* [PATCH] net-ipv6: on device mtu change do not add mtu to mtu-less routes
@ 2016-11-04 21:51 Maciej Żenczykowski
2016-11-07 19:28 ` Hannes Frederic Sowa
2016-11-09 18:20 ` David Miller
0 siblings, 2 replies; 3+ messages in thread
From: Maciej Żenczykowski @ 2016-11-04 21:51 UTC (permalink / raw)
To: Maciej Żenczykowski, David S . Miller; +Cc: netdev, Eric Dumazet
From: Maciej Żenczykowski <maze@google.com>
Routes can specify an mtu explicitly or inherit the mtu from
the underlying device - this inheritance is implemented in
dst->ops->mtu handlers ip6_mtu() and ip6_blackhole_mtu().
Currently changing the mtu of a device adds mtu explicitly
to routes using that device.
ie.
# ip link set dev lo mtu 65536
# ip -6 route add local 2000::1 dev lo
# ip -6 route get 2000::1
local 2000::1 dev lo table local src ... metric 1024 pref medium
# ip link set dev lo mtu 65535
# ip -6 route get 2000::1
local 2000::1 dev lo table local src ... metric 1024 mtu 65535 pref medium
# ip link set dev lo mtu 65536
# ip -6 route get 2000::1
local 2000::1 dev lo table local src ... metric 1024 mtu 65536 pref medium
# ip -6 route del local 2000::1
After this patch the route entry no longer changes unless it already has an mtu.
There is no need: this inheritance is already done in ip6_mtu()
# ip link set dev lo mtu 65536
# ip -6 route add local 2000::1 dev lo
# ip -6 route add local 2000::2 dev lo mtu 2000
# ip -6 route get 2000::1; ip -6 route get 2000::2
local 2000::1 dev lo table local src ... metric 1024 pref medium
local 2000::2 dev lo table local src ... metric 1024 mtu 2000 pref medium
# ip link set dev lo mtu 65535
# ip -6 route get 2000::1; ip -6 route get 2000::2
local 2000::1 dev lo table local src ... metric 1024 pref medium
local 2000::2 dev lo table local src ... metric 1024 mtu 2000 pref medium
# ip link set dev lo mtu 1501
# ip -6 route get 2000::1; ip -6 route get 2000::2
local 2000::1 dev lo table local src ... metric 1024 pref medium
local 2000::2 dev lo table local src ... metric 1024 mtu 1501 pref medium
# ip link set dev lo mtu 65536
# ip -6 route get 2000::1; ip -6 route get 2000::2
local 2000::1 dev lo table local src ... metric 1024 pref medium
local 2000::2 dev lo table local src ... metric 1024 mtu 65536 pref medium
# ip -6 route del local 2000::1
# ip -6 route del local 2000::2
This is desirable because changing device mtu and then resetting it
to the previous value shouldn't change the user visible routing table.
Signed-off-by: Maciej Żenczykowski <maze@google.com>
CC: Eric Dumazet <edumazet@google.com>
---
net/ipv6/route.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 947ed1ded026..fa90d14302f7 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2758,6 +2758,7 @@ static int rt6_mtu_change_route(struct rt6_info *rt, void *p_arg)
PMTU discouvery.
*/
if (rt->dst.dev == arg->dev &&
+ dst_metric_raw(&rt->dst, RTAX_MTU) &&
!dst_metric_locked(&rt->dst, RTAX_MTU)) {
if (rt->rt6i_flags & RTF_CACHE) {
/* For RTF_CACHE with rt6i_pmtu == 0
--
2.8.0.rc3.226.g39d4020
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] net-ipv6: on device mtu change do not add mtu to mtu-less routes
2016-11-04 21:51 [PATCH] net-ipv6: on device mtu change do not add mtu to mtu-less routes Maciej Żenczykowski
@ 2016-11-07 19:28 ` Hannes Frederic Sowa
2016-11-09 18:20 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: Hannes Frederic Sowa @ 2016-11-07 19:28 UTC (permalink / raw)
To: Maciej Żenczykowski, Maciej Żenczykowski,
David S . Miller
Cc: netdev, Eric Dumazet
On 04.11.2016 22:51, Maciej Żenczykowski wrote:
> From: Maciej Żenczykowski <maze@google.com>
>
> Routes can specify an mtu explicitly or inherit the mtu from
> the underlying device - this inheritance is implemented in
> dst->ops->mtu handlers ip6_mtu() and ip6_blackhole_mtu().
