1 files changed, 113 insertions, 63 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 3b2c8e90a475..e6e65f79ade8 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -80,9 +80,7 @@ int sysctl_tcp_timestamps __read_mostly = 1;
 int sysctl_tcp_window_scaling __read_mostly = 1;
 int sysctl_tcp_sack __read_mostly = 1;
 int sysctl_tcp_fack __read_mostly = 1;
-int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
 int sysctl_tcp_max_reordering __read_mostly = 300;
-EXPORT_SYMBOL(sysctl_tcp_reordering);
 int sysctl_tcp_dsack __read_mostly = 1;
 int sysctl_tcp_app_win __read_mostly = 31;
 int sysctl_tcp_adv_win_scale __read_mostly = 1;
@@ -126,6 +124,10 @@ int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2;
 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
 
+#define REXMIT_NONE	0 /* no loss recovery to do */
+#define REXMIT_LOST	1 /* retransmit packets marked lost */
+#define REXMIT_NEW	2 /* FRTO-style transmit of unsent/new packets */
+
 /* Adapt the MSS value used to make delayed ack decision to the
  * real world.
  */
@@ -1210,6 +1212,7 @@ static u8 tcp_sacktag_one(struct sock *sk,
 		sacked |= TCPCB_SACKED_ACKED;
 		state->flag |= FLAG_DATA_SACKED;
 		tp->sacked_out += pcount;
+		tp->delivered += pcount;  /* Out-of-order packets delivered */
 
 		fack_count += pcount;
 
@@ -1821,8 +1824,12 @@ static void tcp_check_reno_reordering(struct sock *sk, const int addend)
 static void tcp_add_reno_sack(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
+	u32 prior_sacked = tp->sacked_out;
+
 	tp->sacked_out++;
 	tcp_check_reno_reordering(sk, 0);
+	if (tp->sacked_out > prior_sacked)
+		tp->delivered++; /* Some out-of-order packet is delivered */
 	tcp_verify_left_out(tp);
 }
 
@@ -1834,6 +1841,7 @@ static void tcp_remove_reno_sacks(struct sock *sk, int acked)
 
 	if (acked > 0) {
 		/* One ACK acked hole. The rest eat duplicate ACKs. */
+		tp->delivered += max_t(int, acked - tp->sacked_out, 1);
 		if (acked - 1 >= tp->sacked_out)
 			tp->sacked_out = 0;
 		else
@@ -1873,6 +1881,7 @@ void tcp_enter_loss(struct sock *sk)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
+	struct net *net = sock_net(sk);
 	struct sk_buff *skb;
 	bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery;
 	bool is_reneg;			/* is receiver reneging on SACKs? */
@@ -1923,9 +1932,9 @@ void tcp_enter_loss(struct sock *sk)
 	 * suggests that the degree of reordering is over-estimated.
 	 */
 	if (icsk->icsk_ca_state <= TCP_CA_Disorder &&
-	    tp->sacked_out >= sysctl_tcp_reordering)
+	    tp->sacked_out >= net->ipv4.sysctl_tcp_reordering)
 		tp->reordering = min_t(unsigned int, tp->reordering,
-				       sysctl_tcp_reordering);
+				       net->ipv4.sysctl_tcp_reordering);
 	tcp_set_ca_state(sk, TCP_CA_Loss);
 	tp->high_seq = tp->snd_nxt;
 	tcp_ecn_queue_cwr(tp);
@@ -2109,6 +2118,7 @@ static bool tcp_time_to_recover(struct sock *sk, int flag)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	__u32 packets_out;
+	int tcp_reordering = sock_net(sk)->ipv4.sysctl_tcp_reordering;
 
 	/* Trick#1: The loss is proven. */
 	if (tp->lost_out)
@@ -2123,7 +2133,7 @@ static bool tcp_time_to_recover(struct sock *sk, int flag)
 	 */
 	packets_out = tp->packets_out;
 	if (packets_out <= tp->reordering &&
-	    tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
+	    tp->sacked_out >= max_t(__u32, packets_out/2, tcp_reordering) &&
 	    !tcp_may_send_now(sk)) {
 		/* We have nothing to send. This connection is limited
 		 * either by receiver window or by application.
@@ -2467,14 +2477,12 @@ static void tcp_init_cwnd_reduction(struct sock *sk)
 	tcp_ecn_queue_cwr(tp);
 }
 
