tcp: TCP Fast Open Server - header & support functions
This patch adds all the necessary data structure and support
functions to implement TFO server side. It also documents a number
of flags for the sysctl_tcp_fastopen knob, and adds a few Linux
extension MIBs.
In addition, it includes the following:
1. a new TCP_FASTOPEN socket option an application must call to
supply a max backlog allowed in order to enable TFO on its listener.
2. A number of key data structures:
"fastopen_rsk" in tcp_sock - for a big socket to access its
request_sock for retransmission and ack processing purpose. It is
non-NULL iff 3WHS not completed.
"fastopenq" in request_sock_queue - points to a per Fast Open
listener data structure "fastopen_queue" to keep track of qlen (# of
outstanding Fast Open requests) and max_qlen, among other things.
"listener" in tcp_request_sock - to point to the original listener
for book-keeping purpose, i.e., to maintain qlen against max_qlen
as part of defense against IP spoofing attack.
3. various data structure and functions, many in tcp_fastopen.c, to
support server side Fast Open cookie operations, including
/proc/sys/net/ipv4/tcp_fastopen_key to allow manual rekeying.
Signed-off-by: H.K. Jerry Chu <hkchu@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index eb125a4..ae46df5 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -110,6 +110,7 @@
#define TCP_REPAIR_QUEUE 20
#define TCP_QUEUE_SEQ 21
#define TCP_REPAIR_OPTIONS 22
+#define TCP_FASTOPEN 23 /* Enable FastOpen on listeners */
struct tcp_repair_opt {
__u32 opt_code;
@@ -246,6 +247,7 @@
/* TCP Fast Open */
#define TCP_FASTOPEN_COOKIE_MIN 4 /* Min Fast Open Cookie size in bytes */
#define TCP_FASTOPEN_COOKIE_MAX 16 /* Max Fast Open Cookie size in bytes */
+#define TCP_FASTOPEN_COOKIE_SIZE 8 /* the size employed by this impl. */
/* TCP Fast Open Cookie as stored in memory */
struct tcp_fastopen_cookie {
@@ -312,9 +314,14 @@
/* Only used by TCP MD5 Signature so far. */
const struct tcp_request_sock_ops *af_specific;
#endif
+ struct sock *listener; /* needed for TFO */
u32 rcv_isn;
u32 snt_isn;
u32 snt_synack; /* synack sent time */
+ u32 rcv_nxt; /* the ack # by SYNACK. For
+ * FastOpen it's the seq#
+ * after data-in-SYN.
+ */
};
static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
@@ -505,14 +512,18 @@
struct tcp_md5sig_info __rcu *md5sig_info;
#endif
-/* TCP fastopen related information */
- struct tcp_fastopen_request *fastopen_req;
-
/* When the cookie options are generated and exchanged, then this
* object holds a reference to them (cookie_values->kref). Also
* contains related tcp_cookie_transactions fields.
*/
struct tcp_cookie_values *cookie_values;
+
+/* TCP fastopen related information */
+ struct tcp_fastopen_request *fastopen_req;
+ /* fastopen_rsk points to request_sock that resulted in this big
+ * socket. Used to retransmit SYNACKs etc.
+ */
+ struct request_sock *fastopen_rsk;
};
enum tsq_flags {
@@ -552,6 +563,34 @@
return (struct tcp_timewait_sock *)sk;
}
+static inline bool tcp_passive_fastopen(const struct sock *sk)
+{
+ return (sk->sk_state == TCP_SYN_RECV &&
+ tcp_sk(sk)->fastopen_rsk != NULL);
+}
+
+static inline bool fastopen_cookie_present(struct tcp_fastopen_cookie *foc)
+{
+ return foc->len != -1;
+}
+
+static inline int fastopen_init_queue(struct sock *sk, int backlog)
+{
+ struct request_sock_queue *queue =
+ &inet_csk(sk)->icsk_accept_queue;
+
+ if (queue->fastopenq == NULL) {
+ queue->fastopenq = kzalloc(
+ sizeof(struct fastopen_queue),
+ sk->sk_allocation);
+ if (queue->fastopenq == NULL)
+ return -ENOMEM;
+ spin_lock_init(&queue->fastopenq->lock);
+ }
+ queue->fastopenq->max_qlen = backlog;
+ return 0;
+}
+
#endif /* __KERNEL__ */
#endif /* _LINUX_TCP_H */