Major changes:
-Possible to disable mechanisms by socket option
-Socket option value boundary check
Signed-off-by: Andreas Petlund <[email protected]>
---
include/linux/sysctl.h | 1 +
include/linux/tcp.h | 3 +++
include/net/tcp.h | 4 ++++
net/ipv4/sysctl_net_ipv4.c | 7 +++++++
net/ipv4/tcp.c | 7 +++++++
net/ipv4/tcp_timer.c | 19 ++++++++++++++++++-
6 files changed, 40 insertions(+), 1 deletions(-)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 9f236cd..d840d75 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_TCP_FORCE_THIN_LINEAR_TIMEOUTS=126,
};
enum {
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 7fee8a4..67da706 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -103,6 +103,7 @@ enum {
#define TCP_CONGESTION 13 /* Congestion control algorithm */
#define TCP_MD5SIG 14 /* TCP MD5 Signature (RFC2385) */
#define TCP_COOKIE_TRANSACTIONS 15 /* TCP Cookie Transactions */
+#define TCP_THIN_LT 16 /* Use linear timeouts for thin streams*/
/* for TCP_INFO socket option */
#define TCPI_OPT_TIMESTAMPS 1
@@ -341,6 +342,8 @@ struct tcp_sock {
u16 advmss; /* Advertised MSS */
u8 frto_counter; /* Number of new acks after RTO */
u8 nonagle; /* Disable Nagle algorithm? */
+ u8 thin_lt : 1,/* Use linear timeouts for thin streams */
+ thin_undef : 7;
/* RTT measurement */
u32 srtt; /* smoothed round trip time << 3 */
diff --git a/include/net/tcp.h b/include/net/tcp.h
index e5e2056..bc5856a 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -196,6 +196,9 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
#define TCP_NAGLE_CORK 2 /* Socket is corked */
#define TCP_NAGLE_PUSH 4 /* Cork is overridden for already queued data */
+/* TCP thin-stream limits */
+#define TCP_THIN_LT_RETRIES 6 /* After 6 linear retries, do exp. backoff */
+
extern struct inet_timewait_death_row tcp_death_row;
/* sysctl variables for tcp */
@@ -241,6 +244,7 @@ extern int sysctl_tcp_workaround_signed_windows;
extern int sysctl_tcp_slow_start_after_idle;
extern int sysctl_tcp_max_ssthresh;
extern int sysctl_tcp_cookie_size;
+extern int sysctl_tcp_force_thin_linear_timeouts;
extern atomic_t tcp_memory_allocated;
extern struct percpu_counter tcp_sockets_allocated;
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 7e3712c..cb2ed35 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -576,6 +576,13 @@ static struct ctl_table ipv4_table[] = {
.proc_handler = proc_dointvec
},
{
+ .procname = "tcp_force_thin_linear_timeouts",
+ .data = &sysctl_tcp_force_thin_linear_timeouts,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec
+ },
+ {
.procname = "udp_mem",
.data = &sysctl_udp_mem,
.maxlen = sizeof(sysctl_udp_mem),
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index d5d69ea..ce9aeb0 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2229,6 +2229,13 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
}
break;
+ case TCP_THIN_LT:
+ if (val < 0 || val > 1)
+ err = -EINVAL;
+ else
+ tp->thin_lt = val;
+ break;
+
case TCP_CORK:
/* When set indicates to always queue non-full frames.
* Later the user clears this option and we transmit
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index de7d1bf..a682479 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -29,6 +29,7 @@ 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_orphan_retries __read_mostly;
+int sysctl_tcp_force_thin_linear_timeouts __read_mostly;
static void tcp_write_timer(unsigned long);
static void tcp_delack_timer(unsigned long);
@@ -415,7 +416,23 @@ void tcp_retransmit_timer(struct sock *sk)
icsk->icsk_retransmits++;
out_reset_timer:
- icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
+ /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
+ * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
+ * might be increased if the stream oscillates between thin and thick,
+ * thus the old value might already be too high compared to the value
+ * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
+ * backoff. Limit to TCP_THIN_LT_RETRIES before initiating exponential
+ * backoff behaviour to avoid continue hammering linear-timeout
+ * retransmissions into a black hole*/
+ if ((tp->thin_lt || sysctl_tcp_force_thin_linear_timeouts) &&
+ tcp_stream_is_thin(sk) && sk->sk_state == TCP_ESTABLISHED &&
+ icsk->icsk_retransmits <= TCP_THIN_LT_RETRIES) {
+ icsk->icsk_backoff = 0;
+ icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
+ } else {
+ /* Use normal (exponential) backoff */
+ icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
+ }
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1))
__sk_dst_reset(sk);
--
1.6.3.3
Le jeudi 11 février 2010 à 13:07 +0100, Andreas Petlund a écrit :
> Major changes:
> -Possible to disable mechanisms by socket option
> -Socket option value boundary check
>
>
> Signed-off-by: Andreas Petlund <[email protected]>
> ---
