1 files changed, 147 insertions, 228 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index b224eb8bce8b..3e07a64ca44e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -88,12 +88,14 @@ int sysctl_tcp_app_win __read_mostly = 31;
 int sysctl_tcp_adv_win_scale __read_mostly = 1;
 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale);
 
+/* rfc5961 challenge ack rate limiting */
+int sysctl_tcp_challenge_ack_limit = 100;
+
 int sysctl_tcp_stdurg __read_mostly;
 int sysctl_tcp_rfc1337 __read_mostly;
 int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
 int sysctl_tcp_frto __read_mostly = 2;
 int sysctl_tcp_frto_response __read_mostly;
-int sysctl_tcp_nometrics_save __read_mostly;
 
 int sysctl_tcp_thin_dupack __read_mostly;
 
@@ -701,7 +703,7 @@ static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
 /* Calculate rto without backoff.  This is the second half of Van Jacobson's
  * routine referred to above.
  */
-static inline void tcp_set_rto(struct sock *sk)
+void tcp_set_rto(struct sock *sk)
 {
         const struct tcp_sock *tp = tcp_sk(sk);
         /* Old crap is replaced with new one. 8)
@@ -728,109 +730,6 @@ static inline void tcp_set_rto(struct sock *sk)
         tcp_bound_rto(sk);
 }
 
-/* Save metrics learned by this TCP session.
-   This function is called only, when TCP finishes successfully
-   i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
- */
-void tcp_update_metrics(struct sock *sk)
-{
-        struct tcp_sock *tp = tcp_sk(sk);
-        struct dst_entry *dst = __sk_dst_get(sk);
-
-        if (sysctl_tcp_nometrics_save)
-                return;
-
-        dst_confirm(dst);
-
-        if (dst && (dst->flags & DST_HOST)) {
-                const struct inet_connection_sock *icsk = inet_csk(sk);
-                int m;
-                unsigned long rtt;
-
-                if (icsk->icsk_backoff || !tp->srtt) {
-                        /* This session failed to estimate rtt. Why?
-                         * Probably, no packets returned in time.
-                         * Reset our results.
-                         */
-                        if (!(dst_metric_locked(dst, RTAX_RTT)))
-                                dst_metric_set(dst, RTAX_RTT, 0);
-                        return;
-                }
-
-                rtt = dst_metric_rtt(dst, RTAX_RTT);
-                m = rtt - tp->srtt;
-
-                /* If newly calculated rtt larger than stored one,
-                 * store new one. Otherwise, use EWMA. Remember,
-                 * rtt overestimation is always better than underestimation.
-                 */
-                if (!(dst_metric_locked(dst, RTAX_RTT))) {
-                        if (m <= 0)
-                                set_dst_metric_rtt(dst, RTAX_RTT, tp->srtt);
-                        else
-                                set_dst_metric_rtt(dst, RTAX_RTT, rtt - (m >> 3));
-                }
-
-                if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
-                        unsigned long var;
-                        if (m < 0)
-                                m = -m;
-
-                        /* Scale deviation to rttvar fixed point */
-                        m >>= 1;
-                        if (m < tp->mdev)
-                                m = tp->mdev;
-
-                        var = dst_metric_rtt(dst, RTAX_RTTVAR);
-                        if (m >= var)
