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 /* Computes the fastopen cookie for the IP path.
76 * The path is a 128 bits long (pad with zeros for IPv4).
78 * The caller must check foc->len to determine if a valid cookie
79 * has been generated successfully.
81 void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
82 struct tcp_fastopen_cookie *foc)
84 __be32 path[4] = { src, dst, 0, 0 };
85 struct tcp_fastopen_context *ctx;
87 tcp_fastopen_init_key_once(true);
90 ctx = rcu_dereference(tcp_fastopen_ctx);
92 crypto_cipher_encrypt_one(ctx->tfm, foc->val, (__u8 *)path);
93 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
98 int tcp_fastopen_create_child(struct sock *sk,
100 struct sk_buff *skb_synack,
101 struct request_sock *req)
103 struct tcp_sock *tp = tcp_sk(sk);
104 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
105 const struct inet_request_sock *ireq = inet_rsk(req);
109 req->num_retrans = 0;
110 req->num_timeout = 0;
113 child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
115 NET_INC_STATS_BH(sock_net(sk),
116 LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
117 kfree_skb(skb_synack);
120 err = ip_build_and_send_pkt(skb_synack, sk, ireq->ir_loc_addr,
121 ireq->ir_rmt_addr, ireq->opt);
122 err = net_xmit_eval(err);
124 tcp_rsk(req)->snt_synack = tcp_time_stamp;
125 /* XXX (TFO) - is it ok to ignore error and continue? */
127 spin_lock(&queue->fastopenq->lock);
128 queue->fastopenq->qlen++;
129 spin_unlock(&queue->fastopenq->lock);
131 /* Initialize the child socket. Have to fix some values to take
132 * into account the child is a Fast Open socket and is created
133 * only out of the bits carried in the SYN packet.
137 tp->fastopen_rsk = req;
138 /* Do a hold on the listner sk so that if the listener is being
139 * closed, the child that has been accepted can live on and still
140 * access listen_lock.
143 tcp_rsk(req)->listener = sk;
145 /* RFC1323: The window in SYN & SYN/ACK segments is never
146 * scaled. So correct it appropriately.
148 tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
150 /* Activate the retrans timer so that SYNACK can be retransmitted.
151 * The request socket is not added to the SYN table of the parent
152 * because it's been added to the accept queue directly.
154 inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
155 TCP_TIMEOUT_INIT, TCP_RTO_MAX);
157 /* Add the child socket directly into the accept queue */
158 inet_csk_reqsk_queue_add(sk, req, child);
160 /* Now finish processing the fastopen child socket. */
161 inet_csk(child)->icsk_af_ops->rebuild_header(child);
162 tcp_init_congestion_control(child);
163 tcp_mtup_init(child);
164 tcp_init_metrics(child);
165 tcp_init_buffer_space(child);
167 /* Queue the data carried in the SYN packet. We need to first
168 * bump skb's refcnt because the caller will attempt to free it.
170 * XXX (TFO) - we honor a zero-payload TFO request for now.
171 * (Any reason not to?)
173 if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq + 1) {
174 /* Don't queue the skb if there is no payload in SYN.
175 * XXX (TFO) - How about SYN+FIN?
177 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
181 __skb_pull(skb, tcp_hdr(skb)->doff * 4);
182 skb_set_owner_r(skb, child);
183 __skb_queue_tail(&child->sk_receive_queue, skb);
184 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
185 tp->syn_data_acked = 1;
187 sk->sk_data_ready(sk);
188 bh_unlock_sock(child);
190 WARN_ON(req->sk == NULL);
193 EXPORT_SYMBOL(tcp_fastopen_create_child);
195 static bool tcp_fastopen_queue_check(struct sock *sk)
197 struct fastopen_queue *fastopenq;
199 /* Make sure the listener has enabled fastopen, and we don't
200 * exceed the max # of pending TFO requests allowed before trying
201 * to validating the cookie in order to avoid burning CPU cycles
204 * XXX (TFO) - The implication of checking the max_qlen before
205 * processing a cookie request is that clients can't differentiate
206 * between qlen overflow causing Fast Open to be disabled
207 * temporarily vs a server not supporting Fast Open at all.
209 fastopenq = inet_csk(sk)->icsk_accept_queue.fastopenq;
210 if (fastopenq == NULL || fastopenq->max_qlen == 0)
213 if (fastopenq->qlen >= fastopenq->max_qlen) {
214 struct request_sock *req1;
215 spin_lock(&fastopenq->lock);
216 req1 = fastopenq->rskq_rst_head;
217 if ((req1 == NULL) || time_after(req1->expires, jiffies)) {
218 spin_unlock(&fastopenq->lock);
219 NET_INC_STATS_BH(sock_net(sk),
220 LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
223 fastopenq->rskq_rst_head = req1->dl_next;
225 spin_unlock(&fastopenq->lock);
231 /* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
232 * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
233 * cookie request (foc->len == 0).
235 bool tcp_fastopen_check(struct sock *sk, struct sk_buff *skb,
236 struct request_sock *req,
237 struct tcp_fastopen_cookie *foc)
239 struct tcp_fastopen_cookie valid_foc = { .len = -1 };
240 bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
242 if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&
243 (syn_data || foc->len >= 0) &&
244 tcp_fastopen_queue_check(sk))) {
249 if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD))
252 tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr,
253 ip_hdr(skb)->daddr, &valid_foc);
255 if (foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
256 foc->len == valid_foc.len &&
257 !memcmp(foc->val, valid_foc.val, foc->len)) {
259 tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
261 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVE);
265 NET_INC_STATS_BH(sock_net(sk), foc->len ?
266 LINUX_MIB_TCPFASTOPENPASSIVEFAIL :
267 LINUX_MIB_TCPFASTOPENCOOKIEREQD);
271 EXPORT_SYMBOL(tcp_fastopen_check);