-static void tcp_cwnd_reduction(struct sock *sk, const int prior_unsacked,
-			       int fast_rexmit, int flag)
+static void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked,
+			       int flag)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	int sndcnt = 0;
 	int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp);
-	int newly_acked_sacked = prior_unsacked -
-				 (tp->packets_out - tp->sacked_out);
 
 	if (newly_acked_sacked <= 0 || WARN_ON_ONCE(!tp->prior_cwnd))
 		return;
@@ -2492,7 +2500,8 @@ static void tcp_cwnd_reduction(struct sock *sk, const int prior_unsacked,
 	} else {
 		sndcnt = min(delta, newly_acked_sacked);
 	}
-	sndcnt = max(sndcnt, (fast_rexmit ? 1 : 0));
+	/* Force a fast retransmit upon entering fast recovery */
+	sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1));
 	tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt;
 }
 
@@ -2537,7 +2546,7 @@ static void tcp_try_keep_open(struct sock *sk)
 	}
 }
 
-static void tcp_try_to_open(struct sock *sk, int flag, const int prior_unsacked)
+static void tcp_try_to_open(struct sock *sk, int flag)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
@@ -2551,8 +2560,6 @@ static void tcp_try_to_open(struct sock *sk, int flag, const int prior_unsacked)
 
 	if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
 		tcp_try_keep_open(sk);
-	} else {
-		tcp_cwnd_reduction(sk, prior_unsacked, 0, flag);
 	}
 }
 
@@ -2662,7 +2669,8 @@ static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
  * recovered or spurious. Otherwise retransmits more on partial ACKs.
  */
-static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
+static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack,
+			     int *rexmit)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	bool recovered = !before(tp->snd_una, tp->high_seq);
@@ -2684,10 +2692,15 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
 				tp->frto = 0; /* Step 3.a. loss was real */
 		} else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) {
 			tp->high_seq = tp->snd_nxt;
-			__tcp_push_pending_frames(sk, tcp_current_mss(sk),
-						  TCP_NAGLE_OFF);
-			if (after(tp->snd_nxt, tp->high_seq))
-				return; /* Step 2.b */
+			/* Step 2.b. Try send new data (but deferred until cwnd
+			 * is updated in tcp_ack()). Otherwise fall back to
+			 * the conventional recovery.
+			 */
+			if (tcp_send_head(sk) &&
+			    after(tcp_wnd_end(tp), tp->snd_nxt)) {
+				*rexmit = REXMIT_NEW;
+				return;
+			}
 			tp->frto = 0;
 		}
 	}
@@ -2706,12 +2719,11 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
 		else if (flag & FLAG_SND_UNA_ADVANCED)
 			tcp_reset_reno_sack(tp);
 	}
-	tcp_xmit_retransmit_queue(sk);
+	*rexmit = REXMIT_LOST;
 }
 
 /* Undo during fast recovery after partial ACK. */
-static bool tcp_try_undo_partial(struct sock *sk, const int acked,
-				 const int prior_unsacked, int flag)
+static bool tcp_try_undo_partial(struct sock *sk, const int acked)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
@@ -2726,10 +2738,8 @@ static bool tcp_try_undo_partial(struct sock *sk, const int acked,
 		 * can undo. Otherwise we clock out new packets but do not
 		 * mark more packets lost or retransmit more.
 		 */
-		if (tp->retrans_out) {
-			tcp_cwnd_reduction(sk, prior_unsacked, 0, flag);
+		if (tp->retrans_out)
 			return true;
-		}
 