-                                var = m;
-                        else
-                                var -= (var - m) >> 2;
-
-                        set_dst_metric_rtt(dst, RTAX_RTTVAR, var);
-                }
-
-                if (tcp_in_initial_slowstart(tp)) {
-                        /* Slow start still did not finish. */
-                        if (dst_metric(dst, RTAX_SSTHRESH) &&
-                            !dst_metric_locked(dst, RTAX_SSTHRESH) &&
-                            (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
-                                dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_cwnd >> 1);
-                        if (!dst_metric_locked(dst, RTAX_CWND) &&
-                            tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
-                                dst_metric_set(dst, RTAX_CWND, tp->snd_cwnd);
-                } else if (tp->snd_cwnd > tp->snd_ssthresh &&
-                           icsk->icsk_ca_state == TCP_CA_Open) {
-                        /* Cong. avoidance phase, cwnd is reliable. */
-                        if (!dst_metric_locked(dst, RTAX_SSTHRESH))
-                                dst_metric_set(dst, RTAX_SSTHRESH,
-                                               max(tp->snd_cwnd >> 1, tp->snd_ssthresh));
-                        if (!dst_metric_locked(dst, RTAX_CWND))
-                                dst_metric_set(dst, RTAX_CWND,
-                                               (dst_metric(dst, RTAX_CWND) +
-                                                tp->snd_cwnd) >> 1);
-                } else {
-                        /* Else slow start did not finish, cwnd is non-sense,
-                           ssthresh may be also invalid.
-                         */
-                        if (!dst_metric_locked(dst, RTAX_CWND))
-                                dst_metric_set(dst, RTAX_CWND,
-                                               (dst_metric(dst, RTAX_CWND) +
-                                                tp->snd_ssthresh) >> 1);
-                        if (dst_metric(dst, RTAX_SSTHRESH) &&
-                            !dst_metric_locked(dst, RTAX_SSTHRESH) &&
-                            tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH))
-                                dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_ssthresh);
-                }
-
-                if (!dst_metric_locked(dst, RTAX_REORDERING)) {
-                        if (dst_metric(dst, RTAX_REORDERING) < tp->reordering &&
-                            tp->reordering != sysctl_tcp_reordering)
-                                dst_metric_set(dst, RTAX_REORDERING, tp->reordering);
-                }
-        }
-}
-
 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst)
 {
         __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
@@ -867,7 +766,7 @@ void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
  * Packet counting of FACK is based on in-order assumptions, therefore TCP
  * disables it when reordering is detected
  */
-static void tcp_disable_fack(struct tcp_sock *tp)
+void tcp_disable_fack(struct tcp_sock *tp)
 {
         /* RFC3517 uses different metric in lost marker => reset on change */
         if (tcp_is_fack(tp))
@@ -881,86 +780,6 @@ static void tcp_dsack_seen(struct tcp_sock *tp)
         tp->rx_opt.sack_ok |= TCP_DSACK_SEEN;
 }
 
