[Patch net v2] net/ipv6: do not copy dst flags on rt init

[Patch net v2] net/ipv6: do not copy dst flags on rt init

[Peter Oskolkov]

DST_NOCOUNT in dst_entry::flags tracks whether the entry counts
toward route cache size (net->ipv6.sysctl.ip6_rt_max_size).

If the flag is NOT set, dst_ops::pcpuc_entries counter is incremented
in dist_init() and decremented in dst_destroy().

This flag is tied to allocation/deallocation of dst_entry and
should not be copied from another dst/route. Otherwise it can happen
that dst_ops::pcpuc_entries counter grows until no new routes can
be allocated because the counter reached ip6_rt_max_size due to
DST_NOCOUNT not set and thus no counter decrements on gc-ed routes.

Fixes: 3b6761d18bc1 ("net/ipv6: Move dst flags to booleans in fib entries")
Cc: David Ahern <dsahern@gmail.com>
Acked-by: Wei Wang <weiwan@google.com>
Signed-off-by: Peter Oskolkov <posk@google.com>
---
 net/ipv6/route.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 3eed045c65a5..480a79f47c52 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -946,8 +946,6 @@ static void ip6_rt_init_dst_reject(struct rt6_info *rt, struct fib6_info *ort)
 
 static void ip6_rt_init_dst(struct rt6_info *rt, struct fib6_info *ort)
 {
-	rt->dst.flags |= fib6_info_dst_flags(ort);
-
 	if (ort->fib6_flags & RTF_REJECT) {
 		ip6_rt_init_dst_reject(rt, ort);
 		return;
-- 
2.19.0.397.gdd90340f6a-goog

Re: [Patch net v2] net/ipv6: do not copy dst flags on rt init

[David Ahern]

On 9/17/18 10:20 AM, Peter Oskolkov wrote:
> DST_NOCOUNT in dst_entry::flags tracks whether the entry counts
> toward route cache size (net->ipv6.sysctl.ip6_rt_max_size).
> 
> If the flag is NOT set, dst_ops::pcpuc_entries counter is incremented
> in dist_init() and decremented in dst_destroy().
> 
> This flag is tied to allocation/deallocation of dst_entry and
> should not be copied from another dst/route. Otherwise it can happen
> that dst_ops::pcpuc_entries counter grows until no new routes can
> be allocated because the counter reached ip6_rt_max_size due to
> DST_NOCOUNT not set and thus no counter decrements on gc-ed routes.
> 
> Fixes: 3b6761d18bc1 ("net/ipv6: Move dst flags to booleans in fib entries")
> Cc: David Ahern <dsahern@gmail.com>
> Acked-by: Wei Wang <weiwan@google.com>
> Signed-off-by: Peter Oskolkov <posk@google.com>
> ---
>  net/ipv6/route.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 3eed045c65a5..480a79f47c52 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -946,8 +946,6 @@ static void ip6_rt_init_dst_reject(struct rt6_info *rt, struct fib6_info *ort)
>  
>  static void ip6_rt_init_dst(struct rt6_info *rt, struct fib6_info *ort)
>  {
> -	rt->dst.flags |= fib6_info_dst_flags(ort);
> -
>  	if (ort->fib6_flags & RTF_REJECT) {
>  		ip6_rt_init_dst_reject(rt, ort);
>  		return;
> 

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

Thanks for the patch.

Re: [Patch net v2] net/ipv6: do not copy dst flags on rt init

[David Miller]

From: Peter Oskolkov <posk@google.com>
Date: Mon, 17 Sep 2018 10:20:53 -0700

> DST_NOCOUNT in dst_entry::flags tracks whether the entry counts
> toward route cache size (net->ipv6.sysctl.ip6_rt_max_size).
> 
> If the flag is NOT set, dst_ops::pcpuc_entries counter is incremented
> in dist_init() and decremented in dst_destroy().
> 
> This flag is tied to allocation/deallocation of dst_entry and
> should not be copied from another dst/route. Otherwise it can happen
> that dst_ops::pcpuc_entries counter grows until no new routes can
> be allocated because the counter reached ip6_rt_max_size due to
> DST_NOCOUNT not set and thus no counter decrements on gc-ed routes.
> 
> Fixes: 3b6761d18bc1 ("net/ipv6: Move dst flags to booleans in fib entries")
> Cc: David Ahern <dsahern@gmail.com>
> Acked-by: Wei Wang <weiwan@google.com>
> Signed-off-by: Peter Oskolkov <posk@google.com>

Applied and queued up for -stable, thank you.