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/include/linux/ipv6.h b/include/linux/ipv6.h
index c6dbcd84a2c71ce43c9821e833ca800b5781f7ff..7e9a789be5e0df0198fbebcded35f1d90bc8a650 100644 (file)
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -18,6 +18,7 @@ struct ipv6_devconf {
        __s32           dad_transmits;
        __s32           rtr_solicits;
        __s32           rtr_solicit_interval;
+       __s32           rtr_solicit_max_interval;
        __s32           rtr_solicit_delay;
        __s32           force_mld_version;
        __s32           mldv1_unsolicited_report_interval;

diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 9826d3a9464c6f7a5d1dc1264af64dcb6c522fdf..f2d0727879472451e0c2815fc68f90b66a4c388c 100644 (file)
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -1,8 +1,9 @@
 #ifndef _ADDRCONF_H
 #define _ADDRCONF_H
 
-#define MAX_RTR_SOLICITATIONS          3
+#define MAX_RTR_SOLICITATIONS          -1              /* unlimited */
 #define RTR_SOLICITATION_INTERVAL      (4*HZ)
+#define RTR_SOLICITATION_MAX_INTERVAL  (3600*HZ)       /* 1 hour */
 
 #define MIN_VALID_LIFETIME             (2*3600)        /* 2 hours */
 

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index 1c8b6820b69476f7247baac12183a6f5f5fe2275..515352c6280a45c6b1783ae4e10760b729b917d0 100644 (file)
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -201,6 +201,7 @@ struct inet6_dev {
        struct ipv6_devstat     stats;
 
        struct timer_list       rs_timer;
+       __s32                   rs_interval;    /* in jiffies */
        __u8                    rs_probes;
 
        __u8                    addr_gen_mode;

diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index 395876060f5087983cfae103b8ed8c16c30bde50..8c2772340c3f1ced21c54d5178365dc6ab973e0f 100644 (file)
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -177,6 +177,7 @@ enum {
        DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
        DEVCONF_DROP_UNSOLICITED_NA,
        DEVCONF_KEEP_ADDR_ON_DOWN,
+       DEVCONF_RTR_SOLICIT_MAX_INTERVAL,
        DEVCONF_MAX
 };
 

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 35d4baa55c9d0267dfb25b84fc31e0bfd0f7177d..87183983724dfeb7e9984d1868e2098b41211d8c 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -112,6 +112,27 @@ static inline u32 cstamp_delta(unsigned long cstamp)
        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 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
        .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 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
        .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 @@ static void addrconf_rs_timer(unsigned long data)
        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 @@ static void addrconf_rs_timer(unsigned long data)
                        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 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
        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 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
 
                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 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
        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 @@ static int inet6_set_iftoken(struct inet6_dev *idev, struct in6_addr *token)
                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 @@ update_lft:
 
        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 ... */
@@ -5777,6 +5807,13 @@ static const struct ctl_table addrconf_sysctl[] = {
                .mode           = 0644,
                .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,