6 files changed, 45 insertions, 25 deletions

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 26461492a847..92bb9434b338 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -316,6 +316,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
         ireq->wscale_ok         = tcp_opt.wscale_ok;
         ireq->tstamp_ok         = tcp_opt.saw_tstamp;
         req->ts_recent          = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
+        treq->snt_synack        = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsecr : 0;
 
         /* We throwed the options of the initial SYN away, so we hope
          * the ACK carries the same options again (see RFC1122 4.2.3.8)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bef9f04c22ba..ea0d2183df4b 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -880,6 +880,11 @@ static void tcp_init_metrics(struct sock *sk)
                 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)) {
@@ -887,10 +892,7 @@ static void tcp_init_metrics(struct sock *sk)
                 tp->reordering = dst_metric(dst, RTAX_REORDERING);
         }
 
-        if (dst_metric(dst, RTAX_RTT) == 0)
-                goto reset;
-
-        if (!tp->srtt && dst_metric_rtt(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
+        if (dst_metric(dst, RTAX_RTT) == 0 || tp->srtt == 0)
                 goto reset;
 
         /* Initial rtt is determined from SYN,SYN-ACK.
@@ -916,19 +918,26 @@ static void tcp_init_metrics(struct sock *sk)
                 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
         }
         tcp_set_rto(sk);
-        if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) {
 reset:
-                /* Play conservative. If timestamps are not
-                 * supported, TCP will fail to recalculate correct
-                 * rtt, if initial rto is too small. FORGET ALL AND RESET!
+        if (tp->srtt == 0) {
+                /* RFC2988bis: 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.
                  */
-                if (!tp->rx_opt.saw_tstamp && tp->srtt) {
-                        tp->srtt = 0;
-                        tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
-                        inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
-                }
+                tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_FALLBACK;
+                inet_csk(sk)->icsk_rto = TCP_TIMEOUT_FALLBACK;
         }
-        tp->snd_cwnd = tcp_init_cwnd(tp, dst);
+        /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
+         * retransmitted. In light of RFC2988bis' 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;
 }
 
@@ -3112,12 +3121,13 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
         tcp_xmit_retransmit_queue(sk);
 }
 
-static void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt)
+void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt)
 {
         tcp_rtt_estimator(sk, seq_rtt);
         tcp_set_rto(sk);
         inet_csk(sk)->icsk_backoff = 0;
 }
+EXPORT_SYMBOL(tcp_valid_rtt_meas);
 
 /* Read draft-ietf-tcplw-high-performance before mucking
  * with this code. (Supersedes RFC1323)
@@ -5806,12 +5816,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                                               tp->rx_opt.snd_wscale;
                                 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
 
-                                /* tcp_ack considers this ACK as duplicate
-                                 * and does not calculate rtt.
-                                 * Force it here.
-                                 */
-                                tcp_ack_update_rtt(sk, 0, 0);
-
                                 if (tp->rx_opt.tstamp_ok)
                                         tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
 
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index a7d6671e33b8..617dee3ccfb1 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -429,8 +429,8 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
                         break;
 
                 icsk->icsk_backoff--;
-                inet_csk(sk)->icsk_rto = __tcp_set_rto(tp) <<
-                                         icsk->icsk_backoff;
+                inet_csk(sk)->icsk_rto = (tp->srtt ? __tcp_set_rto(tp) :
+                        TCP_TIMEOUT_INIT) << icsk->icsk_backoff;
                 tcp_bound_rto(sk);
 
                 skb = tcp_write_queue_head(sk);
@@ -1384,6 +1384,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
                 isn = tcp_v4_init_sequence(skb);
         }
         tcp_rsk(req)->snt_isn = isn;
+        tcp_rsk(req)->snt_synack = tcp_time_stamp;
 
         if (tcp_v4_send_synack(sk, dst, req,
                                (struct request_values *)&tmp_ext) ||
@@ -1458,6 +1459,10 @@ struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
                 newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
 
         tcp_initialize_rcv_mss(newsk);
+        if (tcp_rsk(req)->snt_synack)
+                tcp_valid_rtt_meas(newsk,
+                    tcp_time_stamp - tcp_rsk(req)->snt_synack);
+        newtp->total_retrans = req->retrans;
 
 #ifdef CONFIG_TCP_MD5SIG
         /* Copy over the MD5 key from the original socket */
@@ -1854,7 +1859,7 @@ static int tcp_v4_init_sock(struct sock *sk)
          * algorithms that we must have the following bandaid to talk
          * efficiently to them.  -DaveM
          */
-        tp->snd_cwnd = 2;
+        tp->snd_cwnd = TCP_INIT_CWND;
 
         /* See draft-stevens-tcpca-spec-01 for discussion of the
          * initialization of these values.
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 80b1f80759ab..d2fe4e06b472 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -486,7 +486,7 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
                  * algorithms that we must have the following bandaid to talk
                  * efficiently to them.  -DaveM
                  */
-                newtp->snd_cwnd = 2;
+                newtp->snd_cwnd = TCP_INIT_CWND;
                 newtp->snd_cwnd_cnt = 0;
                 newtp->bytes_acked = 0;
 
@@ -720,6 +720,10 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDEFERACCEPTDROP);
                 return NULL;
         }
+        if (tmp_opt.saw_tstamp && tmp_opt.rcv_tsecr)
+                tcp_rsk(req)->snt_synack = tmp_opt.rcv_tsecr;
+        else if (req->retrans) /* don't take RTT sample if retrans && ~TS */
+                tcp_rsk(req)->snt_synack = 0;
 
         /* OK, ACK is valid, create big socket and
          * feed this segment to it. It will repeat all
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 8b9644a8b697..89d5bf806222 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -223,6 +223,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
         ireq->wscale_ok         = tcp_opt.wscale_ok;
         ireq->tstamp_ok         = tcp_opt.saw_tstamp;
         req->ts_recent          = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
+        treq->snt_synack        = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsecr : 0;
         treq->rcv_isn = ntohl(th->seq) - 1;
         treq->snt_isn = cookie;
 
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d1fd28711ba5..a1ef61a889c3 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1341,6 +1341,7 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
         }
 have_isn:
         tcp_rsk(req)->snt_isn = isn;
+        tcp_rsk(req)->snt_synack = tcp_time_stamp;
 
         security_inet_conn_request(sk, skb, req);
 
@@ -1509,6 +1510,10 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
         tcp_sync_mss(newsk, dst_mtu(dst));
         newtp->advmss = dst_metric_advmss(dst);
         tcp_initialize_rcv_mss(newsk);
+        if (tcp_rsk(req)->snt_synack)
+                tcp_valid_rtt_meas(newsk,
+                    tcp_time_stamp - tcp_rsk(req)->snt_synack);
+        newtp->total_retrans = req->retrans;
 
         newinet->inet_daddr = newinet->inet_saddr = LOOPBACK4_IPV6;
         newinet->inet_rcv_saddr = LOOPBACK4_IPV6;