7 files changed, 323 insertions, 309 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 4e37c71ecd74..bc35e4709e8e 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -366,11 +366,6 @@ static inline bool tcp_passive_fastopen(const struct sock *sk)
                 tcp_sk(sk)->fastopen_rsk != NULL);
 }
 
-static inline bool fastopen_cookie_present(struct tcp_fastopen_cookie *foc)
-{
-        return foc->len != -1;
-}
-
 extern void tcp_sock_destruct(struct sock *sk);
 
 static inline int fastopen_init_queue(struct sock *sk, int backlog)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 3c9418456640..f5d6ca4a9d28 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -220,8 +220,6 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
 #define TFO_SERVER_ENABLE       2
 #define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
 
-/* Process SYN data but skip cookie validation */
-#define TFO_SERVER_COOKIE_NOT_CHKED     0x100
 /* Accept SYN data w/o any cookie option */
 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
 
@@ -230,10 +228,6 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
  */
 #define TFO_SERVER_WO_SOCKOPT1  0x400
 #define TFO_SERVER_WO_SOCKOPT2  0x800
-/* Always create TFO child sockets on a TFO listener even when
- * cookie/data not present. (For testing purpose!)
- */
-#define TFO_SERVER_ALWAYS       0x1000
 
 extern struct inet_timewait_death_row tcp_death_row;
 
@@ -1120,6 +1114,9 @@ static inline void tcp_openreq_init(struct request_sock *req,
         ireq->ir_num = ntohs(tcp_hdr(skb)->dest);
 }
 
+extern void tcp_openreq_init_rwin(struct request_sock *req,
+                                  struct sock *sk, struct dst_entry *dst);
+
 void tcp_enter_memory_pressure(struct sock *sk);
 
 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
@@ -1329,8 +1326,10 @@ void tcp_free_fastopen_req(struct tcp_sock *tp);
 
 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
-void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
-                             struct tcp_fastopen_cookie *foc);
+bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
+                      struct request_sock *req,
+                      struct tcp_fastopen_cookie *foc,
+                      struct dst_entry *dst);
 void tcp_fastopen_init_key_once(bool publish);
 #define TCP_FASTOPEN_KEY_LENGTH 16
 
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index f195d9316e55..62e48cf84e60 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -72,25 +72,224 @@ error:		kfree(ctx);
         return err;
 }
 
-/* Computes the fastopen cookie for the IP path.
- * The path is a 128 bits long (pad with zeros for IPv4).
- *
- * The caller must check foc->len to determine if a valid cookie
- * has been generated successfully.
-*/
-void tcp_fastopen_cookie_gen(__be32 src, __be32 dst,
-                             struct tcp_fastopen_cookie *foc)
+static bool __tcp_fastopen_cookie_gen(const void *path,
+                                      struct tcp_fastopen_cookie *foc)
 {
-        __be32 path[4] = { src, dst, 0, 0 };
         struct tcp_fastopen_context *ctx;
+        bool ok = false;
 
         tcp_fastopen_init_key_once(true);
 