> include/linux/sysctl.h | 1 +
> include/linux/tcp.h | 3 +++
> include/net/tcp.h | 4 ++++
> net/ipv4/sysctl_net_ipv4.c | 7 +++++++
> net/ipv4/tcp.c | 7 +++++++
> net/ipv4/tcp_timer.c | 19 ++++++++++++++++++-
> 6 files changed, 40 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
> index 9f236cd..d840d75 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_TCP_FORCE_THIN_LINEAR_TIMEOUTS=126,
> };
>
> enum {
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index 7fee8a4..67da706 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -103,6 +103,7 @@ enum {
> #define TCP_CONGESTION 13 /* Congestion control algorithm */
> #define TCP_MD5SIG 14 /* TCP MD5 Signature (RFC2385) */
> #define TCP_COOKIE_TRANSACTIONS 15 /* TCP Cookie Transactions */
> +#define TCP_THIN_LT 16 /* Use linear timeouts for thin streams*/
>
> /* for TCP_INFO socket option */
> #define TCPI_OPT_TIMESTAMPS 1
> @@ -341,6 +342,8 @@ struct tcp_sock {
> u16 advmss; /* Advertised MSS */
> u8 frto_counter; /* Number of new acks after RTO */
> u8 nonagle; /* Disable Nagle algorithm? */
> + u8 thin_lt : 1,/* Use linear timeouts for thin streams */
> + thin_undef : 7;
>
> /* RTT measurement */
> u32 srtt; /* smoothed round trip time << 3 */
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index e5e2056..bc5856a 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -196,6 +196,9 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
> #define TCP_NAGLE_CORK 2 /* Socket is corked */
> #define TCP_NAGLE_PUSH 4 /* Cork is overridden for already queued data */
>
> +/* TCP thin-stream limits */
> +#define TCP_THIN_LT_RETRIES 6 /* After 6 linear retries, do exp. backoff */
> +
> extern struct inet_timewait_death_row tcp_death_row;
>
> /* sysctl variables for tcp */
> @@ -241,6 +244,7 @@ extern int sysctl_tcp_workaround_signed_windows;
> extern int sysctl_tcp_slow_start_after_idle;
> extern int sysctl_tcp_max_ssthresh;
> extern int sysctl_tcp_cookie_size;
> +extern int sysctl_tcp_force_thin_linear_timeouts;
>
> extern atomic_t tcp_memory_allocated;
> extern struct percpu_counter tcp_sockets_allocated;
> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
> index 7e3712c..cb2ed35 100644
> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -576,6 +576,13 @@ static struct ctl_table ipv4_table[] = {
> .proc_handler = proc_dointvec
> },
> {
> + .procname = "tcp_force_thin_linear_timeouts",
> + .data = &sysctl_tcp_force_thin_linear_timeouts,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec
> + },
> + {
> .procname = "udp_mem",
> .data = &sysctl_udp_mem,
> .maxlen = sizeof(sysctl_udp_mem),
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index d5d69ea..ce9aeb0 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -2229,6 +2229,13 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
> }
> break;
>
> + case TCP_THIN_LT:
> + if (val < 0 || val > 1)
> + err = -EINVAL;
> + else
> + tp->thin_lt = val;
> + break;
> +
> case TCP_CORK:
> /* When set indicates to always queue non-full frames.
> * Later the user clears this option and we transmit
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index de7d1bf..a682479 100644
> --- a/net/ipv4/tcp_timer.c
> +++ b/net/ipv4/tcp_timer.c
> @@ -29,6 +29,7 @@ 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_orphan_retries __read_mostly;
> +int sysctl_tcp_force_thin_linear_timeouts __read_mostly;
>
> static void tcp_write_timer(unsigned long);
> static void tcp_delack_timer(unsigned long);
> @@ -415,7 +416,23 @@ void tcp_retransmit_timer(struct sock *sk)
> icsk->icsk_retransmits++;
>
> out_reset_timer:
> - icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
> + /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is
> + * used to reset timer, set to 0. Recalculate 'icsk_rto' as this
> + * might be increased if the stream oscillates between thin and thick,
> + * thus the old value might already be too high compared to the value
> + * set by 'tcp_set_rto' in tcp_input.c which resets the rto without
> + * backoff. Limit to TCP_THIN_LT_RETRIES before initiating exponential
> + * backoff behaviour to avoid continue hammering linear-timeout
> + * retransmissions into a black hole*/
> + if ((tp->thin_lt || sysctl_tcp_force_thin_linear_timeouts) &&
> + tcp_stream_is_thin(sk) && sk->sk_state == TCP_ESTABLISHED &&
> + icsk->icsk_retransmits <= TCP_THIN_LT_RETRIES) {
> + icsk->icsk_backoff = 0;
> + icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX);
> + } else {
> + /* Use normal (exponential) backoff */
> + icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
> + }
> inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
> if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1))
> __sk_dst_reset(sk);
Hi Anreas
Could you include a section in Documentation/networking/ip-sysctl.txt
about tcp_force_thin_linear_timeouts setting ?
