1 files changed, 130 insertions, 68 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 179b51e6bda3..3af21296d967 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -318,36 +318,47 @@ static u16 tcp_select_window(struct sock *sk)
 }
 
 /* Packet ECN state for a SYN-ACK */
-static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb)
+static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
 {
+        const struct tcp_sock *tp = tcp_sk(sk);
+
         TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
         if (!(tp->ecn_flags & TCP_ECN_OK))
                 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
+        else if (tcp_ca_needs_ecn(sk))
+                INET_ECN_xmit(sk);
 }
 
 /* Packet ECN state for a SYN.  */
-static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
+static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
 {
         struct tcp_sock *tp = tcp_sk(sk);
 
         tp->ecn_flags = 0;
-        if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1) {
+        if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
+            tcp_ca_needs_ecn(sk)) {
                 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
                 tp->ecn_flags = TCP_ECN_OK;
+                if (tcp_ca_needs_ecn(sk))
+                        INET_ECN_xmit(sk);
         }
 }
 
-static __inline__ void
-TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th)
+static void
+tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th,
+                    struct sock *sk)
 {
-        if (inet_rsk(req)->ecn_ok)
+        if (inet_rsk(req)->ecn_ok) {
                 th->ece = 1;
+                if (tcp_ca_needs_ecn(sk))
+                        INET_ECN_xmit(sk);
+        }
 }
 
 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
  * be sent.
  */
-static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
+static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
                                 int tcp_header_len)
 {
         struct tcp_sock *tp = tcp_sk(sk);
@@ -362,7 +373,7 @@ static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
                                 tcp_hdr(skb)->cwr = 1;
                                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
                         }
-                } else {
+                } else if (!tcp_ca_needs_ecn(sk)) {
                         /* ACK or retransmitted segment: clear ECT|CE */
                         INET_ECN_dontxmit(sk);
                 }
@@ -384,7 +395,7 @@ static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
         TCP_SKB_CB(skb)->tcp_flags = flags;
         TCP_SKB_CB(skb)->sacked = 0;
 
-        shinfo->gso_segs = 1;
+        tcp_skb_pcount_set(skb, 1);
         shinfo->gso_size = 0;
         shinfo->gso_type = 0;
 
@@ -550,7 +561,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
 
         if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
                 opts->options |= OPTION_TS;
-                opts->tsval = TCP_SKB_CB(skb)->when + tp->tsoffset;
+                opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset;
                 opts->tsecr = tp->rx_opt.ts_recent;
                 remaining -= TCPOLEN_TSTAMP_ALIGNED;
         }
@@ -618,7 +629,7 @@ static unsigned int tcp_synack_options(struct sock *sk,
         }
         if (likely(ireq->tstamp_ok)) {
                 opts->options |= OPTION_TS;
-                opts->tsval = TCP_SKB_CB(skb)->when;
+                opts->tsval = tcp_skb_timestamp(skb);
                 opts->tsecr = req->ts_recent;
                 remaining -= TCPOLEN_TSTAMP_ALIGNED;
         }
@@ -647,7 +658,6 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
                                         struct tcp_out_options *opts,
                                         struct tcp_md5sig_key **md5)
 {
-        struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
         struct tcp_sock *tp = tcp_sk(sk);
         unsigned int size = 0;
         unsigned int eff_sacks;
@@ -666,7 +676,7 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
 
