---

yaml
---
r: 255459
b: refs/heads/master
c: 9ad7c04
h: refs/heads/master
i:
  255457: 91c9979
  255455: be6182b
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: aee80b54b235d34d87b25dfbe32f0f0ffee1b544
+refs/heads/master: 9ad7c049f0f79c418e293b1b68cf10d68f54fcdb

trunk/include/linux/tcp.h

@@ -282,6 +282,7 @@ struct tcp_request_sock {
 #endif
 	u32				rcv_isn;
 	u32				snt_isn;
+	u32				snt_synack; /* synack sent time */
 };
 
 static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)

trunk/include/net/tcp.h

@@ -122,7 +122,13 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
 #endif
 #define TCP_RTO_MAX	((unsigned)(120*HZ))
 #define TCP_RTO_MIN	((unsigned)(HZ/5))
-#define TCP_TIMEOUT_INIT ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value	*/
+#define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))	/* RFC2988bis initial RTO value	*/
+#define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value, now
+						 * used as a fallback RTO for the
+						 * initial data transmission if no
+						 * valid RTT sample has been acquired,
+						 * most likely due to retrans in 3WHS.
+						 */
 
 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
 					                 * for local resources.
@@ -295,7 +301,7 @@ static inline void tcp_synq_overflow(struct sock *sk)
 static inline int tcp_synq_no_recent_overflow(const struct sock *sk)
 {
 	unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
-	return time_after(jiffies, last_overflow + TCP_TIMEOUT_INIT);
+	return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
 }
 
 extern struct proto tcp_prot;
@@ -508,6 +514,7 @@ extern void tcp_initialize_rcv_mss(struct sock *sk);
 extern int tcp_mtu_to_mss(struct sock *sk, int pmtu);
 extern int tcp_mss_to_mtu(struct sock *sk, int mss);
 extern void tcp_mtup_init(struct sock *sk);
+extern void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt);
 
 static inline void tcp_bound_rto(const struct sock *sk)
 {

trunk/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)

trunk/net/ipv4/tcp_input.c

@@ -880,17 +880,19 @@ 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)) {
 		tcp_disable_fack(tp);
 		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;
 

trunk/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.

trunk/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

trunk/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;
 

trunk/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;