         rcu_read_lock();
         ctx = rcu_dereference(tcp_fastopen_ctx);
         if (ctx) {
-                crypto_cipher_encrypt_one(ctx->tfm, foc->val, (__u8 *)path);
+                crypto_cipher_encrypt_one(ctx->tfm, foc->val, path);
                 foc->len = TCP_FASTOPEN_COOKIE_SIZE;
+                ok = true;
         }
         rcu_read_unlock();
+        return ok;
+}
+
+/* Generate the fastopen cookie by doing aes128 encryption on both
+ * the source and destination addresses. Pad 0s for IPv4 or IPv4-mapped-IPv6
+ * addresses. For the longer IPv6 addresses use CBC-MAC.
+ *
+ * XXX (TFO) - refactor when TCP_FASTOPEN_COOKIE_SIZE != AES_BLOCK_SIZE.
+ */
+static bool tcp_fastopen_cookie_gen(struct request_sock *req,
+                                    struct sk_buff *syn,
+                                    struct tcp_fastopen_cookie *foc)
+{
+        if (req->rsk_ops->family == AF_INET) {
+                const struct iphdr *iph = ip_hdr(syn);
+
+                __be32 path[4] = { iph->saddr, iph->daddr, 0, 0 };
+                return __tcp_fastopen_cookie_gen(path, foc);
+        }
+
+#if IS_ENABLED(CONFIG_IPV6)
+        if (req->rsk_ops->family == AF_INET6) {
+                const struct ipv6hdr *ip6h = ipv6_hdr(syn);
+                struct tcp_fastopen_cookie tmp;
+
+                if (__tcp_fastopen_cookie_gen(&ip6h->saddr, &tmp)) {
+                        struct in6_addr *buf = (struct in6_addr *) tmp.val;
+                        int i = 4;
+
+                        for (i = 0; i < 4; i++)
+                                buf->s6_addr32[i] ^= ip6h->daddr.s6_addr32[i];
+                        return __tcp_fastopen_cookie_gen(buf, foc);
+                }
+        }
+#endif
+        return false;
+}
+
+static bool tcp_fastopen_create_child(struct sock *sk,
+                                      struct sk_buff *skb,
+                                      struct dst_entry *dst,
+                                      struct request_sock *req)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
+        struct sock *child;
+
+        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)
+                return false;
+
+        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?) but no need to queue the skb since
+         * there is no data. How about SYN+FIN?
+         */
+        if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1) {
+                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->syn_data_acked = 1;
+        }
+        tcp_rsk(req)->rcv_nxt = tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+        sk->sk_data_ready(sk);
+        bh_unlock_sock(child);
+        sock_put(child);
+        WARN_ON(req->sk == NULL);
+        return true;
+}
+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;
+}
+
+/* Returns true if we should perform Fast Open on the SYN. The cookie (foc)
+ * may be updated and return the client in the SYN-ACK later. E.g., Fast Open
+ * cookie request (foc->len == 0).
+ */
+bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
+                      struct request_sock *req,
+                      struct tcp_fastopen_cookie *foc,
+                      struct dst_entry *dst)
+{
+        struct tcp_fastopen_cookie valid_foc = { .len = -1 };
+        bool syn_data = TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq + 1;
+
+        if (!((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) &&
+              (syn_data || foc->len >= 0) &&
+              tcp_fastopen_queue_check(sk))) {
+                foc->len = -1;
+                return false;
+        }
+
+        if (syn_data && (sysctl_tcp_fastopen & TFO_SERVER_COOKIE_NOT_REQD))
+                goto fastopen;
+
+        if (tcp_fastopen_cookie_gen(req, skb, &valid_foc) &&
+            foc->len == TCP_FASTOPEN_COOKIE_SIZE &&
+            foc->len == valid_foc.len &&
+            !memcmp(foc->val, valid_foc.val, foc->len)) {
+                /* Cookie is valid. Create a (full) child socket to accept
+                 * the data in SYN before returning a SYN-ACK to ack the
+                 * data. If we fail to create the socket, fall back and
+                 * ack the ISN only but includes the same cookie.
+                 *
+                 * Note: Data-less SYN with valid cookie is allowed to send
+                 * data in SYN_RECV state.
+                 */
+fastopen:
+                if (tcp_fastopen_create_child(sk, skb, dst, req)) {
+                        foc->len = -1;
+                        NET_INC_STATS_BH(sock_net(sk),
+                                         LINUX_MIB_TCPFASTOPENPASSIVE);
+                        return true;
+                }
+        }
+
+        NET_INC_STATS_BH(sock_net(sk), foc->len ?
+                         LINUX_MIB_TCPFASTOPENPASSIVEFAIL :
+                         LINUX_MIB_TCPFASTOPENCOOKIEREQD);
+        *foc = valid_foc;
+        return false;
 }
+EXPORT_SYMBOL(tcp_try_fastopen);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ad166dcc278f..a2780e5334c9 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -336,8 +336,8 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
         const int code = icmp_hdr(icmp_skb)->code;
         struct sock *sk;
         struct sk_buff *skb;
-        struct request_sock *req;
-        __u32 seq;
+        struct request_sock *fastopen;
+        __u32 seq, snd_una;
         __u32 remaining;
         int err;
         struct net *net = dev_net(icmp_skb->dev);
@@ -378,12 +378,12 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
 
         icsk = inet_csk(sk);
         tp = tcp_sk(sk);
-        req = tp->fastopen_rsk;
         seq = ntohl(th->seq);
+        /* XXX (TFO) - tp->snd_una should be ISN (tcp_create_openreq_child() */
+        fastopen = tp->fastopen_rsk;
+        snd_una = fastopen ? tcp_rsk(fastopen)->snt_isn : tp->snd_una;
         if (sk->sk_state != TCP_LISTEN &&
-            !between(seq, tp->snd_una, tp->snd_nxt) &&
-            (req == NULL || seq != tcp_rsk(req)->snt_isn)) {
-                /* For a Fast Open socket, allow seq to be snt_isn. */
+            !between(seq, snd_una, tp->snd_nxt)) {
                 NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
                 goto out;
         }
@@ -426,11 +426,9 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
                 if (code != ICMP_NET_UNREACH && code != ICMP_HOST_UNREACH)
                         break;
                 if (seq != tp->snd_una  || !icsk->icsk_retransmits ||
-                    !icsk->icsk_backoff)
+                    !icsk->icsk_backoff || fastopen)
                         break;
 