 		if (!tcp_any_retrans_done(sk))
 			tp->retrans_stamp = 0;
@@ -2748,21 +2758,21 @@ static bool tcp_try_undo_partial(struct sock *sk, const int acked,
  * taking into account both packets sitting in receiver's buffer and
  * packets lost by network.
  *
- * Besides that it does CWND reduction, when packet loss is detected
- * and changes state of machine.
+ * Besides that it updates the congestion state when packet loss or ECN
+ * is detected. But it does not reduce the cwnd, it is done by the
+ * congestion control later.
  *
  * It does _not_ decide what to send, it is made in function
  * tcp_xmit_retransmit_queue().
  */
 static void tcp_fastretrans_alert(struct sock *sk, const int acked,
-				  const int prior_unsacked,
-				  bool is_dupack, int flag)
+				  bool is_dupack, int *ack_flag, int *rexmit)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
+	int fast_rexmit = 0, flag = *ack_flag;
 	bool do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
 				    (tcp_fackets_out(tp) > tp->reordering));
-	int fast_rexmit = 0;
 
 	if (WARN_ON(!tp->packets_out && tp->sacked_out))
 		tp->sacked_out = 0;
@@ -2809,8 +2819,10 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 
 	/* Use RACK to detect loss */
 	if (sysctl_tcp_recovery & TCP_RACK_LOST_RETRANS &&
-	    tcp_rack_mark_lost(sk))
+	    tcp_rack_mark_lost(sk)) {
 		flag |= FLAG_LOST_RETRANS;
+		*ack_flag |= FLAG_LOST_RETRANS;
+	}
 
 	/* E. Process state. */
 	switch (icsk->icsk_ca_state) {
@@ -2819,7 +2831,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 			if (tcp_is_reno(tp) && is_dupack)
 				tcp_add_reno_sack(sk);
 		} else {
-			if (tcp_try_undo_partial(sk, acked, prior_unsacked, flag))
+			if (tcp_try_undo_partial(sk, acked))
 				return;
 			/* Partial ACK arrived. Force fast retransmit. */
 			do_lost = tcp_is_reno(tp) ||
@@ -2831,7 +2843,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 		}
 		break;
 	case TCP_CA_Loss:
-		tcp_process_loss(sk, flag, is_dupack);
+		tcp_process_loss(sk, flag, is_dupack, rexmit);
 		if (icsk->icsk_ca_state != TCP_CA_Open &&
 		    !(flag & FLAG_LOST_RETRANS))
 			return;
@@ -2848,7 +2860,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 			tcp_try_undo_dsack(sk);
 
 		if (!tcp_time_to_recover(sk, flag)) {
-			tcp_try_to_open(sk, flag, prior_unsacked);
+			tcp_try_to_open(sk, flag);
 			return;
 		}
 
@@ -2870,8 +2882,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 
 	if (do_lost)
 		tcp_update_scoreboard(sk, fast_rexmit);
-	tcp_cwnd_reduction(sk, prior_unsacked, fast_rexmit, flag);
-	tcp_xmit_retransmit_queue(sk);
+	*rexmit = REXMIT_LOST;
 }
 
 /* Kathleen Nichols' algorithm for tracking the minimum value of
@@ -3096,7 +3107,7 @@ static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb,
  * arrived at the other end.
  */
 static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
-			       u32 prior_snd_una,
+			       u32 prior_snd_una, int *acked,
 			       struct tcp_sacktag_state *sack)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
@@ -3154,10 +3165,13 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 				flag |= FLAG_ORIG_SACK_ACKED;
 		}
 
-		if (sacked & TCPCB_SACKED_ACKED)
+		if (sacked & TCPCB_SACKED_ACKED) {
 			tp->sacked_out -= acked_pcount;
-		else if (tcp_is_sack(tp) && !tcp_skb_spurious_retrans(tp, skb))
-			tcp_rack_advance(tp, &skb->skb_mstamp, sacked);
+		} else if (tcp_is_sack(tp)) {
+			tp->delivered += acked_pcount;
+			if (!tcp_skb_spurious_retrans(tp, skb))
+				tcp_rack_advance(tp, &skb->skb_mstamp, sacked);
+		}
 		if (sacked & TCPCB_LOST)
 			tp->lost_out -= acked_pcount;
 
@@ -3266,6 +3280,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 		}
 	}
 #endif
+	*acked = pkts_acked;
 	return flag;
 }
 
