[PATCH] tcp: Expose the initial RTO via a new sysctl.
From: Benoit Sigoure
Date: Tue May 17 2011 - 03:41:31 EST
Instead of hardcoding the initial RTO to 3s and requiring
the kernel to be recompiled to change it, expose it as a
sysctl that can be tuned at runtime. Leave the default
value unchanged.
Signed-off-by: Benoit Sigoure <tsunanet@xxxxxxxxx>
---
Documentation/networking/ip-sysctl.txt | 6 ++++++
include/linux/sysctl.h | 1 +
include/net/tcp.h | 3 ++-
kernel/sysctl_binary.c | 1 +
net/ipv4/syncookies.c | 2 +-
net/ipv4/sysctl_net_ipv4.c | 11 +++++++++++
net/ipv4/tcp.c | 4 ++--
net/ipv4/tcp_input.c | 8 ++++----
net/ipv4/tcp_ipv4.c | 6 +++---
net/ipv4/tcp_minisocks.c | 6 +++---
net/ipv4/tcp_output.c | 2 +-
net/ipv4/tcp_timer.c | 9 +++++----
net/ipv6/syncookies.c | 2 +-
net/ipv6/tcp_ipv6.c | 6 +++---
14 files changed, 44 insertions(+), 23 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index d3d653a..c381c68 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -384,6 +384,12 @@ tcp_retries2 - INTEGER
RFC 1122 recommends at least 100 seconds for the timeout,
which corresponds to a value of at least 8.
+tcp_initial_rto - INTEGER
+ This value sets the initial retransmit timeout, that is how long
+ the kernel will wait before retransmitting the initial SYN packet.
+
+ RFC 1122 says that this SHOULD be 3 seconds, which is the default.
+
tcp_rfc1337 - BOOLEAN
If set, the TCP stack behaves conforming to RFC1337. If unset,
we are not conforming to RFC, but prevent TCP TIME_WAIT
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 11684d9..96a9b41 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -425,6 +425,7 @@ enum
NET_TCP_ALLOWED_CONG_CONTROL=123,
NET_TCP_MAX_SSTHRESH=124,
NET_TCP_FRTO_RESPONSE=125,
+ NET_IPV4_TCP_INITIAL_RTO=126,
};
enum {
diff --git a/include/net/tcp.h b/include/net/tcp.h
index cda30ea..a2bb0f1 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -213,6 +213,7 @@ extern int sysctl_tcp_syn_retries;
extern int sysctl_tcp_synack_retries;
extern int sysctl_tcp_retries1;
extern int sysctl_tcp_retries2;
+extern int sysctl_tcp_initial_rto;
extern int sysctl_tcp_orphan_retries;
extern int sysctl_tcp_syncookies;
extern int sysctl_tcp_retrans_collapse;
@@ -295,7 +296,7 @@ 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 + sysctl_tcp_initial_rto);
}
extern struct proto tcp_prot;
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index 3b8e028..d608d84 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -354,6 +354,7 @@ static const struct bin_table bin_net_ipv4_table[] = {
{ CTL_INT, NET_IPV4_TCP_KEEPALIVE_INTVL, "tcp_keepalive_intvl" },
{ CTL_INT, NET_IPV4_TCP_RETRIES1, "tcp_retries1" },
{ CTL_INT, NET_IPV4_TCP_RETRIES2, "tcp_retries2" },
+ { CTL_INT, NET_IPV4_TCP_INITIAL_RTO, "tcp_initial_rto" },
{ CTL_INT, NET_IPV4_TCP_FIN_TIMEOUT, "tcp_fin_timeout" },
{ CTL_INT, NET_TCP_SYNCOOKIES, "tcp_syncookies" },
{ CTL_INT, NET_TCP_TW_RECYCLE, "tcp_tw_recycle" },
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 8b44c6d..089bc92 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -186,7 +186,7 @@ __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
* sysctl_tcp_retries1. It's a rather complicated formula (exponential
* backoff) to compute at runtime so it's currently hardcoded here.
*/
-#define COUNTER_TRIES 4
+#define COUNTER_TRIES (sysctl_tcp_initial_rto + 1)
/*
* Check if a ack sequence number is a valid syncookie.
* Return the decoded mss if it is, or 0 if not.
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 321e6e8..24dc21d 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -30,6 +30,8 @@ static int tcp_adv_win_scale_min = -31;
static int tcp_adv_win_scale_max = 31;
static int ip_ttl_min = 1;
static int ip_ttl_max = 255;
+static int tcp_initial_rto_min = TCP_RTO_MIN;
+static int tcp_initial_rto_max = TCP_RTO_MAX;
/* Update system visible IP port range */
static void set_local_port_range(int range[2])
@@ -246,6 +248,15 @@ static struct ctl_table ipv4_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec
},
+ {
+ .procname = "tcp_initial_rto",
+ .data = &sysctl_tcp_initial_rto,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &tcp_initial_rto_min,
+ .extra2 = &tcp_initial_rto_max,
+ },
{
.procname = "tcp_fin_timeout",
.data = &sysctl_tcp_fin_timeout,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b22d450..e9e7c3f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2352,7 +2352,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
case TCP_DEFER_ACCEPT:
/* Translate value in seconds to number of retransmits */
icsk->icsk_accept_queue.rskq_defer_accept =
- secs_to_retrans(val, TCP_TIMEOUT_INIT / HZ,
+ secs_to_retrans(val, sysctl_tcp_initial_rto / HZ,
TCP_RTO_MAX / HZ);
break;
@@ -2539,7 +2539,7 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
break;
case TCP_DEFER_ACCEPT:
val = retrans_to_secs(icsk->icsk_accept_queue.rskq_defer_accept,
- TCP_TIMEOUT_INIT / HZ, TCP_RTO_MAX / HZ);
+ sysctl_tcp_initial_rto / HZ, TCP_RTO_MAX / HZ);
break;
case TCP_WINDOW_CLAMP:
val = tp->window_clamp;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bef9f04..39f6c27 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -890,7 +890,7 @@ static void tcp_init_metrics(struct sock *sk)
if (dst_metric(dst, RTAX_RTT) == 0)
goto reset;
- if (!tp->srtt && dst_metric_rtt(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
+ if (!tp->srtt && dst_metric_rtt(dst, RTAX_RTT) < (sysctl_tcp_initial_rto << 3))
goto reset;
/* Initial rtt is determined from SYN,SYN-ACK.
@@ -916,7 +916,7 @@ 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) {
+ if (inet_csk(sk)->icsk_rto < sysctl_tcp_initial_rto && !tp->rx_opt.saw_tstamp) {
reset:
/* Play conservative. If timestamps are not
* supported, TCP will fail to recalculate correct
@@ -924,8 +924,8 @@ reset:
*/
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 = sysctl_tcp_initial_rto;
+ inet_csk(sk)->icsk_rto = sysctl_tcp_initial_rto;
}
}
tp->snd_cwnd = tcp_init_cwnd(tp, dst);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index f7e6c2c..21920e6 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1383,7 +1383,7 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
want_cookie)
goto drop_and_free;
- inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
+ inet_csk_reqsk_queue_hash_add(sk, req, sysctl_tcp_initial_rto);
return 0;
drop_and_release:
@@ -1834,8 +1834,8 @@ static int tcp_v4_init_sock(struct sock *sk)
tcp_init_xmit_timers(sk);
tcp_prequeue_init(tp);
- icsk->icsk_rto = TCP_TIMEOUT_INIT;
- tp->mdev = TCP_TIMEOUT_INIT;
+ icsk->icsk_rto = sysctl_tcp_initial_rto;
+ tp->mdev = sysctl_tcp_initial_rto;
/* So many TCP implementations out there (incorrectly) count the
* initial SYN frame in their delayed-ACK and congestion control
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 80b1f80..c63ffa0 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -472,8 +472,8 @@ struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req,
tcp_init_wl(newtp, treq->rcv_isn);
newtp->srtt = 0;
- newtp->mdev = TCP_TIMEOUT_INIT;
- newicsk->icsk_rto = TCP_TIMEOUT_INIT;
+ newtp->mdev = sysctl_tcp_initial_rto;
+ newicsk->icsk_rto = sysctl_tcp_initial_rto;
newtp->packets_out = 0;
newtp->retrans_out = 0;
@@ -582,7 +582,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
* it can be estimated (approximately)
* from another data.