>
> Currently changing the mtu of a device adds mtu explicitly
> to routes using that device.
>
> ie.
> # ip link set dev lo mtu 65536
> # ip -6 route add local 2000::1 dev lo
> # ip -6 route get 2000::1
> local 2000::1 dev lo table local src ... metric 1024 pref medium
>
> # ip link set dev lo mtu 65535
> # ip -6 route get 2000::1
> local 2000::1 dev lo table local src ... metric 1024 mtu 65535 pref medium
>
> # ip link set dev lo mtu 65536
> # ip -6 route get 2000::1
> local 2000::1 dev lo table local src ... metric 1024 mtu 65536 pref medium
>
> # ip -6 route del local 2000::1
>
> After this patch the route entry no longer changes unless it already has an mtu.
> There is no need: this inheritance is already done in ip6_mtu()
>
> # ip link set dev lo mtu 65536
> # ip -6 route add local 2000::1 dev lo
> # ip -6 route add local 2000::2 dev lo mtu 2000
> # ip -6 route get 2000::1; ip -6 route get 2000::2
> local 2000::1 dev lo table local src ... metric 1024 pref medium
> local 2000::2 dev lo table local src ... metric 1024 mtu 2000 pref medium
>
> # ip link set dev lo mtu 65535
> # ip -6 route get 2000::1; ip -6 route get 2000::2
> local 2000::1 dev lo table local src ... metric 1024 pref medium
> local 2000::2 dev lo table local src ... metric 1024 mtu 2000 pref medium
>
> # ip link set dev lo mtu 1501
> # ip -6 route get 2000::1; ip -6 route get 2000::2
> local 2000::1 dev lo table local src ... metric 1024 pref medium
> local 2000::2 dev lo table local src ... metric 1024 mtu 1501 pref medium
>
> # ip link set dev lo mtu 65536
> # ip -6 route get 2000::1; ip -6 route get 2000::2
> local 2000::1 dev lo table local src ... metric 1024 pref medium
> local 2000::2 dev lo table local src ... metric 1024 mtu 65536 pref medium
>
> # ip -6 route del local 2000::1
> # ip -6 route del local 2000::2
>
> This is desirable because changing device mtu and then resetting it
> to the previous value shouldn't change the user visible routing table.
>
> Signed-off-by: Maciej Żenczykowski <maze@google.com>
> CC: Eric Dumazet <edumazet@google.com>
> ---
> net/ipv6/route.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 947ed1ded026..fa90d14302f7 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -2758,6 +2758,7 @@ static int rt6_mtu_change_route(struct rt6_info *rt, void *p_arg)
> PMTU discouvery.
> */
> if (rt->dst.dev == arg->dev &&
> + dst_metric_raw(&rt->dst, RTAX_MTU) &&
> !dst_metric_locked(&rt->dst, RTAX_MTU)) {
> if (rt->rt6i_flags & RTF_CACHE) {
> /* For RTF_CACHE with rt6i_pmtu == 0
>
Yep, that makes sense.
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] net-ipv6: on device mtu change do not add mtu to mtu-less routes
2016-11-04 21:51 [PATCH] net-ipv6: on device mtu change do not add mtu to mtu-less routes Maciej Żenczykowski
2016-11-07 19:28 ` Hannes Frederic Sowa
@ 2016-11-09 18:20 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2016-11-09 18:20 UTC (permalink / raw)
To: zenczykowski; +Cc: maze, netdev, edumazet
From: Maciej Żenczykowski <zenczykowski@gmail.com>
Date: Fri, 4 Nov 2016 14:51:54 -0700
> From: Maciej Żenczykowski <maze@google.com>
>
> Routes can specify an mtu explicitly or inherit the mtu from
> the underlying device - this inheritance is implemented in
> dst->ops->mtu handlers ip6_mtu() and ip6_blackhole_mtu().
>
> Currently changing the mtu of a device adds mtu explicitly
> to routes using that device.
...
> This is desirable because changing device mtu and then resetting it
> to the previous value shouldn't change the user visible routing table.
>
> Signed-off-by: Maciej Żenczykowski <maze@google.com>
Applied, thank you.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-11-04 21:51 [PATCH] net-ipv6: on device mtu change do not add mtu to mtu-less routes Maciej Żenczykowski
2016-11-07 19:28 ` Hannes Frederic Sowa
2016-11-09 18:20 ` David Miller
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