Commit f0fdc80b authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'pmtu-probe' 



Fan Du says:

====================
Improvements for TCP PMTU

This patchset performs some improvements and enhancement
for current TCP PMTU as per RFC4821 with the aim to find
optimal mms size quickly, and also be adaptive to route
changes like enlarged path MTU. Then TCP PMTU could be
used to probe a effective pmtu in absence of ICMP message
for tunnels(e.g. vxlan) across different networking stack.

Patch1/4: Set probe mss base to 1024 Bytes per RFC4821
Patch2/4: Do not double probe_size for each probing,
          use a simple binary search to gain maximum performance.
	  mss for next probing.
Patch3/4: Create a probe timer to detect enlarged path MTU.
Patch4/4: Update ip-sysctl.txt for new sysctl knobs.

Changelog:
v5:
  - Zero probe_size before resetting search range.
  - Update ip-sysctl.txt for new sysctl knobs.
v4:
  - Convert probe_size to mss, not directly from search_low/high
  - Clamp probe_threshold
  - Don't adjust search_high in blackhole probe, so drop orignal patch3
v3:
  - Update commit message for patch2
  - Fix pseudo timer delta calculation in patch4
v2:
  - Introduce sysctl_tcp_probe_threshold to control when
    probing will stop, as suggested by John Heffner.
  - Add patch3 to shrink current mss value for search low boundary.
  - Drop cannonical timer usages, implements pseudo timer based on
    32bits jiffies tcp_time_stamp, as suggested by Eric Dumazet.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents aaa4e704 fab42760

Documentation/networking/ip-sysctl.txt

+10 −0
Original line number Diff line number Diff line
@@ -388,6 +388,16 @@ tcp_mtu_probing - INTEGER 
	  1 - Disabled by default, enabled when an ICMP black hole detected

	  2 - Always enabled, use initial MSS of tcp_base_mss.



tcp_probe_interval - INTEGER

	Controls how often to start TCP Packetization-Layer Path MTU

	Discovery reprobe. The default is reprobing every 10 minutes as

	per RFC4821.



tcp_probe_threshold - INTEGER

	Controls when TCP Packetization-Layer Path MTU Discovery probing

	will stop in respect to the width of search range in bytes. Default

	is 8 bytes.



tcp_no_metrics_save - BOOLEAN

	By default, TCP saves various connection metrics in the route cache

	when the connection closes, so that connections established in the

include/net/inet_connection_sock.h

+2 −0
Original line number Diff line number Diff line
@@ -126,6 +126,8 @@ struct inet_connection_sock { 


		/* Information on the current probe. */

		int		  probe_size;



		u32		  probe_timestamp;

	} icsk_mtup;

	u32			  icsk_ca_priv[16];

	u32			  icsk_user_timeout;

include/net/netns/ipv4.h

+2 −0
Original line number Diff line number Diff line
@@ -87,6 +87,8 @@ struct netns_ipv4 { 
	int sysctl_tcp_fwmark_accept;

	int sysctl_tcp_mtu_probing;

	int sysctl_tcp_base_mss;

	int sysctl_tcp_probe_threshold;

	u32 sysctl_tcp_probe_interval;



	struct ping_group_range ping_group_range;

include/net/tcp.h

+7 −1
Original line number Diff line number Diff line
@@ -65,7 +65,13 @@ void tcp_time_wait(struct sock *sk, int state, int timeo); 
#define TCP_MIN_MSS		88U



/* The least MTU to use for probing */

#define TCP_BASE_MSS		512

#define TCP_BASE_MSS		1024



/* probing interval, default to 10 minutes as per RFC4821 */

#define TCP_PROBE_INTERVAL	600



/* Specify interval when tcp mtu probing will stop */

#define TCP_PROBE_THRESHOLD	8



/* After receiving this amount of duplicate ACKs fast retransmit starts. */

#define TCP_FASTRETRANS_THRESH 3

net/ipv4/sysctl_net_ipv4.c

+14 −0
Original line number Diff line number Diff line
@@ -883,6 +883,20 @@ static struct ctl_table ipv4_net_table[] = { 
		.mode		= 0644,

		.proc_handler	= proc_dointvec,

	},

	{

		.procname	= "tcp_probe_threshold",

		.data		= &init_net.ipv4.sysctl_tcp_probe_threshold,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec,

	},

	{

		.procname	= "tcp_probe_interval",

		.data		= &init_net.ipv4.sysctl_tcp_probe_interval,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec,

	},

	{ }

};

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