Subject: Re: [net-next,RFC,1/2] fib: introduce fib notification infrastructure

From: Jiri Pirko <[email-masked]>
Date: Thu, 15 Sep 2016 16:45:16 +0200

Thu, Sep 15, 2016 at 04:41:20PM CEST, [email-masked] wrote:
>On Tue, Sep 6, 2016 at 8:01 AM, Jiri Pirko
><[email-masked]> wrote:
>> From: Jiri Pirko <[email-masked]>
>>
>> This allows to pass information about added/deleted fib entries to
>> whoever is interested. This is done in a very similar way as devinet
>> notifies address additions/removals.
>
>(Sorry for the delayed response here...)
>
>I had tried a slightly different approach, but this one also seems
>reasonable and possibly better -- especially if this can be made more
>generic and shared between ipv4 and ipv6 despite their inherent
>differences.
>
>What I did differently was make a more ipv4-specific change to start
>with that did this:
>
>+#define RTNH_F_MODIFIED                (1 << 7)        /* used for
>internal kernel tracking */
>+
>+#define RTNH_F_COMPARE_MASK    (RTNH_F_DEAD | \
>+                                RTNH_F_LINKDOWN | \
>+                                RTNH_F_MODIFIED) /* used as mask for
>route comparisons */
>
>Then in various cases where the route was modified (fib_sync_up, etc),
>I added this:
>
>+                                nexthop_nh->nh_flags |= RTNH_F_MODIFIED;
>
>Checking for the modified flag was then done in fib_table_update().
>This new function was a rewrite of fib_table_flush() and checks for
>RTNH_F_MODIFIED were done there before calling switchdev infra and
>then announce new routes if routes changed.
>
>The main issue I see right now is that neither userspace nor switchdev
>are notified when a route flag changes.  This needs to be resolved.
>
>I think this RFC is along the proper path to provide notification, but
>I'm not sure that notification will happen when flags change (most
>notably the LNKDOWN flag) and there are some other corner cases that
>could probably be covered as well.
>
>I need to forward-port my patch from where it was to the latest
>net-next and see if these cases I was concerned about were still an
>issue.  I'm happy to do that and see if we can put this all together
>to fix a few of the outstanding issues.

I believe that "modify" can be easily another fib event. Drivers can
react accordingly. I'm close to sending v1 (hopefully tomorrow). I
believe you can base your patchset on top of mine which saves you lot of
time.

