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tcp: TCP Fast Open Server - header & support functions

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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>
This commit is contained in:
Jerry Chu 2012-08-31 12:29:11 +00:00 • committed by David S. Miller
commit 1046716368
9 changed files with 276 additions and 20 deletions
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4
include/linux/snmp.h
View file

@ -241,6 +241,10 @@ enum
LINUX_MIB_TCPCHALLENGEACK, /* TCPChallengeACK */
LINUX_MIB_TCPSYNCHALLENGE, /* TCPSYNChallenge */
LINUX_MIB_TCPFASTOPENACTIVE, /* TCPFastOpenActive */
LINUX_MIB_TCPFASTOPENPASSIVE, /* TCPFastOpenPassive*/
LINUX_MIB_TCPFASTOPENPASSIVEFAIL, /* TCPFastOpenPassiveFail */
LINUX_MIB_TCPFASTOPENLISTENOVERFLOW, /* TCPFastOpenListenOverflow */
LINUX_MIB_TCPFASTOPENCOOKIEREQD, /* TCPFastOpenCookieReqd */
__LINUX_MIB_MAX
};

45
include/linux/tcp.h
View file

@ -110,6 +110,7 @@ enum {
#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 @@ static inline unsigned int tcp_optlen(const struct sk_buff *skb)
/* 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 @@ struct tcp_request_sock {
/* 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_sock {
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 @@ static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
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 */