@@ -3299,21 +3314,36 @@ static inline bool tcp_ack_is_dubious(const struct sock *sk, const int flag)
 /* Decide wheather to run the increase function of congestion control. */
 static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
 {
-	if (tcp_in_cwnd_reduction(sk))
-		return false;
-
 	/* If reordering is high then always grow cwnd whenever data is
 	 * delivered regardless of its ordering. Otherwise stay conservative
 	 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
 	 * new SACK or ECE mark may first advance cwnd here and later reduce
 	 * cwnd in tcp_fastretrans_alert() based on more states.
 	 */
-	if (tcp_sk(sk)->reordering > sysctl_tcp_reordering)
+	if (tcp_sk(sk)->reordering > sock_net(sk)->ipv4.sysctl_tcp_reordering)
 		return flag & FLAG_FORWARD_PROGRESS;
 
 	return flag & FLAG_DATA_ACKED;
 }
 
+/* The "ultimate" congestion control function that aims to replace the rigid
+ * cwnd increase and decrease control (tcp_cong_avoid,tcp_*cwnd_reduction).
+ * It's called toward the end of processing an ACK with precise rate
+ * information. All transmission or retransmission are delayed afterwards.
+ */
+static void tcp_cong_control(struct sock *sk, u32 ack, u32 acked_sacked,
+			     int flag)
+{
+	if (tcp_in_cwnd_reduction(sk)) {
+		/* Reduce cwnd if state mandates */
+		tcp_cwnd_reduction(sk, acked_sacked, flag);
+	} else if (tcp_may_raise_cwnd(sk, flag)) {
+		/* Advance cwnd if state allows */
+		tcp_cong_avoid(sk, ack, acked_sacked);
+	}
+	tcp_update_pacing_rate(sk);
+}
+
 /* Check that window update is acceptable.
  * The function assumes that snd_una<=ack<=snd_next.
  */
@@ -3509,6 +3539,27 @@ static inline void tcp_in_ack_event(struct sock *sk, u32 flags)
 		icsk->icsk_ca_ops->in_ack_event(sk, flags);
 }
 
+/* Congestion control has updated the cwnd already. So if we're in
+ * loss recovery then now we do any new sends (for FRTO) or
+ * retransmits (for CA_Loss or CA_recovery) that make sense.
+ */
+static void tcp_xmit_recovery(struct sock *sk, int rexmit)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	if (rexmit == REXMIT_NONE)
+		return;
+
+	if (unlikely(rexmit == 2)) {
+		__tcp_push_pending_frames(sk, tcp_current_mss(sk),
+					  TCP_NAGLE_OFF);
+		if (after(tp->snd_nxt, tp->high_seq))
+			return;
+		tp->frto = 0;
+	}
+	tcp_xmit_retransmit_queue(sk);
+}
+
 /* This routine deals with incoming acks, but not outgoing ones. */
 static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 {
@@ -3521,8 +3572,9 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	bool is_dupack = false;
 	u32 prior_fackets;
 	int prior_packets = tp->packets_out;
-	const int prior_unsacked = tp->packets_out - tp->sacked_out;
+	u32 prior_delivered = tp->delivered;
 	int acked = 0; /* Number of packets newly acked */
+	int rexmit = REXMIT_NONE; /* Flag to (re)transmit to recover losses */
 
 	sack_state.first_sackt.v64 = 0;
 
@@ -3611,23 +3663,16 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 		goto no_queue;
 
 	/* See if we can take anything off of the retransmit queue. */
-	acked = tp->packets_out;
-	flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una,
+	flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una, &acked,
 				    &sack_state);
-	acked -= tp->packets_out;
 
 	if (tcp_ack_is_dubious(sk, flag)) {
 		is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
-		tcp_fastretrans_alert(sk, acked, prior_unsacked,
-				      is_dupack, flag);
+		tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit);
 	}
 	if (tp->tlp_high_seq)
 		tcp_process_tlp_ack(sk, ack, flag);
 
