Merge remote-tracking branch 'lightnvm/for-next'
[deliverable/linux.git] / net / ipv4 / tcp_fastopen.c
CommitLineData
cf80e0e4 1#include <linux/crypto.h>
10467163 2#include <linux/err.h>
2100c8d2
YC
3#include <linux/init.h>
4#include <linux/kernel.h>
10467163
JC
5#include <linux/list.h>
6#include <linux/tcp.h>
7#include <linux/rcupdate.h>
8#include <linux/rculist.h>
9#include <net/inetpeer.h>
10#include <net/tcp.h>
2100c8d2 11
0d41cca4 12int sysctl_tcp_fastopen __read_mostly = TFO_CLIENT_ENABLE;
10467163
JC
13
14struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
15
16static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
17
222e83d2
HFS
18void tcp_fastopen_init_key_once(bool publish)
19{
20 static u8 key[TCP_FASTOPEN_KEY_LENGTH];
21
22 /* tcp_fastopen_reset_cipher publishes the new context
23 * atomically, so we allow this race happening here.
24 *
25 * All call sites of tcp_fastopen_cookie_gen also check
26 * for a valid cookie, so this is an acceptable risk.
27 */
28 if (net_get_random_once(key, sizeof(key)) && publish)
29 tcp_fastopen_reset_cipher(key, sizeof(key));
30}
31
10467163
JC
32static void tcp_fastopen_ctx_free(struct rcu_head *head)
33{
34 struct tcp_fastopen_context *ctx =
35 container_of(head, struct tcp_fastopen_context, rcu);
36 crypto_free_cipher(ctx->tfm);
37 kfree(ctx);
38}
39
40int tcp_fastopen_reset_cipher(void *key, unsigned int len)
41{
42 int err;
43 struct tcp_fastopen_context *ctx, *octx;
44
45 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
46 if (!ctx)
47 return -ENOMEM;
48 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
49
50 if (IS_ERR(ctx->tfm)) {
51 err = PTR_ERR(ctx->tfm);
52error: kfree(ctx);
53 pr_err("TCP: TFO aes cipher alloc error: %d\n", err);
54 return err;
55 }
56 err = crypto_cipher_setkey(ctx->tfm, key, len);
57 if (err) {
58 pr_err("TCP: TFO cipher key error: %d\n", err);
59 crypto_free_cipher(ctx->tfm);
60 goto error;
61 }
62 memcpy(ctx->key, key, len);
63
64 spin_lock(&tcp_fastopen_ctx_lock);
65
66 octx = rcu_dereference_protected(tcp_fastopen_ctx,
67 lockdep_is_held(&tcp_fastopen_ctx_lock));
68 rcu_assign_pointer(tcp_fastopen_ctx, ctx);
69 spin_unlock(&tcp_fastopen_ctx_lock);
70
71 if (octx)
72 call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
73 return err;
74}
75
3a19ce0e
DL
76static bool __tcp_fastopen_cookie_gen(const void *path,
77 struct tcp_fastopen_cookie *foc)
10467163 78{
10467163 79 struct tcp_fastopen_context *ctx;
3a19ce0e 80 bool ok = false;
10467163
JC
81
82 rcu_read_lock();
83 ctx = rcu_dereference(tcp_fastopen_ctx);
84 if (ctx) {
3a19ce0e 85 crypto_cipher_encrypt_one(ctx->tfm, foc->val, path);
10467163 86 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
3a19ce0e 87 ok = true;
10467163
JC
88 }
89 rcu_read_unlock();
3a19ce0e
DL
90 return ok;
91}
92
93/* Generate the fastopen cookie by doing aes128 encryption on both
94 * the source and destination addresses. Pad 0s for IPv4 or IPv4-mapped-IPv6
95 * addresses. For the longer IPv6 addresses use CBC-MAC.
96 *
97 * XXX (TFO) - refactor when TCP_FASTOPEN_COOKIE_SIZE != AES_BLOCK_SIZE.
