xref: /openbmc/linux/net/ipv4/bpf_tcp_ca.c (revision 25b892b5)
1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2019 Facebook  */
3 
4 #include <linux/types.h>
5 #include <linux/bpf_verifier.h>
6 #include <linux/bpf.h>
7 #include <linux/btf.h>
8 #include <linux/btf_ids.h>
9 #include <linux/filter.h>
10 #include <net/tcp.h>
11 #include <net/bpf_sk_storage.h>
12 
13 /* "extern" is to avoid sparse warning.  It is only used in bpf_struct_ops.c. */
14 extern struct bpf_struct_ops bpf_tcp_congestion_ops;
15 
16 static u32 optional_ops[] = {
17 	offsetof(struct tcp_congestion_ops, init),
18 	offsetof(struct tcp_congestion_ops, release),
19 	offsetof(struct tcp_congestion_ops, set_state),
20 	offsetof(struct tcp_congestion_ops, cwnd_event),
21 	offsetof(struct tcp_congestion_ops, in_ack_event),
22 	offsetof(struct tcp_congestion_ops, pkts_acked),
23 	offsetof(struct tcp_congestion_ops, min_tso_segs),
24 	offsetof(struct tcp_congestion_ops, sndbuf_expand),
25 	offsetof(struct tcp_congestion_ops, cong_control),
26 };
27 
28 static u32 unsupported_ops[] = {
29 	offsetof(struct tcp_congestion_ops, get_info),
30 };
31 
32 static const struct btf_type *tcp_sock_type;
33 static u32 tcp_sock_id, sock_id;
34 
35 static int bpf_tcp_ca_init(struct btf *btf)
36 {
37 	s32 type_id;
38 
39 	type_id = btf_find_by_name_kind(btf, "sock", BTF_KIND_STRUCT);
40 	if (type_id < 0)
41 		return -EINVAL;
42 	sock_id = type_id;
43 
44 	type_id = btf_find_by_name_kind(btf, "tcp_sock", BTF_KIND_STRUCT);
45 	if (type_id < 0)
46 		return -EINVAL;
47 	tcp_sock_id = type_id;
48 	tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
49 
50 	return 0;
51 }
52 
53 static bool is_optional(u32 member_offset)
54 {
55 	unsigned int i;
56 
57 	for (i = 0; i < ARRAY_SIZE(optional_ops); i++) {
58 		if (member_offset == optional_ops[i])
59 			return true;
60 	}
61 
62 	return false;
63 }
64 
65 static bool is_unsupported(u32 member_offset)
66 {
67 	unsigned int i;
68 
69 	for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
70 		if (member_offset == unsupported_ops[i])
71 			return true;
72 	}
73 
74 	return false;
75 }
76 
77 extern struct btf *btf_vmlinux;
78 
79 static bool bpf_tcp_ca_is_valid_access(int off, int size,
80 				       enum bpf_access_type type,
81 				       const struct bpf_prog *prog,
82 				       struct bpf_insn_access_aux *info)
83 {
84 	if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
85 		return false;
86 	if (type != BPF_READ)
87 		return false;
88 	if (off % size != 0)
89 		return false;
90 
91 	if (!btf_ctx_access(off, size, type, prog, info))
92 		return false;
93 
94 	if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
95 		/* promote it to tcp_sock */
96 		info->btf_id = tcp_sock_id;
97 
98 	return true;
99 }
100 
101 static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
102 					const struct btf *btf,
103 					const struct btf_type *t, int off,
104 					int size, enum bpf_access_type atype,
105 					u32 *next_btf_id)
106 {
107 	size_t end;
108 
109 	if (atype == BPF_READ)
110 		return btf_struct_access(log, btf, t, off, size, atype, next_btf_id);
111 
112 	if (t != tcp_sock_type) {