-                /* XXX (TFO) - revisit the following logic for TFO */
-
                 if (sock_owned_by_user(sk))
                         break;
 
@@ -462,14 +460,6 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
                 goto out;
         }
 
-        /* XXX (TFO) - if it's a TFO socket and has been accepted, rather
-         * than following the TCP_SYN_RECV case and closing the socket,
-         * we ignore the ICMP error and keep trying like a fully established
-         * socket. Is this the right thing to do?
-         */
-        if (req && req->sk == NULL)
-                goto out;
-
         switch (sk->sk_state) {
                 struct request_sock *req, **prev;
         case TCP_LISTEN:
@@ -502,10 +492,13 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
                 goto out;
 
         case TCP_SYN_SENT:
-        case TCP_SYN_RECV:  /* Cannot happen.
-                               It can f.e. if SYNs crossed,
-                               or Fast Open.
-                             */
+        case TCP_SYN_RECV:
+                /* Only in fast or simultaneous open. If a fast open socket is
+                 * is already accepted it is treated as a connected one below.
+                 */
+                if (fastopen && fastopen->sk == NULL)
+                        break;
+
                 if (!sock_owned_by_user(sk)) {
                         sk->sk_err = err;
 
@@ -822,7 +815,8 @@ static void tcp_v4_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
  */
 static int tcp_v4_send_synack(struct sock *sk, struct dst_entry *dst,
                               struct request_sock *req,
-                              u16 queue_mapping)
+                              u16 queue_mapping,
+                              struct tcp_fastopen_cookie *foc)
 {
         const struct inet_request_sock *ireq = inet_rsk(req);
         struct flowi4 fl4;
@@ -833,7 +827,7 @@ static int tcp_v4_send_synack(struct sock *sk, struct dst_entry *dst,
         if (!dst && (dst = inet_csk_route_req(sk, &fl4, req)) == NULL)
                 return -1;
 
-        skb = tcp_make_synack(sk, dst, req, NULL);
+        skb = tcp_make_synack(sk, dst, req, foc);
 
         if (skb) {
                 __tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);
@@ -852,7 +846,7 @@ static int tcp_v4_send_synack(struct sock *sk, struct dst_entry *dst,
 
 static int tcp_v4_rtx_synack(struct sock *sk, struct request_sock *req)
 {
-        int res = tcp_v4_send_synack(sk, NULL, req, 0);
+        int res = tcp_v4_send_synack(sk, NULL, req, 0, NULL);
 
         if (!res) {
                 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);
@@ -1260,187 +1254,6 @@ static const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = {
 };
 #endif
 
-static 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;
-        struct fastopen_queue *fastopenq;
-
-        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;
-        }
-        fastopenq = inet_csk(sk)->icsk_accept_queue.fastopenq;
-        /* A FO option is present; bump the counter. */
-        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENPASSIVE);
-
-        /* 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.
-         */
-        if ((sysctl_tcp_fastopen & TFO_SERVER_ENABLE) == 0 ||
-            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);
-                        /* Avoid bumping LINUX_MIB_TCPFASTOPENPASSIVEFAIL*/
-                        foc->len = -1;
-                        return false;
-                }
-                fastopenq->rskq_rst_head = req1->dl_next;
-                fastopenq->qlen--;
-                spin_unlock(&fastopenq->lock);
-                reqsk_free(req1);
-        }
-        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;
-}
-
-static int tcp_v4_conn_req_fastopen(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;
-}
-
 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 {
         struct tcp_options_received tmp_opt;
@@ -1451,12 +1264,10 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
         __be32 saddr = ip_hdr(skb)->saddr;
         __be32 daddr = ip_hdr(skb)->daddr;
         __u32 isn = TCP_SKB_CB(skb)->when;
-        bool want_cookie = false;
+        bool want_cookie = false, fastopen;
         struct flowi4 fl4;
         struct tcp_fastopen_cookie foc = { .len = -1 };
-        struct tcp_fastopen_cookie valid_foc = { .len = -1 };
-        struct sk_buff *skb_synack;
-        int do_fastopen;
+        int err;
 
