tcp_fastopen - INTEGER
Enable TCP Fast Open feature (draft-ietf-tcpm-fastopen) to send data
in the opening SYN packet. To use this feature, the client application
- must not use connect(). Instead, it should use sendmsg() or sendto()
- with MSG_FASTOPEN flag which performs a TCP handshake automatically.
-
- The values (bitmap) are:
- 1: Enables sending data in the opening SYN on the client
- 5: Enables sending data in the opening SYN on the client regardless
- of cookie availability.
+ must use sendmsg() or sendto() with MSG_FASTOPEN flag rather than
+ connect() to perform a TCP handshake automatically.
+
+ The values (bitmap) are
+ 1: Enables sending data in the opening SYN on the client.
+ 2: Enables TCP Fast Open on the server side, i.e., allowing data in
+ a SYN packet to be accepted and passed to the application before
+ 3-way hand shake finishes.
+ 4: Send data in the opening SYN regardless of cookie availability and
+ without a cookie option.
+ 0x100: Accept SYN data w/o validating the cookie.
+ 0x200: Accept data-in-SYN w/o any cookie option present.
+ 0x400/0x800: Enable Fast Open on all listeners regardless of the
+ TCP_FASTOPEN socket option. The two different flags designate two
+ different ways of setting max_qlen without the TCP_FASTOPEN socket
+ option.
Default: 0
+ Note that the client & server side Fast Open flags (1 and 2
+ respectively) must be also enabled before the rest of flags can take
+ effect.
+
+ See include/net/tcp.h and the code for more details.
+
tcp_syn_retries - INTEGER
Number of times initial SYNs for an active TCP connection attempt
will be retransmitted. Should not be higher than 255. Default value
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
};
#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;
/* 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 {
/* 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)
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 {
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 */
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
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,
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)
/* Bit Flags for sysctl_tcp_fastopen */
#define TFO_CLIENT_ENABLE 1
+#define TFO_SERVER_ENABLE 2
#define TFO_CLIENT_NO_COOKIE 4 /* Data in SYN w/o cookie option */
+/* Process SYN data but skip cookie validation */
+#define TFO_SERVER_COOKIE_NOT_CHKED 0x100
+/* Accept SYN data w/o any cookie option */
+#define TFO_SERVER_COOKIE_NOT_REQD 0x200
+
+/* Force enable TFO on all listeners, i.e., not requiring the
+ * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
+ */
+#define TFO_SERVER_WO_SOCKOPT1 0x400
+#define TFO_SERVER_WO_SOCKOPT2 0x800
+/* Always create TFO child sockets on a TFO listener even when
+ * cookie/data not present. (For testing purpose!)
+ */
+#define TFO_SERVER_ALWAYS 0x1000
+
extern struct inet_timewait_death_row tcp_death_row;
/* sysctl variables for tcp */
extern bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst, bool paws_check);
extern bool tcp_remember_stamp(struct sock *sk);
extern bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
-extern void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
- struct tcp_fastopen_cookie *cookie,
- int *syn_loss, unsigned long *last_syn_loss);
-extern void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
- struct tcp_fastopen_cookie *cookie,
- bool syn_lost);