Also, you should provide some documentation to be included in man pages
(man 7 tcp), to Michael Kerrisk ( <[email protected]> ), both for
tcp_force_thin_linear_timeouts and TCP_THIN_LT
(Same applies for patch 3/3 and tcp_force_thin_dupack /
TCP_THIN_DUPACK )
Last year, I'm pretty sure I was on record as thinking this is only a
marginally good idea, that would be better at the application layer.
Also that naming was a bit dicey. Now the names are more descriptive,
but the "force" is a bit overkill.
How about?
NET_TCP_FORCE_THIN_LINEAR_TIMEOUTS -> NET_TCP_THIN_LINEAR_TIMEOUTS
TCP_THIN_LT -> TCP_THIN_LINEAR_TIMEOUTS
TCP_THIN_LT_RETRIES -> TCP_THIN_LINEAR_RETRIES
tcp_force_thin_linear_timeouts -> tcp_thin_linear_timeouts
sysctl_tcp_force_thin_linear_timeouts -> sysctl_tcp_thin_linear_timeouts
tp->thin_lt -> tp->thin_lto
The latter mostly traditional "to" for "timeout", as used most everywhere.
Andreas Petlund wrote:
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index de7d1bf..a682479 100644
> --- a/net/ipv4/tcp_timer.c
> +++ b/net/ipv4/tcp_timer.c
> @@ -29,6 +29,7 @@ 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_orphan_retries __read_mostly;
> +int sysctl_tcp_force_thin_linear_timeouts __read_mostly;
>
Where is the sysctl initialized?
> + if ((tp->thin_lt || sysctl_tcp_force_thin_linear_timeouts) &&
> + tcp_stream_is_thin(sk) && sk->sk_state == TCP_ESTABLISHED &&
> + icsk->icsk_retransmits <= TCP_THIN_LT_RETRIES) {
Just for efficiency, I'd reorder this
+ if (sk->sk_state == TCP_ESTABLISHED &&
+ (tp->thin_lt || sysctl_tcp_force_thin_linear_timeouts) &&
+ tcp_stream_is_thin(sk) &&
+ icsk->icsk_retransmits <= TCP_THIN_LT_RETRIES) {
On 12. feb. 2010 04:52, Eric Dumazet wrote:
>
> Hi Anreas
>
> Could you include a section in Documentation/networking/ip-sysctl.txt
> about tcp_force_thin_linear_timeouts setting ?
>
I 'll submit a draft with the next iteration. thanks for the heads up on the procedure.
It may also be helpful with a separate textfile to describe the thin-stream latency
issues and the mechanisms. I will submit a draft for this also.
> Also, you should provide some documentation to be included in man pages
> (man 7 tcp), to Michael Kerrisk ( <[email protected]> ), both for
> tcp_force_thin_linear_timeouts and TCP_THIN_LT
>
> (Same applies for patch 3/3 and tcp_force_thin_dupack /
> TCP_THIN_DUPACK )
>
I'll make a draft, and mail him as soon as the naming issues are settled.
Best regards,
Andreas
On 12. feb. 2010 12:19, William Allen Simpson wrote:
> Last year, I'm pretty sure I was on record as thinking this is only a
> marginally good idea, that would be better at the application layer.
>
> Also that naming was a bit dicey. Now the names are more descriptive,
> but the "force" is a bit overkill.
>
> How about?
> NET_TCP_FORCE_THIN_LINEAR_TIMEOUTS -> NET_TCP_THIN_LINEAR_TIMEOUTS
> TCP_THIN_LT -> TCP_THIN_LINEAR_TIMEOUTS
> TCP_THIN_LT_RETRIES -> TCP_THIN_LINEAR_RETRIES
> tcp_force_thin_linear_timeouts -> tcp_thin_linear_timeouts
> sysctl_tcp_force_thin_linear_timeouts -> sysctl_tcp_thin_linear_timeouts
> tp->thin_lt -> tp->thin_lto
>
> The latter mostly traditional "to" for "timeout", as used most everywhere.
>
I agree that the _force_-part should be taken out for both patches, and
renaming the lt to lto also makes sense. I'll fix it in the next iteration.
> Just for efficiency, I'd reorder this
> + if (sk->sk_state == TCP_ESTABLISHED &&
> + (tp->thin_lt || sysctl_tcp_force_thin_linear_timeouts) &&
> + tcp_stream_is_thin(sk) &&
> + icsk->icsk_retransmits <= TCP_THIN_LT_RETRIES) {
Thank you for this suggestion. I'll reorder in the next iteration.
Best regards,
Andreas