Re: [PATCH v2 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement.
> On Jan 19, 2021, at 8:22 PM, David Ahern wrote:
>
> On 1/19/21 3:17 PM, praveen chaudhary wrote:
For IPv4:
Config in etc/network/interfaces
```
auto eth0
iface eth0 inet dhcp
metric 4261413864
>>>
>>> how does that work for IPv4? Is the metric passed to the dhclient and it
>>> inserts the route with the given metric or is a dhclient script used to
>>> replace the route after insert?
>>>
>>>
>>
>> Yes, DHCP client picks config under “iface eth0 inet dhcp” line and if
>> metric is configured, then it adds the metric for all added routes.
>
> As I recall ifupdown{2} forks dhclient as a process to handle dhcp
> config, and I believe there is a script that handles adding the default
> route with metric. Meaning ... it is not comparable to an RA.
>
I hope, we both will agree that a fixed metric value on default route learned
via RA
restricts Network Administrators today. And such issues hinder the deployment
of IPv6 only networks. So if we agree that in future we may need to allow a
configurable value for metric then this fix makes good sense.
BTW, kindly let me know if there is a better way to configure this metric. I
think,
sysctl is the only way.
>>
>> Thanks a lot again for spending time for this Review,
>> This feature will help SONiC OS [and others Linux flavors] for better IPv6
>> support, so thanks again.
>
> I think SONiC is an abomination, so that is definitely not the
> motivation for my reviews. :-)
>
Trying to make things better day by day. That is the only solace for Software
Engineers :-).
I really appreciate for your time to review this patch. Cheers.
Re: [PATCH v2 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement.
On 1/19/21 3:17 PM, praveen chaudhary wrote:
>>>
>>> For IPv4:
>>>
>>>
>>> Config in etc/network/interfaces
>>>
>>> ```
>>> auto eth0
>>> iface eth0 inet dhcp
>>>metric 4261413864
>>
>> how does that work for IPv4? Is the metric passed to the dhclient and it
>> inserts the route with the given metric or is a dhclient script used to
>> replace the route after insert?
>>
>>
>
> Yes, DHCP client picks config under “iface eth0 inet dhcp” line and if metric
> is configured, then it adds the metric for all added routes.
As I recall ifupdown{2} forks dhclient as a process to handle dhcp
config, and I believe there is a script that handles adding the default
route with metric. Meaning ... it is not comparable to an RA.
>
> Thanks a lot again for spending time for this Review,
> This feature will help SONiC OS [and others Linux flavors] for better IPv6
> support, so thanks again.
I think SONiC is an abomination, so that is definitely not the
motivation for my reviews. :-)
Re: [PATCH v2 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement.
> On Jan 16, 2021, at 9:13 AM, David Ahern wrote:
>
> On 1/15/21 1:02 AM, Praveen Chaudhary wrote:
>> For IPv4, default route is learned via DHCPv4 and user is allowed to change
>> metric using config etc/network/interfaces. But for IPv6, default route can
>> be learned via RA, for which, currently a fixed metric value 1024 is used.
>>
>> Ideally, user should be able to configure metric on default route for IPv6
>> similar to IPv4. This fix adds sysctl for the same.
>>
>> Signed-off-by: Praveen Chaudhary
>> Signed-off-by: Zhenggen Xu
>>
>> Changes in v1.
>> ---
>
> your trying to be too fancy in the log messages; everything after this
> first '---' is dropped. Just Remove all of the '---' lines and '```' tags.
>
Removed all ‘—‘ and ‘```’ in v3.
>> 1.) Correct the call to rt6_add_dflt_router.
>> ---
>>
>> Changes in v2.
>> [Refer: lkml.org/lkml/2021/1/14/1400]
>> ---
>> 1.) Replace accept_ra_defrtr_metric to ra_defrtr_metric.
>> 2.) Change Type to __u32 instead of __s32.
>> 3.) Change description in Documentation/networking/ip-sysctl.rst.
>> 4.) Use proc_douintvec instead of proc_dointvec.
>> 5.) Code style in ndisc_router_discovery().
>> 6.) Change Type to u32 instead of unsigned int.
>> ---
>>
>> Logs:
>>
>> For IPv4:
>>
>>
>> Config in etc/network/interfaces
>>
>> ```
>> auto eth0
>> iface eth0 inet dhcp
>>metric 4261413864
>
> how does that work for IPv4? Is the metric passed to the dhclient and it
> inserts the route with the given metric or is a dhclient script used to
> replace the route after insert?