-/* Initialize metrics on socket. */
-
-static void tcp_init_metrics(struct sock *sk)
-{
-        struct tcp_sock *tp = tcp_sk(sk);
-        struct dst_entry *dst = __sk_dst_get(sk);
-
-        if (dst == NULL)
-                goto reset;
-
-        dst_confirm(dst);
-
-        if (dst_metric_locked(dst, RTAX_CWND))
-                tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
-        if (dst_metric(dst, RTAX_SSTHRESH)) {
-                tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
-                if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
-                        tp->snd_ssthresh = tp->snd_cwnd_clamp;
-        } else {
-                /* ssthresh may have been reduced unnecessarily during.
-                 * 3WHS. Restore it back to its initial default.
-                 */
-                tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
-        }
-        if (dst_metric(dst, RTAX_REORDERING) &&
-            tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
-                tcp_disable_fack(tp);
-                tcp_disable_early_retrans(tp);
-                tp->reordering = dst_metric(dst, RTAX_REORDERING);
-        }
-
-        if (dst_metric(dst, RTAX_RTT) == 0 || tp->srtt == 0)
-                goto reset;
-
-        /* Initial rtt is determined from SYN,SYN-ACK.
-         * The segment is small and rtt may appear much
-         * less than real one. Use per-dst memory
-         * to make it more realistic.
-         *
-         * A bit of theory. RTT is time passed after "normal" sized packet
-         * is sent until it is ACKed. In normal circumstances sending small
-         * packets force peer to delay ACKs and calculation is correct too.
-         * The algorithm is adaptive and, provided we follow specs, it
-         * NEVER underestimate RTT. BUT! If peer tries to make some clever
-         * tricks sort of "quick acks" for time long enough to decrease RTT
-         * to low value, and then abruptly stops to do it and starts to delay
-         * ACKs, wait for troubles.
-         */
-        if (dst_metric_rtt(dst, RTAX_RTT) > tp->srtt) {
-                tp->srtt = dst_metric_rtt(dst, RTAX_RTT);
-                tp->rtt_seq = tp->snd_nxt;
-        }
-        if (dst_metric_rtt(dst, RTAX_RTTVAR) > tp->mdev) {
-                tp->mdev = dst_metric_rtt(dst, RTAX_RTTVAR);
-                tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
-        }
-        tcp_set_rto(sk);
-reset:
-        if (tp->srtt == 0) {
-                /* RFC6298: 5.7 We've failed to get a valid RTT sample from
-                 * 3WHS. This is most likely due to retransmission,
-                 * including spurious one. Reset the RTO back to 3secs
-                 * from the more aggressive 1sec to avoid more spurious
-                 * retransmission.
-                 */
-                tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_FALLBACK;
-                inet_csk(sk)->icsk_rto = TCP_TIMEOUT_FALLBACK;
-        }
-        /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
-         * retransmitted. In light of RFC6298 more aggressive 1sec
-         * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
-         * retransmission has occurred.
-         */
-        if (tp->total_retrans > 1)
-                tp->snd_cwnd = 1;
-        else
-                tp->snd_cwnd = tcp_init_cwnd(tp, dst);
-        tp->snd_cwnd_stamp = tcp_time_stamp;
-}
-
 static void tcp_update_reordering(struct sock *sk, const int metric,
                                   const int ts)
 {
@@ -2702,7 +2521,7 @@ static void tcp_cwnd_down(struct sock *sk, int flag)
 /* Nothing was retransmitted or returned timestamp is less
  * than timestamp of the first retransmission.
  */
-static inline int tcp_packet_delayed(const struct tcp_sock *tp)
+static inline bool tcp_packet_delayed(const struct tcp_sock *tp)
 {
         return !tp->retrans_stamp ||
                 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
@@ -2763,7 +2582,7 @@ static void tcp_undo_cwr(struct sock *sk, const bool undo_ssthresh)
         tp->snd_cwnd_stamp = tcp_time_stamp;
 }
 