113 		bpf_log(log, "only read is supported\n");
114 		return -EACCES;
115 	}
116 
117 	switch (off) {
118 	case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
119 		end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
120 		break;
121 	case offsetof(struct inet_connection_sock, icsk_ack.pending):
122 		end = offsetofend(struct inet_connection_sock,
123 				  icsk_ack.pending);
124 		break;
125 	case offsetof(struct tcp_sock, snd_cwnd):
126 		end = offsetofend(struct tcp_sock, snd_cwnd);
127 		break;
128 	case offsetof(struct tcp_sock, snd_cwnd_cnt):
129 		end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
130 		break;
131 	case offsetof(struct tcp_sock, snd_ssthresh):
132 		end = offsetofend(struct tcp_sock, snd_ssthresh);
133 		break;
134 	case offsetof(struct tcp_sock, ecn_flags):
135 		end = offsetofend(struct tcp_sock, ecn_flags);
136 		break;
137 	default:
138 		bpf_log(log, "no write support to tcp_sock at off %d\n", off);
139 		return -EACCES;
140 	}
141 
142 	if (off + size > end) {
143 		bpf_log(log,
144 			"write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
145 			off, size, end);
146 		return -EACCES;
147 	}
148 
149 	return NOT_INIT;
150 }
151 
152 BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
153 {
154 	/* bpf_tcp_ca prog cannot have NULL tp */
155 	__tcp_send_ack((struct sock *)tp, rcv_nxt);
156 	return 0;
157 }
158 
159 static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
160 	.func		= bpf_tcp_send_ack,
161 	.gpl_only	= false,
162 	/* In case we want to report error later */
163 	.ret_type	= RET_INTEGER,
164 	.arg1_type	= ARG_PTR_TO_BTF_ID,
165 	.arg1_btf_id	= &tcp_sock_id,
166 	.arg2_type	= ARG_ANYTHING,
167 };
168 
169 static u32 prog_ops_moff(const struct bpf_prog *prog)
170 {
171 	const struct btf_member *m;
172 	const struct btf_type *t;
173 	u32 midx;
174 
175 	midx = prog->expected_attach_type;
176 	t = bpf_tcp_congestion_ops.type;
177 	m = &btf_type_member(t)[midx];
178 
179 	return btf_member_bit_offset(t, m) / 8;
180 }
181 
182 static const struct bpf_func_proto *
183 bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
184 			  const struct bpf_prog *prog)
185 {
186 	switch (func_id) {
187 	case BPF_FUNC_tcp_send_ack:
188 		return &bpf_tcp_send_ack_proto;
189 	case BPF_FUNC_sk_storage_get:
190 		return &bpf_sk_storage_get_proto;
191 	case BPF_FUNC_sk_storage_delete:
192 		return &bpf_sk_storage_delete_proto;
193 	case BPF_FUNC_setsockopt:
194 		/* Does not allow release() to call setsockopt.
195 		 * release() is called when the current bpf-tcp-cc
196 		 * is retiring.  It is not allowed to call
197 		 * setsockopt() to make further changes which
198 		 * may potentially allocate new resources.
199 		 */
200 		if (prog_ops_moff(prog) !=
201 		    offsetof(struct tcp_congestion_ops, release))
202 			return &bpf_sk_setsockopt_proto;
203 		return NULL;
204 	case BPF_FUNC_getsockopt:
205 		/* Since get/setsockopt is usually expected to
206 		 * be available together, disable getsockopt for
207 		 * release also to avoid usage surprise.
208 		 * The bpf-tcp-cc already has a more powerful way
209 		 * to read tcp_sock from the PTR_TO_BTF_ID.
