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-rw-r--r--net/ipv4/inet_diag.c4
-rw-r--r--net/ipv4/proc.c1
-rw-r--r--net/ipv4/sysctl_net_ipv4.c4
-rw-r--r--net/ipv4/tcp_input.c24
-rw-r--r--net/ipv4/tcp_ipv4.c4
-rw-r--r--net/ipv4/tcp_output.c128
-rw-r--r--net/ipv4/tcp_timer.c13
7 files changed, 156 insertions, 22 deletions
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 7afa2c3c788f..8620408af574 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -158,7 +158,9 @@ int inet_sk_diag_fill(struct sock *sk, struct inet_connection_sock *icsk,
#define EXPIRES_IN_MS(tmo) DIV_ROUND_UP((tmo - jiffies) * 1000, HZ)
- if (icsk->icsk_pending == ICSK_TIME_RETRANS) {
+ if (icsk->icsk_pending == ICSK_TIME_RETRANS ||
+ icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
+ icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
r->idiag_timer = 1;
r->idiag_retrans = icsk->icsk_retransmits;
r->idiag_expires = EXPIRES_IN_MS(icsk->icsk_timeout);
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 32030a24e776..4c35911d935f 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -224,6 +224,7 @@ static const struct snmp_mib snmp4_net_list[] = {
SNMP_MIB_ITEM("TCPForwardRetrans", LINUX_MIB_TCPFORWARDRETRANS),
SNMP_MIB_ITEM("TCPSlowStartRetrans", LINUX_MIB_TCPSLOWSTARTRETRANS),
SNMP_MIB_ITEM("TCPTimeouts", LINUX_MIB_TCPTIMEOUTS),
+ SNMP_MIB_ITEM("TCPLossProbes", LINUX_MIB_TCPLOSSPROBES),
SNMP_MIB_ITEM("TCPRenoRecoveryFail", LINUX_MIB_TCPRENORECOVERYFAIL),
SNMP_MIB_ITEM("TCPSackRecoveryFail", LINUX_MIB_TCPSACKRECOVERYFAIL),
SNMP_MIB_ITEM("TCPSchedulerFailed", LINUX_MIB_TCPSCHEDULERFAILED),
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 960fd29d9b8e..cca4550f4082 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -28,7 +28,7 @@
static int zero;
static int one = 1;
-static int two = 2;
+static int four = 4;
static int tcp_retr1_max = 255;
static int ip_local_port_range_min[] = { 1, 1 };
static int ip_local_port_range_max[] = { 65535, 65535 };
@@ -760,7 +760,7 @@ static struct ctl_table ipv4_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &zero,
- .extra2 = &two,
+ .extra2 = &four,
},
{
.procname = "udp_mem",
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0d9bdacce99f..b794f89ac1f2 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -98,7 +98,7 @@ int sysctl_tcp_frto_response __read_mostly;
int sysctl_tcp_thin_dupack __read_mostly;
int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
-int sysctl_tcp_early_retrans __read_mostly = 2;
+int sysctl_tcp_early_retrans __read_mostly = 3;
#define FLAG_DATA 0x01 /* Incoming frame contained data. */
#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
@@ -2150,15 +2150,16 @@ static bool tcp_pause_early_retransmit(struct sock *sk, int flag)
* max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
* available, or RTO is scheduled to fire first.
*/
- if (sysctl_tcp_early_retrans < 2 || (flag & FLAG_ECE) || !tp->srtt)
+ if (sysctl_tcp_early_retrans < 2 || sysctl_tcp_early_retrans > 3 ||
+ (flag & FLAG_ECE) || !tp->srtt)
return false;
delay = max_t(unsigned long, (tp->srtt >> 5), msecs_to_jiffies(2));
if (!time_after(inet_csk(sk)->icsk_timeout, (jiffies + delay)))
return false;
- inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, delay, TCP_RTO_MAX);
- tp->early_retrans_delayed = 1;
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_EARLY_RETRANS, delay,
+ TCP_RTO_MAX);
return true;
}
@@ -2321,7 +2322,7 @@ static bool tcp_time_to_recover(struct sock *sk, int flag)
* interval if appropriate.