-static inline int tcp_may_undo(const struct tcp_sock *tp)
+static inline bool tcp_may_undo(const struct tcp_sock *tp)
 {
         return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp));
 }
@@ -3552,13 +3371,13 @@ static void tcp_ack_probe(struct sock *sk)
         }
 }
 
-static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
+static inline bool tcp_ack_is_dubious(const struct sock *sk, const int flag)
 {
         return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
                 inet_csk(sk)->icsk_ca_state != TCP_CA_Open;
 }
 
-static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
+static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
 {
         const struct tcp_sock *tp = tcp_sk(sk);
         return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
@@ -3568,7 +3387,7 @@ static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
 /* Check that window update is acceptable.
  * The function assumes that snd_una<=ack<=snd_next.
  */
-static inline int tcp_may_update_window(const struct tcp_sock *tp,
+static inline bool tcp_may_update_window(const struct tcp_sock *tp,
                                         const u32 ack, const u32 ack_seq,
                                         const u32 nwin)
 {
@@ -3869,9 +3688,11 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
                         tcp_cong_avoid(sk, ack, prior_in_flight);
         }
 
-        if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
-                dst_confirm(__sk_dst_get(sk));
-
+        if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) {
+                struct dst_entry *dst = __sk_dst_get(sk);
+                if (dst)
+                        dst_confirm(dst);
+        }
         return 1;
 
 no_queue:
@@ -3911,7 +3732,8 @@ old_ack:
  * the fast version below fails.
  */
 void tcp_parse_options(const struct sk_buff *skb, struct tcp_options_received *opt_rx,
-                       const u8 **hvpp, int estab)
+                       const u8 **hvpp, int estab,
+                       struct tcp_fastopen_cookie *foc)
 {
         const unsigned char *ptr;
         const struct tcphdr *th = tcp_hdr(skb);
@@ -4018,8 +3840,25 @@ void tcp_parse_options(const struct sk_buff *skb, struct tcp_options_received *o
                                         break;
                                 }
                                 break;
-                        }
 
+                        case TCPOPT_EXP:
+                                /* Fast Open option shares code 254 using a
+                                 * 16 bits magic number. It's valid only in
+                                 * SYN or SYN-ACK with an even size.
+                                 */
+                                if (opsize < TCPOLEN_EXP_FASTOPEN_BASE ||
+                                    get_unaligned_be16(ptr) != TCPOPT_FASTOPEN_MAGIC ||
+                                    foc == NULL || !th->syn || (opsize & 1))
+                                        break;
+                                foc->len = opsize - TCPOLEN_EXP_FASTOPEN_BASE;
+                                if (foc->len >= TCP_FASTOPEN_COOKIE_MIN &&
+                                    foc->len <= TCP_FASTOPEN_COOKIE_MAX)
+                                        memcpy(foc->val, ptr + 2, foc->len);
+                                else if (foc->len != 0)
+                                        foc->len = -1;
+                                break;
+
+                        }
                         ptr += opsize-2;
                         length -= opsize;
                 }
@@ -4061,7 +3900,7 @@ static bool tcp_fast_parse_options(const struct sk_buff *skb,
                 if (tcp_parse_aligned_timestamp(tp, th))
                         return true;
         }
-        tcp_parse_options(skb, &tp->rx_opt, hvpp, 1);
+        tcp_parse_options(skb, &tp->rx_opt, hvpp, 1, NULL);
         return true;
 }
 
@@ -4167,7 +4006,7 @@ static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
                 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
 }
 
-static inline int tcp_paws_discard(const struct sock *sk,
+static inline bool tcp_paws_discard(const struct sock *sk,
                                    const struct sk_buff *skb)
 {
         const struct tcp_sock *tp = tcp_sk(sk);
@@ -4189,7 +4028,7 @@ static inline int tcp_paws_discard(const struct sock *sk,
  * (borrowed from freebsd)
  */
 
-static inline int tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq)
+static inline bool tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq)
 {
         return  !before(end_seq, tp->rcv_wup) &&
                 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
@@ -4579,8 +4418,8 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 
         TCP_ECN_check_ce(tp, skb);
 
-        if (tcp_try_rmem_schedule(sk, skb->truesize)) {
-                /* TODO: should increment a counter */
+        if (unlikely(tcp_try_rmem_schedule(sk, skb->truesize))) {
+                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFODROP);
                 __kfree_skb(skb);
                 return;
         }
@@ -4589,6 +4428,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
         tp->pred_flags = 0;
         inet_csk_schedule_ack(sk);
 
+        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOQUEUE);
         SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
                    tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
 
@@ -4642,6 +4482,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
         if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) {
                 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
                         /* All the bits are present. Drop. */
+                        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
                         __kfree_skb(skb);
                         skb = NULL;
                         tcp_dsack_set(sk, seq, end_seq);
@@ -4680,6 +4521,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
                 __skb_unlink(skb1, &tp->out_of_order_queue);
                 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
                                  TCP_SKB_CB(skb1)->end_seq);
+                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
                 __kfree_skb(skb1);
         }
 
@@ -5372,7 +5214,7 @@ static __sum16 __tcp_checksum_complete_user(struct sock *sk,
         return result;
 }
 
-static inline int tcp_checksum_complete_user(struct sock *sk,
+static inline bool tcp_checksum_complete_user(struct sock *sk,
                                              struct sk_buff *skb)
 {
         return !skb_csum_unnecessary(skb) &&
@@ -5426,11 +5268,28 @@ out:
 }
 #endif /* CONFIG_NET_DMA */
 
