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1#include <linux/err.h>
2#include <linux/init.h>
3#include <linux/kernel.h>
4#include <linux/list.h>
5#include <linux/tcp.h>
6#include <linux/rcupdate.h>
7#include <linux/rculist.h>
8#include <net/inetpeer.h>
9#include <net/tcp.h>
10
11int sysctl_tcp_fastopen __read_mostly = TFO_CLIENT_ENABLE;
12
13struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
14
15static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
16
17void tcp_fastopen_init_key_once(bool publish)
18{
19 static u8 key[TCP_FASTOPEN_KEY_LENGTH];
20
21 /* tcp_fastopen_reset_cipher publishes the new context
22 * atomically, so we allow this race happening here.
23 *
24 * All call sites of tcp_fastopen_cookie_gen also check
25 * for a valid cookie, so this is an acceptable risk.
26 */
27 if (net_get_random_once(key, sizeof(key)) && publish)
28 tcp_fastopen_reset_cipher(key, sizeof(key));
29}
30
31static void tcp_fastopen_ctx_free(struct rcu_head *head)
32{
33 struct tcp_fastopen_context *ctx =
34 container_of(head, struct tcp_fastopen_context, rcu);
35 crypto_free_cipher(ctx->tfm);
36 kfree(ctx);
37}
38
39int tcp_fastopen_reset_cipher(void *key, unsigned int len)
40{
41 int err;
42 struct tcp_fastopen_context *ctx, *octx;
43
44 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
45 if (!ctx)
46 return -ENOMEM;
47 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
48
49 if (IS_ERR(ctx->tfm)) {
50 err = PTR_ERR(ctx->tfm);
51error: kfree(ctx);
52 pr_err("TCP: TFO aes cipher alloc error: %d\n", err);
53 return err;
54 }
55 err = crypto_cipher_setkey(ctx->tfm, key, len);
56 if (err) {
57 pr_err("TCP: TFO cipher key error: %d\n", err);
58 crypto_free_cipher(ctx->tfm);
59 goto error;
60 }
61 memcpy(ctx->key, key, len);
62
63 spin_lock(&tcp_fastopen_ctx_lock);
64
65 octx = rcu_dereference_protected(tcp_fastopen_ctx,
66 lockdep_is_held(&tcp_fastopen_ctx_lock));
67 rcu_assign_pointer(tcp_fastopen_ctx, ctx);
68 spin_unlock(&tcp_fastopen_ctx_lock);
69
70 if (octx)
71 call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
72 return err;
73}
74
75/* Computes the fastopen cookie for the IP path.
76 * The path is a 128 bits long (pad with zeros for IPv4).
77 *
78 * The caller must check foc->len to determine if a valid cookie
79 * has been generated successfully.
80*/
81void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
82 struct tcp_fastopen_cookie *foc)
83{
84 __be32 path[4] = { src, dst, 0, 0 };
85 struct tcp_fastopen_context *ctx;
86
87 tcp_fastopen_init_key_once(true);
88
89 rcu_read_lock();
90 ctx = rcu_dereference(tcp_fastopen_ctx);
91 if (ctx) {
92 crypto_cipher_encrypt_one(ctx->tfm, foc->val, (__u8 *)path);
93 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
94 }
95 rcu_read_unlock();
96}
1#include <linux/crypto.h>
2#include <linux/err.h>
3#include <linux/init.h>
4#include <linux/kernel.h>
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>
11
12int sysctl_tcp_fastopen __read_mostly = TFO_CLIENT_ENABLE;
13
14struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
15
16static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
17
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
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
76static bool __tcp_fastopen_cookie_gen(const void *path,
77 struct tcp_fastopen_cookie *foc)
78{
79 struct tcp_fastopen_context *ctx;
80 bool ok = false;
81
82 rcu_read_lock();
83 ctx = rcu_dereference(tcp_fastopen_ctx);
84 if (ctx) {
85 crypto_cipher_encrypt_one(ctx->tfm, foc->val, path);
86 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
87 ok = true;
88 }
89 rcu_read_unlock();
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 = &tmp.addr;
117 int i;
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;
126}
127
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);
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);
152 __skb_pull(skb, tcp_hdrlen(skb));
153 sk_forced_mem_schedule(sk, skb->truesize);
154 skb_set_owner_r(skb, sk);
155
156 TCP_SKB_CB(skb)->seq++;
157 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_SYN;
158
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;
167
168 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
169 tcp_fin(sk);
170}
171
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)
176{
177 struct tcp_sock *tp;
178 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
179 struct sock *child;
180 bool own_req;
181
182 req->num_retrans = 0;
183 req->num_timeout = 0;
184 req->sk = NULL;
185
186 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
187 NULL, &own_req);
188 if (!child)
189 return NULL;
190
191 spin_lock(&queue->fastopenq.lock);
192 queue->fastopenq.qlen++;
193 spin_unlock(&queue->fastopenq.lock);
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;
202 tcp_rsk(req)->tfo_listener = true;
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 tp->max_window = tp->snd_wnd;
209
210 /* Activate the retrans timer so that SYNACK can be retransmitted.