*/
- tmp_opt.ts_recent_stamp = get_seconds() - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans);
+ tmp_opt.ts_recent_stamp = get_seconds() - ((sysctl_tcp_initial_rto/HZ)<<req->retrans);
paws_reject = tcp_paws_reject(&tmp_opt, th->rst);
}
}
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 17388c7..e34b0f6 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2599,7 +2599,7 @@ static void tcp_connect_init(struct sock *sk)
tp->rcv_wup = 0;
tp->copied_seq = 0;
- inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
+ inet_csk(sk)->icsk_rto = sysctl_tcp_initial_rto;
inet_csk(sk)->icsk_retransmits = 0;
tcp_clear_retrans(tp);
}
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index ecd44b0..b9da62b 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -29,6 +29,7 @@ int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES;
int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL;
int sysctl_tcp_retries1 __read_mostly = TCP_RETR1;
int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
+int sysctl_tcp_initial_rto __read_mostly = TCP_TIMEOUT_INIT;
int sysctl_tcp_orphan_retries __read_mostly;
int sysctl_tcp_thin_linear_timeouts __read_mostly;
@@ -135,8 +136,8 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
/* This function calculates a "timeout" which is equivalent to the timeout of a
* TCP connection after "boundary" unsuccessful, exponentially backed-off
- * retransmissions with an initial RTO of TCP_RTO_MIN or TCP_TIMEOUT_INIT if
- * syn_set flag is set.
+ * retransmissions with an initial RTO of TCP_RTO_MIN or
+ * sysctl_tcp_initial_rto if syn_set flag is set.
*/
static bool retransmits_timed_out(struct sock *sk,
unsigned int boundary,
@@ -144,7 +145,7 @@ static bool retransmits_timed_out(struct sock *sk,
bool syn_set)
{
unsigned int linear_backoff_thresh, start_ts;
- unsigned int rto_base = syn_set ? TCP_TIMEOUT_INIT : TCP_RTO_MIN;
+ unsigned int rto_base = syn_set ? sysctl_tcp_initial_rto : TCP_RTO_MIN;
if (!inet_csk(sk)->icsk_retransmits)
return false;
@@ -495,7 +496,7 @@ out_unlock:
static void tcp_synack_timer(struct sock *sk)
{
inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
- TCP_TIMEOUT_INIT, TCP_RTO_MAX);
+ sysctl_tcp_initial_rto, TCP_RTO_MAX);
}
void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 352c260..50baaec 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -45,7 +45,7 @@ static __u16 const msstab[] = {
* sysctl_tcp_retries1. It's a rather complicated formula (exponential
* backoff) to compute at runtime so it's currently hardcoded here.
*/
-#define COUNTER_TRIES 4
+#define COUNTER_TRIES (sysctl_tcp_initial_rto + 1)
static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 4f49e5d..7e791e6 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1349,7 +1349,7 @@ have_isn:
want_cookie)
goto drop_and_free;
- inet6_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);
+ inet6_csk_reqsk_queue_hash_add(sk, req, sysctl_tcp_initial_rto);
return 0;
drop_and_release:
@@ -1957,8 +1957,8 @@ static int tcp_v6_init_sock(struct sock *sk)
tcp_init_xmit_timers(sk);
tcp_prequeue_init(tp);
- icsk->icsk_rto = TCP_TIMEOUT_INIT;
- tp->mdev = TCP_TIMEOUT_INIT;
+ icsk->icsk_rto = sysctl_tcp_initial_rto;
+ tp->mdev = sysctl_tcp_initial_rto;
/* So many TCP implementations out there (incorrectly) count the
* initial SYN frame in their delayed-ACK and congestion control
--
1.7.0.4
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