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SubjectRe: [PATCH v2 net-next 1/1] Allow user to set metric on default route learned via Router Advertisement.
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> On Jan 16, 2021, at 9:13 AM, David Ahern <dsahern@gmail.com> 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 <pchaudhary@linkedin.com>
>> Signed-off-by: Zhenggen Xu <zxu@linkedin.com>
>>
>> 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 0xFFFFFFFF:
>> + 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 = &ipv6_devconf.ra_defrtr_metric,
>> + .maxlen = sizeof(u32),
>> + .mode = 0644,
>> + .proc_handler = proc_douintvec,
>> + },
>> {
>> .procname = "accept_ra_min_hop_limit",
>> .data = &ipv6_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
>> +++ b/net/ipv6/ndisc.c
>> @@ -1173,6 +1173,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
>> struct neighbour *neigh = NULL;
>> struct inet6_dev *in6_dev;
>> struct fib6_info *rt = NULL;
>> + u32 defrtr_usr_metric;
>> struct net *net;
>> int lifetime;
>> struct ndisc_options ndopts;
>> @@ -1303,18 +1304,23 @@ static void ndisc_router_discovery(struct sk_buff *skb)
>> return;
>> }
>> }
>> - if (rt && lifetime == 0) {
>> + /* Set default route metric if specified by user */
>> + defrtr_usr_metric = in6_dev->cnf.accept_ra_defrtr_metric;
>
> this tells me you did not compile this version of the patch since the
> 'accept_' has been dropped. Always compile and test every patch before
> sending.

Yeah one patch was pushed bit early. Sorry about that. I will take care of this now onwards.

I have respined the Patch (v3) after addressing your review comments. Build is done in our pipeline.
Build logs: https://dev.azure.com/sonicswitch/build/_build/results?buildId=1669&view=logs&j=011e1ec8-6569-5e69-4f06-baf193d1351e

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.


Praveen
https://github.com/praveen-li


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