         if (likely(tp->rx_opt.tstamp_ok)) {
                 opts->options |= OPTION_TS;
-                opts->tsval = tcb ? tcb->when + tp->tsoffset : 0;
+                opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0;
                 opts->tsecr = tp->rx_opt.ts_recent;
                 size += TCPOLEN_TSTAMP_ALIGNED;
         }
@@ -800,7 +810,7 @@ void tcp_release_cb(struct sock *sk)
                 __sock_put(sk);
         }
         if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) {
-                sk->sk_prot->mtu_reduced(sk);
+                inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
                 __sock_put(sk);
         }
 }
@@ -829,26 +839,38 @@ void tcp_wfree(struct sk_buff *skb)
 {
         struct sock *sk = skb->sk;
         struct tcp_sock *tp = tcp_sk(sk);
+        int wmem;
+
+        /* Keep one reference on sk_wmem_alloc.
+         * Will be released by sk_free() from here or tcp_tasklet_func()
+         */
+        wmem = atomic_sub_return(skb->truesize - 1, &sk->sk_wmem_alloc);
+
+        /* If this softirq is serviced by ksoftirqd, we are likely under stress.
+         * Wait until our queues (qdisc + devices) are drained.
+         * This gives :
+         * - less callbacks to tcp_write_xmit(), reducing stress (batches)
+         * - chance for incoming ACK (processed by another cpu maybe)
+         *   to migrate this flow (skb->ooo_okay will be eventually set)
+         */
+        if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
+                goto out;
 
         if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) &&
             !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) {
                 unsigned long flags;
                 struct tsq_tasklet *tsq;
 
-                /* Keep a ref on socket.
-                 * This last ref will be released in tcp_tasklet_func()
-                 */
-                atomic_sub(skb->truesize - 1, &sk->sk_wmem_alloc);
-
                 /* queue this socket to tasklet queue */
                 local_irq_save(flags);
-                tsq = &__get_cpu_var(tsq_tasklet);
+                tsq = this_cpu_ptr(&tsq_tasklet);
                 list_add(&tp->tsq_node, &tsq->head);
                 tasklet_schedule(&tsq->tasklet);
                 local_irq_restore(flags);
-        } else {
-                sock_wfree(skb);
+                return;
         }
+out:
+        sk_free(sk);
 }
 
 /* This routine actually transmits TCP packets queued in by
@@ -886,8 +908,6 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
                         skb = skb_clone(skb, gfp_mask);
                 if (unlikely(!skb))
                         return -ENOBUFS;
-                /* Our usage of tstamp should remain private */
-                skb->tstamp.tv64 = 0;
         }
 
         inet = inet_sk(sk);
@@ -906,9 +926,13 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
                 tcp_ca_event(sk, CA_EVENT_TX_START);
 
         /* if no packet is in qdisc/device queue, then allow XPS to select
-         * another queue.
+         * another queue. We can be called from tcp_tsq_handler()
+         * which holds one reference to sk_wmem_alloc.
+         *
+         * TODO: Ideally, in-flight pure ACK packets should not matter here.
+         * One way to get this would be to set skb->truesize = 2 on them.
          */
-        skb->ooo_okay = sk_wmem_alloc_get(sk) == 0;
+        skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1);
 
         skb_push(skb, tcp_header_size);
         skb_reset_transport_header(skb);
@@ -916,6 +940,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
         skb_orphan(skb);
         skb->sk = sk;
         skb->destructor = tcp_wfree;
+        skb_set_hash_from_sk(skb, sk);
         atomic_add(skb->truesize, &sk->sk_wmem_alloc);
 
         /* Build TCP header and checksum it. */
@@ -951,7 +976,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 
         tcp_options_write((__be32 *)(th + 1), tp, &opts);
         if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0))
-                TCP_ECN_send(sk, skb, tcp_header_size);
+                tcp_ecn_send(sk, skb, tcp_header_size);
 
 #ifdef CONFIG_TCP_MD5SIG
         /* Calculate the MD5 hash, as we have all we need now */
@@ -974,11 +999,22 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
                 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS,
                               tcp_skb_pcount(skb));
 
+        /* OK, its time to fill skb_shinfo(skb)->gso_segs */
+        skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb);
+
+        /* Our usage of tstamp should remain private */
+        skb->tstamp.tv64 = 0;
+
+        /* Cleanup our debris for IP stacks */
+        memset(skb->cb, 0, max(sizeof(struct inet_skb_parm),
+                               sizeof(struct inet6_skb_parm)));
+
         err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
+
         if (likely(err <= 0))
                 return err;
 
