2 #include <linux/init.h>
3 #include <linux/kernel.h>
4 #include <linux/list.h>
6 #include <linux/rcupdate.h>
7 #include <linux/rculist.h>
8 #include <net/inetpeer.h>
11 int sysctl_tcp_fastopen __read_mostly = TFO_CLIENT_ENABLE;
13 struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
15 static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
17 void tcp_fastopen_init_key_once(bool publish)
19 static u8 key[TCP_FASTOPEN_KEY_LENGTH];
21 /* tcp_fastopen_reset_cipher publishes the new context
22 * atomically, so we allow this race happening here.
24 * All call sites of tcp_fastopen_cookie_gen also check
25 * for a valid cookie, so this is an acceptable risk.
27 if (net_get_random_once(key, sizeof(key)) && publish)
28 tcp_fastopen_reset_cipher(key, sizeof(key));
31 static void tcp_fastopen_ctx_free(struct rcu_head *head)
33 struct tcp_fastopen_context *ctx =
34 container_of(head, struct tcp_fastopen_context, rcu);
35 crypto_free_cipher(ctx->tfm);
39 int tcp_fastopen_reset_cipher(void *key, unsigned int len)
42 struct tcp_fastopen_context *ctx, *octx;
44 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
47 ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
49 if (IS_ERR(ctx->tfm)) {
50 err = PTR_ERR(ctx->tfm);
52 pr_err("TCP: TFO aes cipher alloc error: %d\n", err);
55 err = crypto_cipher_setkey(ctx->tfm, key, len);
57 pr_err("TCP: TFO cipher key error: %d\n", err);
58 crypto_free_cipher(ctx->tfm);
61 memcpy(ctx->key, key, len);
63 spin_lock(&tcp_fastopen_ctx_lock);
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);
71 call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
75 static bool __tcp_fastopen_cookie_gen(const void *path,
76 struct tcp_fastopen_cookie *foc)
78 struct tcp_fastopen_context *ctx;
81 tcp_fastopen_init_key_once(true);
84 ctx = rcu_dereference(tcp_fastopen_ctx);
86 crypto_cipher_encrypt_one(ctx->tfm, foc->val, path);
87 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
94 /* Generate the fastopen cookie by doing aes128 encryption on both
95 * the source and destination addresses. Pad 0s for IPv4 or IPv4-mapped-IPv6
96 * addresses. For the longer IPv6 addresses use CBC-MAC.
98 * XXX (TFO) - refactor when TCP_FASTOPEN_COOKIE_SIZE != AES_BLOCK_SIZE.
100 static bool tcp_fastopen_cookie_gen(struct request_sock *req,
102 struct tcp_fastopen_cookie *foc)
104 if (req->rsk_ops->family == AF_INET) {
105 const struct iphdr *iph = ip_hdr(syn);
107 __be32 path[4] = { iph->saddr, iph->daddr, 0, 0 };
108 return __tcp_fastopen_cookie_gen(path, foc);
111 #if IS_ENABLED(CONFIG_IPV6)
112 if (req->rsk_ops->family == AF_INET6) {
113 const struct ipv6hdr *ip6h = ipv6_hdr(syn);
114 struct tcp_fastopen_cookie tmp;
116 if (__tcp_fastopen_cookie_gen(&ip6h->saddr, &tmp)) {
117 struct in6_addr *buf = (struct in6_addr *) tmp.val;
120 for (i = 0; i < 4; i++)
121 buf->s6_addr32[i] ^= ip6h->daddr.s6_addr32[i];
122 return __tcp_fastopen_cookie_gen(buf, foc);
129 static bool tcp_fastopen_create_child(struct sock *sk,
131 struct dst_entry *dst,
132 struct request_sock *req)
135 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
139 req->num_retrans = 0;
140 req->num_timeout = 0;
143 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
147 spin_lock(&queue->fastopenq->lock);
148 queue->fastopenq->qlen++;
149 spin_unlock(&queue->fastopenq->lock);
151 /* Initialize the child socket. Have to fix some values to take
152 * into account the child is a Fast Open socket and is created
153 * only out of the bits carried in the SYN packet.
157 tp->fastopen_rsk = req;
158 tcp_rsk(req)->tfo_listener = true;
160 /* RFC1323: The window in SYN & SYN/ACK segments is never
161 * scaled. So correct it appropriately.
163 tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
165 /* Activate the retrans timer so that SYNACK can be retransmitted.
166 * The request socket is not added to the SYN table of the parent
167 * because it's been added to the accept queue directly.
