xref: /openbmc/linux/net/ipv4/bpf_tcp_ca.c (revision 5edb7691)
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/filter.h>
9 #include <net/tcp.h>
10 
11 static u32 optional_ops[] = {
12 	offsetof(struct tcp_congestion_ops, init),
13 	offsetof(struct tcp_congestion_ops, release),
14 	offsetof(struct tcp_congestion_ops, set_state),
15 	offsetof(struct tcp_congestion_ops, cwnd_event),
16 	offsetof(struct tcp_congestion_ops, in_ack_event),
17 	offsetof(struct tcp_congestion_ops, pkts_acked),
18 	offsetof(struct tcp_congestion_ops, min_tso_segs),
19 	offsetof(struct tcp_congestion_ops, sndbuf_expand),
20 	offsetof(struct tcp_congestion_ops, cong_control),
21 };
22 
23 static u32 unsupported_ops[] = {
24 	offsetof(struct tcp_congestion_ops, get_info),
25 };
26 
27 static const struct btf_type *tcp_sock_type;
28 static u32 tcp_sock_id, sock_id;
29 
30 static int bpf_tcp_ca_init(struct btf *btf)
31 {
32 	s32 type_id;
33 
34 	type_id = btf_find_by_name_kind(btf, "sock", BTF_KIND_STRUCT);
35 	if (type_id < 0)
36 		return -EINVAL;
37 	sock_id = type_id;
38 
39 	type_id = btf_find_by_name_kind(btf, "tcp_sock", BTF_KIND_STRUCT);
40 	if (type_id < 0)
41 		return -EINVAL;
42 	tcp_sock_id = type_id;
43 	tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
44 
45 	return 0;
46 }
47 
48 static bool is_optional(u32 member_offset)
49 {
50 	unsigned int i;
51 
52 	for (i = 0; i < ARRAY_SIZE(optional_ops); i++) {
53 		if (member_offset == optional_ops[i])
54 			return true;
55 	}
56 
57 	return false;
58 }
59 
60 static bool is_unsupported(u32 member_offset)
61 {
62 	unsigned int i;
63 
64 	for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
65 		if (member_offset == unsupported_ops[i])
66 			return true;
67 	}
68 
69 	return false;
70 }
71 
72 extern struct btf *btf_vmlinux;
73 
74 static bool bpf_tcp_ca_is_valid_access(int off, int size,
75 				       enum bpf_access_type type,
76 				       const struct bpf_prog *prog,
77 				       struct bpf_insn_access_aux *info)
78 {
79 	if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
80 		return false;
81 	if (type != BPF_READ)
82 		return false;
83 	if (off % size != 0)
84 		return false;
85 
86 	if (!btf_ctx_access(off, size, type, prog, info))
87 		return false;
88 
89 	if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
90 		/* promote it to tcp_sock */
91 		info->btf_id = tcp_sock_id;
92 
93 	return true;
94 }
95 
96 static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
97 					const struct btf_type *t, int off,
98 					int size, enum bpf_access_type atype,
99 					u32 *next_btf_id)
100 {
101 	size_t end;
102 
103 	if (atype == BPF_READ)
104 		return btf_struct_access(log, t, off, size, atype, next_btf_id);
105 
106 	if (t != tcp_sock_type) {
107 		bpf_log(log, "only read is supported\n");
108 		return -EACCES;
109 	}
110 
111 	switch (off) {
112 	case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
113 		end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
114 		break;
115 	case offsetof(struct inet_connection_sock, icsk_ack.pending):
116 		end = offsetofend(struct inet_connection_sock,
117 				  icsk_ack.pending);
118 		break;
119 	case offsetof(struct tcp_sock, snd_cwnd):
120 		end = offsetofend(struct tcp_sock, snd_cwnd);
121 		break;
122 	case offsetof(struct tcp_sock, snd_cwnd_cnt):
123 		end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
124 		break;
125 	case offsetof(struct tcp_sock, snd_ssthresh):
126 		end = offsetofend(struct tcp_sock, snd_ssthresh);
127 		break;
128 	case offsetof(struct tcp_sock, ecn_flags):