         /* Never answer to SYNs send to broadcast or multicast */
         if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
@@ -1555,52 +1366,24 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 
                 isn = tcp_v4_init_sequence(skb);
         }
-        tcp_rsk(req)->snt_isn = isn;
-
-        if (dst == NULL) {
-                dst = inet_csk_route_req(sk, &fl4, req);
-                if (dst == NULL)
-                        goto drop_and_free;
-        }
-        do_fastopen = tcp_fastopen_check(sk, skb, req, &foc, &valid_foc);
-
-        /* We don't call tcp_v4_send_synack() directly because we need
-         * to make sure a child socket can be created successfully before
-         * sending back synack!
-         *
-         * XXX (TFO) - Ideally one would simply call tcp_v4_send_synack()
-         * (or better yet, call tcp_send_synack() in the child context
-         * directly, but will have to fix bunch of other code first)
-         * after syn_recv_sock() except one will need to first fix the
-         * latter to remove its dependency on the current implementation
-         * of tcp_v4_send_synack()->tcp_select_initial_window().
-         */
-        skb_synack = tcp_make_synack(sk, dst, req,
-            fastopen_cookie_present(&valid_foc) ? &valid_foc : NULL);
-
-        if (skb_synack) {
-                __tcp_v4_send_check(skb_synack, ireq->ir_loc_addr, ireq->ir_rmt_addr);
-                skb_set_queue_mapping(skb_synack, skb_get_queue_mapping(skb));
-        } else
+        if (!dst && (dst = inet_csk_route_req(sk, &fl4, req)) == NULL)
                 goto drop_and_free;
 
-        if (likely(!do_fastopen)) {
-                int err;
-                err = ip_build_and_send_pkt(skb_synack, sk, ireq->ir_loc_addr,
-                     ireq->ir_rmt_addr, ireq->opt);
-                err = net_xmit_eval(err);
+        tcp_rsk(req)->snt_isn = isn;
+        tcp_rsk(req)->snt_synack = tcp_time_stamp;
+        tcp_openreq_init_rwin(req, sk, dst);
+        fastopen = !want_cookie &&
+                   tcp_try_fastopen(sk, skb, req, &foc, dst);
+        err = tcp_v4_send_synack(sk, dst, req,
+                                 skb_get_queue_mapping(skb), &foc);
+        if (!fastopen) {
                 if (err || want_cookie)
                         goto drop_and_free;
 
                 tcp_rsk(req)->snt_synack = tcp_time_stamp;
                 tcp_rsk(req)->listener = NULL;
-                /* Add the request_sock to the SYN table */
                 inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
-                if (fastopen_cookie_present(&foc) && foc.len != 0)
-                        NET_INC_STATS_BH(sock_net(sk),
-                            LINUX_MIB_TCPFASTOPENPASSIVEFAIL);
-        } else if (tcp_v4_conn_req_fastopen(sk, skb, skb_synack, req))
-                goto drop_and_free;
+        }
 
         return 0;
 
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 05c1b155251d..e68e0d4af6c9 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -362,6 +362,37 @@ void tcp_twsk_destructor(struct sock *sk)
 }
 EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
 
+void tcp_openreq_init_rwin(struct request_sock *req,
+                           struct sock *sk, struct dst_entry *dst)
+{
+        struct inet_request_sock *ireq = inet_rsk(req);
+        struct tcp_sock *tp = tcp_sk(sk);
+        __u8 rcv_wscale;
+        int mss = dst_metric_advmss(dst);
+
+        if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
+                mss = tp->rx_opt.user_mss;
+
+        /* Set this up on the first call only */
+        req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
+
+        /* limit the window selection if the user enforce a smaller rx buffer */
+        if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
+            (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
+                req->window_clamp = tcp_full_space(sk);
+
+        /* tcp_full_space because it is guaranteed to be the first packet */
+        tcp_select_initial_window(tcp_full_space(sk),
+                mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
+                &req->rcv_wnd,
+                &req->window_clamp,
+                ireq->wscale_ok,
+                &rcv_wscale,
+                dst_metric(dst, RTAX_INITRWND));
+        ireq->rcv_wscale = rcv_wscale;
+}
+EXPORT_SYMBOL(tcp_openreq_init_rwin);
+
 static inline void TCP_ECN_openreq_child(struct tcp_sock *tp,
                                          struct request_sock *req)
 {
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 694711a140d4..3d61c52bdf79 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -627,7 +627,7 @@ static unsigned int tcp_synack_options(struct sock *sk,
                 if (unlikely(!ireq->tstamp_ok))
                         remaining -= TCPOLEN_SACKPERM_ALIGNED;
         }
-        if (foc != NULL) {
+        if (foc != NULL && foc->len >= 0) {
                 u32 need = TCPOLEN_EXP_FASTOPEN_BASE + foc->len;
                 need = (need + 3) & ~3U;  /* Align to 32 bits */
                 if (remaining >= need) {
@@ -2803,27 +2803,6 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
         if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
                 mss = tp->rx_opt.user_mss;
 