>
>
>>
>> Signed-off-by: Jiri Pirko <[email-masked]>
>> ---
>>  include/net/ip_fib.h | 19 +++++++++++++++++++
>>  net/ipv4/fib_trie.c  | 43 +++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 62 insertions(+)
>>
>> diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
>> index 4079fc1..9ad7ba9 100644
>> --- a/include/net/ip_fib.h
>> +++ b/include/net/ip_fib.h
>> @@ -22,6 +22,7 @@
>>  #include <net/fib_rules.h>
>>  #include <net/inetpeer.h>
>>  #include <linux/percpu.h>
>> +#include <linux/notifier.h>
>>
>>  struct fib_config {
>>         u8                      fc_dst_len;
>> @@ -184,6 +185,24 @@ __be32 fib_info_update_nh_saddr(struct net *net, struct fib_nh *nh);
>>  #define FIB_RES_PREFSRC(net, res)      ((res).fi->fib_prefsrc ? : \
>>                                          FIB_RES_SADDR(net, res))
>>
>> +struct fib_notifier_info {
>> +       u32 dst;
>> +       int dst_len;
>> +       struct fib_info *fi;
>> +       u8 tos;
>> +       u8 type;
>> +       u32 tb_id;
>> +       u32 nlflags;
>> +};
>> +
>> +enum fib_event_type {
>> +       FIB_EVENT_TYPE_ADD,
>> +       FIB_EVENT_TYPE_DEL,
>> +};
>> +
>> +int register_fib_notifier(struct notifier_block *nb);
>> +int unregister_fib_notifier(struct notifier_block *nb);
>> +
>>  struct fib_table {
>>         struct hlist_node       tb_hlist;
>>         u32                     tb_id;
>> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
>> index e2ffc2a..19ec471 100644
>> --- a/net/ipv4/fib_trie.c
>> +++ b/net/ipv4/fib_trie.c
>> @@ -73,6 +73,7 @@
>>  #include <linux/slab.h>
>>  #include <linux/export.h>
>>  #include <linux/vmalloc.h>
>> +#include <linux/notifier.h>
>>  #include <net/net_namespace.h>
>>  #include <net/ip.h>
>>  #include <net/protocol.h>
>> @@ -84,6 +85,36 @@
>>  #include <trace/events/fib.h>
>>  #include "fib_lookup.h"
>>
>> +static BLOCKING_NOTIFIER_HEAD(fib_chain);
>> +
>> +int register_fib_notifier(struct notifier_block *nb)
>> +{
>> +       return blocking_notifier_chain_register(&fib_chain, nb);
>> +}
>> +EXPORT_SYMBOL(register_fib_notifier);
>> +
>> +int unregister_fib_notifier(struct notifier_block *nb)
>> +{
>> +       return blocking_notifier_chain_unregister(&fib_chain, nb);
>> +}
>> +EXPORT_SYMBOL(unregister_fib_notifier);
>> +
>> +static int call_fib_notifiers(enum fib_event_type event_type, u32 dst,
>> +                             int dst_len, struct fib_info *fi,
>> +                             u8 tos, u8 type, u32 tb_id, u32 nlflags)
>> +{
>> +       struct fib_notifier_info info = {
>> +               .dst = dst,
>> +               .dst_len = dst_len,
>> +               .fi = fi,
>> +               .tos = tos,
>> +               .type = type,
>> +               .tb_id = tb_id,
>> +               .nlflags = nlflags,
>> +       };
>> +       return blocking_notifier_call_chain(&fib_chain, event_type, &info);
>> +}
>> +
>>  #define MAX_STAT_DEPTH 32
>>
>>  #define KEYLENGTH      (8*sizeof(t_key))
>> @@ -1190,6 +1221,10 @@ int fib_table_insert(struct fib_table *tb, struct fib_config *cfg)
>>                         fib_release_info(fi_drop);
>>                         if (state & FA_S_ACCESSED)
>>                                 rt_cache_flush(cfg->fc_nlinfo.nl_net);
>> +
>> +                       call_fib_notifiers(FIB_EVENT_TYPE_ADD, key, plen, fi,
>> +                                          new_fa->fa_tos, cfg->fc_type,
>> +                                          tb->tb_id, cfg->fc_nlflags);
>>                         rtmsg_fib(RTM_NEWROUTE, htonl(key), new_fa, plen,
>>                                 tb->tb_id, &cfg->fc_nlinfo, NLM_F_REPLACE);
>>
>> @@ -1241,6 +1276,8 @@ int fib_table_insert(struct fib_table *tb, struct fib_config *cfg)
>>                 tb->tb_num_default++;
>>
>>         rt_cache_flush(cfg->fc_nlinfo.nl_net);
>> +       call_fib_notifiers(FIB_EVENT_TYPE_ADD, key, plen, fi, tos,
>> +                          cfg->fc_type, tb->tb_id, cfg->fc_nlflags);
>>         rtmsg_fib(RTM_NEWROUTE, htonl(key), new_fa, plen, new_fa->tb_id,
>>                   &cfg->fc_nlinfo, nlflags);
>>  succeeded:
>> @@ -1542,6 +1579,8 @@ int fib_table_delete(struct fib_table *tb, struct fib_config *cfg)
>>         switchdev_fib_ipv4_del(key, plen, fa_to_delete->fa_info, tos,
>>                                cfg->fc_type, tb->tb_id);
>>
>> +       call_fib_notifiers(FIB_EVENT_TYPE_DEL, key, plen, fa_to_delete->fa_info,
>> +                          tos, cfg->fc_type, tb->tb_id, 0);
>>         rtmsg_fib(RTM_DELROUTE, htonl(key), fa_to_delete, plen, tb->tb_id,
>>                   &cfg->fc_nlinfo, 0);
>>
>> @@ -1857,6 +1896,10 @@ int fib_table_flush(struct fib_table *tb)
>>                         switchdev_fib_ipv4_del(n->key, KEYLENGTH - fa->fa_slen,
>>                                                fi, fa->fa_tos, fa->fa_type,
>>                                                tb->tb_id);
>> +                       call_fib_notifiers(FIB_EVENT_TYPE_DEL, n->key,
>> +                                          KEYLENGTH - fa->fa_slen,
>> +                                          fi, fa->fa_tos, fa->fa_type,
>> +                                          tb->tb_id, 0);
>>                         hlist_del_rcu(&fa->fa_list);
>>                         fib_release_info(fa->fa_info);
>>                         alias_free_mem_rcu(fa);