129 		end = offsetofend(struct tcp_sock, ecn_flags);
130 		break;
131 	default:
132 		bpf_log(log, "no write support to tcp_sock at off %d\n", off);
133 		return -EACCES;
134 	}
135 
136 	if (off + size > end) {
137 		bpf_log(log,
138 			"write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
139 			off, size, end);
140 		return -EACCES;
141 	}
142 
143 	return NOT_INIT;
144 }
145 
146 BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
147 {
148 	/* bpf_tcp_ca prog cannot have NULL tp */
149 	__tcp_send_ack((struct sock *)tp, rcv_nxt);
150 	return 0;
151 }
152 
153 static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
154 	.func		= bpf_tcp_send_ack,
155 	.gpl_only	= false,
156 	/* In case we want to report error later */
157 	.ret_type	= RET_INTEGER,
158 	.arg1_type	= ARG_PTR_TO_BTF_ID,
159 	.arg2_type	= ARG_ANYTHING,
160 	.btf_id		= &tcp_sock_id,
161 };
162 
163 static const struct bpf_func_proto *
164 bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
165 			  const struct bpf_prog *prog)
166 {
167 	switch (func_id) {
168 	case BPF_FUNC_tcp_send_ack:
169 		return &bpf_tcp_send_ack_proto;
170 	default:
171 		return bpf_base_func_proto(func_id);
172 	}
173 }
174 
175 static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
176 	.get_func_proto		= bpf_tcp_ca_get_func_proto,
177 	.is_valid_access	= bpf_tcp_ca_is_valid_access,
178 	.btf_struct_access	= bpf_tcp_ca_btf_struct_access,
179 };
180 
181 static int bpf_tcp_ca_init_member(const struct btf_type *t,
182 				  const struct btf_member *member,
183 				  void *kdata, const void *udata)
184 {
185 	const struct tcp_congestion_ops *utcp_ca;
186 	struct tcp_congestion_ops *tcp_ca;
187 	int prog_fd;
188 	u32 moff;
189 
190 	utcp_ca = (const struct tcp_congestion_ops *)udata;
191 	tcp_ca = (struct tcp_congestion_ops *)kdata;
192 
193 	moff = btf_member_bit_offset(t, member) / 8;
194 	switch (moff) {
195 	case offsetof(struct tcp_congestion_ops, flags):
196 		if (utcp_ca->flags & ~TCP_CONG_MASK)
197 			return -EINVAL;
198 		tcp_ca->flags = utcp_ca->flags;
199 		return 1;
200 	case offsetof(struct tcp_congestion_ops, name):
201 		if (bpf_obj_name_cpy(tcp_ca->name, utcp_ca->name,
202 				     sizeof(tcp_ca->name)) <= 0)
203 			return -EINVAL;
204 		if (tcp_ca_find(utcp_ca->name))
205 			return -EEXIST;
206 		return 1;
207 	}
208 
209 	if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))
210 		return 0;
211 
212 	/* Ensure bpf_prog is provided for compulsory func ptr */
213 	prog_fd = (int)(*(unsigned long *)(udata + moff));
214 	if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))
215 		return -EINVAL;
216 
217 	return 0;
218 }
219 
220 static int bpf_tcp_ca_check_member(const struct btf_type *t,
221 				   const struct btf_member *member)
222 {
223 	if (is_unsupported(btf_member_bit_offset(t, member) / 8))
224 		return -ENOTSUPP;
225 	return 0;
226 }
227 
228 static int bpf_tcp_ca_reg(void *kdata)
229 {
230 	return tcp_register_congestion_control(kdata);
231 }
232 
233 static void bpf_tcp_ca_unreg(void *kdata)
234 {
235 	tcp_unregister_congestion_control(kdata);
236 }
237 
238 /* Avoid sparse warning.  It is only used in bpf_struct_ops.c. */
239 extern struct bpf_struct_ops bpf_tcp_congestion_ops;
240 
241 struct bpf_struct_ops bpf_tcp_congestion_ops = {
242 	.verifier_ops = &bpf_tcp_ca_verifier_ops,
243 	.reg = bpf_tcp_ca_reg,
244 	.unreg = bpf_tcp_ca_unreg,
245 	.check_member = bpf_tcp_ca_check_member,
246 	.init_member = bpf_tcp_ca_init_member,
247 	.init = bpf_tcp_ca_init,
248 	.name = "tcp_congestion_ops",
249 };
250