*/
if (tp->do_early_retrans && !tp->retrans_out && tp->sacked_out &&
- (tp->packets_out == (tp->sacked_out + 1) && tp->packets_out < 4) &&
+ (tp->packets_out >= (tp->sacked_out + 1) && tp->packets_out < 4) &&
!tcp_may_send_now(sk))
return !tcp_pause_early_retransmit(sk, flag);
@@ -3081,6 +3082,7 @@ static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
*/
void tcp_rearm_rto(struct sock *sk)
{
+ const struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
/* If the retrans timer is currently being used by Fast Open
@@ -3094,12 +3096,13 @@ void tcp_rearm_rto(struct sock *sk)
} else {
u32 rto = inet_csk(sk)->icsk_rto;
/* Offset the time elapsed after installing regular RTO */
- if (tp->early_retrans_delayed) {
+ if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
+ icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
struct sk_buff *skb = tcp_write_queue_head(sk);
const u32 rto_time_stamp = TCP_SKB_CB(skb)->when + rto;
s32 delta = (s32)(rto_time_stamp - tcp_time_stamp);
/* delta may not be positive if the socket is locked
- * when the delayed ER timer fires and is rescheduled.
+ * when the retrans timer fires and is rescheduled.
*/
if (delta > 0)
rto = delta;
@@ -3107,7 +3110,6 @@ void tcp_rearm_rto(struct sock *sk)
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto,
TCP_RTO_MAX);
}
- tp->early_retrans_delayed = 0;
}
/* This function is called when the delayed ER timer fires. TCP enters
@@ -3601,7 +3603,8 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
if (after(ack, tp->snd_nxt))
goto invalid_ack;
- if (tp->early_retrans_delayed)
+ if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
+ icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
tcp_rearm_rto(sk);
if (after(ack, prior_snd_una))
@@ -3678,6 +3681,9 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
if (dst)
dst_confirm(dst);
}
+
+ if (icsk->icsk_pending == ICSK_TIME_RETRANS)
+ tcp_schedule_loss_probe(sk);
return 1;
no_queue:
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 8cdee120a50c..b7ab868c8284 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2703,7 +2703,9 @@ static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i, int *len)
__u16 srcp = ntohs(inet->inet_sport);
int rx_queue;
- if (icsk->icsk_pending == ICSK_TIME_RETRANS) {
+ if (icsk->icsk_pending == ICSK_TIME_RETRANS ||
+ icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
+ icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
timer_active = 1;
timer_expires = icsk->icsk_timeout;
} else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e2b4461074da..beb63dbc85f5 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -74,6 +74,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
/* Account for new data that has been sent to the network. */
static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
{
+ struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
unsigned int prior_packets = tp->packets_out;
@@ -85,7 +86,8 @@ static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
tp->frto_counter = 3;
tp->packets_out += tcp_skb_pcount(skb);
- if (!prior_packets || tp->early_retrans_delayed)
+ if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
+ icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
tcp_rearm_rto(sk);
}
@@ -1959,6 +1961,9 @@ static int tcp_mtu_probe(struct sock *sk)
* snd_up-64k-mss .. snd_up cannot be large. However, taking into
* account rare use of URG, this is not a big flaw.
*
+ * Send at most one packet when push_one > 0. Temporarily ignore
+ * cwnd limit to force at most one packet out when push_one == 2.
+
* Returns true, if no segments are in flight and we have queued segments,
* but cannot send anything now because of SWS or another problem.
*/
@@ -1994,8 +1999,13 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
goto repair; /* Skip network transmission */
cwnd_quota = tcp_cwnd_test(tp, skb);
- if (!cwnd_quota)
- break;
+ if (!cwnd_quota) {
+ if (push_one == 2)
+ /* Force out a loss probe pkt. */
+ cwnd_quota = 1;
+ else
+ break;
+ }
if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
break;
@@ -2049,10 +2059,120 @@ repair:
if (likely(sent_pkts)) {
if (tcp_in_cwnd_reduction(sk))
tp->prr_out += sent_pkts;
+
+ /* Send one loss probe per tail loss episode. */
+ if (push_one != 2)
+ tcp_schedule_loss_probe(sk);
tcp_cwnd_validate(sk);
return false;
}
- return !tp->packets_out && tcp_send_head(sk);
+ return (push_one == 2) || (!tp->packets_out && tcp_send_head(sk));
+}
+
+bool tcp_schedule_loss_probe(struct sock *sk)
+{
+ struct inet_connection_sock *icsk = inet_csk(sk);
+ struct tcp_sock *tp = tcp_sk(sk);
+ u32 timeout, tlp_time_stamp, rto_time_stamp;
+ u32 rtt = tp->srtt >> 3;
+
+ if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS))
+ return false;
+ /* No consecutive loss probes. */
+ if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) {
+ tcp_rearm_rto(sk);
+ return false;
+ }
+ /* Don't do any loss probe on a Fast Open connection before 3WHS
+ * finishes.
