Re: [PATCH 3/4] icmp6: Respect lifetime values in a RA

Re: [PATCH 3/4] icmp6: Respect lifetime values in a RA

[Denis Kenzior]

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On 1/3/22 08:18, Andrew Zaborowski wrote:
> If the router lifetime is 0 in a RA that router is not supposed to be
> added to the Default Router List in RFC4861:
> 
> "A value of zero indicates that the router is not to be used as a
> default router."
> 

You may want to put this into the code directly.

> "A router might want to send Router Advertisements without advertising
> itself as a default router.  For instance, a router might advertise
> prefixes for stateless address autoconfiguration while not wishing to
> forward packets.  Such a router sets the Router Lifetime field in
> outgoing advertisements to zero."
> 

But yes, this part makes sense and no objections here.

> Also set the lifetime values on the routes to those received so that the
> user of, say, l_icmp6_client_get_router(), can also determine whether
> there is a default router.

Note that we do not re-upload the routes to the kernel on every RA received. 
See the TODO comment in icmp6_client_handle_message().  Once lifetime expires, 
the route will be removed -> internet is broke.  Please at least sanity test the 
changes you're sending out or label them as RFC if you haven't done so.

> ---
>   ell/icmp6.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 

Regards,
-Denis

Re: [PATCH 3/4] icmp6: Respect lifetime values in a RA

[Andrew Zaborowski]

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On Mon, 3 Jan 2022 at 20:01, Denis Kenzior <denkenz(a)gmail.com> wrote:
> On 1/3/22 08:18, Andrew Zaborowski wrote:
> > "A value of zero indicates that the router is not to be used as a
> > default router."
> >
>
> You may want to put this into the code directly.

Ok, for some reason we don't quote the RFC in this file.

>
> > Also set the lifetime values on the routes to those received so that the
> > user of, say, l_icmp6_client_get_router(), can also determine whether
> > there is a default router.
>
> Note that we do not re-upload the routes to the kernel on every RA received.
> See the TODO comment in icmp6_client_handle_message().  Once lifetime expires,
> the route will be removed -> internet is broke.  Please at least sanity test the
> changes you're sending out or label them as RFC if you haven't done so.

Ok, I've dropped the l_icmp6_client_set_rtnl() use locally in IWD so
this wouldn't have shown up even if the router had set a short
lifetime.  But I need some way for the user to check if there's a
default gateway.

Best regards

[PATCH 3/4] icmp6: Respect lifetime values in a RA

[Andrew Zaborowski]

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If the router lifetime is 0 in a RA that router is not supposed to be
added to the Default Router List in RFC4861:

"A value of zero indicates that the router is not to be used as a
default router."

"A router might want to send Router Advertisements without advertising
itself as a default router.  For instance, a router might advertise
prefixes for stateless address autoconfiguration while not wishing to
forward packets.  Such a router sets the Router Lifetime field in
outgoing advertisements to zero."

Also set the lifetime values on the routes to those received so that the
user of, say, l_icmp6_client_get_router(), can also determine whether
there is a default router.
---
 ell/icmp6.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/ell/icmp6.c b/ell/icmp6.c
index 42fe67d..93c1701 100644
--- a/ell/icmp6.c
+++ b/ell/icmp6.c
@@ -299,9 +299,10 @@ static void icmp6_client_setup_routes(struct l_icmp6_client *client)
 	l_rtnl_route_set_protocol(rt, RTPROT_RA);
 	l_rtnl_route_set_mtu(rt, ra->mtu);
 	l_rtnl_route_set_priority(rt, client->route_priority);
+	l_rtnl_route_set_lifetime(rt, ra->lifetime);
 	l_queue_push_tail(client->routes, rt);
 
-	if (client->rtnl)
+	if (client->rtnl && ra->lifetime)
 		l_rtnl_route_add(client->rtnl, client->ifindex, rt,
 					NULL, NULL, NULL);
 
@@ -322,6 +323,7 @@ static void icmp6_client_setup_routes(struct l_icmp6_client *client)
 		l_rtnl_route_set_protocol(rt, RTPROT_RA);
 		l_rtnl_route_set_mtu(rt, ra->mtu);
 		l_rtnl_route_set_priority(rt, client->route_priority);
+		l_rtnl_route_set_lifetime(rt, info->valid_lifetime);
 		l_queue_push_tail(client->routes, rt);
 
 		if (client->rtnl)
-- 
2.32.0