98 */
99static bool tcp_fastopen_cookie_gen(struct request_sock *req,
100 struct sk_buff *syn,
101 struct tcp_fastopen_cookie *foc)
102{
103 if (req->rsk_ops->family == AF_INET) {
104 const struct iphdr *iph = ip_hdr(syn);
105
106 __be32 path[4] = { iph->saddr, iph->daddr, 0, 0 };
107 return __tcp_fastopen_cookie_gen(path, foc);
108 }
109
110#if IS_ENABLED(CONFIG_IPV6)
111 if (req->rsk_ops->family == AF_INET6) {
112 const struct ipv6hdr *ip6h = ipv6_hdr(syn);
113 struct tcp_fastopen_cookie tmp;
114
115 if (__tcp_fastopen_cookie_gen(&ip6h->saddr, &tmp)) {
116 struct in6_addr *buf = (struct in6_addr *) tmp.val;
41c91996 117 int i;
3a19ce0e
DL
118
119 for (i = 0; i < 4; i++)
120 buf->s6_addr32[i] ^= ip6h->daddr.s6_addr32[i];
121 return __tcp_fastopen_cookie_gen(buf, foc);
122 }
123 }
124#endif
125 return false;
10467163 126}
5b7ed089 127
61d2bcae
ED
128
129/* If an incoming SYN or SYNACK frame contains a payload and/or FIN,
130 * queue this additional data / FIN.
131 */
132void tcp_fastopen_add_skb(struct sock *sk, struct sk_buff *skb)
133{
134 struct tcp_sock *tp = tcp_sk(sk);
135
136 if (TCP_SKB_CB(skb)->end_seq == tp->rcv_nxt)
137 return;
138
139 skb = skb_clone(skb, GFP_ATOMIC);
140 if (!skb)
141 return;
142
143 skb_dst_drop(skb);
a44d6eac
MKL
144 /* segs_in has been initialized to 1 in tcp_create_openreq_child().
145 * Hence, reset segs_in to 0 before calling tcp_segs_in()
146 * to avoid double counting. Also, tcp_segs_in() expects
147 * skb->len to include the tcp_hdrlen. Hence, it should
148 * be called before __skb_pull().
149 */
150 tp->segs_in = 0;
151 tcp_segs_in(tp, skb);
61d2bcae 152 __skb_pull(skb, tcp_hdrlen(skb));
76061f63 153 sk_forced_mem_schedule(sk, skb->truesize);
61d2bcae
ED
154 skb_set_owner_r(skb, sk);
155
9d691539
ED
156 TCP_SKB_CB(skb)->seq++;
157 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
158
61d2bcae
ED
159 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
160 __skb_queue_tail(&sk->sk_receive_queue, skb);
161 tp->syn_data_acked = 1;
162
163 /* u64_stats_update_begin(&tp->syncp) not needed here,
164 * as we certainly are not changing upper 32bit value (0)
165 */
166 tp->bytes_received = skb->len;
e3e17b77
ED
167
168 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
169 tcp_fin(sk);
61d2bcae
ED
170}
171
7c85af88
ED
172static struct sock *tcp_fastopen_create_child(struct sock *sk,
173 struct sk_buff *skb,
174 struct dst_entry *dst,
175 struct request_sock *req)
5b7ed089 176{
17846376 177 struct tcp_sock *tp;
5b7ed089 178 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
5b7ed089 179 struct sock *child;
5e0724d0 180 bool own_req;
5b7ed089
YC
181
182 req->num_retrans = 0;
183 req->num_timeout = 0;
184 req->sk = NULL;
185
5e0724d0
ED
186 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
187 NULL, &own_req);
51456b29 188 if (!child)
7c85af88 189 return NULL;
5b7ed089 190
0536fcc0
ED
191 spin_lock(&queue->fastopenq.lock);
192 queue->fastopenq.qlen++;
193 spin_unlock(&queue->fastopenq.lock);
5b7ed089
YC
194
195 /* Initialize the child socket. Have to fix some values to take
196 * into account the child is a Fast Open socket and is created
197 * only out of the bits carried in the SYN packet.
198 */
199 tp = tcp_sk(child);
200
201 tp->fastopen_rsk = req;
9439ce00 202 tcp_rsk(req)->tfo_listener = true;
5b7ed089
YC
203
204 /* RFC1323: The window in SYN & SYN/ACK segments is never
205 * scaled. So correct it appropriately.
206 */
207 tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
208
209 /* Activate the retrans timer so that SYNACK can be retransmitted.
ca6fb065 210 * The request socket is not added to the ehash
5b7ed089
YC
211 * because it's been added to the accept queue directly.
