Add support for sockets in time-wait state.
ao_info as well as all keys are inherited on transition to time-wait
socket. The lifetime of ao_info is now protected by ref counter, so
that tcp_ao_destroy_sock() will destruct it only when the last user is
gone.

Co-developed-by: Francesco Ruggeri <redacted>
Signed-off-by: Francesco Ruggeri <redacted>
Co-developed-by: Salam Noureddine <redacted>
Signed-off-by: Salam Noureddine <redacted>
Signed-off-by: Dmitry Safonov <redacted>
Acked-by: David Ahern <dsahern@kernel.org>
---
 include/linux/tcp.h      |  3 ++
 include/net/tcp_ao.h     | 11 ++++-
 net/ipv4/tcp_ao.c        | 46 +++++++++++++++++---
 net/ipv4/tcp_ipv4.c      | 92 +++++++++++++++++++++++++++++++---------
 net/ipv4/tcp_minisocks.c |  4 +-
 net/ipv4/tcp_output.c    |  2 +-
 net/ipv6/tcp_ipv6.c      | 72 ++++++++++++++++++++++---------
 7 files changed, 181 insertions(+), 49 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index c38778b0baa0..51458219be4e 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h

@@ -512,6 +512,9 @@ struct tcp_timewait_sock {
 #ifdef CONFIG_TCP_MD5SIG
        struct tcp_md5sig_key     *tw_md5_key;
 #endif
+#ifdef CONFIG_TCP_AO
+       struct tcp_ao_info      __rcu *ao_info;
+#endif
 };

 static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index 629ab0365b83..af2caf7e76fc 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h

@@ -85,6 +85,7 @@ struct tcp_ao_info {
                                __unused        :31;
        __be32                  lisn;
        __be32                  risn;
+       atomic_t                refcnt;         /* Protects twsk destruction */