1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43#include <linux/module.h>
44#include <linux/mm.h>
45#include <net/tcp.h>
46#include <linux/inet_diag.h>
47
48#define DCTCP_MAX_ALPHA 1024U
49
50struct dctcp {
51 u32 acked_bytes_ecn;
52 u32 acked_bytes_total;
53 u32 prior_snd_una;
54 u32 prior_rcv_nxt;
55 u32 dctcp_alpha;
56 u32 next_seq;
57 u32 ce_state;
58 u32 delayed_ack_reserved;
59};
60
61static unsigned int dctcp_shift_g __read_mostly = 4;
62module_param(dctcp_shift_g, uint, 0644);
63MODULE_PARM_DESC(dctcp_shift_g, "parameter g for updating dctcp_alpha");
64
65static unsigned int dctcp_alpha_on_init __read_mostly = DCTCP_MAX_ALPHA;
66module_param(dctcp_alpha_on_init, uint, 0644);
67MODULE_PARM_DESC(dctcp_alpha_on_init, "parameter for initial alpha value");
68
69static unsigned int dctcp_clamp_alpha_on_loss __read_mostly;
70module_param(dctcp_clamp_alpha_on_loss, uint, 0644);
71MODULE_PARM_DESC(dctcp_clamp_alpha_on_loss,
72 "parameter for clamping alpha on loss");
73
74static struct tcp_congestion_ops dctcp_reno;
75
76static void dctcp_reset(const struct tcp_sock *tp, struct dctcp *ca)
77{
78 ca->next_seq = tp->snd_nxt;
79
80 ca->acked_bytes_ecn = 0;
81 ca->acked_bytes_total = 0;
82}
83
84static void dctcp_init(struct sock *sk)
85{
86 const struct tcp_sock *tp = tcp_sk(sk);
87
88 if ((tp->ecn_flags & TCP_ECN_OK) ||
89 (sk->sk_state == TCP_LISTEN ||
90 sk->sk_state == TCP_CLOSE)) {
91 struct dctcp *ca = inet_csk_ca(sk);
92
93 ca->prior_snd_una = tp->snd_una;
94 ca->prior_rcv_nxt = tp->rcv_nxt;
95
96 ca->dctcp_alpha = min(dctcp_alpha_on_init, DCTCP_MAX_ALPHA);
97
98 ca->delayed_ack_reserved = 0;
99 ca->ce_state = 0;
100
101 dctcp_reset(tp, ca);
102 return;
103 }
104
105
106
107
108 inet_csk(sk)->icsk_ca_ops = &dctcp_reno;
109 INET_ECN_dontxmit(sk);
110}
111
112static u32 dctcp_ssthresh(struct sock *sk)
113{
114 const struct dctcp *ca = inet_csk_ca(sk);
115 struct tcp_sock *tp = tcp_sk(sk);
116
117 return max(tp->snd_cwnd - ((tp->snd_cwnd * ca->dctcp_alpha) >> 11U), 2U);
118}
119
120
121
122
123
124
125
126static void dctcp_ce_state_0_to_1(struct sock *sk)
127{
128 struct dctcp *ca = inet_csk_ca(sk);
129 struct tcp_sock *tp = tcp_sk(sk);
130
131
132
133
134 if (!ca->ce_state && ca->delayed_ack_reserved) {
135 u32 tmp_rcv_nxt;
136
137
138 tmp_rcv_nxt = tp->rcv_nxt;
139
140
141 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
142 tp->rcv_nxt = ca->prior_rcv_nxt;
143
144 tcp_send_ack(sk);
145
146
147 tp->rcv_nxt = tmp_rcv_nxt;
148 }
149
150 ca->prior_rcv_nxt = tp->rcv_nxt;
151 ca->ce_state = 1;
152
153 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
154}
155
156static void dctcp_ce_state_1_to_0(struct sock *sk)
157{
158 struct dctcp *ca = inet_csk_ca(sk);
159 struct tcp_sock *tp = tcp_sk(sk);
160
161
162
163
164 if (ca->ce_state && ca->delayed_ack_reserved) {
165 u32 tmp_rcv_nxt;
166
167
168 tmp_rcv_nxt = tp->rcv_nxt;
169
170
171 tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
172 tp->rcv_nxt = ca->prior_rcv_nxt;
173
174 tcp_send_ack(sk);
175
176
177 tp->rcv_nxt = tmp_rcv_nxt;
178 }
179
180 ca->prior_rcv_nxt = tp->rcv_nxt;
181 ca->ce_state = 0;
182
183 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
184}
185
186static void dctcp_update_alpha(struct sock *sk, u32 flags)
187{
188 const struct tcp_sock *tp = tcp_sk(sk);
189 struct dctcp *ca = inet_csk_ca(sk);
190 u32 acked_bytes = tp->snd_una - ca->prior_snd_una;
191
192
193
194
195 if (acked_bytes == 0 && !(flags & CA_ACK_WIN_UPDATE))
196 acked_bytes = inet_csk(sk)->icsk_ack.rcv_mss;
197 if (acked_bytes) {
198 ca->acked_bytes_total += acked_bytes;