169 inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
170 TCP_TIMEOUT_INIT, TCP_RTO_MAX);
172 atomic_set(&req->rsk_refcnt, 1);
173 /* Add the child socket directly into the accept queue */
174 inet_csk_reqsk_queue_add(sk, req, child);
176 /* Now finish processing the fastopen child socket. */
177 inet_csk(child)->icsk_af_ops->rebuild_header(child);
178 tcp_init_congestion_control(child);
179 tcp_mtup_init(child);
180 tcp_init_metrics(child);
181 tcp_init_buffer_space(child);
183 /* Queue the data carried in the SYN packet. We need to first
184 * bump skb's refcnt because the caller will attempt to free it.
185 * Note that IPv6 might also have used skb_get() trick
186 * in tcp_v6_conn_request() to keep this SYN around (treq->pktopts)
187 * So we need to eventually get a clone of the packet,
188 * before inserting it in sk_receive_queue.
190 * XXX (TFO) - we honor a zero-payload TFO request for now,
191 * (any reason not to?) but no need to queue the skb since
192 * there is no data. How about SYN+FIN?
194 end_seq = TCP_SKB_CB(skb)->end_seq;
195 if (end_seq != TCP_SKB_CB(skb)->seq + 1) {
196 struct sk_buff *skb2;
198 if (unlikely(skb_shared(skb)))
199 skb2 = skb_clone(skb, GFP_ATOMIC);
205 __skb_pull(skb2, tcp_hdrlen(skb));
206 skb_set_owner_r(skb2, child);
207 __skb_queue_tail(&child->sk_receive_queue, skb2);
208 tp->syn_data_acked = 1;
210 end_seq = TCP_SKB_CB(skb)->seq + 1;
213 tcp_rsk(req)->rcv_nxt = tp->rcv_nxt = end_seq;
214 sk->sk_data_ready(sk);
215 bh_unlock_sock(child);
217 WARN_ON(req->sk == NULL);
221 static bool tcp_fastopen_queue_check(struct sock *sk)
223 struct fastopen_queue *fastopenq;
225 /* Make sure the listener has enabled fastopen, and we don't
226 * exceed the max # of pending TFO requests allowed before trying
227 * to validating the cookie in order to avoid burning CPU cycles
230 * XXX (TFO) - The implication of checking the max_qlen before
231 * processing a cookie request is that clients can't differentiate
232 * between qlen overflow causing Fast Open to be disabled
233 * temporarily vs a server not supporting Fast Open at all.
235 fastopenq = inet_csk(sk)->icsk_accept_queue.fastopenq;
236 if (fastopenq == NULL || fastopenq->max_qlen == 0)
239 if (fastopenq->qlen >= fastopenq->max_qlen) {
240 struct request_sock *req1;
241 spin_lock(&fastopenq->lock);
242 req1 = fastopenq->rskq_rst_head;
243 if (!req1 || time_after(req1->rsk_timer.expires, jiffies)) {
244 spin_unlock(&fastopenq->lock);
245 NET_INC_STATS_BH(sock_net(sk),
246 LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
249 fastopenq->rskq_rst_head = req1->dl_next;
251 spin_unlock(&fastopenq->lock);
257 /* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
258 * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
259 * cookie request (foc->len == 0).
261 bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
262 struct request_sock *req,
263 struct tcp_fastopen_cookie *foc,
264 struct dst_entry *dst)
266 struct tcp_fastopen_cookie valid_foc = { .len = -1 };
267 bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
269 if (foc->len == 0) /* Client requests a cookie */
270 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENCOOKIEREQD);
272 if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&
273 (syn_data || foc->len >= 0) &&
274 tcp_fastopen_queue_check(sk))) {
279 if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD))
282 if (foc->len >= 0 && /* Client presents or requests a cookie */
283 tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
284 foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
285 foc->len == valid_foc.len &&
286 !memcmp(foc->val, valid_foc.val, foc->len)) {
287 /* Cookie is valid. Create a (full) child socket to accept
288 * the data in SYN before returning a SYN-ACK to ack the
289 * data. If we fail to create the socket, fall back and
290 * ack the ISN only but includes the same cookie.
292 * Note: Data-less SYN with valid cookie is allowed to send
293 * data in SYN_RECV state.
296 if (tcp_fastopen_create_child(sk, skb, dst, req)) {
298 NET_INC_STATS_BH(sock_net(sk),
299 LINUX_MIB_TCPFASTOPENPASSIVE);
302 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
303 } else if (foc->len > 0) /* Client presents an invalid cookie */
304 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
309 EXPORT_SYMBOL(tcp_try_fastopen);