+static void tcp_send_challenge_ack(struct sock *sk)
+{
+        /* unprotected vars, we dont care of overwrites */
+        static u32 challenge_timestamp;
+        static unsigned int challenge_count;
+        u32 now = jiffies / HZ;
+
+        if (now != challenge_timestamp) {
+                challenge_timestamp = now;
+                challenge_count = 0;
+        }
+        if (++challenge_count <= sysctl_tcp_challenge_ack_limit) {
+                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK);
+                tcp_send_ack(sk);
+        }
+}
+
 /* Does PAWS and seqno based validation of an incoming segment, flags will
  * play significant role here.
  */
-static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
-                              const struct tcphdr *th, int syn_inerr)
+static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
+                                  const struct tcphdr *th, int syn_inerr)
 {
         const u8 *hash_location;
         struct tcp_sock *tp = tcp_sk(sk);
@@ -5455,14 +5314,26 @@ static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
                  * an acknowledgment should be sent in reply (unless the RST
                  * bit is set, if so drop the segment and return)".
                  */
-                if (!th->rst)
+                if (!th->rst) {
+                        if (th->syn)
+                                goto syn_challenge;
                         tcp_send_dupack(sk, skb);
+                }
                 goto discard;
         }
 
         /* Step 2: check RST bit */
         if (th->rst) {
-                tcp_reset(sk);
+                /* RFC 5961 3.2 :
+                 * If sequence number exactly matches RCV.NXT, then
+                 *     RESET the connection
+                 * else
+                 *     Send a challenge ACK
+                 */
+                if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt)
+                        tcp_reset(sk);
+                else
+                        tcp_send_challenge_ack(sk);
                 goto discard;
         }
 
@@ -5473,20 +5344,23 @@ static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
 
         /* step 3: check security and precedence [ignored] */
 
-        /* step 4: Check for a SYN in window. */
-        if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
+        /* step 4: Check for a SYN
+         * RFC 5691 4.2 : Send a challenge ack
+         */
+        if (th->syn) {
+syn_challenge:
                 if (syn_inerr)
                         TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
-                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
-                tcp_reset(sk);
-                return -1;
+                NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE);
+                tcp_send_challenge_ack(sk);
+                goto discard;
         }
 
-        return 1;
+        return true;
 
 discard:
         __kfree_skb(skb);
-        return 0;
+        return false;
 }
 
 /*
@@ -5516,7 +5390,6 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
                         const struct tcphdr *th, unsigned int len)
 {
         struct tcp_sock *tp = tcp_sk(sk);
-        int res;
 
         /*
          *      Header prediction.
@@ -5693,9 +5566,8 @@ slow_path:
          *      Standard slow path.
          */
 
-        res = tcp_validate_incoming(sk, skb, th, 1);
-        if (res <= 0)
-                return -res;
+        if (!tcp_validate_incoming(sk, skb, th, 1))
+                return 0;
 
 step5:
         if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0)
@@ -5729,8 +5601,10 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
 
         tcp_set_state(sk, TCP_ESTABLISHED);
 
-        if (skb != NULL)
+        if (skb != NULL) {
+                sk->sk_rx_dst = dst_clone(skb_dst(skb));
                 security_inet_conn_established(sk, skb);
+        }
 
         /* Make sure socket is routed, for correct metrics.  */
         icsk->icsk_af_ops->rebuild_header(sk);
@@ -5760,6 +5634,45 @@ void tcp_finish_connect(struct sock *sk, struct sk_buff *skb)
         }
 }
 