+ */
+ if (sk->sk_state == TCP_SYN_RECV)
+ return false;
+
+ /* TLP is only scheduled when next timer event is RTO. */
+ if (icsk->icsk_pending != ICSK_TIME_RETRANS)
+ return false;
+
+ /* Schedule a loss probe in 2*RTT for SACK capable connections
+ * in Open state, that are either limited by cwnd or application.
+ */
+ if (sysctl_tcp_early_retrans < 3 || !rtt || !tp->packets_out ||
+ !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open)
+ return false;
+
+ if ((tp->snd_cwnd > tcp_packets_in_flight(tp)) &&
+ tcp_send_head(sk))
+ return false;
+
+ /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
+ * for delayed ack when there's one outstanding packet.
+ */
+ timeout = rtt << 1;
+ if (tp->packets_out == 1)
+ timeout = max_t(u32, timeout,
+ (rtt + (rtt >> 1) + TCP_DELACK_MAX));
+ timeout = max_t(u32, timeout, msecs_to_jiffies(10));
+
+ /* If RTO is shorter, just schedule TLP in its place. */
+ tlp_time_stamp = tcp_time_stamp + timeout;
+ rto_time_stamp = (u32)inet_csk(sk)->icsk_timeout;
+ if ((s32)(tlp_time_stamp - rto_time_stamp) > 0) {
+ s32 delta = rto_time_stamp - tcp_time_stamp;
+ if (delta > 0)
+ timeout = delta;
+ }
+
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout,
+ TCP_RTO_MAX);
+ return true;
+}
+
+/* When probe timeout (PTO) fires, send a new segment if one exists, else
+ * retransmit the last segment.
+ */
+void tcp_send_loss_probe(struct sock *sk)
+{
+ struct sk_buff *skb;
+ int pcount;
+ int mss = tcp_current_mss(sk);
+ int err = -1;
+
+ if (tcp_send_head(sk) != NULL) {
+ err = tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC);
+ goto rearm_timer;
+ }
+
+ /* Retransmit last segment. */
+ skb = tcp_write_queue_tail(sk);
+ if (WARN_ON(!skb))
+ goto rearm_timer;
+
+ pcount = tcp_skb_pcount(skb);
+ if (WARN_ON(!pcount))
+ goto rearm_timer;
+
+ if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) {
+ if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss)))
+ goto rearm_timer;
+ skb = tcp_write_queue_tail(sk);
+ }
+
+ if (WARN_ON(!skb || !tcp_skb_pcount(skb)))
+ goto rearm_timer;
+
+ /* Probe with zero data doesn't trigger fast recovery. */
+ if (skb->len > 0)
+ err = __tcp_retransmit_skb(sk, skb);
+
+rearm_timer:
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+ inet_csk(sk)->icsk_rto,
+ TCP_RTO_MAX);
+
+ if (likely(!err))
+ NET_INC_STATS_BH(sock_net(sk),
+ LINUX_MIB_TCPLOSSPROBES);
+ return;
}
/* Push out any pending frames which were held back due to
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index b78aac30c498..ecd61d54147f 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -342,10 +342,6 @@ void tcp_retransmit_timer(struct sock *sk)
struct tcp_sock *tp = tcp_sk(sk);
struct inet_connection_sock *icsk = inet_csk(sk);
- if (tp->early_retrans_delayed) {
- tcp_resume_early_retransmit(sk);
- return;
- }
if (tp->fastopen_rsk) {
WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
sk->sk_state != TCP_FIN_WAIT1);
@@ -495,13 +491,20 @@ void tcp_write_timer_handler(struct sock *sk)
}
event = icsk->icsk_pending;
- icsk->icsk_pending = 0;
switch (event) {
+ case ICSK_TIME_EARLY_RETRANS:
+ tcp_resume_early_retransmit(sk);
+ break;
+ case ICSK_TIME_LOSS_PROBE:
+ tcp_send_loss_probe(sk);
+ break;
case ICSK_TIME_RETRANS:
+ icsk->icsk_pending = 0;
tcp_retransmit_timer(sk);
break;
case ICSK_TIME_PROBE0:
+ icsk->icsk_pending = 0;
tcp_probe_timer(sk);
break;
}
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.