net: change accept_ra_min_rtr_lft to affect all RA lifetimes

accept_ra_min_rtr_lft only considered the lifetime of the default route and discarded entire RAs accordingly.

This change renames accept_ra_min_rtr_lft to accept_ra_min_lft, and applies the value to individual RA sections; in particular, router lifetime, PIO preferred lifetime, and RIO lifetime. If any of those lifetimes are lower than the configured value, the specific RA section is ignored.

In order for the sysctl to be useful to Android, it should really apply to all lifetimes in the RA, since that is what determines the minimum frequency at which RAs must be processed by the kernel. Android uses hardware offloads to drop RAs for a fraction of the minimum of all lifetimes present in the RA (some networks have very frequent RAs (5s) with high lifetimes (2h)). Despite this, we have encountered networks that set the router lifetime to 30s which results in very frequent CPU wakeups. Instead of disabling IPv6 (and dropping IPv6 ethertype in the WiFi firmware) entirely on such networks, it seems better to ignore the misconfigured routers while still processing RAs from other IPv6 routers on the same network (i.e. to support IoT applications).

The previous implementation dropped the entire RA based on router lifetime. This turned out to be hard to expand to the other lifetimes present in the RA in a consistent manner; dropping the entire RA based on RIO/PIO lifetimes would essentially require parsing the whole thing twice.

Fixes 1671bcfd76fd ("net: add sysctl accept_ra_min_rtr_lft")

Cc Maciej Żenczykowski <[email protected]>

Cc Lorenzo Colitti <[email protected]>

Cc David Ahern <[email protected]>

Signed-off-by Patrick Rohr <[email protected]>

---
 Documentation/networking/ip-sysctl.rst |  8 ++++----
 include/linux/ipv6.h                   |  2 +-
 include/uapi/linux/ipv6.h              |  2 +-
 net/ipv6/addrconf.c                    | 14 ++++++++-----
 net/ipv6/ndisc.c                       | 27 +++++++++++---------------
 5 files changed, 26 insertions(+), 27 deletions(-)

Documentation/networking/ip-sysctl.rst +0 -0

index 37603ad6126b..a66054d0763a 100644

Quoted 45 lines · Patrick Rohr

accept_ra_min_rtr_lft only considered the lifetime of the default route and discarded entire RAs accordingly.

This change renames accept_ra_min_rtr_lft to accept_ra_min_lft, and applies the value to individual RA sections; in particular, router lifetime, PIO preferred lifetime, and RIO lifetime. If any of those lifetimes are lower than the configured value, the specific RA section is ignored.

In order for the sysctl to be useful to Android, it should really apply to all lifetimes in the RA, since that is what determines the minimum frequency at which RAs must be processed by the kernel. Android uses hardware offloads to drop RAs for a fraction of the minimum of all lifetimes present in the RA (some networks have very frequent RAs (5s) with high lifetimes (2h)). Despite this, we have encountered networks that set the router lifetime to 30s which results in very frequent CPU wakeups. Instead of disabling IPv6 (and dropping IPv6 ethertype in the WiFi firmware) entirely on such networks, it seems better to ignore the misconfigured routers while still processing RAs from other IPv6 routers on the same network (i.e. to support IoT applications).

The previous implementation dropped the entire RA based on router lifetime. This turned out to be hard to expand to the other lifetimes present in the RA in a consistent manner; dropping the entire RA based on RIO/PIO lifetimes would essentially require parsing the whole thing twice.

Fixes 1671bcfd76fd ("net: add sysctl accept_ra_min_rtr_lft")

Cc Maciej Żenczykowski <[email protected]>

Cc Lorenzo Colitti <[email protected]>

Cc David Ahern <[email protected]>

Signed-off-by Patrick Rohr <[email protected]>

---
 Documentation/networking/ip-sysctl.rst |  8 ++++----
 include/linux/ipv6.h                   |  2 +-
 include/uapi/linux/ipv6.h              |  2 +-
 net/ipv6/addrconf.c                    | 14 ++++++++-----
 net/ipv6/ndisc.c                       | 27 +++++++++++---------------
 5 files changed, 26 insertions(+), 27 deletions(-)

Documentation/networking/ip-sysctl.rst +0 -0

index 37603ad6126b..a66054d0763a 100644

Documentation/networking/ip-sysctl.rst accept_ra_min_hop_limit - INTEGER · line 2292

Quoted 7 lines

Documentation/networking/ip-sysctl.rst +2 -2

@@ -2288,11 +2288,11 @@ accept_ra_min_hop_limit - INTEGER
 
      Default: 1
 
-accept_ra_min_rtr_lft - INTEGER
-     Minimum acceptable router lifetime in Router Advertisement.
+accept_ra_min_lft - INTEGER
+     Minimum acceptable lifetime value in Router Advertisement.

