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net: ipv6/addrconf: introduce a regen_min_advance sysctl

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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: Alex Henrie <alexhenrie24@gmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Alex Henrie 2024-02-13 23:26:31 -07:00 committed by Paolo Abeni
parent 2aa8f155b0
commit a5fcea2d2f
4 changed files with 24 additions and 3 deletions
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10
Documentation/networking/ip-sysctl.rst
View file

@ -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.

1
include/linux/ipv6.h
View file

@ -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;

5
include/net/addrconf.h
View file

@ -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)

11
net/ipv6/addrconf.c
View file

@ -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,