extern void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
extern void tcp_disable_fack(struct tcp_sock *tp);
extern void tcp_close(struct sock *sk, long timeout);
extern void tcp_cwnd_application_limited(struct sock *sk);
extern void tcp_resume_early_retransmit(struct sock *sk);
extern void tcp_rearm_rto(struct sock *sk);
+extern void tcp_reset(struct sock *sk);
/* tcp_timer.c */
extern void tcp_init_xmit_timers(struct sock *);
extern int tcp_mss_to_mtu(struct sock *sk, int mss);
extern void tcp_mtup_init(struct sock *sk);
extern void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt);
+extern void tcp_init_buffer_space(struct sock *sk);
static inline void tcp_bound_rto(const struct sock *sk)
{
req->rcv_wnd = 0; /* So that tcp_send_synack() knows! */
req->cookie_ts = 0;
tcp_rsk(req)->rcv_isn = TCP_SKB_CB(skb)->seq;
+ tcp_rsk(req)->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
req->mss = rx_opt->mss_clamp;
req->ts_recent = rx_opt->saw_tstamp ? rx_opt->rcv_tsval : 0;
ireq->tstamp_ok = rx_opt->tstamp_ok;
extern int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
const struct tcp_md5sig_key *key);
+/* From tcp_fastopen.c */
+extern void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
+ struct tcp_fastopen_cookie *cookie,
+ int *syn_loss, unsigned long *last_syn_loss);
+extern void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
+ struct tcp_fastopen_cookie *cookie,
+ bool syn_lost);
struct tcp_fastopen_request {
/* Fast Open cookie. Size 0 means a cookie request */
struct tcp_fastopen_cookie cookie;
struct msghdr *data; /* data in MSG_FASTOPEN */
u16 copied; /* queued in tcp_connect() */
};
-
void tcp_free_fastopen_req(struct tcp_sock *tp);
+extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
+int tcp_fastopen_reset_cipher(void *key, unsigned int len);
+void tcp_fastopen_cookie_gen(__be32 addr, struct tcp_fastopen_cookie *foc);
+
+#define TCP_FASTOPEN_KEY_LENGTH 16
+
+/* Fastopen key context */
+struct tcp_fastopen_context {
+ struct crypto_cipher __rcu *tfm;
+ __u8 key[TCP_FASTOPEN_KEY_LENGTH];
+ struct rcu_head rcu;
+};
+
/* write queue abstraction */
static inline void tcp_write_queue_purge(struct sock *sk)
{
SNMP_MIB_ITEM("TCPChallengeACK", LINUX_MIB_TCPCHALLENGEACK),
SNMP_MIB_ITEM("TCPSYNChallenge", LINUX_MIB_TCPSYNCHALLENGE),
SNMP_MIB_ITEM("TCPFastOpenActive", LINUX_MIB_TCPFASTOPENACTIVE),
+ SNMP_MIB_ITEM("TCPFastOpenPassive", LINUX_MIB_TCPFASTOPENPASSIVE),
+ SNMP_MIB_ITEM("TCPFastOpenPassiveFail", LINUX_MIB_TCPFASTOPENPASSIVEFAIL),
+ SNMP_MIB_ITEM("TCPFastOpenListenOverflow", LINUX_MIB_TCPFASTOPENLISTENOVERFLOW),
+ SNMP_MIB_ITEM("TCPFastOpenCookieReqd", LINUX_MIB_TCPFASTOPENCOOKIEREQD),
SNMP_MIB_SENTINEL
};
return 0;
}
+int proc_tcp_fastopen_key(ctl_table *ctl, int write, void __user *buffer,
+ size_t *lenp, loff_t *ppos)
+{
+ ctl_table tbl = { .maxlen = (TCP_FASTOPEN_KEY_LENGTH * 2 + 10) };
+ struct tcp_fastopen_context *ctxt;
+ int ret;
+ u32 user_key[4]; /* 16 bytes, matching TCP_FASTOPEN_KEY_LENGTH */
+
+ tbl.data = kmalloc(tbl.maxlen, GFP_KERNEL);
+ if (!tbl.data)
+ return -ENOMEM;
+
+ rcu_read_lock();
+ ctxt = rcu_dereference(tcp_fastopen_ctx);
+ if (ctxt)
+ memcpy(user_key, ctxt->key, TCP_FASTOPEN_KEY_LENGTH);
+ rcu_read_unlock();
+
+ snprintf(tbl.data, tbl.maxlen, "%08x-%08x-%08x-%08x",
+ user_key[0], user_key[1], user_key[2], user_key[3]);
+ ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+
+ if (write && ret == 0) {
