Re: [PATCH net-next v2 5/5] lwtunnel: Limit number of recursions on output to 5

[Thomas Graf]

On 11/01/16 at 12:52pm, kbuild test robot wrote:
> Hi Thomas,
> 
> [auto build test ERROR on net-next/master]
> 
> url:
> https://github.com/0day-ci/linux/commits/Thomas-Graf/bpf-BPF-for-lightweight-tunnel-encapsulation/20161101-084038
> config: arm64-allmodconfig (attached as .config)
> compiler: aarch64-linux-gnu-gcc (Debian 6.1.1-9) 6.1.1 20160705
> reproduce:
> wget 
> https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross
>  -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # save the attached .config to linux build tree
> make.cross ARCH=arm64 
> 
> All errors (new ones prefixed by >>):
> 
>net/built-in.o: In function `bpf_output':
> >> ncsi-manage.c:(.text+0x8e9f4): undefined reference to 
> >> `ip6_route_output_flags'

Needs
depends on IPV6_MULTIPLE_TABLES || IPV6=n 

Compile testing with IPV6=y and IPV6_MULTIPLE_TABLES=n would have been
great. I'll submit a v3 after some time has passed to review the new
rerouting bits.

Re: [PATCH net-next v2 5/5] lwtunnel: Limit number of recursions on output to 5

[kbuild test robot]

Hi Thomas,

[auto build test ERROR on net-next/master]

url:
https://github.com/0day-ci/linux/commits/Thomas-Graf/bpf-BPF-for-lightweight-tunnel-encapsulation/20161101-084038
config: arm64-allmodconfig (attached as .config)
compiler: aarch64-linux-gnu-gcc (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
wget 
https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross
 -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=arm64 

All errors (new ones prefixed by >>):

   net/built-in.o: In function `bpf_output':
>> ncsi-manage.c:(.text+0x8e9f4): undefined reference to 
>> `ip6_route_output_flags'

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation


.config.gz
Description: application/gzip

[PATCH net-next v2 5/5] lwtunnel: Limit number of recursions on output to 5

[Thomas Graf]

Signed-off-by: Thomas Graf 
---
 net/core/lwtunnel.c | 14 +-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/net/core/lwtunnel.c b/net/core/lwtunnel.c
index 554d901..6363d0b 100644
--- a/net/core/lwtunnel.c
+++ b/net/core/lwtunnel.c
@@ -231,6 +231,10 @@ int lwtunnel_cmp_encap(struct lwtunnel_state *a, struct 
lwtunnel_state *b)
 }
 EXPORT_SYMBOL(lwtunnel_cmp_encap);
 
+/* Per CPU recursion counter for dst_output() redirections via LWT */
+#define DST_RECURSION_LIMIT 5
+DEFINE_PER_CPU(int, dst_recursion);
+
 int lwtunnel_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
struct dst_entry *dst = skb_dst(skb);
@@ -246,11 +250,19 @@ int lwtunnel_output(struct net *net, struct sock *sk, 
struct sk_buff *skb)
lwtstate->type > LWTUNNEL_ENCAP_MAX)
return 0;
 
+   if (unlikely(__this_cpu_read(dst_recursion) > DST_RECURSION_LIMIT)) {
+   net_crit_ratelimited("lwt: recursion limit reached of 
redirected dst_output calls\n");
+   return -EFAULT;
+   }
+
ret = -EOPNOTSUPP;
rcu_read_lock();
ops = rcu_dereference(lwtun_encaps[lwtstate->type]);
-   if (likely(ops && ops->output))
+   if (likely(ops && ops->output)) {
+   __this_cpu_inc(dst_recursion);
ret = ops->output(net, sk, skb);
+   __this_cpu_dec(dst_recursion);
+   }
rcu_read_unlock();
 
if (ret == -EOPNOTSUPP)
-- 
2.7.4