>
>
Yes, DHCP client picks config under “iface eth0 inet dhcp” line and if metric
is configured, then it adds the metric for all added routes.
>> diff --git a/Documentation/networking/ip-sysctl.rst
>> b/Documentation/networking/ip-sysctl.rst
>> index dd2b12a32b73..c4b8d4b8d213 100644
>> --- a/Documentation/networking/ip-sysctl.rst
>> +++ b/Documentation/networking/ip-sysctl.rst
>> @@ -1871,6 +1871,18 @@ accept_ra_defrtr - BOOLEAN
>> - enabled if accept_ra is enabled.
>> - disabled if accept_ra is disabled.
>>
>> +ra_defrtr_metric - INTEGER
>> +Route metric for default route learned in Router Advertisement. This
>> value
>> +will be assigned as metric for the default route learned via IPv6 Router
>> +Advertisement. Takes affect only if accept_ra_defrtr' is enabled.
>
> stray ' after accept_ra_defrtr
>
Removed.
>> +
>> +Possible values are:
>> +0:
>> +default value will be used for route metric
>> +i.e. IP6_RT_PRIO_USER 1024.
>> +1 to 0x:
>> +current value will be used for route metric.
>> +
>> accept_ra_from_local - BOOLEAN
>> Accept RA with source-address that is found on local machine
>> if the RA is otherwise proper and able to be accepted.
>
>
>
>> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
>> index eff2cacd5209..b13d3213e58f 100644
>> --- a/net/ipv6/addrconf.c
>> +++ b/net/ipv6/addrconf.c
>> @@ -205,6 +205,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
>> .max_desync_factor = MAX_DESYNC_FACTOR,
>> .max_addresses = IPV6_MAX_ADDRESSES,
>> .accept_ra_defrtr = 1,
>> +.ra_defrtr_metric = 0,
>
> make the the '=' align column wise with the existing entries; seems like
> your new line is missing a tab
Fixed.
>
>> .accept_ra_from_local = 0,
>> .accept_ra_min_hop_limit= 1,
>> .accept_ra_pinfo= 1,
>> @@ -260,6 +261,7 @@ static struct ipv6_devconf ipv6_devconf_dflt
>> __read_mostly = {
>> .max_desync_factor = MAX_DESYNC_FACTOR,
>> .max_addresses = IPV6_MAX_ADDRESSES,
>> .accept_ra_defrtr = 1,
>> +.ra_defrtr_metric = 0,
>
> same here
Fixed.
>
>> .accept_ra_from_local = 0,
>> .accept_ra_min_hop_limit= 1,
>> .accept_ra_pinfo= 1,
>> @@ -5475,6 +5477,7 @@ static inline void ipv6_store_devconf(struct
>> ipv6_devconf *cnf,
>> array[DEVCONF_MAX_DESYNC_FACTOR] = cnf->max_desync_factor;
>> array[DEVCONF_MAX_ADDRESSES] = cnf->max_addresses;
>> array[DEVCONF_ACCEPT_RA_DEFRTR] = cnf->accept_ra_defrtr;
>> +array[DEVCONF_RA_DEFRTR_METRIC] = cnf->ra_defrtr_metric;
>> array[DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT] = cnf->accept_ra_min_hop_limit;
>> array[DEVCONF_ACCEPT_RA_PINFO] = cnf->accept_ra_pinfo;
>> #ifdef CONFIG_IPV6_ROUTER_PREF
>> @@ -6667,6 +6670,13 @@ static const struct ctl_table addrconf_sysctl[] = {
>> .mode = 0644,
>> .proc_handler = proc_dointvec,
>> },
>> +{
>> +.procname = "ra_defrtr_metric",
>> +.data = _devconf.ra_defrtr_metric,
>> +.maxlen =
Re: [PATCH v2 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement.
On 1/15/21 1:02 AM, Praveen Chaudhary wrote:
> For IPv4, default route is learned via DHCPv4 and user is allowed to change
> metric using config etc/network/interfaces. But for IPv6, default route can
> be learned via RA, for which, currently a fixed metric value 1024 is used.
>
> Ideally, user should be able to configure metric on default route for IPv6
> similar to IPv4. This fix adds sysctl for the same.
>
> Signed-off-by: Praveen Chaudhary
> Signed-off-by: Zhenggen Xu
>
> Changes in v1.
> ---
your trying to be too fancy in the log messages; everything after this
first '---' is dropped. Just Remove all of the '---' lines and '```' tags.
