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ipv6: Fix dst_entry refcnt bugs in ip6_tunnel

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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>
This commit is contained in:
Martin KaFai Lau 2015-09-15 14:30:07 -07:00 • committed by David S. Miller
commit cdf3464e6c
3 changed files with 123 additions and 48 deletions
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11
include/net/ip6_tunnel.h
View file

@ -32,6 +32,12 @@ struct __ip6_tnl_parm {
__be32 o_key;
};
struct ip6_tnl_dst {
spinlock_t lock;
struct dst_entry *dst;
u32 cookie;
};
/* IPv6 tunnel */
struct ip6_tnl {
struct ip6_tnl __rcu *next; /* next tunnel in list */
@ -39,8 +45,7 @@ struct ip6_tnl {
struct net *net; /* netns for packet i/o */
struct __ip6_tnl_parm parms; /* tunnel configuration parameters */
struct flowi fl; /* flowi template for xmit */
struct dst_entry *dst_cache; /* cached dst */
u32 dst_cookie;
struct ip6_tnl_dst __percpu *dst_cache; /* cached dst */
int err_count;
unsigned long err_time;
@ -61,6 +66,8 @@ struct ipv6_tlv_tnl_enc_lim {
} __packed;
struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t);
int ip6_tnl_dst_init(struct ip6_tnl *t);
void ip6_tnl_dst_destroy(struct ip6_tnl *t);
void ip6_tnl_dst_reset(struct ip6_tnl *t);
void ip6_tnl_dst_set(struct ip6_tnl *t, struct dst_entry *dst);
int ip6_tnl_rcv_ctl(struct ip6_tnl *t, const struct in6_addr *laddr,