-        if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
-                __u8 rcv_wscale;
-                /* Set this up on the first call only */
-                req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
-
-                /* limit the window selection if the user enforce a smaller rx buffer */
-                if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
-                    (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0))
-                        req->window_clamp = tcp_full_space(sk);
-
-                /* tcp_full_space because it is guaranteed to be the first packet */
-                tcp_select_initial_window(tcp_full_space(sk),
-                        mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
-                        &req->rcv_wnd,
-                        &req->window_clamp,
-                        ireq->wscale_ok,
-                        &rcv_wscale,
-                        dst_metric(dst, RTAX_INITRWND));
-                ireq->rcv_wscale = rcv_wscale;
-        }
-
         memset(&opts, 0, sizeof(opts));
 #ifdef CONFIG_SYN_COOKIES
         if (unlikely(req->cookie_ts))
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 7fa67439f4d6..3a267bf14f2f 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -340,7 +340,8 @@ static void tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
         struct sock *sk;
         int err;
         struct tcp_sock *tp;
-        __u32 seq;
+        struct request_sock *fastopen;
+        __u32 seq, snd_una;
         struct net *net = dev_net(skb->dev);
 
         sk = inet6_lookup(net, &tcp_hashinfo, &hdr->daddr,
@@ -371,8 +372,11 @@ static void tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 
         tp = tcp_sk(sk);
         seq = ntohl(th->seq);
+        /* XXX (TFO) - tp->snd_una should be ISN (tcp_create_openreq_child() */
+        fastopen = tp->fastopen_rsk;
+        snd_una = fastopen ? tcp_rsk(fastopen)->snt_isn : tp->snd_una;
         if (sk->sk_state != TCP_LISTEN &&
-            !between(seq, tp->snd_una, tp->snd_nxt)) {
+            !between(seq, snd_una, tp->snd_nxt)) {
                 NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
                 goto out;
         }
@@ -436,8 +440,13 @@ static void tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                 goto out;
 
         case TCP_SYN_SENT:
-        case TCP_SYN_RECV:  /* Cannot happen.
-                               It can, it SYNs are crossed. --ANK */
+        case TCP_SYN_RECV:
+                /* Only in fast or simultaneous open. If a fast open socket is
+                 * is already accepted it is treated as a connected one below.
+                 */
+                if (fastopen && fastopen->sk == NULL)
+                        break;
+
                 if (!sock_owned_by_user(sk)) {
                         sk->sk_err = err;
                         sk->sk_error_report(sk);                /* Wake people up to see the error (see connect in sock.c) */
@@ -463,7 +472,8 @@ out:
 static int tcp_v6_send_synack(struct sock *sk, struct dst_entry *dst,
                               struct flowi6 *fl6,
                               struct request_sock *req,
-                              u16 queue_mapping)
+                              u16 queue_mapping,
+                              struct tcp_fastopen_cookie *foc)
 {
         struct inet_request_sock *ireq = inet_rsk(req);
         struct ipv6_pinfo *np = inet6_sk(sk);
@@ -474,7 +484,7 @@ static int tcp_v6_send_synack(struct sock *sk, struct dst_entry *dst,
         if (!dst && (dst = inet6_csk_route_req(sk, fl6, req)) == NULL)
                 goto done;
 
-        skb = tcp_make_synack(sk, dst, req, NULL);
+        skb = tcp_make_synack(sk, dst, req, foc);
 
         if (skb) {
                 __tcp_v6_send_check(skb, &ireq->ir_v6_loc_addr,
@@ -498,7 +508,7 @@ static int tcp_v6_rtx_synack(struct sock *sk, struct request_sock *req)
         struct flowi6 fl6;
         int res;
 
