa | 114 | unsigned int i; |
83e3609e ACM |
115 | |
116 | for (i = 0; i < lopt->nr_table_entries; i++) { | |
117 | struct request_sock *req; | |
118 | ||
119 | while ((req = lopt->syn_table[i]) != NULL) { | |
120 | lopt->syn_table[i] = req->dl_next; | |
121 | lopt->qlen--; | |
122 | reqsk_free(req); | |
123 | } | |
124 | } | |
125 | } | |
126 | ||
547b792c | 127 | WARN_ON(lopt->qlen != 0); |
72a3effa ED |
128 | if (lopt_size > PAGE_SIZE) |
129 | vfree(lopt); | |
130 | else | |
131 | kfree(lopt); | |
83e3609e ACM |
132 | } |
133 | ||
8336886f JC |
134 | /* |
135 | * This function is called to set a Fast Open socket's "fastopen_rsk" field | |
136 | * to NULL when a TFO socket no longer needs to access the request_sock. | |
137 | * This happens only after 3WHS has been either completed or aborted (e.g., | |
138 | * RST is received). | |
139 | * | |
140 | * Before TFO, a child socket is created only after 3WHS is completed, | |
141 | * hence it never needs to access the request_sock. things get a lot more | |
142 | * complex with TFO. A child socket, accepted or not, has to access its | |
143 | * request_sock for 3WHS processing, e.g., to retransmit SYN-ACK pkts, | |
144 | * until 3WHS is either completed or aborted. Afterwards the req will stay | |
145 | * until either the child socket is accepted, or in the rare case when the | |
146 | * listener is closed before the child is accepted. | |
147 | * | |
148 | * In short, a request socket is only freed after BOTH 3WHS has completed | |
149 | * (or aborted) and the child socket has been accepted (or listener closed). | |
150 | * When a child socket is accepted, its corresponding req->sk is set to | |
151 | * NULL since it's no longer needed. More importantly, "req->sk == NULL" | |
152 | * will be used by the code below to determine if a child socket has been | |
153 | * accepted or not, and the check is protected by the fastopenq->lock | |
154 | * described below. | |
155 | * | |
156 | * Note that fastopen_rsk is only accessed from the child socket's context | |
157 | * with its socket lock held. But a request_sock (req) can be accessed by | |
158 | * both its child socket through fastopen_rsk, and a listener socket through | |
159 | * icsk_accept_queue.rskq_accept_head. To protect the access a simple spin | |
160 | * lock per listener "icsk->icsk_accept_queue.fastopenq->lock" is created. | |
161 | * only in the rare case when both the listener and the child locks are held, | |
162 | * e.g., in inet_csk_listen_stop() do we not need to acquire the lock. | |
163 | * The lock also protects other fields such as fastopenq->qlen, which is | |
164 | * decremented by this function when fastopen_rsk is no longer needed. | |
165 | * | |
166 | * Note that another solution was to simply use the existing socket lock | |
167 | * from the listener. But first socket lock is difficult to use. It is not | |
168 | * a simple spin lock - one must consider sock_owned_by_user() and arrange | |
169 | * to use sk_add_backlog() stuff. But what really makes it infeasible is the | |
170 | * locking hierarchy violation. E.g., inet_csk_listen_stop() may try to | |
171 | * acquire a child's lock while holding listener's socket lock. A corner | |
172 | * case might also exist in tcp_v4_hnd_req() that will trigger this locking | |
173 | * order. | |
174 | * | |
175 | * When a TFO req is created, it needs to sock_hold its listener to prevent | |
176 | * the latter data structure from going away. | |
177 | * | |
178 | * This function also sets "treq->listener" to NULL and unreference listener | |
179 | * socket. treq->listener is used by the listener so it is protected by the | |
180 | * fastopenq->lock in this function. | |
181 | */ | |
182 | void reqsk_fastopen_remove(struct sock *sk, struct request_sock *req, | |
183 | bool reset) | |
184 | { | |
185 | struct sock *lsk = tcp_rsk(req)->listener; | |
186 | struct fastopen_queue *fastopenq = | |
187 | inet_csk(lsk)->icsk_accept_queue.fastopenq; | |
188 | ||
189 | BUG_ON(!spin_is_locked(&sk->sk_lock.slock) && !sock_owned_by_user(sk)); | |
190 | ||
191 | tcp_sk(sk)->fastopen_rsk = NULL; | |
192 | spin_lock_bh(&fastopenq->lock); | |
193 | fastopenq->qlen--; | |
194 | tcp_rsk(req)->listener = NULL; | |
195 | if (req->sk) /* the child socket hasn't been accepted yet */ | |
196 | goto out; | |
197 | ||
198 | if (!reset || lsk->sk_state != TCP_LISTEN) { | |
199 | /* If the listener has been closed don't bother with the | |
200 | * special RST handling below. | |
201 | */ | |
202 | spin_unlock_bh(&fastopenq->lock); | |
203 | sock_put(lsk); | |
204 | reqsk_free(req); | |
205 | return; | |
206 | } | |
207 | /* Wait for 60secs before removing a req that has triggered RST. | |
208 | * This is a simple defense against TFO spoofing attack - by | |
209 | * counting the req against fastopen.max_qlen, and disabling | |
210 | * TFO when the qlen exceeds max_qlen. | |
211 | * | |
212 | * For more details see CoNext'11 "TCP Fast Open" paper. | |
213 | */ | |
214 | req->expires = jiffies + 60*HZ; | |
215 | if (fastopenq->rskq_rst_head == NULL) | |
216 | fastopenq->rskq_rst_head = req; | |
217 | else | |
218 | fastopenq->rskq_rst_tail->dl_next = req; | |
219 | ||
220 | req->dl_next = NULL; | |
221 | fastopenq->rskq_rst_tail = req; | |
222 | fastopenq->qlen++; | |
223 | out: | |
224 | spin_unlock_bh(&fastopenq->lock); | |
225 | sock_put(lsk); | |
226 | return; | |
227 | } |