Problems in the current dst_entry cache in the ip6_tunnel:
1. ip6_tnl_dst_set is racy. There is no lock to protect it:
- One major problem is that the dst refcnt gets messed up. F.e.
the same dst_cache can be released multiple times and then
triggering the infamous dst refcnt < 0 warning message.
- Another issue is the inconsistency between dst_cache and
dst_cookie.
It can be reproduced by adding and removing the ip6gre tunnel
while running a super_netperf TCP_CRR test.
2. ip6_tnl_dst_get does not take the dst refcnt before returning
the dst.
This patch:
1. Create a percpu dst_entry cache in ip6_tnl
2. Use a spinlock to protect the dst_cache operations
3. ip6_tnl_dst_get always takes the dst refcnt before returning
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
cdf3464e6c