199 ca->prior_snd_una = tp->snd_una;
200
201 if (flags & CA_ACK_ECE)
202 ca->acked_bytes_ecn += acked_bytes;
203 }
204
205
206 if (!before(tp->snd_una, ca->next_seq)) {
207 u64 bytes_ecn = ca->acked_bytes_ecn;
208 u32 alpha = ca->dctcp_alpha;
209
210
211
212 alpha -= alpha >> dctcp_shift_g;
213 if (bytes_ecn) {
214
215
216
217 bytes_ecn <<= (10 - dctcp_shift_g);
218 do_div(bytes_ecn, max(1U, ca->acked_bytes_total));
219
220 alpha = min(alpha + (u32)bytes_ecn, DCTCP_MAX_ALPHA);
221 }
222
223
224
225
226 WRITE_ONCE(ca->dctcp_alpha, alpha);
227 dctcp_reset(tp, ca);
228 }
229}
230
231static void dctcp_state(struct sock *sk, u8 new_state)
232{
233 if (dctcp_clamp_alpha_on_loss && new_state == TCP_CA_Loss) {
234 struct dctcp *ca = inet_csk_ca(sk);
235
236
237
238
239
240
241
242
243
244 ca->dctcp_alpha = DCTCP_MAX_ALPHA;
245 }
246}
247
248static void dctcp_update_ack_reserved(struct sock *sk, enum tcp_ca_event ev)
249{
250 struct dctcp *ca = inet_csk_ca(sk);
251
252 switch (ev) {
253 case CA_EVENT_DELAYED_ACK:
254 if (!ca->delayed_ack_reserved)
255 ca->delayed_ack_reserved = 1;
256 break;
257 case CA_EVENT_NON_DELAYED_ACK:
258 if (ca->delayed_ack_reserved)
259 ca->delayed_ack_reserved = 0;
260 break;
261 default:
262
263 break;
264 }
265}
266
267static void dctcp_cwnd_event(struct sock *sk, enum tcp_ca_event ev)
268{
269 switch (ev) {
270 case CA_EVENT_ECN_IS_CE:
271 dctcp_ce_state_0_to_1(sk);
272 break;
273 case CA_EVENT_ECN_NO_CE:
274 dctcp_ce_state_1_to_0(sk);
275 break;
276 case CA_EVENT_DELAYED_ACK:
277 case CA_EVENT_NON_DELAYED_ACK:
278 dctcp_update_ack_reserved(sk, ev);
279 break;
280 default:
281
282 break;
283 }
284}
285
286static size_t dctcp_get_info(struct sock *sk, u32 ext, int *attr,
287 union tcp_cc_info *info)
288{
289 const struct dctcp *ca = inet_csk_ca(sk);
290
291
292
293
294 if (ext & (1 << (INET_DIAG_DCTCPINFO - 1)) ||
295 ext & (1 << (INET_DIAG_VEGASINFO - 1))) {
296 memset(info, 0, sizeof(struct tcp_dctcp_info));
297 if (inet_csk(sk)->icsk_ca_ops != &dctcp_reno) {
298 info->dctcp.dctcp_enabled = 1;
299 info->dctcp.dctcp_ce_state = (u16) ca->ce_state;
300 info->dctcp.dctcp_alpha = ca->dctcp_alpha;
301 info->dctcp.dctcp_ab_ecn = ca->acked_bytes_ecn;
302 info->dctcp.dctcp_ab_tot = ca->acked_bytes_total;
303 }
304
305 *attr = INET_DIAG_DCTCPINFO;
306 return sizeof(*info);
307 }
308 return 0;
309}
310
311static struct tcp_congestion_ops dctcp __read_mostly = {
312 .init = dctcp_init,
313 .in_ack_event = dctcp_update_alpha,
314 .cwnd_event = dctcp_cwnd_event,
315 .ssthresh = dctcp_ssthresh,
316 .cong_avoid = tcp_reno_cong_avoid,
317 .set_state = dctcp_state,
318 .get_info = dctcp_get_info,
319 .flags = TCP_CONG_NEEDS_ECN,
320 .owner = THIS_MODULE,
321 .name = "dctcp",
322};
323
324static struct tcp_congestion_ops dctcp_reno __read_mostly = {
325 .ssthresh = tcp_reno_ssthresh,
326 .cong_avoid = tcp_reno_cong_avoid,
327 .get_info = dctcp_get_info,
328 .owner = THIS_MODULE,
329 .name = "dctcp-reno",
330};
331
332static int __init dctcp_register(void)
333{
334 BUILD_BUG_ON(sizeof(struct dctcp) > ICSK_CA_PRIV_SIZE);
335 return tcp_register_congestion_control(&dctcp);
336}
337
338static void __exit dctcp_unregister(void)
339{
340 tcp_unregister_congestion_control(&dctcp);
341}
342
343module_init(dctcp_register);
344module_exit(dctcp_unregister);
345
346MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
347MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
348MODULE_AUTHOR("Glenn Judd <glenn.judd@morganstanley.com>");
349
350MODULE_LICENSE("GPL v2");
351MODULE_DESCRIPTION("DataCenter TCP (DCTCP)");
352