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Commit | Line | Data |
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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
ef456144 CG |
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 | |
538950a1 CG |
5 | * the first socket. An optional BPF program can also be configured for |
6 | * selecting the socket index from the array of available sockets. | |
ef456144 CG |
7 | */ |
8 | ||
9 | #include <net/sock_reuseport.h> | |
538950a1 | 10 | #include <linux/bpf.h> |
ef456144 CG |
11 | #include <linux/rcupdate.h> |
12 | ||
13 | #define INIT_SOCKS 128 | |
14 | ||
15 | static DEFINE_SPINLOCK(reuseport_lock); | |
16 | ||
822f9bb1 | 17 | static struct sock_reuseport *__reuseport_alloc(unsigned int max_socks) |
ef456144 | 18 | { |
822f9bb1 | 19 | unsigned int size = sizeof(struct sock_reuseport) + |
ef456144 CG |
20 | sizeof(struct sock *) * max_socks; |
21 | struct sock_reuseport *reuse = kzalloc(size, GFP_ATOMIC); | |
22 | ||
23 | if (!reuse) | |
24 | return NULL; | |
25 | ||
26 | reuse->max_socks = max_socks; | |
27 | ||
538950a1 | 28 | RCU_INIT_POINTER(reuse->prog, NULL); |
ef456144 CG |
29 | return reuse; |
30 | } | |
31 | ||
32 | int reuseport_alloc(struct sock *sk) | |
33 | { | |
34 | struct sock_reuseport *reuse; | |
35 | ||
36 | /* bh lock used since this function call may precede hlist lock in | |
37 | * soft irq of receive path or setsockopt from process context | |
38 | */ | |
39 | spin_lock_bh(&reuseport_lock); | |
1b5f962e CG |
40 | |
41 | /* Allocation attempts can occur concurrently via the setsockopt path | |
42 | * and the bind/hash path. Nothing to do when we lose the race. | |
43 | */ | |
44 | if (rcu_dereference_protected(sk->sk_reuseport_cb, | |
45 | lockdep_is_held(&reuseport_lock))) | |
46 | goto out; | |
47 | ||
ef456144 CG |
48 | reuse = __reuseport_alloc(INIT_SOCKS); |
49 | if (!reuse) { | |
50 | spin_unlock_bh(&reuseport_lock); | |
51 | return -ENOMEM; | |
52 | } | |
53 | ||
54 | reuse->socks[0] = sk; | |
55 | reuse->num_socks = 1; | |
56 | rcu_assign_pointer(sk->sk_reuseport_cb, reuse); | |
57 | ||
1b5f962e | 58 | out: |
ef456144 CG |
59 | spin_unlock_bh(&reuseport_lock); |
60 | ||
61 | return 0; | |
62 | } | |
63 | EXPORT_SYMBOL(reuseport_alloc); | |
64 | ||
65 | static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse) | |
66 | { | |
67 | struct sock_reuseport *more_reuse; | |
68 | u32 more_socks_size, i; | |
69 | ||
70 | more_socks_size = reuse->max_socks * 2U; | |
71 | if (more_socks_size > U16_MAX) | |
72 | return NULL; | |
73 | ||
74 | more_reuse = __reuseport_alloc(more_socks_size); | |
75 | if (!more_reuse) | |
76 | return NULL; | |
77 | ||
78 | more_reuse->max_socks = more_socks_size; | |
79 | more_reuse->num_socks = reuse->num_socks; | |
538950a1 | 80 | more_reuse->prog = reuse->prog; |
ef456144 CG |
81 | |
82 | memcpy(more_reuse->socks, reuse->socks, | |
83 | reuse->num_socks * sizeof(struct sock *)); | |
84 | ||
85 | for (i = 0; i < reuse->num_socks; ++i) | |
86 | rcu_assign_pointer(reuse->socks[i]->sk_reuseport_cb, | |
87 | more_reuse); | |