+ if (sscanf(tbl.data, "%x-%x-%x-%x", user_key, user_key + 1,
+ user_key + 2, user_key + 3) != 4) {
+ ret = -EINVAL;
+ goto bad_key;
+ }
+ tcp_fastopen_reset_cipher(user_key, TCP_FASTOPEN_KEY_LENGTH);
+ }
+
+bad_key:
+ pr_debug("proc FO key set 0x%x-%x-%x-%x <- 0x%s: %u\n",
+ user_key[0], user_key[1], user_key[2], user_key[3],
+ (char *)tbl.data, ret);
+ kfree(tbl.data);
+ return ret;
+}
+
static struct ctl_table ipv4_table[] = {
{
.procname = "tcp_timestamps",
.proc_handler = proc_dointvec,
},
{
+ .procname = "tcp_fastopen_key",
+ .mode = 0600,
+ .maxlen = ((TCP_FASTOPEN_KEY_LENGTH * 2) + 10),
+ .proc_handler = proc_tcp_fastopen_key,
+ },
+ {
.procname = "tcp_tw_recycle",
.data = &tcp_death_row.sysctl_tw_recycle,
.maxlen = sizeof(int),
+#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/tcp.h>
+#include <linux/rcupdate.h>
+#include <linux/rculist.h>
+#include <net/inetpeer.h>
+#include <net/tcp.h>
-int sysctl_tcp_fastopen;
+int sysctl_tcp_fastopen __read_mostly;
+
+struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
+
+static DEFINE_SPINLOCK(tcp_fastopen_ctx_lock);
+
+static void tcp_fastopen_ctx_free(struct rcu_head *head)
+{
+ struct tcp_fastopen_context *ctx =
+ container_of(head, struct tcp_fastopen_context, rcu);
+ crypto_free_cipher(ctx->tfm);
+ kfree(ctx);
+}
+
+int tcp_fastopen_reset_cipher(void *key, unsigned int len)
+{
+ int err;
+ struct tcp_fastopen_context *ctx, *octx;
+
+ ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+ ctx->tfm = crypto_alloc_cipher("aes", 0, 0);
+
+ if (IS_ERR(ctx->tfm)) {
+ err = PTR_ERR(ctx->tfm);
+error: kfree(ctx);
+ pr_err("TCP: TFO aes cipher alloc error: %d\n", err);
+ return err;
+ }
+ err = crypto_cipher_setkey(ctx->tfm, key, len);
+ if (err) {
+ pr_err("TCP: TFO cipher key error: %d\n", err);
+ crypto_free_cipher(ctx->tfm);
+ goto error;
+ }
+ memcpy(ctx->key, key, len);
+
+ spin_lock(&tcp_fastopen_ctx_lock);
+
+ octx = rcu_dereference_protected(tcp_fastopen_ctx,
+ lockdep_is_held(&tcp_fastopen_ctx_lock));
+ rcu_assign_pointer(tcp_fastopen_ctx, ctx);
+ spin_unlock(&tcp_fastopen_ctx_lock);
+
+ if (octx)
+ call_rcu(&octx->rcu, tcp_fastopen_ctx_free);
+ return err;
+}
+
+/* Computes the fastopen cookie for the peer.
+ * The peer address is a 128 bits long (pad with zeros for IPv4).
+ *
+ * The caller must check foc->len to determine if a valid cookie
+ * has been generated successfully.
+*/
+void tcp_fastopen_cookie_gen(__be32 addr, struct tcp_fastopen_cookie *foc)
+{
+ __be32 peer_addr[4] = { addr, 0, 0, 0 };
+ struct tcp_fastopen_context *ctx;
+
+ rcu_read_lock();
+ ctx = rcu_dereference(tcp_fastopen_ctx);
+ if (ctx) {
+ crypto_cipher_encrypt_one(ctx->tfm,
+ foc->val,
+ (__u8 *)peer_addr);
+ foc->len = TCP_FASTOPEN_COOKIE_SIZE;
+ }
+ rcu_read_unlock();
+}
static int __init tcp_fastopen_init(void)
{
+ __u8 key[TCP_FASTOPEN_KEY_LENGTH];
+
+ get_random_bytes(key, sizeof(key));
+ tcp_fastopen_reset_cipher(key, sizeof(key));
return 0;
}
/* 4. Try to fixup all. It is made immediately after connection enters
* established state.
*/
-static void tcp_init_buffer_space(struct sock *sk)
+void tcp_init_buffer_space(struct sock *sk)
{
struct tcp_sock *tp = tcp_sk(sk);
int maxwin;
}
/* When we get a reset we do this. */
-static void tcp_reset(struct sock *sk)
+void tcp_reset(struct sock *sk)
{
/* We want the right error as BSD sees it (and indeed as we do). */
switch (sk->sk_state) {
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