tcp: move fastopen functions to tcp_fastopen.c

Move common TFO functions that will be used by both v4 and v6
to tcp_fastopen.c. Create a helper tcp_fastopen_queue_check().

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Daniel Lee <longinus00@gmail.com>
Signed-off-by: Jerry Chu <hkchu@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 190 insertions, 0 deletions

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index f195d9316e55..0606c91d9d0b 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -94,3 +94,193 @@ void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
         }
         rcu_read_unlock();
 }
+
+int tcp_fastopen_create_child(struct sock *sk,
+                              struct sk_buff *skb,
+                              struct sk_buff *skb_synack,
+                              struct request_sock *req)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
+        const struct inet_request_sock *ireq = inet_rsk(req);
+        struct sock *child;
+        int err;
+
+        req->num_retrans = 0;
+        req->num_timeout = 0;
+        req->sk = NULL;
+
+        child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL);
+        if (child == NULL) {
+                NET_INC_STATS_BH(sock_net(sk),
+                                 LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
+                kfree_skb(skb_synack);
+                return -1;
+        }
+        err = ip_build_and_send_pkt(skb_synack, sk, ireq->ir_loc_addr,
+                                    ireq->ir_rmt_addr, ireq->opt);
+        err = net_xmit_eval(err);
+        if (!err)
+                tcp_rsk(req)->snt_synack = tcp_time_stamp;
+        /* XXX (TFO) - is it ok to ignore error and continue? */
+
+        spin_lock(&queue->fastopenq->lock);
+        queue->fastopenq->qlen++;
+        spin_unlock(&queue->fastopenq->lock);
+
+        /* Initialize the child socket. Have to fix some values to take
+         * into account the child is a Fast Open socket and is created
+         * only out of the bits carried in the SYN packet.
+         */
+        tp = tcp_sk(child);
+
+        tp->fastopen_rsk = req;
+        /* Do a hold on the listner sk so that if the listener is being
+         * closed, the child that has been accepted can live on and still
+         * access listen_lock.
+         */
+        sock_hold(sk);
+        tcp_rsk(req)->listener = sk;
+
+        /* RFC1323: The window in SYN & SYN/ACK segments is never
+         * scaled. So correct it appropriately.
+         */
+        tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
+
+        /* Activate the retrans timer so that SYNACK can be retransmitted.
+         * The request socket is not added to the SYN table of the parent
+         * because it's been added to the accept queue directly.
+         */
+        inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS,
+                                  TCP_TIMEOUT_INIT, TCP_RTO_MAX);
+
+        /* Add the child socket directly into the accept queue */
+        inet_csk_reqsk_queue_add(sk, req, child);
+
+        /* Now finish processing the fastopen child socket. */
+        inet_csk(child)->icsk_af_ops->rebuild_header(child);
+        tcp_init_congestion_control(child);
+        tcp_mtup_init(child);
+        tcp_init_metrics(child);
+        tcp_init_buffer_space(child);
+
+        /* Queue the data carried in the SYN packet. We need to first
+         * bump skb's refcnt because the caller will attempt to free it.
+         *
+         * XXX (TFO) - we honor a zero-payload TFO request for now.
+         * (Any reason not to?)
+         */
+        if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq + 1) {
+                /* Don't queue the skb if there is no payload in SYN.
+                 * XXX (TFO) - How about SYN+FIN?
+                 */
+                tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+        } else {
+                skb = skb_get(skb);
+                skb_dst_drop(skb);
+                __skb_pull(skb, tcp_hdr(skb)->doff * 4);
+                skb_set_owner_r(skb, child);
+                __skb_queue_tail(&child->sk_receive_queue, skb);
+                tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+                tp->syn_data_acked = 1;
+        }
+        sk->sk_data_ready(sk);
+        bh_unlock_sock(child);
+        sock_put(child);
+        WARN_ON(req->sk == NULL);
+        return 0;
+}
+EXPORT_SYMBOL(tcp_fastopen_create_child);
+
+static bool tcp_fastopen_queue_check(struct sock *sk)
+{
+        struct fastopen_queue *fastopenq;
+
+        /* Make sure the listener has enabled fastopen, and we don't
+         * exceed the max # of pending TFO requests allowed before trying
+         * to validating the cookie in order to avoid burning CPU cycles
+         * unnecessarily.
+         *
+         * XXX (TFO) - The implication of checking the max_qlen before
+         * processing a cookie request is that clients can't differentiate
+         * between qlen overflow causing Fast Open to be disabled
+         * temporarily vs a server not supporting Fast Open at all.
+         */
+        fastopenq = inet_csk(sk)->icsk_accept_queue.fastopenq;
+        if (fastopenq == NULL || fastopenq->max_qlen == 0)
+                return false;
+
+        if (fastopenq->qlen >= fastopenq->max_qlen) {
+                struct request_sock *req1;
+                spin_lock(&fastopenq->lock);
+                req1 = fastopenq->rskq_rst_head;
+                if ((req1 == NULL) || time_after(req1->expires, jiffies)) {
+                        spin_unlock(&fastopenq->lock);
+                        NET_INC_STATS_BH(sock_net(sk),
+                                         LINUX_MIB_TCPFASTOPENLISTENOVERFLOW);
+                        return false;
+                }
+                fastopenq->rskq_rst_head = req1->dl_next;
+                fastopenq->qlen--;
+                spin_unlock(&fastopenq->lock);
+                reqsk_free(req1);
+        }
+        return true;
+}
+
+bool tcp_fastopen_check(struct sock *sk, struct sk_buff *skb,
+                        struct request_sock *req,
+                        struct tcp_fastopen_cookie *foc,
+                        struct tcp_fastopen_cookie *valid_foc)
+{
+        bool skip_cookie = false;
+
+        if (likely(!fastopen_cookie_present(foc))) {
+                /* See include/net/tcp.h for the meaning of these knobs */
+                if ((sysctl_tcp_fastopen & TFO_SERVER_ALWAYS) ||
+                    ((sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD) &&
+                    (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1)))
+                        skip_cookie = true; /* no cookie to validate */
+                else
+                        return false;
+        }
+        /* A FO option is present; bump the counter. */
+        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVE);
+
+        if ((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) == 0 ||
+            !tcp_fastopen_queue_check(sk))
+                return false;
+
+        if (skip_cookie) {
+                tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+                return true;
+        }
+
+        if (foc->len == TCP_FASTOPEN_COOKIE_SIZE) {
+                if ((sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_CHKED) == 0) {
+                        tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr,
+                                                ip_hdr(skb)->daddr, valid_foc);
+                        if ((valid_foc->len != TCP_FASTOPEN_COOKIE_SIZE) ||
+                            memcmp(&foc->val[0], &valid_foc->val[0],
+                            TCP_FASTOPEN_COOKIE_SIZE) != 0)
+                                return false;
+                        valid_foc->len = -1;
+                }
+                /* Acknowledge the data received from the peer. */
+                tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+                return true;
+        } else if (foc->len == 0) { /* Client requesting a cookie */
+                tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr,
+                                        ip_hdr(skb)->daddr, valid_foc);
+                NET_INC_STATS_BH(sock_net(sk),
+                    LINUX_MIB_TCPFASTOPENCOOKIEREQD);
+        } else {
+                /* Client sent a cookie with wrong size. Treat it
+                 * the same as invalid and return a valid one.
+                 */
+                tcp_fastopen_cookie_gen(ip_hdr(skb)->saddr,
+                                        ip_hdr(skb)->daddr, valid_foc);
+        }
+        return false;
+}
+EXPORT_SYMBOL(tcp_fastopen_check);