+static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
+                                    struct tcp_fastopen_cookie *cookie)
+{
+        struct tcp_sock *tp = tcp_sk(sk);
+        struct sk_buff *data = tp->syn_data ? tcp_write_queue_head(sk) : NULL;
+        u16 mss = tp->rx_opt.mss_clamp;
+        bool syn_drop;
+
+        if (mss == tp->rx_opt.user_mss) {
+                struct tcp_options_received opt;
+                const u8 *hash_location;
+
+                /* Get original SYNACK MSS value if user MSS sets mss_clamp */
+                tcp_clear_options(&opt);
+                opt.user_mss = opt.mss_clamp = 0;
+                tcp_parse_options(synack, &opt, &hash_location, 0, NULL);
+                mss = opt.mss_clamp;
+        }
+
+        if (!tp->syn_fastopen)  /* Ignore an unsolicited cookie */
+                cookie->len = -1;
+
+        /* The SYN-ACK neither has cookie nor acknowledges the data. Presumably
+         * the remote receives only the retransmitted (regular) SYNs: either
+         * the original SYN-data or the corresponding SYN-ACK is lost.
+         */
+        syn_drop = (cookie->len <= 0 && data &&
+                    inet_csk(sk)->icsk_retransmits);
+
+        tcp_fastopen_cache_set(sk, mss, cookie, syn_drop);
+
+        if (data) { /* Retransmit unacked data in SYN */
+                tcp_retransmit_skb(sk, data);
+                tcp_rearm_rto(sk);
+                return true;
+        }
+        return false;
+}
+
 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
                                          const struct tcphdr *th, unsigned int len)
 {
@@ -5767,9 +5680,10 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
         struct inet_connection_sock *icsk = inet_csk(sk);
         struct tcp_sock *tp = tcp_sk(sk);
         struct tcp_cookie_values *cvp = tp->cookie_values;
+        struct tcp_fastopen_cookie foc = { .len = -1 };
         int saved_clamp = tp->rx_opt.mss_clamp;
 
-        tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0);
+        tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0, &foc);
 
         if (th->ack) {
                 /* rfc793:
@@ -5779,11 +5693,9 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
                  *        If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
                  *        a reset (unless the RST bit is set, if so drop
                  *        the segment and return)"
-                 *
-                 *  We do not send data with SYN, so that RFC-correct
-                 *  test reduces to:
                  */
-                if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
+                if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) ||
+                    after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt))
                         goto reset_and_undo;
 
                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
@@ -5895,6 +5807,10 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 
                 tcp_finish_connect(sk, skb);
 
+                if ((tp->syn_fastopen || tp->syn_data) &&
+                    tcp_rcv_fastopen_synack(sk, skb, &foc))
+                        return -1;
+
                 if (sk->sk_write_pending ||
                     icsk->icsk_accept_queue.rskq_defer_accept ||
                     icsk->icsk_ack.pingpong) {
@@ -6013,7 +5929,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
         struct tcp_sock *tp = tcp_sk(sk);
         struct inet_connection_sock *icsk = inet_csk(sk);
         int queued = 0;
-        int res;
 
         tp->rx_opt.saw_tstamp = 0;
 
@@ -6068,9 +5983,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                 return 0;
         }
 
-        res = tcp_validate_incoming(sk, skb, th, 0);
-        if (res <= 0)
-                return -res;
+        if (!tcp_validate_incoming(sk, skb, th, 0))
+                return 0;
 
         /* step 5: check the ACK field */
         if (th->ack) {
@@ -6126,9 +6040,14 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 
                 case TCP_FIN_WAIT1:
                         if (tp->snd_una == tp->write_seq) {
+                                struct dst_entry *dst;
+
                                 tcp_set_state(sk, TCP_FIN_WAIT2);
                                 sk->sk_shutdown |= SEND_SHUTDOWN;
-                                dst_confirm(__sk_dst_get(sk));
+
+                                dst = __sk_dst_get(sk);
+                                if (dst)
+                                        dst_confirm(dst);
 
                                 if (!sock_flag(sk, SOCK_DEAD))
                                         /* Wake up lingering close() */