ipv6 addrconf: implement RFC7559 router solicitation backoff
This implements:
https://tools.ietf.org/html/rfc7559
Backoff is performed according to RFC3315 section 14:
https://tools.ietf.org/html/rfc3315#section-14
We allow setting /proc/sys/net/ipv6/conf/*/router_solicitations
to a negative value meaning an unlimited number of retransmits,
and we make this the new default (inline with the RFC).
We also add a new setting:
/proc/sys/net/ipv6/conf/*/router_solicitation_max_interval
defaulting to 1 hour (per RFC recommendation).
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Acked-by: Erik Kline <ek@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 35d4baa..8718398 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -112,6 +112,27 @@
return (cstamp - INITIAL_JIFFIES) * 100UL / HZ;
}
+static inline s32 rfc3315_s14_backoff_init(s32 irt)
+{
+ /* multiply 'initial retransmission time' by 0.9 .. 1.1 */
+ u64 tmp = (900000 + prandom_u32() % 200001) * (u64)irt;
+ do_div(tmp, 1000000);
+ return (s32)tmp;
+}
+
+static inline s32 rfc3315_s14_backoff_update(s32 rt, s32 mrt)
+{
+ /* multiply 'retransmission timeout' by 1.9 .. 2.1 */
+ u64 tmp = (1900000 + prandom_u32() % 200001) * (u64)rt;
+ do_div(tmp, 1000000);
+ if ((s32)tmp > mrt) {
+ /* multiply 'maximum retransmission time' by 0.9 .. 1.1 */
+ tmp = (900000 + prandom_u32() % 200001) * (u64)mrt;
+ do_div(tmp, 1000000);
+ }
+ return (s32)tmp;
+}
+
#ifdef CONFIG_SYSCTL
static int addrconf_sysctl_register(struct inet6_dev *idev);
static void addrconf_sysctl_unregister(struct inet6_dev *idev);
@@ -187,6 +208,7 @@
.dad_transmits = 1,
.rtr_solicits = MAX_RTR_SOLICITATIONS,
.rtr_solicit_interval = RTR_SOLICITATION_INTERVAL,
+ .rtr_solicit_max_interval = RTR_SOLICITATION_MAX_INTERVAL,
.rtr_solicit_delay = MAX_RTR_SOLICITATION_DELAY,
.use_tempaddr = 0,
.temp_valid_lft = TEMP_VALID_LIFETIME,
@@ -232,6 +254,7 @@
.dad_transmits = 1,
.rtr_solicits = MAX_RTR_SOLICITATIONS,
.rtr_solicit_interval = RTR_SOLICITATION_INTERVAL,
+ .rtr_solicit_max_interval = RTR_SOLICITATION_MAX_INTERVAL,
.rtr_solicit_delay = MAX_RTR_SOLICITATION_DELAY,
.use_tempaddr = 0,
.temp_valid_lft = TEMP_VALID_LIFETIME,
@@ -3687,7 +3710,7 @@
if (idev->if_flags & IF_RA_RCVD)
goto out;
- if (idev->rs_probes++ < idev->cnf.rtr_solicits) {
+ if (idev->rs_probes++ < idev->cnf.rtr_solicits || idev->cnf.rtr_solicits < 0) {
write_unlock(&idev->lock);
if (!ipv6_get_lladdr(dev, &lladdr, IFA_F_TENTATIVE))
ndisc_send_rs(dev, &lladdr,
@@ -3696,11 +3719,13 @@
goto put;
write_lock(&idev->lock);
+ idev->rs_interval = rfc3315_s14_backoff_update(
+ idev->rs_interval, idev->cnf.rtr_solicit_max_interval);
/* The wait after the last probe can be shorter */
addrconf_mod_rs_timer(idev, (idev->rs_probes ==
idev->cnf.rtr_solicits) ?
idev->cnf.rtr_solicit_delay :
- idev->cnf.rtr_solicit_interval);
+ idev->rs_interval);
} else {
/*
* Note: we do not support deprecated "all on-link"
@@ -3949,7 +3974,7 @@
send_mld = ifp->scope == IFA_LINK && ipv6_lonely_lladdr(ifp);
send_rs = send_mld &&
ipv6_accept_ra(ifp->idev) &&
- ifp->idev->cnf.rtr_solicits > 0 &&
+ ifp->idev->cnf.rtr_solicits != 0 &&
(dev->flags&IFF_LOOPBACK) == 0;
read_unlock_bh(&ifp->idev->lock);
@@ -3971,10 +3996,11 @@
write_lock_bh(&ifp->idev->lock);
spin_lock(&ifp->lock);
+ ifp->idev->rs_interval = rfc3315_s14_backoff_init(
+ ifp->idev->cnf.rtr_solicit_interval);
ifp->idev->rs_probes = 1;
ifp->idev->if_flags |= IF_RS_SENT;
- addrconf_mod_rs_timer(ifp->idev,
- ifp->idev->cnf.rtr_solicit_interval);
+ addrconf_mod_rs_timer(ifp->idev, ifp->idev->rs_interval);
spin_unlock(&ifp->lock);
write_unlock_bh(&ifp->idev->lock);
}
@@ -4891,6 +4917,8 @@
array[DEVCONF_RTR_SOLICITS] = cnf->rtr_solicits;
array[DEVCONF_RTR_SOLICIT_INTERVAL] =
jiffies_to_msecs(cnf->rtr_solicit_interval);
+ array[DEVCONF_RTR_SOLICIT_MAX_INTERVAL] =
+ jiffies_to_msecs(cnf->rtr_solicit_max_interval);
array[DEVCONF_RTR_SOLICIT_DELAY] =
jiffies_to_msecs(cnf->rtr_solicit_delay);
array[DEVCONF_FORCE_MLD_VERSION] = cnf->force_mld_version;
@@ -5099,7 +5127,7 @@
return -EINVAL;
if (!ipv6_accept_ra(idev))
return -EINVAL;
- if (idev->cnf.rtr_solicits <= 0)
+ if (idev->cnf.rtr_solicits == 0)
return -EINVAL;
write_lock_bh(&idev->lock);
@@ -5128,8 +5156,10 @@
if (update_rs) {
idev->if_flags |= IF_RS_SENT;
+ idev->rs_interval = rfc3315_s14_backoff_init(
+ idev->cnf.rtr_solicit_interval);
idev->rs_probes = 1;
- addrconf_mod_rs_timer(idev, idev->cnf.rtr_solicit_interval);
+ addrconf_mod_rs_timer(idev, idev->rs_interval);
}
/* Well, that's kinda nasty ... */
@@ -5778,6 +5808,13 @@
.proc_handler = proc_dointvec_jiffies,
},
{
+ .procname = "router_solicitation_max_interval",
+ .data = &ipv6_devconf.rtr_solicit_max_interval,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_jiffies,
+ },
+ {
.procname = "router_solicitation_delay",
.data = &ipv6_devconf.rtr_solicit_delay,
.maxlen = sizeof(int),