Hi Patrick, all,

I am concerned about UAPI-breakage aspects of changing the name of a sysctl. Can we discuss that?

Quoted 57 lines · Simon Horman

Quoted 45 lines · Patrick Rohr

accept_ra_min_rtr_lft only considered the lifetime of the default route and discarded entire RAs accordingly.

This change renames accept_ra_min_rtr_lft to accept_ra_min_lft, and applies the value to individual RA sections; in particular, router lifetime, PIO preferred lifetime, and RIO lifetime. If any of those lifetimes are lower than the configured value, the specific RA section is ignored.

In order for the sysctl to be useful to Android, it should really apply to all lifetimes in the RA, since that is what determines the minimum frequency at which RAs must be processed by the kernel. Android uses hardware offloads to drop RAs for a fraction of the minimum of all lifetimes present in the RA (some networks have very frequent RAs (5s) with high lifetimes (2h)). Despite this, we have encountered networks that set the router lifetime to 30s which results in very frequent CPU wakeups. Instead of disabling IPv6 (and dropping IPv6 ethertype in the WiFi firmware) entirely on such networks, it seems better to ignore the misconfigured routers while still processing RAs from other IPv6 routers on the same network (i.e. to support IoT applications).

The previous implementation dropped the entire RA based on router lifetime. This turned out to be hard to expand to the other lifetimes present in the RA in a consistent manner; dropping the entire RA based on RIO/PIO lifetimes would essentially require parsing the whole thing twice.

Fixes 1671bcfd76fd ("net: add sysctl accept_ra_min_rtr_lft")

Cc Maciej Żenczykowski <[email protected]>

Cc Lorenzo Colitti <[email protected]>

Cc David Ahern <[email protected]>

Signed-off-by Patrick Rohr <[email protected]>

---
 Documentation/networking/ip-sysctl.rst |  8 ++++----
 include/linux/ipv6.h                   |  2 +-
 include/uapi/linux/ipv6.h              |  2 +-
 net/ipv6/addrconf.c                    | 14 ++++++++-----
 net/ipv6/ndisc.c                       | 27 +++++++++++---------------
 5 files changed, 26 insertions(+), 27 deletions(-)

Documentation/networking/ip-sysctl.rst +0 -0

index 37603ad6126b..a66054d0763a 100644

Documentation/networking/ip-sysctl.rst accept_ra_min_hop_limit - INTEGER · line 2292

Quoted 7 lines

Documentation/networking/ip-sysctl.rst +2 -2

@@ -2288,11 +2288,11 @@ accept_ra_min_hop_limit - INTEGER
 
      Default: 1
 
-accept_ra_min_rtr_lft - INTEGER
-     Minimum acceptable router lifetime in Router Advertisement.
+accept_ra_min_lft - INTEGER
+     Minimum acceptable lifetime value in Router Advertisement.

Hi Patrick, all,

Quoted 2 lines

I am concerned about UAPI-breakage aspects of changing the name of a sysctl. Can we discuss that?

This isn't uapi yet as it (the old name) was only merged a few days ago.

accept_ra_min_rtr_lft only considered the lifetime of the default route and discarded entire RAs accordingly.

This change renames accept_ra_min_rtr_lft to accept_ra_min_lft, and applies the value to individual RA sections; in particular, router lifetime, PIO preferred lifetime, and RIO lifetime. If any of those lifetimes are lower than the configured value, the specific RA section is ignored.

In order for the sysctl to be useful to Android, it should really apply to all lifetimes in the RA, since that is what determines the minimum frequency at which RAs must be processed by the kernel. Android uses hardware offloads to drop RAs for a fraction of the minimum of all lifetimes present in the RA (some networks have very frequent RAs (5s) with high lifetimes (2h)). Despite this, we have encountered networks that set the router lifetime to 30s which results in very frequent CPU wakeups. Instead of disabling IPv6 (and dropping IPv6 ethertype in the WiFi firmware) entirely on such networks, it seems better to ignore the misconfigured routers while still processing RAs from other IPv6 routers on the same network (i.e. to support IoT applications).

The previous implementation dropped the entire RA based on router lifetime. This turned out to be hard to expand to the other lifetimes present in the RA in a consistent manner; dropping the entire RA based on RIO/PIO lifetimes would essentially require parsing the whole thing twice.