-        res = tcp_v6_send_synack(sk, NULL, &fl6, req, 0);
+        res = tcp_v6_send_synack(sk, NULL, &fl6, req, 0, NULL);
         if (!res) {
                 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);
                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
@@ -917,7 +927,12 @@ static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
 static void tcp_v6_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
                                   struct request_sock *req)
 {
-        tcp_v6_send_ack(skb, tcp_rsk(req)->snt_isn + 1, tcp_rsk(req)->rcv_isn + 1,
+        /* sk->sk_state == TCP_LISTEN -> for regular TCP_SYN_RECV
+         * sk->sk_state == TCP_SYN_RECV -> for Fast Open.
+         */
+        tcp_v6_send_ack(skb, (sk->sk_state == TCP_LISTEN) ?
+                        tcp_rsk(req)->snt_isn + 1 : tcp_sk(sk)->snd_nxt,
+                        tcp_rsk(req)->rcv_nxt,
                         req->rcv_wnd, tcp_time_stamp, req->ts_recent, sk->sk_bound_dev_if,
                         tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr),
                         0, 0);
@@ -969,8 +984,10 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
         struct tcp_sock *tp = tcp_sk(sk);
         __u32 isn = TCP_SKB_CB(skb)->when;
         struct dst_entry *dst = NULL;
+        struct tcp_fastopen_cookie foc = { .len = -1 };
+        bool want_cookie = false, fastopen;
         struct flowi6 fl6;
-        bool want_cookie = false;
+        int err;
 
         if (skb->protocol == htons(ETH_P_IP))
                 return tcp_v4_conn_request(sk, skb);
@@ -1001,7 +1018,7 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
         tcp_clear_options(&tmp_opt);
         tmp_opt.mss_clamp = IPV6_MIN_MTU - sizeof(struct tcphdr) - sizeof(struct ipv6hdr);
         tmp_opt.user_mss = tp->rx_opt.user_mss;
-        tcp_parse_options(skb, &tmp_opt, 0, NULL);
+        tcp_parse_options(skb, &tmp_opt, 0, want_cookie ? NULL : &foc);
 
         if (want_cookie && !tmp_opt.saw_tstamp)
                 tcp_clear_options(&tmp_opt);
@@ -1074,19 +1091,27 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
                 isn = tcp_v6_init_sequence(skb);
         }
 have_isn:
-        tcp_rsk(req)->snt_isn = isn;
 
         if (security_inet_conn_request(sk, skb, req))
                 goto drop_and_release;
 
-        if (tcp_v6_send_synack(sk, dst, &fl6, req,
-                               skb_get_queue_mapping(skb)) ||
-            want_cookie)
+        if (!dst && (dst = inet6_csk_route_req(sk, &fl6, req)) == NULL)
                 goto drop_and_free;
 
+        tcp_rsk(req)->snt_isn = isn;
         tcp_rsk(req)->snt_synack = tcp_time_stamp;
-        tcp_rsk(req)->listener = NULL;
-        inet6_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
+        tcp_openreq_init_rwin(req, sk, dst);
+        fastopen = !want_cookie &&
+                   tcp_try_fastopen(sk, skb, req, &foc, dst);
+        err = tcp_v6_send_synack(sk, dst, &fl6, req,
+                                 skb_get_queue_mapping(skb), &foc);
+        if (!fastopen) {
+                if (err || want_cookie)
+                        goto drop_and_free;
+
+                tcp_rsk(req)->listener = NULL;
+                inet6_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
+        }
         return 0;
 
 drop_and_release:
@@ -1760,6 +1785,7 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
         const struct inet_sock *inet = inet_sk(sp);
         const struct tcp_sock *tp = tcp_sk(sp);
         const struct inet_connection_sock *icsk = inet_csk(sp);
+        struct fastopen_queue *fastopenq = icsk->icsk_accept_queue.fastopenq;
 
         dest  = &sp->sk_v6_daddr;
         src   = &sp->sk_v6_rcv_saddr;
@@ -1802,7 +1828,9 @@ static void get_tcp6_sock(struct seq_file *seq, struct sock *sp, int i)
                    jiffies_to_clock_t(icsk->icsk_ack.ato),
                    (icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
                    tp->snd_cwnd,
-                   tcp_in_initial_slowstart(tp) ? -1 : tp->snd_ssthresh
+                   sp->sk_state == TCP_LISTEN ?
+                        (fastopenq ? fastopenq->max_qlen : 0) :
+                        (tcp_in_initial_slowstart(tp) ? -1 : tp->snd_ssthresh)
                    );
 }