88 | ||
538950a1 CG |
89 | /* Note: we use kfree_rcu here instead of reuseport_free_rcu so |
90 | * that reuse and more_reuse can temporarily share a reference | |
91 | * to prog. | |
92 | */ | |
ef456144 CG |
93 | kfree_rcu(reuse, rcu); |
94 | return more_reuse; | |
95 | } | |
96 | ||
97 | /** | |
98 | * reuseport_add_sock - Add a socket to the reuseport group of another. | |
99 | * @sk: New socket to add to the group. | |
100 | * @sk2: Socket belonging to the existing reuseport group. | |
101 | * May return ENOMEM and not add socket to group under memory pressure. | |
102 | */ | |
b4ace4f1 | 103 | int reuseport_add_sock(struct sock *sk, struct sock *sk2) |
ef456144 CG |
104 | { |
105 | struct sock_reuseport *reuse; | |
106 | ||
b4ace4f1 CG |
107 | if (!rcu_access_pointer(sk2->sk_reuseport_cb)) { |
108 | int err = reuseport_alloc(sk2); | |
109 | ||
110 | if (err) | |
111 | return err; | |
112 | } | |
113 | ||
ef456144 CG |
114 | spin_lock_bh(&reuseport_lock); |
115 | reuse = rcu_dereference_protected(sk2->sk_reuseport_cb, | |
116 | lockdep_is_held(&reuseport_lock)), | |
117 | WARN_ONCE(rcu_dereference_protected(sk->sk_reuseport_cb, | |
118 | lockdep_is_held(&reuseport_lock)), | |
119 | "socket already in reuseport group"); | |
120 | ||
121 | if (reuse->num_socks == reuse->max_socks) { | |
122 | reuse = reuseport_grow(reuse); | |
123 | if (!reuse) { | |
124 | spin_unlock_bh(&reuseport_lock); | |
125 | return -ENOMEM; | |
126 | } | |
127 | } | |
128 | ||
129 | reuse->socks[reuse->num_socks] = sk; | |
130 | /* paired with smp_rmb() in reuseport_select_sock() */ | |
131 | smp_wmb(); | |
132 | reuse->num_socks++; | |
133 | rcu_assign_pointer(sk->sk_reuseport_cb, reuse); | |
134 | ||
135 | spin_unlock_bh(&reuseport_lock); | |
136 | ||
137 | return 0; | |
138 | } | |
ef456144 | 139 | |
538950a1 CG |
140 | static void reuseport_free_rcu(struct rcu_head *head) |
141 | { | |
142 | struct sock_reuseport *reuse; | |
143 | ||
144 | reuse = container_of(head, struct sock_reuseport, rcu); | |
145 | if (reuse->prog) | |
146 | bpf_prog_destroy(reuse->prog); | |
147 | kfree(reuse); | |
148 | } | |
149 | ||
ef456144 CG |
150 | void reuseport_detach_sock(struct sock *sk) |
151 | { | |
152 | struct sock_reuseport *reuse; | |
153 | int i; | |
154 | ||
155 | spin_lock_bh(&reuseport_lock); | |
156 | reuse = rcu_dereference_protected(sk->sk_reuseport_cb, | |
157 | lockdep_is_held(&reuseport_lock)); | |
158 | rcu_assign_pointer(sk->sk_reuseport_cb, NULL); | |
159 | ||
160 | for (i = 0; i < reuse->num_socks; i++) { | |
161 | if (reuse->socks[i] == sk) { | |
162 | reuse->socks[i] = reuse->socks[reuse->num_socks - 1]; | |
163 | reuse->num_socks--; | |
164 | if (reuse->num_socks == 0) | |
538950a1 | 165 | call_rcu(&reuse->rcu, reuseport_free_rcu); |
ef456144 CG |
166 | break; |
167 | } | |
168 | } | |
169 | spin_unlock_bh(&reuseport_lock); | |
170 | } | |
171 | EXPORT_SYMBOL(reuseport_detach_sock); | |
172 | ||
538950a1 CG |
173 | static struct sock *run_bpf(struct sock_reuseport *reuse, u16 socks, |
174 | struct bpf_prog *prog, struct sk_buff *skb, | |
175 | int hdr_len) | |
