[PATCH] ipv6 addrconf: implement RFC7559 router solicitation backoff

[PATCH] ipv6 addrconf: implement RFC7559 router solicitation backoff

[Maciej Żenczykowski]

From: Maciej Żenczykowski <maze@google.com>

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>
---
 include/linux/ipv6.h      |  1 +
 include/net/addrconf.h    |  3 ++-
 include/net/if_inet6.h    |  1 +
 include/uapi/linux/ipv6.h |  1 +
 net/ipv6/addrconf.c       | 51 ++++++++++++++++++++++++++++++++++++++++-------
 5 files changed, 49 insertions(+), 8 deletions(-)

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index c6dbcd84a2c7..7e9a789be5e0 100644
--- 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 9826d3a9464c..f2d072787947 100644
--- 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 1c8b6820b694..515352c6280a 100644
--- 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 395876060f50..8c2772340c3f 100644
--- 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 2f1f5d439788..49bee9bc5ff3 100644
--- 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 ... */
@@ -5778,6 +5808,13 @@ static const struct ctl_table addrconf_sysctl[] = {
 		.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),
-- 
2.8.0.rc3.226.g39d4020

Re: [PATCH] ipv6 addrconf: implement RFC7559 router solicitation backoff

[Hannes Frederic Sowa]

Hello,

On Wed, Sep 28, 2016, at 08:57, Maciej Żenczykowski wrote:
> From: Maciej Żenczykowski <maze@google.com>
> 
> 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>
> ---
>  include/linux/ipv6.h      |  1 +
>  include/net/addrconf.h    |  3 ++-
>  include/net/if_inet6.h    |  1 +
>  include/uapi/linux/ipv6.h |  1 +
>  net/ipv6/addrconf.c       | 51
>  ++++++++++++++++++++++++++++++++++++++++-------
>  5 files changed, 49 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
> index c6dbcd84a2c7..7e9a789be5e0 100644
> --- 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 9826d3a9464c..f2d072787947 100644
> --- 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 1c8b6820b694..515352c6280a 100644
> --- 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 395876060f50..8c2772340c3f 100644
> --- 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 2f1f5d439788..49bee9bc5ff3 100644
> --- 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);

Could you use msecs_to_jiffies here to make the units more clear like I
proposed in the last mail? Or is there a reason not to?

Bye,
Hannes

Re: [PATCH] ipv6 addrconf: implement RFC7559 router solicitation backoff

[Maciej Żenczykowski]

I'm not sure what line you're referring to.

There are *no* outright jiffies or msecs in this patch, with the
exception of the (3600*HZ) line which is already obvious enough.

The 900000 200001 1900000 1000000 constants are not jiffies nor
miliseconds, they're simply numbers, such that 900000/1000000 = 0.9
and 200001/1000000 =~ 0.2 (the +1 is to deal with 0) and
1900000/1000000 = 1.9

Re: [PATCH] ipv6 addrconf: implement RFC7559 router solicitation backoff

[Erik Kline]

Passes my local unittest for this behaviour.

Acked-by: Erik Kline <ek@google.com>

Re: [PATCH] ipv6 addrconf: implement RFC7559 router solicitation backoff

[David Miller]

From: Maciej Żenczykowski <zenczykowski@gmail.com>
Date: Tue, 27 Sep 2016 23:57:58 -0700

> From: Maciej Żenczykowski <maze@google.com>
> 
> 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>

Applied to net-next, thanks.

Re: [PATCH 5/7] ipv6 addrconf: implement RFC7559 router solicitation backoff

[Maciej Żenczykowski]

Ok, so that seems to have all sorts of __divdi3 or __aeabi_ldivmod
undefined errors on 32-bit platforms (ie. arm/m68k/i386).

[PATCH] ipv6 addrconf: implement RFC7559 router solicitation backoff

[Maciej Żenczykowski]

From: Maciej Żenczykowski <maze@google.com>

This implements:
  https://tools.ietf.org/html/rfc7559

Backoff is performed according to RFC3315 section 14:
  https://tools.ietf.org/html/rfc3315#section-14

Signed-off-by: Maciej Żenczykowski <maze@google.com>
---
 include/net/if_inet6.h |  1 +
 net/ipv6/addrconf.c    | 31 +++++++++++++++++++++++++++----
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index 1c8b6820b694..515352c6280a 100644
--- 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/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 255be34cdbce..6384a1cde056 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -112,6 +112,24 @@ static inline u32 cstamp_delta(unsigned long cstamp)
 	return (cstamp - INITIAL_JIFFIES) * 100UL / HZ;
 }
 
+static inline s32 rfc3315_s14_backoff_init(s32 initial)
+{
+	u32 r = (9 << 20) / 10 + (prandom_u32() % ((2 << 20) / 10 + 1));
+	s32 v = initial * (u64)r >> 20;       /* ~ multiply by 0.9 .. 1.1 */
+	return v;
+}
+
+static inline s32 rfc3315_s14_backoff_update(s32 cur, s32 ceiling)
+{
+	u32 r = (19 << 20) / 10 + (prandom_u32() % ((2 << 20) / 10 + 1));
+	s32 v = cur * (u64)r >> 20;           /* ~ multiply by 1.9 .. 2.1 */
+	if (v > ceiling) {
+		r -= 1 << 20;
+		v = ceiling * (u64)r >> 20;   /* ~ multiply by 0.9 .. 1.1 */
+	}
+	return v;
+}
+
 #ifdef CONFIG_SYSCTL
 static int addrconf_sysctl_register(struct inet6_dev *idev);
 static void addrconf_sysctl_unregister(struct inet6_dev *idev);
@@ -3698,11 +3716,13 @@ 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"
@@ -3973,10 +3993,11 @@ 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);
 	}
@@ -5132,8 +5153,10 @@ 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 ... */
-- 
2.8.0.rc3.226.g39d4020

Re: [PATCH] ipv6 addrconf: implement RFC7559 router solicitation backoff

[David Miller]

Please do not do this.

When you need to repsin a patch in a patch series to fix
or otherwise resolve something, you must make a fresh
resubmission of the entire patch series.

You also must properly mark the resubmission with a
proper indication that this is a new version of the
patch series by saying, for example, "[PATCH v2 ..."
in the Subject lines.

Thanks.