blob: 7f830ff67f08c318717e809221d1586f17948185 [file] [log] [blame]
* NET Generic infrastructure for Network protocols.
* Definitions for request_sock
* Authors: Arnaldo Carvalho de Melo <>
* From code originally in include/net/tcp.h
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/bug.h>
#include <net/sock.h>
struct request_sock;
struct sk_buff;
struct dst_entry;
struct proto;
struct request_sock_ops {
int family;
int obj_size;
struct kmem_cache *slab;
char *slab_name;
int (*rtx_syn_ack)(struct sock *sk,
struct request_sock *req);
void (*send_ack)(struct sock *sk, struct sk_buff *skb,
struct request_sock *req);
void (*send_reset)(struct sock *sk,
struct sk_buff *skb);
void (*destructor)(struct request_sock *req);
void (*syn_ack_timeout)(struct sock *sk,
struct request_sock *req);
int inet_rtx_syn_ack(struct sock *parent, struct request_sock *req);
/* struct request_sock - mini sock to represent a connection request
struct request_sock {
struct sock_common __req_common;
struct request_sock *dl_next;
u16 mss;
u8 num_retrans; /* number of retransmits */
u8 cookie_ts:1; /* syncookie: encode tcpopts in timestamp */
u8 num_timeout:7; /* number of timeouts */
/* The following two fields can be easily recomputed I think -AK */
u32 window_clamp; /* window clamp at creation time */
u32 rcv_wnd; /* rcv_wnd offered first time */
u32 ts_recent;
unsigned long expires;
const struct request_sock_ops *rsk_ops;
struct sock *sk;
u32 secid;
u32 peer_secid;
static inline struct request_sock *reqsk_alloc(const struct request_sock_ops *ops)
struct request_sock *req = kmem_cache_alloc(ops->slab, GFP_ATOMIC);
if (req != NULL)
req->rsk_ops = ops;
return req;
static inline void __reqsk_free(struct request_sock *req)
kmem_cache_free(req->rsk_ops->slab, req);
static inline void reqsk_free(struct request_sock *req)
extern int sysctl_max_syn_backlog;
/** struct listen_sock - listen state
* @max_qlen_log - log_2 of maximal queued SYNs/REQUESTs
struct listen_sock {
u8 max_qlen_log;
u8 synflood_warned;
/* 2 bytes hole, try to use */
int qlen;
int qlen_young;
int clock_hand;
u32 hash_rnd;
u32 nr_table_entries;
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
* @rskq_accept_tail - FIFO tail of established children
* @rskq_defer_accept - User waits for some data after accept()
* @syn_wait_lock - serializer
* %syn_wait_lock is necessary only to avoid proc interface having to grab the main
* lock sock while browsing the listening hash (otherwise it's deadlock prone).
* This lock is acquired in read mode only from listening_get_next() seq_file
* op and it's acquired in write mode _only_ from code that is actively
* changing rskq_accept_head. All readers that are holding the master sock lock
* don't need to grab this lock in read mode too as rskq_accept_head. writes
* are always protected from the main sock lock.
struct request_sock_queue {
struct request_sock *rskq_accept_head;
struct request_sock *rskq_accept_tail;
rwlock_t syn_wait_lock;
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.
int reqsk_queue_alloc(struct request_sock_queue *queue,
unsigned int nr_table_entries);
void __reqsk_queue_destroy(struct request_sock_queue *queue);
void reqsk_queue_destroy(struct request_sock_queue *queue);
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)
struct request_sock *req = queue->rskq_accept_head;
queue->rskq_accept_head = NULL;
return req;
static inline int reqsk_queue_empty(struct request_sock_queue *queue)
return queue->rskq_accept_head == NULL;
static inline void reqsk_queue_unlink(struct request_sock_queue *queue,
struct request_sock *req,
struct request_sock **prev_req)
*prev_req = req->dl_next;
static inline void reqsk_queue_add(struct request_sock_queue *queue,
struct request_sock *req,
struct sock *parent,
struct sock *child)
req->sk = child;
if (queue->rskq_accept_head == NULL)
queue->rskq_accept_head = req;
queue->rskq_accept_tail->dl_next = req;
queue->rskq_accept_tail = req;
req->dl_next = NULL;
static inline struct request_sock *reqsk_queue_remove(struct request_sock_queue *queue)
struct request_sock *req = queue->rskq_accept_head;
WARN_ON(req == NULL);
queue->rskq_accept_head = req->dl_next;
if (queue->rskq_accept_head == NULL)
queue->rskq_accept_tail = NULL;
return req;
static inline int reqsk_queue_removed(struct request_sock_queue *queue,
struct request_sock *req)
struct listen_sock *lopt = queue->listen_opt;
if (req->num_timeout == 0)
return --lopt->qlen;
static inline int reqsk_queue_added(struct request_sock_queue *queue)
struct listen_sock *lopt = queue->listen_opt;
const int prev_qlen = lopt->qlen;
return prev_qlen;
static inline int reqsk_queue_len(const struct request_sock_queue *queue)
return queue->listen_opt != NULL ? queue->listen_opt->qlen : 0;
static inline int reqsk_queue_len_young(const struct request_sock_queue *queue)
return queue->listen_opt->qlen_young;
static inline int reqsk_queue_is_full(const struct request_sock_queue *queue)
return queue->listen_opt->qlen >> queue->listen_opt->max_qlen_log;
static inline void reqsk_queue_hash_req(struct request_sock_queue *queue,
u32 hash, struct request_sock *req,
unsigned long timeout)
struct listen_sock *lopt = queue->listen_opt;
req->expires = jiffies + timeout;
req->num_retrans = 0;
req->num_timeout = 0;
req->sk = NULL;
req->dl_next = lopt->syn_table[hash];
lopt->syn_table[hash] = req;
#endif /* _REQUEST_SOCK_H */