176 | { | |
177 | struct sk_buff *nskb = NULL; | |
178 | u32 index; | |
179 | ||
180 | if (skb_shared(skb)) { | |
181 | nskb = skb_clone(skb, GFP_ATOMIC); | |
182 | if (!nskb) | |
183 | return NULL; | |
184 | skb = nskb; | |
185 | } | |
186 | ||
187 | /* temporarily advance data past protocol header */ | |
188 | if (!pskb_pull(skb, hdr_len)) { | |
00ce3a15 | 189 | kfree_skb(nskb); |
538950a1 CG |
190 | return NULL; |
191 | } | |
192 | index = bpf_prog_run_save_cb(prog, skb); | |
193 | __skb_push(skb, hdr_len); | |
194 | ||
195 | consume_skb(nskb); | |
196 | ||
197 | if (index >= socks) | |
198 | return NULL; | |
199 | ||
200 | return reuse->socks[index]; | |
201 | } | |
202 | ||
ef456144 CG |
203 | /** |
204 | * reuseport_select_sock - Select a socket from an SO_REUSEPORT group. | |
205 | * @sk: First socket in the group. | |
538950a1 CG |
206 | * @hash: When no BPF filter is available, use this hash to select. |
207 | * @skb: skb to run through BPF filter. | |
208 | * @hdr_len: BPF filter expects skb data pointer at payload data. If | |
209 | * the skb does not yet point at the payload, this parameter represents | |
210 | * how far the pointer needs to advance to reach the payload. | |
ef456144 CG |
211 | * Returns a socket that should receive the packet (or NULL on error). |
212 | */ | |
538950a1 CG |
213 | struct sock *reuseport_select_sock(struct sock *sk, |
214 | u32 hash, | |
215 | struct sk_buff *skb, | |
216 | int hdr_len) | |
ef456144 CG |
217 | { |
218 | struct sock_reuseport *reuse; | |
538950a1 | 219 | struct bpf_prog *prog; |
ef456144 CG |
220 | struct sock *sk2 = NULL; |
221 | u16 socks; | |
222 | ||
223 | rcu_read_lock(); | |
224 | reuse = rcu_dereference(sk->sk_reuseport_cb); | |
225 | ||
226 | /* if memory allocation failed or add call is not yet complete */ | |
227 | if (!reuse) | |
228 | goto out; | |
229 | ||
538950a1 | 230 | prog = rcu_dereference(reuse->prog); |
ef456144 CG |
231 | socks = READ_ONCE(reuse->num_socks); |
232 | if (likely(socks)) { | |
233 | /* paired with smp_wmb() in reuseport_add_sock() */ | |
234 | smp_rmb(); | |
235 | ||
538950a1 CG |
236 | if (prog && skb) |
237 | sk2 = run_bpf(reuse, socks, prog, skb, hdr_len); | |
238 | else | |
239 | sk2 = reuse->socks[reciprocal_scale(hash, socks)]; | |
ef456144 CG |
240 | } |
241 | ||
242 | out: | |
243 | rcu_read_unlock(); | |
244 | return sk2; | |
245 | } | |
246 | EXPORT_SYMBOL(reuseport_select_sock); | |
538950a1 CG |
247 | |
248 | struct bpf_prog * | |
249 | reuseport_attach_prog(struct sock *sk, struct bpf_prog *prog) | |
250 | { | |
251 | struct sock_reuseport *reuse; | |
252 | struct bpf_prog *old_prog; | |
253 | ||
254 | spin_lock_bh(&reuseport_lock); | |
255 | reuse = rcu_dereference_protected(sk->sk_reuseport_cb, | |
256 | lockdep_is_held(&reuseport_lock)); | |
257 | old_prog = rcu_dereference_protected(reuse->prog, | |
258 | lockdep_is_held(&reuseport_lock)); | |
259 | rcu_assign_pointer(reuse->prog, prog); | |
260 | spin_unlock_bh(&reuseport_lock); | |
261 | ||
262 | return old_prog; | |
263 | } | |
264 | EXPORT_SYMBOL(reuseport_attach_prog); |