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[mirror_ubuntu-eoan-kernel.git] / net / core / sock_reuseport.c
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b2441318 1// SPDX-License-Identifier: GPL-2.0
ef456144
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2/*
3 * To speed up listener socket lookup, create an array to store all sockets
4 * listening on the same port. This allows a decision to be made after finding
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5 * the first socket. An optional BPF program can also be configured for
6 * selecting the socket index from the array of available sockets.
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7 */
8
9#include <net/sock_reuseport.h>
538950a1 10#include <linux/bpf.h>
736b4602 11#include <linux/idr.h>
8217ca65 12#include <linux/filter.h>
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13#include <linux/rcupdate.h>
14
15#define INIT_SOCKS 128
16
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17DEFINE_SPINLOCK(reuseport_lock);
18
19#define REUSEPORT_MIN_ID 1
20static DEFINE_IDA(reuseport_ida);
21
22int reuseport_get_id(struct sock_reuseport *reuse)
23{
24 int id;
25
26 if (reuse->reuseport_id)
27 return reuse->reuseport_id;
28
29 id = ida_simple_get(&reuseport_ida, REUSEPORT_MIN_ID, 0,
30 /* Called under reuseport_lock */
31 GFP_ATOMIC);
32 if (id < 0)
33 return id;
34
35 reuse->reuseport_id = id;
36
37 return reuse->reuseport_id;
38}
ef456144 39
822f9bb1 40static struct sock_reuseport *__reuseport_alloc(unsigned int max_socks)
ef456144 41{
822f9bb1 42 unsigned int size = sizeof(struct sock_reuseport) +
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43 sizeof(struct sock *) * max_socks;
44 struct sock_reuseport *reuse = kzalloc(size, GFP_ATOMIC);
45
46 if (!reuse)
47 return NULL;
48
49 reuse->max_socks = max_socks;
50
538950a1 51 RCU_INIT_POINTER(reuse->prog, NULL);
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52 return reuse;
53}
54
2dbb9b9e 55int reuseport_alloc(struct sock *sk, bool bind_inany)
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56{
57 struct sock_reuseport *reuse;
58
59 /* bh lock used since this function call may precede hlist lock in
60 * soft irq of receive path or setsockopt from process context
61 */
62 spin_lock_bh(&reuseport_lock);
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63
64 /* Allocation attempts can occur concurrently via the setsockopt path
65 * and the bind/hash path. Nothing to do when we lose the race.
66 */
2dbb9b9e
MKL
67 reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
68 lockdep_is_held(&reuseport_lock));
69 if (reuse) {
70 /* Only set reuse->bind_inany if the bind_inany is true.
71 * Otherwise, it will overwrite the reuse->bind_inany
72 * which was set by the bind/hash path.
73 */
74 if (bind_inany)
75 reuse->bind_inany = bind_inany;
1b5f962e 76 goto out;
2dbb9b9e 77 }
1b5f962e 78
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79 reuse = __reuseport_alloc(INIT_SOCKS);
80 if (!reuse) {
81 spin_unlock_bh(&reuseport_lock);
82 return -ENOMEM;
83 }
84
85 reuse->socks[0] = sk;
86 reuse->num_socks = 1;
2dbb9b9e 87 reuse->bind_inany = bind_inany;
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88 rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
89
1b5f962e 90out:
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91 spin_unlock_bh(&reuseport_lock);
92
93 return 0;
94}
95EXPORT_SYMBOL(reuseport_alloc);
96
97static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
98{
99 struct sock_reuseport *more_reuse;
100 u32 more_socks_size, i;
101
102 more_socks_size = reuse->max_socks * 2U;
103 if (more_socks_size > U16_MAX)
104 return NULL;
105
106 more_reuse = __reuseport_alloc(more_socks_size);
107 if (!more_reuse)
108 return NULL;
109
110 more_reuse->max_socks = more_socks_size;
111 more_reuse->num_socks = reuse->num_socks;
538950a1 112 more_reuse->prog = reuse->prog;
736b4602 113 more_reuse->reuseport_id = reuse->reuseport_id;
2dbb9b9e 114 more_reuse->bind_inany = reuse->bind_inany;
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115
116 memcpy(more_reuse->socks, reuse->socks,
117 reuse->num_socks * sizeof(struct sock *));
40a1227e 118 more_reuse->synq_overflow_ts = READ_ONCE(reuse->synq_overflow_ts);
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119
120 for (i = 0; i < reuse->num_socks; ++i)
121 rcu_assign_pointer(reuse->socks[i]->sk_reuseport_cb,
122 more_reuse);
123
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124 /* Note: we use kfree_rcu here instead of reuseport_free_rcu so
125 * that reuse and more_reuse can temporarily share a reference
126 * to prog.