> 1.) Correct the call to rt6_add_dflt_router.
> ---
>
> Changes in v2.
> [Refer: lkml.org/lkml/2021/1/14/1400]
> ---
> 1.) Replace accept_ra_defrtr_metric to ra_defrtr_metric.
> 2.) Change Type to __u32 instead of __s32.
> 3.) Change description in Documentation/networking/ip-sysctl.rst.
> 4.) Use proc_douintvec instead of proc_dointvec.
> 5.) Code style in ndisc_router_discovery().
> 6.) Change Type to u32 instead of unsigned int.
> ---
>
> Logs:
>
> For IPv4:
>
>
> Config in etc/network/interfaces
>
> ```
> auto eth0
> iface eth0 inet dhcp
> metric 4261413864
how does that work for IPv4? Is the metric passed to the dhclient and it
inserts the route with the given metric or is a dhclient script used to
replace the route after insert?
> diff --git a/Documentation/networking/ip-sysctl.rst
> b/Documentation/networking/ip-sysctl.rst
> index dd2b12a32b73..c4b8d4b8d213 100644
> --- a/Documentation/networking/ip-sysctl.rst
> +++ b/Documentation/networking/ip-sysctl.rst
> @@ -1871,6 +1871,18 @@ accept_ra_defrtr - BOOLEAN
> - enabled if accept_ra is enabled.
> - disabled if accept_ra is disabled.
>
> +ra_defrtr_metric - INTEGER
> + Route metric for default route learned in Router Advertisement. This
> value
> + will be assigned as metric for the default route learned via IPv6 Router
> + Advertisement. Takes affect only if accept_ra_defrtr' is enabled.
stray ' after accept_ra_defrtr
> +
> + Possible values are:
> + 0:
> + default value will be used for route metric
> + i.e. IP6_RT_PRIO_USER 1024.
> + 1 to 0x:
> + current value will be used for route metric.
> +
> accept_ra_from_local - BOOLEAN
> Accept RA with source-address that is found on local machine
> if the RA is otherwise proper and able to be accepted.
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index eff2cacd5209..b13d3213e58f 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -205,6 +205,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
> .max_desync_factor = MAX_DESYNC_FACTOR,
> .max_addresses = IPV6_MAX_ADDRESSES,
> .accept_ra_defrtr = 1,
> + .ra_defrtr_metric = 0,
make the the '=' align column wise with the existing entries; seems like
your new line is missing a tab
> .accept_ra_from_local = 0,
> .accept_ra_min_hop_limit= 1,
> .accept_ra_pinfo= 1,
> @@ -260,6 +261,7 @@ static struct ipv6_devconf ipv6_devconf_dflt
> __read_mostly = {
> .max_desync_factor = MAX_DESYNC_FACTOR,
> .max_addresses = IPV6_MAX_ADDRESSES,
> .accept_ra_defrtr = 1,
> + .ra_defrtr_metric = 0,
same here
> .accept_ra_from_local = 0,
> .accept_ra_min_hop_limit= 1,
> .accept_ra_pinfo= 1,
> @@ -5475,6 +5477,7 @@ static inline void ipv6_store_devconf(struct
> ipv6_devconf *cnf,
> array[DEVCONF_MAX_DESYNC_FACTOR] = cnf->max_desync_factor;
> array[DEVCONF_MAX_ADDRESSES] = cnf->max_addresses;
> array[DEVCONF_ACCEPT_RA_DEFRTR] = cnf->accept_ra_defrtr;
> + array[DEVCONF_RA_DEFRTR_METRIC] = cnf->ra_defrtr_metric;
> array[DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT] = cnf->accept_ra_min_hop_limit;
> array[DEVCONF_ACCEPT_RA_PINFO] = cnf->accept_ra_pinfo;
> #ifdef CONFIG_IPV6_ROUTER_PREF
> @@ -6667,6 +6670,13 @@ static const struct ctl_table addrconf_sysctl[] = {
> .mode = 0644,
> .proc_handler = proc_dointvec,
> },
> + {
> + .procname = "ra_defrtr_metric",
> + .data = _devconf.ra_defrtr_metric,
> + .maxlen = sizeof(u32),
> + .mode = 0644,
> + .proc_handler = proc_douintvec,
> + },
> {
> .procname = "accept_ra_min_hop_limit",
> .data = _devconf.accept_ra_min_hop_limit,
> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
> index 76717478f173..2bffed49f5c0 100644
> --- a/net/ipv6/ndisc.c
>
[PATCH v2 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement.
