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Merge branch 'net-ipv6-addrconf-ensure-that-temporary-addresses-preferred-lifetimes-are-long-enough'

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Alex Henrie says:

====================
net: ipv6/addrconf: ensure that temporary addresses' preferred lifetimes are long enough

v2 corrects and updates the documentation for these features.

Changes from v1:
- Update the typical minimum lifetime stated in the documentation, and
  make it a range to emphasize the variability
- Fix spelling of "determine" in the documentation
- Mention RFC 8981's requirements in the documentation
- Arrange variables in "reverse Christmas tree"
- Update documentation of what happens if temp_prefered_lft is less
  than the minimum required lifetime

Thanks to David, Paolo, and Dan for your feedback.
====================

Link: https://lore.kernel.org/r/20240214062711.608363-1-alexhenrie24@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Paolo Abeni
2024-02-15 15:34:42 +01:00
parent ea578703b0 f4bcbf360a
commit dfe7f12788
4 changed files with 68 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
Documentation/networking/ip-sysctl.rst
View File

@ -2503,7 +2503,7 @@ use_tempaddr - INTEGER
temp_valid_lft - INTEGER
valid lifetime (in seconds) for temporary addresses. If less than the
minimum required lifetime (typically 5 seconds), temporary addresses
minimum required lifetime (typically 5-7 seconds), temporary addresses
will not be created.
Default: 172800 (2 days)
@ -2511,7 +2511,7 @@ temp_valid_lft - INTEGER
temp_prefered_lft - INTEGER
Preferred lifetime (in seconds) for temporary addresses. If
temp_prefered_lft is less than the minimum required lifetime (typically
5 seconds), temporary addresses will not be created. If
5-7 seconds), the preferred lifetime is the minimum required. If
temp_prefered_lft is greater than temp_valid_lft, the preferred lifetime
is temp_valid_lft.
@ -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)

67
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,
@ -1339,12 +1341,20 @@ out:
in6_ifa_put(ifp);
}
static unsigned long ipv6_get_regen_advance(struct inet6_dev *idev)
{
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;
}
static int ipv6_create_tempaddr(struct inet6_ifaddr *ifp, bool block)
{
struct inet6_dev *idev = ifp->idev;
unsigned long tmp_tstamp, age;
unsigned long regen_advance;
unsigned long now = jiffies;
u32 if_public_preferred_lft;
s32 cnf_temp_preferred_lft;
struct inet6_ifaddr *ift;
struct ifa6_config cfg;
@ -1380,9 +1390,7 @@ retry:
age = (now - ifp->tstamp) / HZ;
regen_advance = idev->cnf.regen_max_retry *
idev->cnf.dad_transmits *
max(NEIGH_VAR(idev->nd_parms, RETRANS_TIME), HZ/100) / HZ;
regen_advance = ipv6_get_regen_advance(idev);
/* recalculate max_desync_factor each time and update
* idev->desync_factor if it's larger
@ -1402,11 +1410,13 @@ retry:
}
}
if_public_preferred_lft = ifp->prefered_lft;
memset(&cfg, 0, sizeof(cfg));
cfg.valid_lft = min_t(__u32, ifp->valid_lft,
idev->cnf.temp_valid_lft + age);
cfg.preferred_lft = cnf_temp_preferred_lft + age - idev->desync_factor;
cfg.preferred_lft = min_t(__u32, ifp->prefered_lft, cfg.preferred_lft);
cfg.preferred_lft = min_t(__u32, if_public_preferred_lft, cfg.preferred_lft);
cfg.preferred_lft = min_t(__u32, cfg.valid_lft, cfg.preferred_lft);
cfg.plen = ifp->prefix_len;
@ -1415,19 +1425,41 @@ retry:
write_unlock_bh(&idev->lock);
/* A temporary address is created only if this calculated Preferred
* Lifetime is greater than REGEN_ADVANCE time units. In particular,
* an implementation must not create a temporary address with a zero
* Preferred Lifetime.
/* From RFC 4941:
*
* A temporary address is created only if this calculated Preferred
* Lifetime is greater than REGEN_ADVANCE time units. In
* particular, an implementation must not create a temporary address
* with a zero Preferred Lifetime.
*
* ...
*
* When creating a temporary address, the lifetime values MUST be
* derived from the corresponding prefix as follows:
*
* ...
*
* * Its Preferred Lifetime is the lower of the Preferred Lifetime
* of the public address or TEMP_PREFERRED_LIFETIME -
* DESYNC_FACTOR.
*
* To comply with the RFC's requirements, clamp the preferred lifetime
* to a minimum of regen_advance, unless that would exceed valid_lft or
* ifp->prefered_lft.
*
* Use age calculation as in addrconf_verify to avoid unnecessary
* temporary addresses being generated.
*/
age = (now - tmp_tstamp + ADDRCONF_TIMER_FUZZ_MINUS) / HZ;
if (cfg.preferred_lft <= regen_advance + age) {
in6_ifa_put(ifp);
in6_dev_put(idev);
ret = -1;
goto out;
cfg.preferred_lft = regen_advance + age + 1;
if (cfg.preferred_lft > cfg.valid_lft ||
cfg.preferred_lft > if_public_preferred_lft) {
in6_ifa_put(ifp);
in6_dev_put(idev);
ret = -1;
goto out;
}
}
cfg.ifa_flags = IFA_F_TEMPORARY;
@ -4595,9 +4627,7 @@ restart:
!ifp->regen_count && ifp->ifpub) {
/* This is a non-regenerated temporary addr. */
unsigned long regen_advance = ifp->idev->cnf.regen_max_retry *
ifp->idev->cnf.dad_transmits *
max(NEIGH_VAR(ifp->idev->nd_parms, RETRANS_TIME), HZ/100) / HZ;
unsigned long regen_advance = ipv6_get_regen_advance(ifp->idev);
if (age + regen_advance >= ifp->prefered_lft) {
struct inet6_ifaddr *ifpub = ifp->ifpub;
@ -6816,6 +6846,13 @@ 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,