127 */
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128 kfree_rcu(reuse, rcu);
129 return more_reuse;
130}
131
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132static void reuseport_free_rcu(struct rcu_head *head)
133{
134 struct sock_reuseport *reuse;
135
136 reuse = container_of(head, struct sock_reuseport, rcu);
8217ca65 137 sk_reuseport_prog_free(rcu_dereference_protected(reuse->prog, 1));
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138 if (reuse->reuseport_id)
139 ida_simple_remove(&reuseport_ida, reuse->reuseport_id);
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140 kfree(reuse);
141}
142
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143/**
144 * reuseport_add_sock - Add a socket to the reuseport group of another.
145 * @sk: New socket to add to the group.
146 * @sk2: Socket belonging to the existing reuseport group.
147 * May return ENOMEM and not add socket to group under memory pressure.
148 */
2dbb9b9e 149int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
ef456144 150{
4db428a7 151 struct sock_reuseport *old_reuse, *reuse;
ef456144 152
b4ace4f1 153 if (!rcu_access_pointer(sk2->sk_reuseport_cb)) {
2dbb9b9e 154 int err = reuseport_alloc(sk2, bind_inany);
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155
156 if (err)
157 return err;
158 }
159
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160 spin_lock_bh(&reuseport_lock);
161 reuse = rcu_dereference_protected(sk2->sk_reuseport_cb,
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ED
162 lockdep_is_held(&reuseport_lock));
163 old_reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
164 lockdep_is_held(&reuseport_lock));
165 if (old_reuse && old_reuse->num_socks != 1) {
166 spin_unlock_bh(&reuseport_lock);
167 return -EBUSY;
168 }
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169
170 if (reuse->num_socks == reuse->max_socks) {
171 reuse = reuseport_grow(reuse);
172 if (!reuse) {
173 spin_unlock_bh(&reuseport_lock);
174 return -ENOMEM;
175 }
176 }
177
178 reuse->socks[reuse->num_socks] = sk;
179 /* paired with smp_rmb() in reuseport_select_sock() */
180 smp_wmb();
181 reuse->num_socks++;
182 rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
183
184 spin_unlock_bh(&reuseport_lock);
185
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ED
186 if (old_reuse)
187 call_rcu(&old_reuse->rcu, reuseport_free_rcu);
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188 return 0;
189}
76c6d988 190EXPORT_SYMBOL(reuseport_add_sock);
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191
192void reuseport_detach_sock(struct sock *sk)
193{
194 struct sock_reuseport *reuse;
195 int i;
196
197 spin_lock_bh(&reuseport_lock);
198 reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
199 lockdep_is_held(&reuseport_lock));
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MKL
200
201 /* At least one of the sk in this reuseport group is added to
202 * a bpf map. Notify the bpf side. The bpf map logic will
203 * remove the sk if it is indeed added to a bpf map.
