diff mbox series

[net-next,v2,2/3] net: ipv6/addrconf: introduce a regen_min_advance sysctl

Message ID 20240214062711.608363-3-alexhenrie24@gmail.com (mailing list archive)
State Accepted
Commit a5fcea2d2f790aa90b6e996d411ae2cf8db55186
Delegated to: Netdev Maintainers
Headers show
Series net: ipv6/addrconf: ensure that temporary addresses' preferred lifetimes are long enough | expand

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netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 2871 this patch: 2871
netdev/build_tools success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 2 maintainers not CCed: linux-doc@vger.kernel.org corbet@lwn.net
netdev/build_clang success Errors and warnings before: 1053 this patch: 1053
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 3085 this patch: 3085
netdev/checkpatch warning CHECK: spaces preferred around that '*' (ctx:VxV)
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-02-15--00-00 (tests: 1443)

Commit Message

Alex Henrie Feb. 14, 2024, 6:26 a.m. UTC 
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>
---
 Documentation/networking/ip-sysctl.rst | 10 ++++++++++
 include/linux/ipv6.h                   |  1 +
 include/net/addrconf.h                 |  5 +++--
 net/ipv6/addrconf.c                    | 11 ++++++++++-
 4 files changed, 24 insertions(+), 3 deletions(-)

Comments

David Ahern Feb. 14, 2024, 3:39 p.m. UTC | #1 
On 2/13/24 11:26 PM, Alex Henrie wrote:
> 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>
> ---
>  Documentation/networking/ip-sysctl.rst | 10 ++++++++++
>  include/linux/ipv6.h                   |  1 +
>  include/net/addrconf.h                 |  5 +++--
>  net/ipv6/addrconf.c                    | 11 ++++++++++-
>  4 files changed, 24 insertions(+), 3 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>
diff mbox series

Patch

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 458305931345..407d917d1a36 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -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.
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 5e605e384aac..ef3aa060a289 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -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;
diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 61ebe723ee4d..30d6f1e84e46 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -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)
 
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 68516493404a..9af56b73d08c 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -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,