211 * The request socket is not added to the ehash
212 * because it's been added to the accept queue directly.
213 */
214 inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
215 TCP_TIMEOUT_INIT, TCP_RTO_MAX);
216
217 atomic_set(&req->rsk_refcnt, 2);
218
219 /* Now finish processing the fastopen child socket. */
220 inet_csk(child)->icsk_af_ops->rebuild_header(child);
221 tcp_init_congestion_control(child);
222 tcp_mtup_init(child);
223 tcp_init_metrics(child);
224 tcp_init_buffer_space(child);
225
226 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
227
228 tcp_fastopen_add_skb(child, skb);
229
230 tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
231 tp->rcv_wup = tp->rcv_nxt;
232 /* tcp_conn_request() is sending the SYNACK,
233 * and queues the child into listener accept queue.
234 */
235 return child;
236}
237
238static bool tcp_fastopen_queue_check(struct sock *sk)
239{
240 struct fastopen_queue *fastopenq;
241
242 /* Make sure the listener has enabled fastopen, and we don't
243 * exceed the max # of pending TFO requests allowed before trying
244 * to validating the cookie in order to avoid burning CPU cycles
245 * unnecessarily.
246 *
247 * XXX (TFO) - The implication of checking the max_qlen before
248 * processing a cookie request is that clients can't differentiate
249 * between qlen overflow causing Fast Open to be disabled
250 * temporarily vs a server not supporting Fast Open at all.
251 */
252 fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
253 if (fastopenq->max_qlen == 0)
254 return false;
255
256 if (fastopenq->qlen >= fastopenq->max_qlen) {
257 struct request_sock *req1;
258 spin_lock(&fastopenq->lock);
259 req1 = fastopenq->rskq_rst_head;
260 if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
261 __NET_INC_STATS(sock_net(sk),
262 LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
263 spin_unlock(&fastopenq->lock);
264 return false;
265 }
266 fastopenq->rskq_rst_head = req1->dl_next;
267 fastopenq->qlen--;
268 spin_unlock(&fastopenq->lock);
269 reqsk_put(req1);
270 }
271 return true;
272}
273
274/* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
275 * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
276 * cookie request (foc->len == 0).
277 */
278struct sock *tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
279 struct request_sock *req,
280 struct tcp_fastopen_cookie *foc,
281 struct dst_entry *dst)
282{
283 struct tcp_fastopen_cookie valid_foc = { .len = -1 };
284 bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
285 struct sock *child;
286
287 if (foc->len == 0) /* Client requests a cookie */
288 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
289
290 if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&
291 (syn_data || foc->len >= 0) &&
292 tcp_fastopen_queue_check(sk))) {
293 foc->len = -1;
294 return NULL;
295 }
296
297 if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD))
298 goto fastopen;
299
300 if (foc->len >= 0 && /* Client presents or requests a cookie */
301 tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
302 foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
303 foc->len == valid_foc.len &&
304 !memcmp(foc->val, valid_foc.val, foc->len)) {
305 /* Cookie is valid. Create a (full) child socket to accept
306 * the data in SYN before returning a SYN-ACK to ack the
307 * data. If we fail to create the socket, fall back and
308 * ack the ISN only but includes the same cookie.
309 *
310 * Note: Data-less SYN with valid cookie is allowed to send
311 * data in SYN_RECV state.
312 */
313fastopen:
314 child = tcp_fastopen_create_child(sk, skb, dst, req);
315 if (child) {
316 foc->len = -1;
317 NET_INC_STATS(sock_net(sk),
318 LINUX_MIB_TCPFASTOPENPASSIVE);
319 return child;
320 }
321 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
322 } else if (foc->len > 0) /* Client presents an invalid cookie */
323 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
324
325 valid_foc.exp = foc->exp;
326 *foc = valid_foc;
327 return NULL;
328}