-        tcp_enter_cwr(sk, 1);
+        tcp_enter_cwr(sk);
 
         return net_xmit_eval(err);
 }
@@ -994,7 +1030,7 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
 
         /* Advance write_seq and place onto the write_queue. */
         tp->write_seq = TCP_SKB_CB(skb)->end_seq;
-        skb_header_release(skb);
+        __skb_header_release(skb);
         tcp_add_write_queue_tail(sk, skb);
         sk->sk_wmem_queued += skb->truesize;
         sk_mem_charge(sk, skb->truesize);
@@ -1013,11 +1049,11 @@ static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
                 /* Avoid the costly divide in the normal
                  * non-TSO case.
                  */
-                shinfo->gso_segs = 1;
+                tcp_skb_pcount_set(skb, 1);
                 shinfo->gso_size = 0;
                 shinfo->gso_type = 0;
         } else {
-                shinfo->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
+                tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now));
                 shinfo->gso_size = mss_now;
                 shinfo->gso_type = sk->sk_gso_type;
         }
@@ -1068,6 +1104,21 @@ static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int de
         tcp_verify_left_out(tp);
 }
 
+static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2)
+{
+        struct skb_shared_info *shinfo = skb_shinfo(skb);
+
+        if (unlikely(shinfo->tx_flags & SKBTX_ANY_TSTAMP) &&
+            !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) {
+                struct skb_shared_info *shinfo2 = skb_shinfo(skb2);
+                u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP;
+
+                shinfo->tx_flags &= ~tsflags;
+                shinfo2->tx_flags |= tsflags;
+                swap(shinfo->tskey, shinfo2->tskey);
+        }
+}
+
 /* Function to create two new TCP segments.  Shrinks the given segment
  * to the specified size and appends a new segment with the rest of the
  * packet to the list.  This won't be called frequently, I hope.
@@ -1130,11 +1181,8 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
 
         buff->ip_summed = skb->ip_summed;
 
-        /* Looks stupid, but our code really uses when of
-         * skbs, which it never sent before. --ANK
-         */
-        TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
         buff->tstamp = skb->tstamp;
+        tcp_fragment_tstamp(skb, buff);
 
         old_factor = tcp_skb_pcount(skb);
 
@@ -1154,7 +1202,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
         }
 
         /* Link BUFF into the send queue. */
-        skb_header_release(buff);
+        __skb_header_release(buff);
         tcp_insert_write_queue_after(skb, buff, sk);
 
         return 0;
@@ -1651,13 +1699,14 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
 
         buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
         skb_split(skb, buff, len);
+        tcp_fragment_tstamp(skb, buff);
 
         /* Fix up tso_factor for both original and new SKB.  */
         tcp_set_skb_tso_segs(sk, skb, mss_now);
         tcp_set_skb_tso_segs(sk, buff, mss_now);
 
         /* Link BUFF into the send queue. */
-        skb_header_release(buff);
+        __skb_header_release(buff);
         tcp_insert_write_queue_after(skb, buff, sk);
 
         return 0;
@@ -1856,8 +1905,8 @@ static int tcp_mtu_probe(struct sock *sk)
         tcp_init_tso_segs(sk, nskb, nskb->len);
 
         /* We're ready to send.  If this fails, the probe will
-         * be resegmented into mss-sized pieces by tcp_write_xmit(). */
-        TCP_SKB_CB(nskb)->when = tcp_time_stamp;
+         * be resegmented into mss-sized pieces by tcp_write_xmit().
+         */
         if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
                 /* Decrement cwnd here because we are sending
                  * effectively two packets. */
@@ -1916,8 +1965,11 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
                 tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
                 BUG_ON(!tso_segs);
 
-                if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE)
+                if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
+                        /* "skb_mstamp" is used as a start point for the retransmit timer */
+                        skb_mstamp_get(&skb->skb_mstamp);
                         goto repair; /* Skip network transmission */
+                }
 
                 cwnd_quota = tcp_cwnd_test(tp, skb);
                 if (!cwnd_quota) {
@@ -1979,8 +2031,6 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
                     unlikely(tso_fragment(sk, skb, limit, mss_now, gfp)))
                         break;
 
