[PATCH v3 25/36] net/tcp-ao: Add static_key for TCP-AO

Dmitry Safonov
2022-10-27T20:52:03Z

Similarly to TCP-MD5, add a static key to TCP-AO that is patched out
when there are no keys on a machine and dynamically enabled with the
first setsockopt(TCP_AO) adds a key on any socket. The static key is as
well dynamically disabled later when the socket is destructed.

The lifetime of enabled static key here is the same as ao_info: it is
enabled on allocation, passed over from full socket to twsk and
destructed when ao_info is scheduled for destruction.

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
include/net/tcp_ao.h | 2 ++
net/ipv4/tcp_ao.c | 15 +++++++++++++++
net/ipv4/tcp_input.c | 42 ++++++++++++++++++++++++++++--------------
3 files changed, 45 insertions(+), 14 deletions(-)

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index 67f5273396ec..0923cd3b6b45 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -131,6 +131,8 @@ do { \

#ifdef CONFIG_TCP_AO
/* TCP-AO structures and functions */
+#include <linux/jump_label.h>
+extern struct static_key_false_deferred tcp_ao_needed;

struct tcp4_ao_context {
__be32 saddr;
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 46df1d455889..494fa5e1428c 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -17,6 +17,9 @@
#include <net/ipv6.h>
#include <net/icmp.h>

+DEFINE_STATIC_KEY_DEFERRED_FALSE(tcp_ao_needed, HZ);
+EXPORT_SYMBOL(tcp_ao_needed);
+
int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx,
unsigned int len)
{
@@ -58,6 +61,9 @@ bool tcp_ao_ignore_icmp(struct sock *sk, int type, int code)
struct tcp_ao_info *ao;
bool ignore_icmp = false;

+ if (!static_branch_unlikely(&tcp_ao_needed.key))
+ return false;
+
/* RFC5925, 7.8:
* >> A TCP-AO implementation MUST default to ignore incoming ICMPv4
* messages of Type 3 (destination unreachable), Codes 2-4 (protocol
@@ -148,6 +154,9 @@ struct tcp_ao_key *tcp_ao_do_lookup_sndid(const struct sock *sk, u8 keyid)
struct tcp_ao_key *key;
struct tcp_ao_info *ao;

+ if (!static_branch_unlikely(&tcp_ao_needed.key))
+ return NULL;
+
if (sk->sk_state == TCP_TIME_WAIT)
ao = rcu_dereference_check(tcp_twsk(sk)->ao_info,
lockdep_sock_is_held(sk));
@@ -232,6 +241,9 @@ struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
struct tcp_ao_key *key;
struct tcp_ao_info *ao;

+ if (!static_branch_unlikely(&tcp_ao_needed.key))
+ return NULL;
+
ao = rcu_dereference_check(tcp_sk(sk)->ao_info,
lockdep_sock_is_held(sk));
if (!ao)
@@ -319,6 +331,7 @@ void tcp_ao_destroy_sock(struct sock *sk, bool twsk)
}

kfree_rcu(ao, rcu);
+ static_branch_slow_dec_deferred(&tcp_ao_needed);
}

void tcp_ao_time_wait(struct tcp_timewait_sock *tcptw, struct tcp_sock *tp)
@@ -1078,6 +1091,7 @@ int tcp_ao_copy_all_matching(const struct sock *sk, struct sock *newsk,

sk_gso_disable(newsk);
rcu_assign_pointer(tcp_sk(newsk)->ao_info, new_ao);
+ atomic_inc(&tcp_ao_needed.key.key.enabled);
}

return 0;
@@ -1605,6 +1619,7 @@ static int tcp_ao_add_cmd(struct sock *sk, unsigned short int family,
if (first) {
sk_gso_disable(sk);
rcu_assign_pointer(tcp_sk(sk)->ao_info, ao_info);
+ static_branch_inc(&tcp_ao_needed.key);
}

/* Can't fail: the key with sndid/rcvid was just added */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2ba46d5db421..3f1f5c0e78ae 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3524,17 +3524,14 @@ static inline bool tcp_may_update_window(const struct tcp_sock *tp,
(ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd);
}

-/* If we update tp->snd_una, also update tp->bytes_acked */
-static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
+static void tcp_snd_sne_update(struct tcp_sock *tp, u32 ack)
{
- u32 delta = ack - tp->snd_una;
#ifdef CONFIG_TCP_AO
struct tcp_ao_info *ao;
-#endif

- sock_owned_by_me((struct sock *)tp);
- tp->bytes_acked += delta;
-#ifdef CONFIG_TCP_AO
+ if (!static_branch_unlikely(&tcp_ao_needed.key))
+ return;
+
ao = rcu_dereference_protected(tp->ao_info,
lockdep_sock_is_held((struct sock *)tp));
if (ao) {
@@ -3543,20 +3540,27 @@ static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
ao->snd_sne_seq = ack;
}
#endif
+}
+
+/* If we update tp->snd_una, also update tp->bytes_acked */
+static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
+{
+ u32 delta = ack - tp->snd_una;
+
+ sock_owned_by_me((struct sock *)tp);
+ tp->bytes_acked += delta;
+ tcp_snd_sne_update(tp, ack);
tp->snd_una = ack;
}

-/* If we update tp->rcv_nxt, also update tp->bytes_received */
-static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq)
+static void tcp_rcv_sne_update(struct tcp_sock *tp, u32 seq)
{
- u32 delta = seq - tp->rcv_nxt;
#ifdef CONFIG_TCP_AO
struct tcp_ao_info *ao;
-#endif

- sock_owned_by_me((struct sock *)tp);
- tp->bytes_received += delta;
-#ifdef CONFIG_TCP_AO
+ if (!static_branch_unlikely(&tcp_ao_needed.key))
+ return;
+
ao = rcu_dereference_protected(tp->ao_info,
lockdep_sock_is_held((struct sock *)tp));
if (ao) {
@@ -3565,6 +3569,16 @@ static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq)
ao->rcv_sne_seq = seq;
}
#endif
+}
+
+/* If we update tp->rcv_nxt, also update tp->bytes_received */
+static void tcp_rcv_nxt_update(struct tcp_sock *tp, u32 seq)
+{
+ u32 delta = seq - tp->rcv_nxt;
+
+ sock_owned_by_me((struct sock *)tp);
+ tp->bytes_received += delta;
+ tcp_rcv_sne_update(tp, seq);
WRITE_ONCE(tp->rcv_nxt, seq);
}

--
2.38.1