Commit a5fcea2d authored by Alex Henrie's avatar Alex Henrie Committed by Paolo Abeni
Browse files

net: ipv6/addrconf: introduce a regen_min_advance sysctl 

In RFC 8981, REGEN_ADVANCE cannot be less than 2 seconds, and the RFC
does not permit the creation of temporary addresses with lifetimes
shorter than that:

> When processing a Router Advertisement with a
> Prefix Information option carrying a prefix for the purposes of
> address autoconfiguration (i.e., the A bit is set), the host MUST
> perform the following steps:

> 5.  A temporary address is created only if this calculated preferred
>     lifetime is greater than REGEN_ADVANCE time units.

However, some users want to change their IPv6 address as frequently as
possible regardless of the RFC's arbitrary minimum lifetime. For the
benefit of those users, add a regen_min_advance sysctl parameter that
can be set to below or above 2 seconds.

Link: https://datatracker.ietf.org/doc/html/rfc8981


Signed-off-by: default avatarAlex Henrie <alexhenrie24@gmail.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 2aa8f155

Documentation/networking/ip-sysctl.rst

+10 −0
Original line number Diff line number Diff line
@@ -2535,6 +2535,16 @@ max_desync_factor - INTEGER 


	Default: 600



regen_min_advance - INTEGER

	How far in advance (in seconds), at minimum, to create a new temporary

	address before the current one is deprecated. This value is added to

	the amount of time that may be required for duplicate address detection

	to determine when to create a new address. Linux permits setting this

	value to less than the default of 2 seconds, but a value less than 2

	does not conform to RFC 8981.



	Default: 2



regen_max_retry - INTEGER

	Number of attempts before give up attempting to generate

	valid temporary addresses.

include/linux/ipv6.h

+1 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ struct ipv6_devconf { 
	__s32		use_tempaddr;

	__s32		temp_valid_lft;

	__s32		temp_prefered_lft;

	__s32		regen_min_advance;

	__s32		regen_max_retry;

	__s32		max_desync_factor;

	__s32		max_addresses;

include/net/addrconf.h

+3 −2
Original line number Diff line number Diff line
@@ -8,8 +8,9 @@ 


#define MIN_VALID_LIFETIME		(2*3600)	/* 2 hours */



#define TEMP_VALID_LIFETIME		(7*86400)

#define TEMP_PREFERRED_LIFETIME		(86400)

#define TEMP_VALID_LIFETIME		(7*86400)       /* 1 week */

#define TEMP_PREFERRED_LIFETIME		(86400)         /* 24 hours */

#define REGEN_MIN_ADVANCE		(2)             /* 2 seconds */

#define REGEN_MAX_RETRY			(3)

#define MAX_DESYNC_FACTOR		(600)

net/ipv6/addrconf.c

+10 −1
Original line number Diff line number Diff line
@@ -195,6 +195,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = { 
	.use_tempaddr		= 0,

	.temp_valid_lft		= TEMP_VALID_LIFETIME,

	.temp_prefered_lft	= TEMP_PREFERRED_LIFETIME,

	.regen_min_advance	= REGEN_MIN_ADVANCE,

	.regen_max_retry	= REGEN_MAX_RETRY,

	.max_desync_factor	= MAX_DESYNC_FACTOR,

	.max_addresses		= IPV6_MAX_ADDRESSES,
@@ -257,6 +258,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = { 
	.use_tempaddr		= 0,

	.temp_valid_lft		= TEMP_VALID_LIFETIME,

	.temp_prefered_lft	= TEMP_PREFERRED_LIFETIME,

	.regen_min_advance	= REGEN_MIN_ADVANCE,

	.regen_max_retry	= REGEN_MAX_RETRY,

	.max_desync_factor	= MAX_DESYNC_FACTOR,

	.max_addresses		= IPV6_MAX_ADDRESSES,
@@ -1341,7 +1343,7 @@ static void ipv6_del_addr(struct inet6_ifaddr *ifp) 


static unsigned long ipv6_get_regen_advance(struct inet6_dev *idev)

{

	return 2 + idev->cnf.regen_max_retry *

	return idev->cnf.regen_min_advance + idev->cnf.regen_max_retry *

			idev->cnf.dad_transmits *

			max(NEIGH_VAR(idev->nd_parms, RETRANS_TIME), HZ/100) / HZ;

}
@@ -6819,6 +6821,13 @@ static const struct ctl_table addrconf_sysctl[] = { 
		.mode		= 0644,

		.proc_handler	= proc_dointvec,

	},

	{

		.procname       = "regen_min_advance",

		.data           = &ipv6_devconf.regen_min_advance,

		.maxlen         = sizeof(int),

		.mode           = 0644,

		.proc_handler   = proc_dointvec,

	},

	{

		.procname	= "regen_max_retry",

		.data		= &ipv6_devconf.regen_max_retry,