-                TCP_SKB_CB(skb)->when = tcp_time_stamp;
-
                 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
                         break;
 
@@ -2076,10 +2126,7 @@ bool tcp_schedule_loss_probe(struct sock *sk)
 static bool skb_still_in_host_queue(const struct sock *sk,
                                     const struct sk_buff *skb)
 {
-        const struct sk_buff *fclone = skb + 1;
-
-        if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
-                     fclone->fclone == SKB_FCLONE_CLONE)) {
+        if (unlikely(skb_fclone_busy(skb))) {
                 NET_INC_STATS_BH(sock_net(sk),
                                  LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
                 return true;
@@ -2478,7 +2525,6 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
         /* Make a copy, if the first transmission SKB clone we made
          * is still in somebody's hands, else make a clone.
          */
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
 
         /* make sure skb->data is aligned on arches that require it
          * and check if ack-trimming & collapsing extended the headroom
@@ -2523,7 +2569,7 @@ int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
 
                 /* Save stamp of the first retransmit. */
                 if (!tp->retrans_stamp)
-                        tp->retrans_stamp = TCP_SKB_CB(skb)->when;
+                        tp->retrans_stamp = tcp_skb_timestamp(skb);
 
                 /* snd_nxt is stored to detect loss of retransmitted segment,
                  * see tcp_input.c tcp_sacktag_write_queue().
@@ -2731,7 +2777,6 @@ void tcp_send_active_reset(struct sock *sk, gfp_t priority)
         tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
                              TCPHDR_ACK | TCPHDR_RST);
         /* Send it off. */
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
         if (tcp_transmit_skb(sk, skb, 0, priority))
                 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
 
@@ -2759,7 +2804,7 @@ int tcp_send_synack(struct sock *sk)
                         if (nskb == NULL)
                                 return -ENOMEM;
                         tcp_unlink_write_queue(skb, sk);
-                        skb_header_release(nskb);
+                        __skb_header_release(nskb);
                         __tcp_add_write_queue_head(sk, nskb);
                         sk_wmem_free_skb(sk, skb);
                         sk->sk_wmem_queued += nskb->truesize;
@@ -2768,9 +2813,8 @@ int tcp_send_synack(struct sock *sk)
                 }
 
                 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK;
-                TCP_ECN_send_synack(tcp_sk(sk), skb);
+                tcp_ecn_send_synack(sk, skb);
         }
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
         return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
 }
 
@@ -2814,10 +2858,10 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
         memset(&opts, 0, sizeof(opts));
 #ifdef CONFIG_SYN_COOKIES
         if (unlikely(req->cookie_ts))
-                TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
+                skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req);
         else
 #endif
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
+        skb_mstamp_get(&skb->skb_mstamp);
         tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, &md5,
                                              foc) + sizeof(*th);
 
@@ -2828,7 +2872,7 @@ struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
         memset(th, 0, sizeof(struct tcphdr));
         th->syn = 1;
         th->ack = 1;
-        TCP_ECN_make_synack(req, th);
+        tcp_ecn_make_synack(req, th, sk);
         th->source = htons(ireq->ir_num);
         th->dest = ireq->ir_rmt_port;
         /* Setting of flags are superfluous here for callers (and ECE is
@@ -2935,7 +2979,7 @@ static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb)
         struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);
 
         tcb->end_seq += skb->len;
-        skb_header_release(skb);
+        __skb_header_release(skb);
         __tcp_add_write_queue_tail(sk, skb);
         sk->sk_wmem_queued += skb->truesize;
         sk_mem_charge(sk, skb->truesize);
@@ -3065,9 +3109,9 @@ int tcp_connect(struct sock *sk)
         skb_reserve(buff, MAX_TCP_HEADER);
 
         tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
-        tp->retrans_stamp = TCP_SKB_CB(buff)->when = tcp_time_stamp;
+        tp->retrans_stamp = tcp_time_stamp;
         tcp_connect_queue_skb(sk, buff);
-        TCP_ECN_send_syn(sk, buff);
+        tcp_ecn_send_syn(sk, buff);
 
