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authorJerry Chu <hkchu@google.com>2012-08-31 16:29:11 +0400
committerDavid S. Miller <davem@davemloft.net>2012-09-01 04:02:18 +0400
commit1046716368979dee857a2b8a91c4a8833f21b9cb (patch)
treefdda70278e6fa56c27d242fb1a0ec9b7e3e81d38 /include/net/request_sock.h
parent2a35cfa591ac63f17815c2d9432b799e37527980 (diff)
downloadlinux-1046716368979dee857a2b8a91c4a8833f21b9cb.tar.xz
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>
Diffstat (limited to 'include/net/request_sock.h')
-rw-r--r--include/net/request_sock.h36
1 files changed, 36 insertions, 0 deletions
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index 4c0766e201e3..c3cdd6c9f448 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -106,6 +106,34 @@ struct listen_sock {
struct request_sock *syn_table[0];
};
+/*
+ * For a TCP Fast Open listener -
+ * lock - protects the access to all the reqsk, which is co-owned by
+ * the listener and the child socket.
+ * qlen - pending TFO requests (still in TCP_SYN_RECV).
+ * max_qlen - max TFO reqs allowed before TFO is disabled.
+ *
+ * XXX (TFO) - ideally these fields can be made as part of "listen_sock"
+ * structure above. But there is some implementation difficulty due to
+ * listen_sock being part of request_sock_queue hence will be freed when
+ * a listener is stopped. But TFO related fields may continue to be
+ * accessed even after a listener is closed, until its sk_refcnt drops
+ * to 0 implying no more outstanding TFO reqs. One solution is to keep
+ * listen_opt around until sk_refcnt drops to 0. But there is some other
+ * complexity that needs to be resolved. E.g., a listener can be disabled
+ * temporarily through shutdown()->tcp_disconnect(), and re-enabled later.
+ */
+struct fastopen_queue {
+ struct request_sock *rskq_rst_head; /* Keep track of past TFO */
+ struct request_sock *rskq_rst_tail; /* requests that caused RST.
+ * This is part of the defense
+ * against spoofing attack.
+ */
+ spinlock_t lock;
+ int qlen; /* # of pending (TCP_SYN_RECV) reqs */
+ int max_qlen; /* != 0 iff TFO is currently enabled */
+};
+
/** struct request_sock_queue - queue of request_socks
*
* @rskq_accept_head - FIFO head of established children
@@ -129,6 +157,12 @@ struct request_sock_queue {
u8 rskq_defer_accept;
/* 3 bytes hole, try to pack */
struct listen_sock *listen_opt;
+ struct fastopen_queue *fastopenq; /* This is non-NULL iff TFO has been
+ * enabled on this listener. Check
+ * max_qlen != 0 in fastopen_queue
+ * to determine if TFO is enabled
+ * right at this moment.
+ */
};
extern int reqsk_queue_alloc(struct request_sock_queue *queue,
@@ -136,6 +170,8 @@ extern int reqsk_queue_alloc(struct request_sock_queue *queue,
extern void __reqsk_queue_destroy(struct request_sock_queue *queue);
extern void reqsk_queue_destroy(struct request_sock_queue *queue);
+extern void reqsk_fastopen_remove(struct sock *sk,
+ struct request_sock *req, bool reset);
static inline struct request_sock *
reqsk_queue_yank_acceptq(struct request_sock_queue *queue)