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Message-Id: <200708292052.NAA21975@tardy.cup.hp.com>
Date: Wed, 29 Aug 2007 13:52:16 -0700 (PDT)
From: Rick Jones <rick.jones2@...com>
To: netdev@...r.kernel.org
Subject: [PATCH] make _minimum_ TCP retransmission timeout configurable
Enable configuration of the minimum TCP Retransmission Timeout via
a new sysctl "tcp_rto_min" to help those who's networks (eg cellular)
have quite variable RTTs avoid spurrious RTOs.
Signed-off-by: Rick Jones <rick.jones2@...com>
Signed-off-by: Lamont Jones <lamont@...com>
---
diff -r 1559df81a153 Documentation/networking/ip-sysctl.txt
--- a/Documentation/networking/ip-sysctl.txt Mon Aug 13 05:00:33 2007 +0000
+++ b/Documentation/networking/ip-sysctl.txt Wed Aug 22 10:42:55 2007 -0700
@@ -339,6 +339,13 @@ tcp_rmem - vector of 3 INTEGERs: min, de
selected receiver buffers for TCP socket. This value does not override
net.core.rmem_max, "static" selection via SO_RCVBUF does not use this.
Default: 87380*2 bytes.
+
+tcp_rto_min - INTEGER
+ The minimum value for the TCP Retransmission Timeout, expressed
+ in milliseconds for the convenience of the user.
+ This is bounded at the low-end by TCP_RTO_MIN and by TCP_RTO_MAX at
+ the high-end.
+ Default: 200.
tcp_sack - BOOLEAN
Enable select acknowledgments (SACKS).
diff -r 1559df81a153 include/linux/sysctl.h
--- a/include/linux/sysctl.h Mon Aug 13 05:00:33 2007 +0000
+++ b/include/linux/sysctl.h Wed Aug 22 10:42:55 2007 -0700
@@ -441,6 +441,7 @@ enum
NET_TCP_ALLOWED_CONG_CONTROL=123,
NET_TCP_MAX_SSTHRESH=124,
NET_TCP_FRTO_RESPONSE=125,
+ NET_TCP_RTO_MIN=126,
};
enum {
diff -r 1559df81a153 include/net/tcp.h
--- a/include/net/tcp.h Mon Aug 13 05:00:33 2007 +0000
+++ b/include/net/tcp.h Wed Aug 22 10:42:55 2007 -0700
@@ -232,6 +232,7 @@ extern int sysctl_tcp_workaround_signed_
extern int sysctl_tcp_workaround_signed_windows;
extern int sysctl_tcp_slow_start_after_idle;
extern int sysctl_tcp_max_ssthresh;
+extern unsigned int sysctl_tcp_rto_min;
extern atomic_t tcp_memory_allocated;
extern atomic_t tcp_sockets_allocated;
diff -r 1559df81a153 net/ipv4/sysctl_net_ipv4.c
--- a/net/ipv4/sysctl_net_ipv4.c Mon Aug 13 05:00:33 2007 +0000
+++ b/net/ipv4/sysctl_net_ipv4.c Wed Aug 22 10:42:55 2007 -0700
@@ -186,6 +186,36 @@ static int strategy_allowed_congestion_c
}
+/* if there is ever a proc_dointvec_ms_jiffies_minmax we can get rid
+ of this routine */
+
+static int proc_tcp_rto_min(ctl_table *ctl, int write, struct file *filp,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ int *valp = ctl->data;
+ int oldval = *valp;
+ int ret;
+
+ ret = proc_dointvec_ms_jiffies(ctl, write, filp, buffer, lenp, ppos);
+ if (ret)
+ return ret;
+
+ /* some bounds checking would be in order */
+ if (write && *valp != oldval) {
+ if (*valp < (int)TCP_RTO_MIN) {
+ *valp = oldval;
+ return -EINVAL;
+ }
+ if (*valp > (int)TCP_RTO_MAX) {
+ *valp = oldval;
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+
ctl_table ipv4_table[] = {
{
.ctl_name = NET_IPV4_TCP_TIMESTAMPS,
@@ -819,6 +849,14 @@ ctl_table ipv4_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
+ {
+ .ctl_name = NET_TCP_RTO_MIN,
+ .procname = "tcp_rto_min",
+ .data = &sysctl_tcp_rto_min,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_tcp_rto_min
+ },
{ .ctl_name = 0 }
};
diff -r 1559df81a153 net/ipv4/tcp_input.c
--- a/net/ipv4/tcp_input.c Mon Aug 13 05:00:33 2007 +0000
+++ b/net/ipv4/tcp_input.c Wed Aug 22 10:42:55 2007 -0700
@@ -91,6 +91,8 @@ int sysctl_tcp_nometrics_save __read_mos
int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
int sysctl_tcp_abc __read_mostly;
+
+unsigned int sysctl_tcp_rto_min __read_mostly = TCP_RTO_MIN;
#define FLAG_DATA 0x01 /* Incoming frame contained data. */
#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
@@ -616,13 +618,13 @@ static void tcp_rtt_estimator(struct soc
if (tp->mdev_max < tp->rttvar)
tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
tp->rtt_seq = tp->snd_nxt;
- tp->mdev_max = TCP_RTO_MIN;
+ tp->mdev_max = sysctl_tcp_rto_min;
}
} else {
/* no previous measure. */
tp->srtt = m<<3; /* take the measured time to be rtt */
tp->mdev = m<<1; /* make sure rto = 3*rtt */
- tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
+ tp->mdev_max = tp->rttvar = max(tp->mdev, sysctl_tcp_rto_min);
tp->rtt_seq = tp->snd_nxt;
}
}
@@ -843,7 +845,7 @@ static void tcp_init_metrics(struct sock
}
if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
tp->mdev = dst_metric(dst, RTAX_RTTVAR);
- tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
+ tp->mdev_max = tp->rttvar = max(tp->mdev, sysctl_tcp_rto_min);
}
tcp_set_rto(sk);
tcp_bound_rto(sk);
-
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