[PATCH] ipv6: Allow non-gateway ECMP for IPv6

[PATCH] ipv6: Allow non-gateway ECMP for IPv6

[Thomas Winter]

It is valid to have static routes where the nexthop
is an interface not an address such as tunnels.
For IPv4 it was possible to use ECMP on these routes
but not for IPv6.

Signed-off-by: Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
Cc: David Ahern <dsahern@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
---
 include/net/ip6_route.h | 3 +--
 net/ipv6/ip6_fib.c      | 3 ---
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 08b132381984..abceb5864d99 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -68,8 +68,7 @@ static inline bool rt6_need_strict(const struct in6_addr *daddr)
 
 static inline bool rt6_qualify_for_ecmp(const struct rt6_info *rt)
 {
-	return (rt->rt6i_flags & (RTF_GATEWAY|RTF_ADDRCONF|RTF_DYNAMIC)) ==
-	       RTF_GATEWAY;
+	return (rt->rt6i_flags & (RTF_ADDRCONF | RTF_DYNAMIC)) == 0;
 }
 
 void ip6_route_input(struct sk_buff *skb);
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index deab2db6692e..3c97c29d4401 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -934,9 +934,6 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
 			 * list.
 			 * Only static routes (which don't have flag
 			 * RTF_EXPIRES) are used for ECMPv6.
-			 *
-			 * To avoid long list, we only had siblings if the
-			 * route have a gateway.
 			 */
 			if (rt_can_ecmp &&
 			    rt6_qualify_for_ecmp(iter))
-- 
2.17.0

Re: [PATCH] ipv6: Allow non-gateway ECMP for IPv6

[David Ahern]

On 4/30/18 3:15 PM, Thomas Winter wrote:
> It is valid to have static routes where the nexthop
> is an interface not an address such as tunnels.
> For IPv4 it was possible to use ECMP on these routes
> but not for IPv6.
> 
> Signed-off-by: Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
> Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
> ---
>  include/net/ip6_route.h | 3 +--
>  net/ipv6/ip6_fib.c      | 3 ---
>  2 files changed, 1 insertion(+), 5 deletions(-)
> 

Interesting. Existing code inserts the dev nexthop as a separate route.

Change looks good to me.

Acked-by: David Ahern <dsahern@gmail.com>

Re: [PATCH] ipv6: Allow non-gateway ECMP for IPv6

[Ido Schimmel]

On Mon, Apr 30, 2018 at 08:59:10PM -0600, David Ahern wrote:
> On 4/30/18 3:15 PM, Thomas Winter wrote:
> > It is valid to have static routes where the nexthop
> > is an interface not an address such as tunnels.
> > For IPv4 it was possible to use ECMP on these routes
> > but not for IPv6.
> > 
> > Signed-off-by: Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
> > Cc: David Ahern <dsahern@gmail.com>
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
> > Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
> > ---
> >  include/net/ip6_route.h | 3 +--
> >  net/ipv6/ip6_fib.c      | 3 ---
> >  2 files changed, 1 insertion(+), 5 deletions(-)
> > 
> 
> Interesting. Existing code inserts the dev nexthop as a separate route.
> 
> Change looks good to me.
> 
> Acked-by: David Ahern <dsahern@gmail.com>

Thanks for the Cc, David. I'll need to adjust mlxsw to support this.
Specifically, mlxsw_sp_fib6_rt_can_mp().

BTW, I hit this bug while looking into this:
https://patchwork.ozlabs.org/patch/907050/

Re: [PATCH] ipv6: Allow non-gateway ECMP for IPv6

[David Miller]

From: Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
Date: Tue,  1 May 2018 09:15:29 +1200

> It is valid to have static routes where the nexthop
> is an interface not an address such as tunnels.
> For IPv4 it was possible to use ECMP on these routes
> but not for IPv6.
> 
> Signed-off-by: Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>

Applied, thank you.