1 files changed, 77 insertions, 17 deletions

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 896e9df..c7adcb5 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -640,7 +640,7 @@ static unsigned int tcp_synack_options(struct request_sock *req,
 	}
 	if (likely(ireq->tstamp_ok)) {
 		opts->options |= OPTION_TS;
-		opts->tsval = tcp_skb_timestamp(skb);
+		opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off;
 		opts->tsecr = req->ts_recent;
 		remaining -= TCPOLEN_TSTAMP_ALIGNED;
 	}
@@ -1514,6 +1514,18 @@ static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
 		if (sysctl_tcp_slow_start_after_idle &&
 		    (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
 			tcp_cwnd_application_limited(sk);
+
+		/* The following conditions together indicate the starvation
+		 * is caused by insufficient sender buffer:
+		 * 1) just sent some data (see tcp_write_xmit)
+		 * 2) not cwnd limited (this else condition)
+		 * 3) no more data to send (null tcp_send_head )
+		 * 4) application is hitting buffer limit (SOCK_NOSPACE)
+		 */
+		if (!tcp_send_head(sk) && sk->sk_socket &&
+		    test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) &&
+		    (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT))
+			tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED);
 	}
 }
 
@@ -2081,6 +2093,47 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb,
 	return false;
 }
 
+static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new)
+{
+	const u32 now = tcp_time_stamp;
+
+	if (tp->chrono_type > TCP_CHRONO_UNSPEC)
+		tp->chrono_stat[tp->chrono_type - 1] += now - tp->chrono_start;
+	tp->chrono_start = now;
+	tp->chrono_type = new;
+}
+
+void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	/* If there are multiple conditions worthy of tracking in a
+	 * chronograph then the highest priority enum takes precedence
+	 * over the other conditions. So that if something "more interesting"
+	 * starts happening, stop the previous chrono and start a new one.
+	 */
+	if (type > tp->chrono_type)
+		tcp_chrono_set(tp, type);
+}
+
+void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+
+	/* There are multiple conditions worthy of tracking in a
+	 * chronograph, so that the highest priority enum takes
+	 * precedence over the other conditions (see tcp_chrono_start).
+	 * If a condition stops, we only stop chrono tracking if
+	 * it's the "most interesting" or current chrono we are
+	 * tracking and starts busy chrono if we have pending data.
+	 */
+	if (tcp_write_queue_empty(sk))
+		tcp_chrono_set(tp, TCP_CHRONO_UNSPEC);
+	else if (type == tp->chrono_type)
+		tcp_chrono_set(tp, TCP_CHRONO_BUSY);
+}
+
 /* This routine writes packets to the network.  It advances the
  * send_head.  This happens as incoming acks open up the remote
  * window for us.
@@ -2103,7 +2156,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 	unsigned int tso_segs, sent_pkts;
 	int cwnd_quota;
 	int result;
-	bool is_cwnd_limited = false;
+	bool is_cwnd_limited = false, is_rwnd_limited = false;
 	u32 max_segs;
 
 	sent_pkts = 0;
@@ -2140,8 +2193,10 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
 				break;
 		}
 
-		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
+		if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) {
+			is_rwnd_limited = true;
 			break;
+		}
 
 		if (tso_segs == 1) {
 			if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
@@ -2186,6 +2241,11 @@ repair:
 			break;
 	}
 
+	if (is_rwnd_limited)
+		tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED);
+	else
+		tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED);
+
 	if (likely(sent_pkts)) {
 		if (tcp_in_cwnd_reduction(sk))
 			tp->prr_out += sent_pkts;
@@ -2514,7 +2574,7 @@ void tcp_skb_collapse_tstamp(struct sk_buff *skb,
 }
 
 /* Collapses two adjacent SKB's during retransmission. */
-static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
+static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
@@ -2525,13 +2585,17 @@ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 
 	BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
 
+	if (next_skb_size) {
+		if (next_skb_size <= skb_availroom(skb))
+			skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
+				      next_skb_size);
+		else if (!skb_shift(skb, next_skb, next_skb_size))
+			return false;
+	}
 	tcp_highest_sack_combine(sk, next_skb, skb);
 
 	tcp_unlink_write_queue(next_skb, sk);
 
-	skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
-				  next_skb_size);
-
 	if (next_skb->ip_summed == CHECKSUM_PARTIAL)
 		skb->ip_summed = CHECKSUM_PARTIAL;
 
@@ -2560,6 +2624,7 @@ static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 	tcp_skb_collapse_tstamp(skb, next_skb);
 
 	sk_wmem_free_skb(sk, next_skb);
+	return true;
 }
 
 /* Check if coalescing SKBs is legal. */
@@ -2567,14 +2632,11 @@ static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb)
 {
 	if (tcp_skb_pcount(skb) > 1)
 		return false;
-	/* TODO: SACK collapsing could be used to remove this condition */
-	if (skb_shinfo(skb)->nr_frags != 0)
-		return false;
 	if (skb_cloned(skb))
 		return false;
 	if (skb == tcp_send_head(sk))
 		return false;
-	/* Some heurestics for collapsing over SACK'd could be invented */
+	/* Some heuristics for collapsing over SACK'd could be invented */
 	if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
 		return false;
 
@@ -2612,16 +2674,12 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
 
 		if (space < 0)
 			break;
-		/* Punt if not enough space exists in the first SKB for
-		 * the data in the second
-		 */
-		if (skb->len > skb_availroom(to))
-			break;
 
 		if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
 			break;
 
-		tcp_collapse_retrans(sk, to);
+		if (!tcp_collapse_retrans(sk, to))
+			break;
 	}
 }
 
@@ -3300,6 +3358,8 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
 	fo->copied = space;
 
 	tcp_connect_queue_skb(sk, syn_data);
+	if (syn_data->len)
+		tcp_chrono_start(sk, TCP_CHRONO_BUSY);
 
 	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);