Messages in this thread | | | Subject | Re: [PATCH] tcp: Expose the initial RTO via a new sysctl. | From | Eric Dumazet <> | Date | Tue, 17 May 2011 10:07:57 +0200 |
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Le mardi 17 mai 2011 à 00:40 -0700, Benoit Sigoure a écrit : > 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. >
I wont discuss if introducing a new sysctl is welcomed, only on patch issues. I believe some work in IETF is done to reduce the 3sec value to 1sec anyway.
> Signed-off-by: Benoit Sigoure <tsunanet@gmail.com> > --- > 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. > +
units ? seconds ? ms ? jiffies ? I suggest using ms as external interface.
> 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,
We dont add new values here anymore, only anonymous ones.
> }; > > 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" },
no need here. sysctl() is deprecated.
> { 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)
Are you sure of this ?
If HZ=1000, sysctl_tcp_initial_rto is 3000
COUNTER_TRIES goes from 4 to 3004
> /* > * 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;
warning its jiffies units here.
> +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,
so unit is jiffies ? Really its not a good thing. Use ms instead.
Consider proc_dointvec_ms_jiffies(), here.
> + .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,
Here you assume sysctl_tcp_initial_rto is expressed in jiffies ? Oh well...
> 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))
Here you assume jiffies unit again. I wonder how this was tested :(
Please fix this and chose a definitive unit.
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