Fixes 1671bcfd76fd ("net: add sysctl accept_ra_min_rtr_lft")

Cc Maciej Żenczykowski <[email protected]>

Cc Lorenzo Colitti <[email protected]>

Cc David Ahern <[email protected]>

Signed-off-by Patrick Rohr <[email protected]>

---
 Documentation/networking/ip-sysctl.rst |  8 ++++----
 include/linux/ipv6.h                   |  2 +-
 include/uapi/linux/ipv6.h              |  2 +-
 net/ipv6/addrconf.c                    | 14 ++++++++-----
 net/ipv6/ndisc.c                       | 27 +++++++++++---------------
 5 files changed, 26 insertions(+), 27 deletions(-)

Documentation/networking/ip-sysctl.rst +4 -4

index 37603ad6126b..a66054d0763a 100644
@@ -2288,11 +2288,11 @@ accept_ra_min_hop_limit - INTEGER
 
        Default: 1
 
-accept_ra_min_rtr_lft - INTEGER
-       Minimum acceptable router lifetime in Router Advertisement.
+accept_ra_min_lft - INTEGER
+       Minimum acceptable lifetime value in Router Advertisement.
 
-       RAs with a router lifetime less than this value shall be
-       ignored. RAs with a router lifetime of 0 are unaffected.
+       RA sections with a lifetime less than this value shall be
+       ignored. Zero lifetimes stay unaffected.
 
        Default: 0
 

include/linux/ipv6.h +1 -1

index 0295b47c10a3..5883551b1ee8 100644
@@ -33,7 +33,7 @@ struct ipv6_devconf {
        __s32           accept_ra_defrtr;
        __u32           ra_defrtr_metric;
        __s32           accept_ra_min_hop_limit;
-       __s32           accept_ra_min_rtr_lft;
+       __s32           accept_ra_min_lft;
        __s32           accept_ra_pinfo;
        __s32           ignore_routes_with_linkdown;
 #ifdef CONFIG_IPV6_ROUTER_PREF

include/uapi/linux/ipv6.h +1 -1

index 8b6bcbf6ed4a..cf592d7b630f 100644
@@ -198,7 +198,7 @@ enum {
        DEVCONF_IOAM6_ID_WIDE,
        DEVCONF_NDISC_EVICT_NOCARRIER,
        DEVCONF_ACCEPT_UNTRACKED_NA,
-       DEVCONF_ACCEPT_RA_MIN_RTR_LFT,
+       DEVCONF_ACCEPT_RA_MIN_LFT,
        DEVCONF_MAX
 };
 

net/ipv6/addrconf.c +9 -5

index 19eb4b3d26ea..7f7d2b677711 100644
@@ -202,7 +202,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
        .ra_defrtr_metric       = IP6_RT_PRIO_USER,
        .accept_ra_from_local   = 0,
        .accept_ra_min_hop_limit= 1,
-       .accept_ra_min_rtr_lft  = 0,
+       .accept_ra_min_lft      = 0,
        .accept_ra_pinfo        = 1,
 #ifdef CONFIG_IPV6_ROUTER_PREF
        .accept_ra_rtr_pref     = 1,

@@ -263,7 +263,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
        .ra_defrtr_metric       = IP6_RT_PRIO_USER,
        .accept_ra_from_local   = 0,
        .accept_ra_min_hop_limit= 1,
-       .accept_ra_min_rtr_lft  = 0,
+       .accept_ra_min_lft      = 0,
        .accept_ra_pinfo        = 1,
 #ifdef CONFIG_IPV6_ROUTER_PREF
        .accept_ra_rtr_pref     = 1,

@@ -2727,6 +2727,10 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len, bool sllao)
                return;
        }
 
+       if (valid_lft != 0 && valid_lft < in6_dev->cnf.accept_ra_min_lft) {
+               return;
+       }
+
        /*
         *      Two things going on here:
         *      1) Add routes for on-link prefixes

@@ -5598,7 +5602,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
        array[DEVCONF_IOAM6_ID_WIDE] = cnf->ioam6_id_wide;
        array[DEVCONF_NDISC_EVICT_NOCARRIER] = cnf->ndisc_evict_nocarrier;
        array[DEVCONF_ACCEPT_UNTRACKED_NA] = cnf->accept_untracked_na;
-       array[DEVCONF_ACCEPT_RA_MIN_RTR_LFT] = cnf->accept_ra_min_rtr_lft;
+       array[DEVCONF_ACCEPT_RA_MIN_LFT] = cnf->accept_ra_min_lft;
 }
 
 static inline size_t inet6_ifla6_size(void)

@@ -6793,8 +6797,8 @@ static const struct ctl_table addrconf_sysctl[] = {
                .proc_handler   = proc_dointvec,
        },
        {
-               .procname       = "accept_ra_min_rtr_lft",
-               .data           = &ipv6_devconf.accept_ra_min_rtr_lft,
+               .procname       = "accept_ra_min_lft",
+               .data           = &ipv6_devconf.accept_ra_min_lft,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,

net/ipv6/ndisc.c +11 -17

index 29ddad1c1a2f..eeb60888187f 100644
@@ -1280,8 +1280,6 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
        if (!ndisc_parse_options(skb->dev, opt, optlen, &ndopts))
                return SKB_DROP_REASON_IPV6_NDISC_BAD_OPTIONS;
 