For IPv4, default route is learned via DHCPv4 and user is allowed to change metric using config etc/network/interfaces. But for IPv6, default route can be learned via RA, for which, currently a fixed metric value 1024 is used. Ideally, user should be able to configure metric on default route for IPv6 similar to IPv4. This fix adds sysctl for the same. Signed-off-by: Praveen Chaudhary Signed-off-by: Zhenggen Xu Changes in v1. --- 1.) Correct the call to rt6_add_dflt_router. --- Changes in v2. [Ref: lkml/2021/1/14/1400] --- 1.) Replace accept_ra_defrtr_metric to ra_defrtr_metric. 2.) Change Type to __u32 instead of __s32. 3.) Change description in Documentation/networking/ip-sysctl.rst. 4.) Use proc_douintvec instead of proc_dointvec. 5.) Code style in ndisc_router_discovery(). 6.) Change Type to u32 instead of unsigned int. --- Reported-by: kernel test robot Logs: For IPv4: Config in etc/network/interfaces ``` auto eth0 iface eth0 inet dhcp metric 4261413864 ``` IPv4 Kernel Route Table: ``` $ ip route list default via 172.21.47.1 dev eth0 metric 4261413864 ``` FRR Table, if a static route is configured. [In real scenario, it is useful to prefer BGP learned default route over DHCPv4 default route.] ``` Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF, I - IS-IS, B - BGP, P - PIM, E - EIGRP, N - NHRP, T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP, > - selected route, * - FIB route S>* 0.0.0.0/0 [20/0] is directly connected, eth0, 00:00:03 K 0.0.0.0/0 [254/1000] via 172.21.47.1, eth0, 6d08h51m ``` ***i.e. User can prefer Default Router learned via Routing Protocol in IPv4.*** ***Similar behavior is not possible for IPv6, without this fix.*** After fix [for IPv6]: ``` sudo sysctl -w net.ipv6.conf.eth0.net.ipv6.conf.eth0.ra_defrtr_metric=1996489705 ``` IP monitor: [When IPv6 RA is received] ``` default via fe80::xx16::feb3:ce8e dev eth0 proto ra metric 1996489705 pref high ``` Kernel IPv6 routing table ``` $ ip -6 route list default via fe80::be16:65ff:feb3:ce8e dev eth0 proto ra metric 1996489705 expires 21sec hoplimit 64 pref high ``` FRR Table, if a static route is configured. [In real scenario, it is useful to prefer BGP learned default route over IPv6 RA default route.] ``` Codes: K - kernel route, C - connected, S - static, R - RIPng, O - OSPFv3, I - IS-IS, B - BGP, N - NHRP, T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP, > - selected route, * - FIB route S>* ::/0 [20/0] is directly connected, eth0, 00:00:06 K ::/0 [119/1001] via fe80::xx16::feb3:ce8e, eth0, 6d07h43m ``` If the metric is changed later, the effect will be seen only when next IPv6 RA is received, because the default route must be fully controlled by RA msg. Below metric is changed from 1996489705 to 1996489704. ``` $ sudo sysctl -w net.ipv6.conf.eth0.ra_defrtr_metric=1996489704 net.ipv6.conf.eth0.ra_defrtr_metric = 1996489704 ``` IP monitor: [On next IPv6 RA msg, Kernel deletes prev route and installs new route with updated metric] ``` Deleted default via fe80::xx16::feb3:ce8e dev eth0 proto ra metric 1996489705 expires 3sec hoplimit 64 pref high default via fe80::xx16::feb3:ce8e dev eth0 proto ra metric 1996489704 pref high ``` --- Documentation/networking/ip-sysctl.rst | 12 include/linux/ipv6.h | 1 + include/net/ip6_route.h| 3 ++- include/uapi/linux/ipv6.h | 1 + include/uapi/linux/sysctl.h| 1 + net/ipv6/addrconf.c| 10 ++ net/ipv6/ndisc.c | 14 ++ net/ipv6/route.c | 5 +++-- 8 files changed, 40 insertions(+), 7 deletions(-) diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index dd2b12a32b73..c4b8d4b8d213 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -1871,6 +1871,18 @@ accept_ra_defrtr - BOOLEAN - enabled if accept_ra is enabled. - disabled if accept_ra is disabled.
Re: [PATCH v2 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement.