         /* Send off SYN; include data in Fast Open. */
         err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) :
@@ -3099,6 +3143,8 @@ void tcp_send_delayed_ack(struct sock *sk)
         int ato = icsk->icsk_ack.ato;
         unsigned long timeout;
 
+        tcp_ca_event(sk, CA_EVENT_DELAYED_ACK);
+
         if (ato > TCP_DELACK_MIN) {
                 const struct tcp_sock *tp = tcp_sk(sk);
                 int max_ato = HZ / 2;
@@ -3155,6 +3201,8 @@ void tcp_send_ack(struct sock *sk)
         if (sk->sk_state == TCP_CLOSE)
                 return;
 
+        tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK);
+
         /* We are not putting this on the write queue, so
          * tcp_transmit_skb() will set the ownership to this
          * sock.
@@ -3173,9 +3221,10 @@ void tcp_send_ack(struct sock *sk)
         tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
 
         /* Send it off, this clears delayed acks for us. */
-        TCP_SKB_CB(buff)->when = tcp_time_stamp;
+        skb_mstamp_get(&buff->skb_mstamp);
         tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC));
 }
+EXPORT_SYMBOL_GPL(tcp_send_ack);
 
 /* This routine sends a packet with an out of date sequence
  * number. It assumes the other end will try to ack it.
@@ -3205,7 +3254,7 @@ static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
          * send it.
          */
         tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK);
-        TCP_SKB_CB(skb)->when = tcp_time_stamp;
+        skb_mstamp_get(&skb->skb_mstamp);
         return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
 }
 
@@ -3249,7 +3298,6 @@ int tcp_write_wakeup(struct sock *sk)
                         tcp_set_skb_tso_segs(sk, skb, mss);
 
                 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH;
-                TCP_SKB_CB(skb)->when = tcp_time_stamp;
                 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
                 if (!err)
                         tcp_event_new_data_sent(sk, skb);
@@ -3268,6 +3316,7 @@ void tcp_send_probe0(struct sock *sk)
 {
         struct inet_connection_sock *icsk = inet_csk(sk);
         struct tcp_sock *tp = tcp_sk(sk);
+        unsigned long probe_max;
         int err;
 
         err = tcp_write_wakeup(sk);
@@ -3283,9 +3332,7 @@ void tcp_send_probe0(struct sock *sk)
                 if (icsk->icsk_backoff < sysctl_tcp_retries2)
                         icsk->icsk_backoff++;
                 icsk->icsk_probes_out++;
-                inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
-                                          min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
-                                          TCP_RTO_MAX);
+                probe_max = TCP_RTO_MAX;
         } else {
                 /* If packet was not sent due to local congestion,
                  * do not backoff and do not remember icsk_probes_out.
@@ -3295,9 +3342,24 @@ void tcp_send_probe0(struct sock *sk)
                  */
                 if (!icsk->icsk_probes_out)
                         icsk->icsk_probes_out = 1;
-                inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
-                                          min(icsk->icsk_rto << icsk->icsk_backoff,
-                                              TCP_RESOURCE_PROBE_INTERVAL),
-                                          TCP_RTO_MAX);
+                probe_max = TCP_RESOURCE_PROBE_INTERVAL;
+        }
+        inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
+                                  inet_csk_rto_backoff(icsk, probe_max),
+                                  TCP_RTO_MAX);
+}
+
+int tcp_rtx_synack(struct sock *sk, struct request_sock *req)
+{
+        const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific;
+        struct flowi fl;
+        int res;
+
+        res = af_ops->send_synack(sk, NULL, &fl, 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);
         }
+        return res;
 }
+EXPORT_SYMBOL(tcp_rtx_synack);