-       lifetime = ntohs(ra_msg->icmph.icmp6_rt_lifetime);
-
        if (!ipv6_accept_ra(in6_dev)) {
                ND_PRINTK(2, info,
                          "RA: %s, did not accept ra for dev: %s\n",

@@ -1289,13 +1287,6 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
                goto skip_linkparms;
        }
 
-       if (lifetime != 0 && lifetime < in6_dev->cnf.accept_ra_min_rtr_lft) {
-               ND_PRINTK(2, info,
-                         "RA: router lifetime (%ds) is too short: %s\n",
-                         lifetime, skb->dev->name);
-               goto skip_linkparms;
-       }
-
 #ifdef CONFIG_IPV6_NDISC_NODETYPE
        /* skip link-specific parameters from interior routers */
        if (skb->ndisc_nodetype == NDISC_NODETYPE_NODEFAULT) {

@@ -1336,6 +1327,14 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
                goto skip_defrtr;
        }
 
+       lifetime = ntohs(ra_msg->icmph.icmp6_rt_lifetime);
+       if (lifetime != 0 && lifetime < in6_dev->cnf.accept_ra_min_lft) {
+               ND_PRINTK(2, info,
+                         "RA: router lifetime (%ds) is too short: %s\n",
+                         lifetime, skb->dev->name);
+               goto skip_defrtr;
+       }
+
        /* Do not accept RA with source-addr found on local machine unless
         * accept_ra_from_local is set to true.
         */

@@ -1499,13 +1498,6 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
                goto out;
        }
 
-       if (lifetime != 0 && lifetime < in6_dev->cnf.accept_ra_min_rtr_lft) {
-               ND_PRINTK(2, info,
-                         "RA: router lifetime (%ds) is too short: %s\n",
-                         lifetime, skb->dev->name);
-               goto out;
-       }
-
 #ifdef CONFIG_IPV6_ROUTE_INFO
        if (!in6_dev->cnf.accept_ra_from_local &&
            ipv6_chk_addr(dev_net(in6_dev->dev), &ipv6_hdr(skb)->saddr,

@@ -1530,6 +1522,9 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
                        if (ri->prefix_len == 0 &&
                            !in6_dev->cnf.accept_ra_defrtr)
                                continue;
+                       if (ri->lifetime != 0 &&
+                           ntohl(ri->lifetime) < in6_dev->cnf.accept_ra_min_lft)
+                               continue;
                        if (ri->prefix_len < in6_dev->cnf.accept_ra_rt_info_min_plen)
                                continue;
                        if (ri->prefix_len > in6_dev->cnf.accept_ra_rt_info_max_plen)
--

2.41.0.487.g6d72f3e995-goog

accept_ra_min_rtr_lft only considered the lifetime of the default route and discarded entire RAs accordingly.

This change renames accept_ra_min_rtr_lft to accept_ra_min_lft, and applies the value to individual RA sections; in particular, router lifetime, PIO preferred lifetime, and RIO lifetime. If any of those lifetimes are lower than the configured value, the specific RA section is ignored.

In order for the sysctl to be useful to Android, it should really apply to all lifetimes in the RA, since that is what determines the minimum frequency at which RAs must be processed by the kernel. Android uses hardware offloads to drop RAs for a fraction of the minimum of all lifetimes present in the RA (some networks have very frequent RAs (5s) with high lifetimes (2h)). Despite this, we have encountered networks that set the router lifetime to 30s which results in very frequent CPU wakeups. Instead of disabling IPv6 (and dropping IPv6 ethertype in the WiFi firmware) entirely on such networks, it seems better to ignore the misconfigured routers while still processing RAs from other IPv6 routers on the same network (i.e. to support IoT applications).

The previous implementation dropped the entire RA based on router lifetime. This turned out to be hard to expand to the other lifetimes present in the RA in a consistent manner; dropping the entire RA based on RIO/PIO lifetimes would essentially require parsing the whole thing twice.

Fixes 1671bcfd76fd ("net: add sysctl accept_ra_min_rtr_lft")

Cc Maciej Żenczykowski <[email protected]>

Cc Lorenzo Colitti <[email protected]>

Cc David Ahern <[email protected]>

Signed-off-by Patrick Rohr <[email protected]>

---
 Documentation/networking/ip-sysctl.rst |  8 ++++----
 include/linux/ipv6.h                   |  2 +-
 include/uapi/linux/ipv6.h              |  2 +-
 net/ipv6/addrconf.c                    | 14 ++++++++-----
 net/ipv6/ndisc.c                       | 27 +++++++++++---------------
 5 files changed, 26 insertions(+), 27 deletions(-)