204 */
205 if (reuse->reuseport_id)
206 bpf_sk_reuseport_detach(sk);
207
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208 rcu_assign_pointer(sk->sk_reuseport_cb, NULL);
209
210 for (i = 0; i < reuse->num_socks; i++) {
211 if (reuse->socks[i] == sk) {
212 reuse->socks[i] = reuse->socks[reuse->num_socks - 1];
213 reuse->num_socks--;
214 if (reuse->num_socks == 0)
538950a1 215 call_rcu(&reuse->rcu, reuseport_free_rcu);
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216 break;
217 }
218 }
219 spin_unlock_bh(&reuseport_lock);
220}
221EXPORT_SYMBOL(reuseport_detach_sock);
222
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223static struct sock *run_bpf_filter(struct sock_reuseport *reuse, u16 socks,
224 struct bpf_prog *prog, struct sk_buff *skb,
225 int hdr_len)
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226{
227 struct sk_buff *nskb = NULL;
228 u32 index;
229
230 if (skb_shared(skb)) {
231 nskb = skb_clone(skb, GFP_ATOMIC);
232 if (!nskb)
233 return NULL;
234 skb = nskb;
235 }
236
237 /* temporarily advance data past protocol header */
238 if (!pskb_pull(skb, hdr_len)) {
00ce3a15 239 kfree_skb(nskb);
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240 return NULL;
241 }
242 index = bpf_prog_run_save_cb(prog, skb);
243 __skb_push(skb, hdr_len);
244
245 consume_skb(nskb);
246
247 if (index >= socks)
248 return NULL;
249
250 return reuse->socks[index];
251}
252
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253/**
254 * reuseport_select_sock - Select a socket from an SO_REUSEPORT group.
255 * @sk: First socket in the group.
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256 * @hash: When no BPF filter is available, use this hash to select.
257 * @skb: skb to run through BPF filter.
258 * @hdr_len: BPF filter expects skb data pointer at payload data. If
259 * the skb does not yet point at the payload, this parameter represents
260 * how far the pointer needs to advance to reach the payload.
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261 * Returns a socket that should receive the packet (or NULL on error).
262 */
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263struct sock *reuseport_select_sock(struct sock *sk,
264 u32 hash,
265 struct sk_buff *skb,
266 int hdr_len)
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267{
268 struct sock_reuseport *reuse;
538950a1 269 struct bpf_prog *prog;
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CG
270 struct sock *sk2 = NULL;
271 u16 socks;
272
273 rcu_read_lock();
274 reuse = rcu_dereference(sk->sk_reuseport_cb);
275
276 /* if memory allocation failed or add call is not yet complete */
277 if (!reuse)
278 goto out;
279
538950a1 280 prog = rcu_dereference(reuse->prog);
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CG
281 socks = READ_ONCE(reuse->num_socks);
282 if (likely(socks)) {
283 /* paired with smp_wmb() in reuseport_add_sock() */
284 smp_rmb();
285
8217ca65
MKL
286 if (!prog || !skb)
287 goto select_by_hash;
288
289 if (prog->type == BPF_PROG_TYPE_SK_REUSEPORT)
290 sk2 = bpf_run_sk_reuseport(reuse, sk, prog, skb, hash);
291 else
292 sk2 = run_bpf_filter(reuse, socks, prog, skb, hdr_len);
e94a62f5 293
8217ca65 294select_by_hash:
e94a62f5
PA
295 /* no bpf or invalid bpf result: fall back to hash usage */
296 if (!sk2)
538950a1 297 sk2 = reuse->socks[reciprocal_scale(hash, socks)];
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CG
298 }
299
300out:
301 rcu_read_unlock();
302 return sk2;
303}
304EXPORT_SYMBOL(reuseport_select_sock);
538950a1 305
8217ca65 306int reuseport_attach_prog(struct sock *sk, struct bpf_prog *prog)
538950a1
CG
307{
308 struct sock_reuseport *reuse;
309 struct bpf_prog *old_prog;
310
8217ca65
MKL
311 if (sk_unhashed(sk) && sk->sk_reuseport) {
312 int err = reuseport_alloc(sk, false);
313
314 if (err)
315 return err;
316 } else if (!rcu_access_pointer(sk->sk_reuseport_cb)) {
317 /* The socket wasn't bound with SO_REUSEPORT */
318 return -EINVAL;
319 }
320
538950a1
CG
321 spin_lock_bh(&reuseport_lock);
322 reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
323 lockdep_is_held(&reuseport_lock));
324 old_prog = rcu_dereference_protected(reuse->prog,
325 lockdep_is_held(&reuseport_lock));
326 rcu_assign_pointer(reuse->prog, prog);
327 spin_unlock_bh(&reuseport_lock);
328
8217ca65
MKL
329 sk_reuseport_prog_free(old_prog);
330 return 0;
538950a1
CG
331}
332EXPORT_SYMBOL(reuseport_attach_prog);