-	/* Advance cwnd if state allows */
-	if (tcp_may_raise_cwnd(sk, flag))
-		tcp_cong_avoid(sk, ack, acked);
-
 	if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) {
 		struct dst_entry *dst = __sk_dst_get(sk);
 		if (dst)
@@ -3636,14 +3681,14 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 
 	if (icsk->icsk_pending == ICSK_TIME_RETRANS)
 		tcp_schedule_loss_probe(sk);
-	tcp_update_pacing_rate(sk);
+	tcp_cong_control(sk, ack, tp->delivered - prior_delivered, flag);
+	tcp_xmit_recovery(sk, rexmit);
 	return 1;
 
 no_queue:
 	/* If data was DSACKed, see if we can undo a cwnd reduction. */
 	if (flag & FLAG_DSACKING_ACK)
-		tcp_fastretrans_alert(sk, acked, prior_unsacked,
-				      is_dupack, flag);
+		tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit);
 	/* If this ack opens up a zero window, clear backoff.  It was
 	 * being used to time the probes, and is probably far higher than
 	 * it needs to be for normal retransmission.
@@ -3666,8 +3711,8 @@ old_ack:
 	if (TCP_SKB_CB(skb)->sacked) {
 		flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
 						&sack_state);
-		tcp_fastretrans_alert(sk, acked, prior_unsacked,
-				      is_dupack, flag);
+		tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit);
+		tcp_xmit_recovery(sk, rexmit);
 	}
 
 	SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
@@ -3998,7 +4043,7 @@ void tcp_reset(struct sock *sk)
  *
  *	If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
  */
-static void tcp_fin(struct sock *sk)
+void tcp_fin(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
@@ -5512,6 +5557,9 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack,
 	tp->syn_data_acked = tp->syn_data;
 	if (tp->syn_data_acked)
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE);
+
+	tcp_fastopen_add_skb(sk, synack);
+
 	return false;
 }
 
@@ -6118,9 +6166,10 @@ static bool tcp_syn_flood_action(const struct sock *sk,
 	struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 	const char *msg = "Dropping request";
 	bool want_cookie = false;
+	struct net *net = sock_net(sk);
 
 #ifdef CONFIG_SYN_COOKIES
-	if (sysctl_tcp_syncookies) {
+	if (net->ipv4.sysctl_tcp_syncookies) {
 		msg = "Sending cookies";
 		want_cookie = true;
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPREQQFULLDOCOOKIES);
@@ -6129,7 +6178,7 @@ static bool tcp_syn_flood_action(const struct sock *sk,
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPREQQFULLDROP);
 
 	if (!queue->synflood_warned &&
-	    sysctl_tcp_syncookies != 2 &&
+	    net->ipv4.sysctl_tcp_syncookies != 2 &&
 	    xchg(&queue->synflood_warned, 1) == 0)
 		pr_info("%s: Possible SYN flooding on port %d. %s.  Check SNMP counters.\n",
 			proto, ntohs(tcp_hdr(skb)->dest), msg);
@@ -6162,6 +6211,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 	__u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn;
 	struct tcp_options_received tmp_opt;
 	struct tcp_sock *tp = tcp_sk(sk);
+	struct net *net = sock_net(sk);
 	struct sock *fastopen_sk = NULL;
 	struct dst_entry *dst = NULL;
 	struct request_sock *req;
@@ -6172,7 +6222,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 	 * limitations, they conserve resources and peer is
 	 * evidently real one.
 	 */
-	if ((sysctl_tcp_syncookies == 2 ||
+	if ((net->ipv4.sysctl_tcp_syncookies == 2 ||
 	     inet_csk_reqsk_queue_is_full(sk)) && !isn) {
 		want_cookie = tcp_syn_flood_action(sk, skb, rsk_ops->slab_name);
 		if (!want_cookie)
@@ -6238,7 +6288,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 			}
 		}
 		/* Kill the following clause, if you dislike this way. */
-		else if (!sysctl_tcp_syncookies &&
+		else if (!net->ipv4.sysctl_tcp_syncookies &&
 			 (sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
 			  (sysctl_max_syn_backlog >> 2)) &&
 			 !tcp_peer_is_proven(req, dst, false,