Hi Praveen,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on 139711f033f636cc78b6aaf7363252241b9698ef]
url:
https://github.com/0day-ci/linux/commits/Praveen-Chaudhary/Allow-user-to-set-metric-on-default-route-learned-via-Router-Advertisement/20210115-160758
base:139711f033f636cc78b6aaf7363252241b9698ef
config: nds32-randconfig-r015-20210115 (attached as .config)
compiler: nds32le-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
wget
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O
~/bin/make.cross
chmod +x ~/bin/make.cross
#
https://github.com/0day-ci/linux/commit/35f232fe80f8b50430aee1c6e534cba119c88de8
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review
Praveen-Chaudhary/Allow-user-to-set-metric-on-default-route-learned-via-Router-Advertisement/20210115-160758
git checkout 35f232fe80f8b50430aee1c6e534cba119c88de8
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross
ARCH=nds32
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot
All errors (new ones prefixed by >>):
net/ipv6/ndisc.c: In function 'ndisc_router_discovery':
>> net/ipv6/ndisc.c:1308:35: error: 'struct ipv6_devconf' has no member named
>> 'accept_ra_defrtr_metric'; did you mean 'accept_ra_defrtr'?
1308 | defrtr_usr_metric = in6_dev->cnf.accept_ra_defrtr_metric;
| ^~~
| accept_ra_defrtr
Kconfig warnings: (for reference only)
WARNING: unmet direct dependencies detected for FRAME_POINTER
Depends on DEBUG_KERNEL && (M68K || UML || SUPERH) ||
ARCH_WANT_FRAME_POINTERS
Selected by
- LATENCYTOP && DEBUG_KERNEL && STACKTRACE_SUPPORT && PROC_FS && !MIPS &&
!PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86
vim +1308 net/ipv6/ndisc.c
1241
1242 if (in6_dev->if_flags & IF_RS_SENT) {
1243 /*
1244 * flag that an RA was received after an RS was
sent
1245 * out on this interface.
1246 */
1247 in6_dev->if_flags |= IF_RA_RCVD;
1248 }
1249
1250 /*
1251 * Remember the managed/otherconf flags from most recently
1252 * received RA message (RFC 2462) -- yoshfuji
1253 */
1254 old_if_flags = in6_dev->if_flags;
1255 in6_dev->if_flags = (in6_dev->if_flags & ~(IF_RA_MANAGED |
1256 IF_RA_OTHERCONF)) |
1257 (ra_msg->icmph.icmp6_addrconf_managed ?
1258 IF_RA_MANAGED : 0) |
1259 (ra_msg->icmph.icmp6_addrconf_other ?
1260 IF_RA_OTHERCONF : 0);
1261
1262 if (old_if_flags != in6_dev->if_flags)
1263 send_ifinfo_notify = true;
1264
1265 if (!in6_dev->cnf.accept_ra_defrtr) {
1266 ND_PRINTK(2, info,
1267"RA: %s, defrtr is false for dev: %s\n",
1268__func__, skb->dev->name);
1269 goto skip_defrtr;
1270 }
1271
1272 /* Do not accept RA with source-addr found on local machine
unless
1273 * accept_ra_from_local is set to true.
1274 */
1275 net = dev_net(in6_dev->dev);
1276 if (!in6_dev->cnf.accept_ra_from_local &&
1277 ipv6_chk_addr(net, _hdr(skb)->saddr, in6_dev->dev, 0))
{
1278 ND_PRINTK(2, info,
1279"RA from local address detected on dev: %s:
default router ignored\n",
1280skb->dev->name);
1281 goto skip_defrtr;
1282 }
1283
1284 lifetime = ntohs(ra_msg->icmph.icmp6_rt_lifetime);
1285
1286 #ifdef CONFIG_IPV6_ROUTER_PREF
1287 pref = ra_msg->icmph.icmp6_router_pref;
1288 /* 10b is handled as if it were 00b (medium) */
1289 if (pref == ICMPV6_ROUTER_PREF_INVALID ||
1290 !in6_dev->cnf.accept_ra_rtr_pref)
1291 pref = ICMPV6_ROUTER_PREF_MEDIUM;
1292 #endif
1293 /* routes added from RAs do not use nexthop objects */
1294 rt = rt6_get_dflt_router(net, _hdr(skb)->saddr, skb->dev);
1295 if (rt) {
1296 neigh = ip6_neigh_lookup(>fib6_nh->fib_nh_gw6,
1297 rt->fib6_nh->fib_nh_dev, NULL,
1298_hdr(skb)->saddr);
1299 if (!neigh) {
1300 ND_PRINTK(0, err,
1301
[PATCH v2 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement.