212 */
213 inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
214 TCP_TIMEOUT_INIT, TCP_RTO_MAX);
215
ca6fb065 216 atomic_set(&req->rsk_refcnt, 2);
5b7ed089
YC
217
218 /* Now finish processing the fastopen child socket. */
219 inet_csk(child)->icsk_af_ops->rebuild_header(child);
220 tcp_init_congestion_control(child);
221 tcp_mtup_init(child);
222 tcp_init_metrics(child);
223 tcp_init_buffer_space(child);
224
61d2bcae
ED
225 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
226
227 tcp_fastopen_add_skb(child, skb);
228
229 tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
28b346cb 230 tp->rcv_wup = tp->rcv_nxt;
7656d842
ED
231 /* tcp_conn_request() is sending the SYNACK,
232 * and queues the child into listener accept queue.
7c85af88 233 */
7c85af88 234 return child;
5b7ed089 235}
5b7ed089
YC
236
237static bool tcp_fastopen_queue_check(struct sock *sk)
238{
239 struct fastopen_queue *fastopenq;
240
241 /* Make sure the listener has enabled fastopen, and we don't
242 * exceed the max # of pending TFO requests allowed before trying
243 * to validating the cookie in order to avoid burning CPU cycles
244 * unnecessarily.
245 *
246 * XXX (TFO) - The implication of checking the max_qlen before
247 * processing a cookie request is that clients can't differentiate
248 * between qlen overflow causing Fast Open to be disabled
249 * temporarily vs a server not supporting Fast Open at all.
250 */
0536fcc0
ED
251 fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
252 if (fastopenq->max_qlen == 0)
5b7ed089
YC
253 return false;
254
255 if (fastopenq->qlen >= fastopenq->max_qlen) {
256 struct request_sock *req1;
257 spin_lock(&fastopenq->lock);
258 req1 = fastopenq->rskq_rst_head;
fa76ce73 259 if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
02a1d6e7
ED
260 __NET_INC_STATS(sock_net(sk),
261 LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
c10d9310 262 spin_unlock(&fastopenq->lock);
5b7ed089
YC
263 return false;
264 }
265 fastopenq->rskq_rst_head = req1->dl_next;
266 fastopenq->qlen--;
267 spin_unlock(&fastopenq->lock);
13854e5a 268 reqsk_put(req1);
5b7ed089
YC
269 }
270 return true;
271}
272
89278c9d
YC
273/* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
274 * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
275 * cookie request (foc->len == 0).
276 */
7c85af88
ED
277struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
278 struct request_sock *req,
279 struct tcp_fastopen_cookie *foc,
280 struct dst_entry *dst)
5b7ed089 281{
89278c9d
YC
282 struct tcp_fastopen_cookie valid_foc = { .len = -1 };
283 bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
7c85af88 284 struct sock *child;
5b7ed089 285
531c94a9 286 if (foc->len == 0) /* Client requests a cookie */
c10d9310 287 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
531c94a9 288
89278c9d
YC
289 if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&
290 (syn_data || foc->len >= 0) &&
291 tcp_fastopen_queue_check(sk))) {
292 foc->len = -1;
7c85af88 293 return NULL;
5b7ed089
YC
294 }
295
89278c9d
YC
296 if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD))
297 goto fastopen;
298
531c94a9
YC
299 if (foc->len >= 0 && /* Client presents or requests a cookie */
300 tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
3a19ce0e 301 foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
89278c9d
YC
302 foc->len == valid_foc.len &&
303 !memcmp(foc->val, valid_foc.val, foc->len)) {
843f4a55
YC
304 /* Cookie is valid. Create a (full) child socket to accept
305 * the data in SYN before returning a SYN-ACK to ack the
306 * data. If we fail to create the socket, fall back and
307 * ack the ISN only but includes the same cookie.
308 *
309 * Note: Data-less SYN with valid cookie is allowed to send
310 * data in SYN_RECV state.
311 */
89278c9d 312fastopen:
7c85af88
ED
313 child = tcp_fastopen_create_child(sk, skb, dst, req);
314 if (child) {
843f4a55 315 foc->len = -1;
c10d9310
ED
316 NET_INC_STATS(sock_net(sk),
317 LINUX_MIB_TCPFASTOPENPASSIVE);
7c85af88 318 return child;
843f4a55 319 }
c10d9310 320 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
531c94a9 321 } else if (foc->len > 0) /* Client presents an invalid cookie */
c10d9310 322 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
89278c9d 323
7f9b838b 324 valid_foc.exp = foc->exp;
89278c9d 325 *foc = valid_foc;
7c85af88 326 return NULL;
5b7ed089 327}
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