210 		 */
211 		if (prog_ops_moff(prog) !=
212 		    offsetof(struct tcp_congestion_ops, release))
213 			return &bpf_sk_getsockopt_proto;
214 		return NULL;
215 	default:
216 		return bpf_base_func_proto(func_id);
217 	}
218 }
219 
220 BTF_SET_START(bpf_tcp_ca_kfunc_ids)
221 BTF_ID(func, tcp_reno_ssthresh)
222 BTF_ID(func, tcp_reno_cong_avoid)
223 BTF_ID(func, tcp_reno_undo_cwnd)
224 BTF_ID(func, tcp_slow_start)
225 BTF_ID(func, tcp_cong_avoid_ai)
226 #ifdef CONFIG_X86
227 #ifdef CONFIG_DYNAMIC_FTRACE
228 #if IS_BUILTIN(CONFIG_TCP_CONG_CUBIC)
229 BTF_ID(func, cubictcp_init)
230 BTF_ID(func, cubictcp_recalc_ssthresh)
231 BTF_ID(func, cubictcp_cong_avoid)
232 BTF_ID(func, cubictcp_state)
233 BTF_ID(func, cubictcp_cwnd_event)
234 BTF_ID(func, cubictcp_acked)
235 #endif
236 #if IS_BUILTIN(CONFIG_TCP_CONG_DCTCP)
237 BTF_ID(func, dctcp_init)
238 BTF_ID(func, dctcp_update_alpha)
239 BTF_ID(func, dctcp_cwnd_event)
240 BTF_ID(func, dctcp_ssthresh)
241 BTF_ID(func, dctcp_cwnd_undo)
242 BTF_ID(func, dctcp_state)
243 #endif
244 #if IS_BUILTIN(CONFIG_TCP_CONG_BBR)
245 BTF_ID(func, bbr_init)
246 BTF_ID(func, bbr_main)
247 BTF_ID(func, bbr_sndbuf_expand)
248 BTF_ID(func, bbr_undo_cwnd)
249 BTF_ID(func, bbr_cwnd_event)
250 BTF_ID(func, bbr_ssthresh)
251 BTF_ID(func, bbr_min_tso_segs)
252 BTF_ID(func, bbr_set_state)
253 #endif
254 #endif  /* CONFIG_DYNAMIC_FTRACE */
255 #endif	/* CONFIG_X86 */
256 BTF_SET_END(bpf_tcp_ca_kfunc_ids)
257 
258 static bool bpf_tcp_ca_check_kfunc_call(u32 kfunc_btf_id)
259 {
260 	return btf_id_set_contains(&bpf_tcp_ca_kfunc_ids, kfunc_btf_id);
261 }
262 
263 static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
264 	.get_func_proto		= bpf_tcp_ca_get_func_proto,
265 	.is_valid_access	= bpf_tcp_ca_is_valid_access,
266 	.btf_struct_access	= bpf_tcp_ca_btf_struct_access,
267 	.check_kfunc_call	= bpf_tcp_ca_check_kfunc_call,
268 };
269 
270 static int bpf_tcp_ca_init_member(const struct btf_type *t,
271 				  const struct btf_member *member,
272 				  void *kdata, const void *udata)
273 {
274 	const struct tcp_congestion_ops *utcp_ca;
275 	struct tcp_congestion_ops *tcp_ca;
276 	int prog_fd;
277 	u32 moff;
278 
279 	utcp_ca = (const struct tcp_congestion_ops *)udata;
280 	tcp_ca = (struct tcp_congestion_ops *)kdata;
281 
282 	moff = btf_member_bit_offset(t, member) / 8;
283 	switch (moff) {
284 	case offsetof(struct tcp_congestion_ops, flags):
285 		if (utcp_ca->flags & ~TCP_CONG_MASK)
286 			return -EINVAL;
287 		tcp_ca->flags = utcp_ca->flags;
288 		return 1;
289 	case offsetof(struct tcp_congestion_ops, name):
290 		if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
291 				     sizeof(tcp_ca->name)) <= 0)
292 			return -EINVAL;
293 		if (tcp_ca_find(utcp_ca->name))
294 			return -EEXIST;
295 		return 1;
296 	}
297 
298 	if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))
299 		return 0;
300 
301 	/* Ensure bpf_prog is provided for compulsory func ptr */
302 	prog_fd = (int)(*(unsigned long *)(udata + moff));
303 	if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))
304 		return -EINVAL;
305 
306 	return 0;
307 }
308 
309 static int bpf_tcp_ca_check_member(const struct btf_type *t,
310 				   const struct btf_member *member)
311 {
312 	if (is_unsupported(btf_member_bit_offset(t, member) / 8))
313 		return -ENOTSUPP;
314 	return 0;
315 }
316 
317 static int bpf_tcp_ca_reg(void *kdata)
318 {
319 	return tcp_register_congestion_control(kdata);
320 }
321 
322 static void bpf_tcp_ca_unreg(void *kdata)
323 {
324 	tcp_unregister_congestion_control(kdata);
325 }
326 
327 struct bpf_struct_ops bpf_tcp_congestion_ops = {
328 	.verifier_ops = &bpf_tcp_ca_verifier_ops,
329 	.reg = bpf_tcp_ca_reg,
330 	.unreg = bpf_tcp_ca_unreg,
331 	.check_member = bpf_tcp_ca_check_member,
332 	.init_member = bpf_tcp_ca_init_member,
333 	.init = bpf_tcp_ca_init,
334 	.name = "tcp_congestion_ops",
335 };
336