On Thu, Apr 14, 2022 at 3:37 AM David Ahern <dsahern@xxxxxxxxxx> wrote:
>
> On 4/13/22 8:34 AM, Arun Ajith S wrote:
> > diff --git a/tools/testing/selftests/net/ndisc_unsolicited_na_test.py b/tools/testing/selftests/net/ndisc_unsolicited_na_test.py
> > new file mode 100755
> > index 000000000000..f508657ee126
> > --- /dev/null
> > +++ b/tools/testing/selftests/net/ndisc_unsolicited_na_test.py
> > @@ -0,0 +1,255 @@
> > +#!/bin/bash
>
> that file name suffix should be .sh since it is a bash script; not .py
>
> other than that looks good to me.
>
> Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
Hi David,
It has been pointed out to me that I might have read RFC9131 in a
narrower sense than what was intended.
The behavior of adding a new entry in the neighbour cache on receiving
a NA if none exists presently
shouldn't be limited to unsolicited NAs like in my original patch,
rather it should extend to all NAs.
I am quoting from the RFC below
| When a valid Neighbor Advertisement is received (either solicited
| or unsolicited), the Neighbor Cache is searched for the target's
| entry. If no entry exists:
|
| * Hosts SHOULD silently discard the advertisement. There is no
| need to create an entry if none exists, since the recipient has
| apparently not initiated any communication with the target.
|
| * Routers SHOULD create a new entry for the target address with
| the link-layer address set to the Target Link-Layer Address
| Option (if supplied). The entry's reachability state MUST be
| set to STALE. If the received Neighbor Advertisement does not
| contain the Target Link-Layer Address Option, the advertisement
| SHOULD be silently discarded.
I want to fix this, but this would mean the sysctl name
accept_unsolicited_na is no longer appropriate
I see that the net-next window for 5.19 is still open and changing the
sysctl name
wouldn't mean changing an existing interface.
I was thinking of renaming the sysctl to accept_untracked_na to
highlight that we are accepting NAs even if there is
no corresponding entry tracked in the neighbor cache.
Also, there's an error in my comment, where I say "pass up the stack"
as we don't pass NAs up the stack.
The comment can be updated as:
/* RFC 9131 updates original Neighbour Discovery RFC 4861.
* NAs with Target LL Address option without a corresponding
* entry in the neighbour cache can now create a STALE neighbour
* cache entry on routers.
*
* entry accept fwding solicited behaviour
* ------- ------ ------ --------- ----------------------
* present X X 0 Set state to STALE
* present X X 1 Set state to REACHABLE
* absent 0 X X Do nothing
* absent 1 0 X Do nothing
* absent 1 1 X Add a new STALE entry
*/
In summary
1. accept=0 keeps original(5.18) behavior for all cases.
2. accept=1 changes original behavior for entry=asbent, fwding=1 case
provided the NA had specified target link-layer address.
Please let me know what you think.
Thanks,
Arun