For IPv4, default route is learned via DHCPv4 and user is allowed to change metric using config etc/network/interfaces. But for IPv6, default route can be learned via RA, for which, currently a fixed metric value 1024 is used. Ideally, user should be able to configure metric on default route for IPv6 similar to IPv4. This fix adds sysctl for the same. Signed-off-by: Praveen Chaudhary Signed-off-by: Zhenggen Xu Changes in v1. --- 1.) Correct the call to rt6_add_dflt_router. --- Changes in v2. [Refer: lkml.org/lkml/2021/1/14/1400] --- 1.) Replace accept_ra_defrtr_metric to ra_defrtr_metric. 2.) Change Type to __u32 instead of __s32. 3.) Change description in Documentation/networking/ip-sysctl.rst. 4.) Use proc_douintvec instead of proc_dointvec. 5.) Code style in ndisc_router_discovery(). 6.) Change Type to u32 instead of unsigned int. --- Logs: For IPv4: Config in etc/network/interfaces ``` auto eth0 iface eth0 inet dhcp metric 4261413864 ``` IPv4 Kernel Route Table: ``` $ ip route list default via 172.21.47.1 dev eth0 metric 4261413864 ``` FRR Table, if a static route is configured. [In real scenario, it is useful to prefer BGP learned default route over DHCPv4 default route.] ``` Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF, I - IS-IS, B - BGP, P - PIM, E - EIGRP, N - NHRP, T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP, > - selected route, * - FIB route S>* 0.0.0.0/0 [20/0] is directly connected, eth0, 00:00:03 K 0.0.0.0/0 [254/1000] via 172.21.47.1, eth0, 6d08h51m ``` ***i.e. User can prefer Default Router learned via Routing Protocol in IPv4.*** ***Similar behavior is not possible for IPv6, without this fix.*** After fix [for IPv6]: ``` sudo sysctl -w net.ipv6.conf.eth0.net.ipv6.conf.eth0.ra_defrtr_metric=1996489705 ``` IP monitor: [When IPv6 RA is received] ``` default via fe80::xx16::feb3:ce8e dev eth0 proto ra metric 1996489705 pref high ``` Kernel IPv6 routing table ``` $ ip -6 route list default via fe80::be16:65ff:feb3:ce8e dev eth0 proto ra metric 1996489705 expires 21sec hoplimit 64 pref high ``` FRR Table, if a static route is configured. [In real scenario, it is useful to prefer BGP learned default route over IPv6 RA default route.] ``` Codes: K - kernel route, C - connected, S - static, R - RIPng, O - OSPFv3, I - IS-IS, B - BGP, N - NHRP, T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP, > - selected route, * - FIB route S>* ::/0 [20/0] is directly connected, eth0, 00:00:06 K ::/0 [119/1001] via fe80::xx16::feb3:ce8e, eth0, 6d07h43m ``` If the metric is changed later, the effect will be seen only when next IPv6 RA is received, because the default route must be fully controlled by RA msg. Below metric is changed from 1996489705 to 1996489704. ``` $ sudo sysctl -w net.ipv6.conf.eth0.ra_defrtr_metric=1996489704 net.ipv6.conf.eth0.ra_defrtr_metric = 1996489704 ``` IP monitor: [On next IPv6 RA msg, Kernel deletes prev route and installs new route with updated metric] ``` Deleted default via fe80::xx16::feb3:ce8e dev eth0 proto ra metric 1996489705 expires 3sec hoplimit 64 pref high default via fe80::xx16::feb3:ce8e dev eth0 proto ra metric 1996489704 pref high ``` --- Documentation/networking/ip-sysctl.rst | 12 include/linux/ipv6.h | 1 + include/net/ip6_route.h| 3 ++- include/uapi/linux/ipv6.h | 1 + include/uapi/linux/sysctl.h| 1 + net/ipv6/addrconf.c| 10 ++ net/ipv6/ndisc.c | 14 ++ net/ipv6/route.c | 5 +++-- 8 files changed, 40 insertions(+), 7 deletions(-) diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index dd2b12a32b73..c4b8d4b8d213 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -1871,6 +1871,18 @@ accept_ra_defrtr - BOOLEAN - enabled if accept_ra is enabled. - disabled if accept_ra is disabled. +ra_defrtr_metric - INTEGER +
