| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-id: <4B707901.50905@tvk.rwth-aachen.de>
Date: Mon, 08 Feb 2010 21:50:09 +0100
From: Damian Lukowski <damian@....rwth-aachen.de>
To: Andreas Petlund <apetlund@...ula.no>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
Eric Dumazet <eric.dumazet@...il.com>,
Arnd Hannemann <hannemann@...s.rwth-aachen.de>,
LKML <linux-kernel@...r.kernel.org>, shemminger@...tta.com,
David Miller <davem@...emloft.net>,
william.allen.simpson@...il.com
Subject: Re: [net-next PATCH v2 2/3] net: TCP thin linear timeouts
Andreas Petlund schrieb:
> Major change: Limit number of thin linear timeout tries to TCP_THIN_LT_RETRIES (currently 6).
>
>>>From ec71404702149bc9197c749e5d1d68656c87f98f Mon Sep 17 00:00:00 2001
> From: Andreas Petlund <apetlund@...ula.no>
> Date: Mon, 8 Feb 2010 14:05:53 +0100
> Subject: [PATCH 2/3] net: TCP thin linear timeouts
>
>
> Signed-off-by: Andreas Petlund <apetlund@...ula.no>
> ---
> 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 | 5 +++++
> net/ipv4/tcp_timer.c | 19 ++++++++++++++++++-
> 6 files changed, 38 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..cbc1ee3 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -2229,6 +2229,11 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
> }
> break;
>
> + case TCP_THIN_LT:
> + if (val)
> + tp->thin_lt = 1;
> + 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..f01a585 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;
Hi,
I think, this value should be at least 1, as icsk_backoff
might be decreased to -1 and used for bit-shifting in tcp_v4_err().
A lower boundary check might be even better.
Regards
Damian
> + 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);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists