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- /*
- * INET An implementation of the TCP/IP protocol suite for the LINUX
- * operating system. INET is implemented using the BSD Socket
- * interface as the means of communication with the user level.
- *
- * Implementation of the Transmission Control Protocol(TCP).
- *
- * Version: $Id: tcp_minisocks.c,v 1.15 2002/02/01 22:01:04 davem Exp $
- *
- * Authors: Ross Biro
- * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
- * Mark Evans, <evansmp@uhura.aston.ac.uk>
- * Corey Minyard <wf-rch!minyard@relay.EU.net>
- * Florian La Roche, <flla@stud.uni-sb.de>
- * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
- * Linus Torvalds, <torvalds@cs.helsinki.fi>
- * Alan Cox, <gw4pts@gw4pts.ampr.org>
- * Matthew Dillon, <dillon@apollo.west.oic.com>
- * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
- * Jorge Cwik, <jorge@laser.satlink.net>
- */
- #include <linux/config.h>
- #include <linux/mm.h>
- #include <linux/module.h>
- #include <linux/sysctl.h>
- #include <linux/workqueue.h>
- #include <net/tcp.h>
- #include <net/inet_common.h>
- #include <net/xfrm.h>
- #ifdef CONFIG_SYSCTL
- #define SYNC_INIT 0 /* let the user enable it */
- #else
- #define SYNC_INIT 1
- #endif
- int sysctl_tcp_tw_recycle;
- int sysctl_tcp_max_tw_buckets = NR_FILE*2;
- int sysctl_tcp_syncookies = SYNC_INIT;
- int sysctl_tcp_abort_on_overflow;
- static void tcp_tw_schedule(struct tcp_tw_bucket *tw, int timeo);
- static __inline__ int tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win)
- {
- if (seq == s_win)
- return 1;
- if (after(end_seq, s_win) && before(seq, e_win))
- return 1;
- return (seq == e_win && seq == end_seq);
- }
- /* New-style handling of TIME_WAIT sockets. */
- int tcp_tw_count;
- /* Must be called with locally disabled BHs. */
- static void tcp_timewait_kill(struct tcp_tw_bucket *tw)
- {
- struct inet_ehash_bucket *ehead;
- struct inet_bind_hashbucket *bhead;
- struct inet_bind_bucket *tb;
- /* Unlink from established hashes. */
- ehead = &tcp_ehash[tw->tw_hashent];
- write_lock(&ehead->lock);
- if (hlist_unhashed(&tw->tw_node)) {
- write_unlock(&ehead->lock);
- return;
- }
- __hlist_del(&tw->tw_node);
- sk_node_init(&tw->tw_node);
- write_unlock(&ehead->lock);
- /* Disassociate with bind bucket. */
- bhead = &tcp_bhash[inet_bhashfn(tw->tw_num, tcp_bhash_size)];
- spin_lock(&bhead->lock);
- tb = tw->tw_tb;
- __hlist_del(&tw->tw_bind_node);
- tw->tw_tb = NULL;
- inet_bind_bucket_destroy(tcp_bucket_cachep, tb);
- spin_unlock(&bhead->lock);
- #ifdef SOCK_REFCNT_DEBUG
- if (atomic_read(&tw->tw_refcnt) != 1) {
- printk(KERN_DEBUG "tw_bucket %p refcnt=%d\n", tw,
- atomic_read(&tw->tw_refcnt));
- }
- #endif
- tcp_tw_put(tw);
- }
- /*
- * * Main purpose of TIME-WAIT state is to close connection gracefully,
- * when one of ends sits in LAST-ACK or CLOSING retransmitting FIN
- * (and, probably, tail of data) and one or more our ACKs are lost.
- * * What is TIME-WAIT timeout? It is associated with maximal packet
- * lifetime in the internet, which results in wrong conclusion, that
- * it is set to catch "old duplicate segments" wandering out of their path.
- * It is not quite correct. This timeout is calculated so that it exceeds
- * maximal retransmission timeout enough to allow to lose one (or more)
- * segments sent by peer and our ACKs. This time may be calculated from RTO.
- * * When TIME-WAIT socket receives RST, it means that another end
- * finally closed and we are allowed to kill TIME-WAIT too.
- * * Second purpose of TIME-WAIT is catching old duplicate segments.
- * Well, certainly it is pure paranoia, but if we load TIME-WAIT
- * with this semantics, we MUST NOT kill TIME-WAIT state with RSTs.
- * * If we invented some more clever way to catch duplicates
- * (f.e. based on PAWS), we could truncate TIME-WAIT to several RTOs.
- *
- * The algorithm below is based on FORMAL INTERPRETATION of RFCs.
- * When you compare it to RFCs, please, read section SEGMENT ARRIVES
- * from the very beginning.
- *
- * NOTE. With recycling (and later with fin-wait-2) TW bucket
- * is _not_ stateless. It means, that strictly speaking we must
- * spinlock it. I do not want! Well, probability of misbehaviour
- * is ridiculously low and, seems, we could use some mb() tricks
- * to avoid misread sequence numbers, states etc. --ANK
- */
- enum tcp_tw_status
- tcp_timewait_state_process(struct tcp_tw_bucket *tw, struct sk_buff *skb,
- struct tcphdr *th, unsigned len)
- {
- struct tcp_options_received tmp_opt;
- int paws_reject = 0;
- tmp_opt.saw_tstamp = 0;
- if (th->doff > (sizeof(struct tcphdr) >> 2) && tw->tw_ts_recent_stamp) {
- tcp_parse_options(skb, &tmp_opt, 0);
- if (tmp_opt.saw_tstamp) {
- tmp_opt.ts_recent = tw->tw_ts_recent;
- tmp_opt.ts_recent_stamp = tw->tw_ts_recent_stamp;
- paws_reject = tcp_paws_check(&tmp_opt, th->rst);
- }
- }
- if (tw->tw_substate == TCP_FIN_WAIT2) {
- /* Just repeat all the checks of tcp_rcv_state_process() */
- /* Out of window, send ACK */
- if (paws_reject ||
- !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
- tw->tw_rcv_nxt,
- tw->tw_rcv_nxt + tw->tw_rcv_wnd))
- return TCP_TW_ACK;
- if (th->rst)
- goto kill;
- if (th->syn && !before(TCP_SKB_CB(skb)->seq, tw->tw_rcv_nxt))
- goto kill_with_rst;
- /* Dup ACK? */
- if (!after(TCP_SKB_CB(skb)->end_seq, tw->tw_rcv_nxt) ||
- TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) {
- tcp_tw_put(tw);
- return TCP_TW_SUCCESS;
- }
- /* New data or FIN. If new data arrive after half-duplex close,
- * reset.
- */
- if (!th->fin ||
- TCP_SKB_CB(skb)->end_seq != tw->tw_rcv_nxt + 1) {
- kill_with_rst:
- tcp_tw_deschedule(tw);
- tcp_tw_put(tw);
- return TCP_TW_RST;
- }
- /* FIN arrived, enter true time-wait state. */
- tw->tw_substate = TCP_TIME_WAIT;
- tw->tw_rcv_nxt = TCP_SKB_CB(skb)->end_seq;
- if (tmp_opt.saw_tstamp) {
- tw->tw_ts_recent_stamp = xtime.tv_sec;
- tw->tw_ts_recent = tmp_opt.rcv_tsval;
- }
- /* I am shamed, but failed to make it more elegant.
- * Yes, it is direct reference to IP, which is impossible
- * to generalize to IPv6. Taking into account that IPv6
- * do not undertsnad recycling in any case, it not
- * a big problem in practice. --ANK */
- if (tw->tw_family == AF_INET &&
- sysctl_tcp_tw_recycle && tw->tw_ts_recent_stamp &&
- tcp_v4_tw_remember_stamp(tw))
- tcp_tw_schedule(tw, tw->tw_timeout);
- else
- tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
- return TCP_TW_ACK;
- }
- /*
- * Now real TIME-WAIT state.
- *
- * RFC 1122:
- * "When a connection is [...] on TIME-WAIT state [...]
- * [a TCP] MAY accept a new SYN from the remote TCP to
- * reopen the connection directly, if it:
- *
- * (1) assigns its initial sequence number for the new
- * connection to be larger than the largest sequence
- * number it used on the previous connection incarnation,
- * and
- *
- * (2) returns to TIME-WAIT state if the SYN turns out
- * to be an old duplicate".
- */
- if (!paws_reject &&
- (TCP_SKB_CB(skb)->seq == tw->tw_rcv_nxt &&
- (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) {
- /* In window segment, it may be only reset or bare ack. */
- if (th->rst) {
- /* This is TIME_WAIT assasination, in two flavors.
- * Oh well... nobody has a sufficient solution to this
- * protocol bug yet.
- */
- if (sysctl_tcp_rfc1337 == 0) {
- kill:
- tcp_tw_deschedule(tw);
- tcp_tw_put(tw);
- return TCP_TW_SUCCESS;
- }
- }
- tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
- if (tmp_opt.saw_tstamp) {
- tw->tw_ts_recent = tmp_opt.rcv_tsval;
- tw->tw_ts_recent_stamp = xtime.tv_sec;
- }
- tcp_tw_put(tw);
- return TCP_TW_SUCCESS;
- }
- /* Out of window segment.
- All the segments are ACKed immediately.
- The only exception is new SYN. We accept it, if it is
- not old duplicate and we are not in danger to be killed
- by delayed old duplicates. RFC check is that it has
- newer sequence number works at rates <40Mbit/sec.
- However, if paws works, it is reliable AND even more,
- we even may relax silly seq space cutoff.
- RED-PEN: we violate main RFC requirement, if this SYN will appear
- old duplicate (i.e. we receive RST in reply to SYN-ACK),
- we must return socket to time-wait state. It is not good,
- but not fatal yet.
- */
- if (th->syn && !th->rst && !th->ack && !paws_reject &&
- (after(TCP_SKB_CB(skb)->seq, tw->tw_rcv_nxt) ||
- (tmp_opt.saw_tstamp && (s32)(tw->tw_ts_recent - tmp_opt.rcv_tsval) < 0))) {
- u32 isn = tw->tw_snd_nxt + 65535 + 2;
- if (isn == 0)
- isn++;
- TCP_SKB_CB(skb)->when = isn;
- return TCP_TW_SYN;
- }
- if (paws_reject)
- NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
- if(!th->rst) {
- /* In this case we must reset the TIMEWAIT timer.
- *
- * If it is ACKless SYN it may be both old duplicate
- * and new good SYN with random sequence number <rcv_nxt.
- * Do not reschedule in the last case.
- */
- if (paws_reject || th->ack)
- tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
- /* Send ACK. Note, we do not put the bucket,
- * it will be released by caller.
- */
- return TCP_TW_ACK;
- }
- tcp_tw_put(tw);
- return TCP_TW_SUCCESS;
- }
- /* Enter the time wait state. This is called with locally disabled BH.
- * Essentially we whip up a timewait bucket, copy the
- * relevant info into it from the SK, and mess with hash chains
- * and list linkage.
- */
- static void __tcp_tw_hashdance(struct sock *sk, struct tcp_tw_bucket *tw)
- {
- const struct inet_sock *inet = inet_sk(sk);
- struct inet_ehash_bucket *ehead = &tcp_ehash[sk->sk_hashent];
- struct inet_bind_hashbucket *bhead;
- /* Step 1: Put TW into bind hash. Original socket stays there too.
- Note, that any socket with inet->num != 0 MUST be bound in
- binding cache, even if it is closed.
- */
- bhead = &tcp_bhash[inet_bhashfn(inet->num, tcp_bhash_size)];
- spin_lock(&bhead->lock);
- tw->tw_tb = inet->bind_hash;
- BUG_TRAP(inet->bind_hash);
- tw_add_bind_node(tw, &tw->tw_tb->owners);
- spin_unlock(&bhead->lock);
- write_lock(&ehead->lock);
- /* Step 2: Remove SK from established hash. */
- if (__sk_del_node_init(sk))
- sock_prot_dec_use(sk->sk_prot);
- /* Step 3: Hash TW into TIMEWAIT half of established hash table. */
- tw_add_node(tw, &(ehead + tcp_ehash_size)->chain);
- atomic_inc(&tw->tw_refcnt);
- write_unlock(&ehead->lock);
- }
- /*
- * Move a socket to time-wait or dead fin-wait-2 state.
- */
- void tcp_time_wait(struct sock *sk, int state, int timeo)
- {
- struct tcp_tw_bucket *tw = NULL;
- struct tcp_sock *tp = tcp_sk(sk);
- int recycle_ok = 0;
- if (sysctl_tcp_tw_recycle && tp->rx_opt.ts_recent_stamp)
- recycle_ok = tp->af_specific->remember_stamp(sk);
- if (tcp_tw_count < sysctl_tcp_max_tw_buckets)
- tw = kmem_cache_alloc(tcp_timewait_cachep, SLAB_ATOMIC);
- if(tw != NULL) {
- struct inet_sock *inet = inet_sk(sk);
- int rto = (tp->rto<<2) - (tp->rto>>1);
- /* Give us an identity. */
- tw->tw_daddr = inet->daddr;
- tw->tw_rcv_saddr = inet->rcv_saddr;
- tw->tw_bound_dev_if = sk->sk_bound_dev_if;
- tw->tw_num = inet->num;
- tw->tw_state = TCP_TIME_WAIT;
- tw->tw_substate = state;
- tw->tw_sport = inet->sport;
- tw->tw_dport = inet->dport;
- tw->tw_family = sk->sk_family;
- tw->tw_reuse = sk->sk_reuse;
- tw->tw_rcv_wscale = tp->rx_opt.rcv_wscale;
- atomic_set(&tw->tw_refcnt, 1);
- tw->tw_hashent = sk->sk_hashent;
- tw->tw_rcv_nxt = tp->rcv_nxt;
- tw->tw_snd_nxt = tp->snd_nxt;
- tw->tw_rcv_wnd = tcp_receive_window(tp);
- tw->tw_ts_recent = tp->rx_opt.ts_recent;
- tw->tw_ts_recent_stamp = tp->rx_opt.ts_recent_stamp;
- tw_dead_node_init(tw);
- #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
- if (tw->tw_family == PF_INET6) {
- struct ipv6_pinfo *np = inet6_sk(sk);
- ipv6_addr_copy(&tw->tw_v6_daddr, &np->daddr);
- ipv6_addr_copy(&tw->tw_v6_rcv_saddr, &np->rcv_saddr);
- tw->tw_v6_ipv6only = np->ipv6only;
- } else {
- memset(&tw->tw_v6_daddr, 0, sizeof(tw->tw_v6_daddr));
- memset(&tw->tw_v6_rcv_saddr, 0, sizeof(tw->tw_v6_rcv_saddr));
- tw->tw_v6_ipv6only = 0;
- }
- #endif
- /* Linkage updates. */
- __tcp_tw_hashdance(sk, tw);
- /* Get the TIME_WAIT timeout firing. */
- if (timeo < rto)
- timeo = rto;
- if (recycle_ok) {
- tw->tw_timeout = rto;
- } else {
- tw->tw_timeout = TCP_TIMEWAIT_LEN;
- if (state == TCP_TIME_WAIT)
- timeo = TCP_TIMEWAIT_LEN;
- }
- tcp_tw_schedule(tw, timeo);
- tcp_tw_put(tw);
- } else {
- /* Sorry, if we're out of memory, just CLOSE this
- * socket up. We've got bigger problems than
- * non-graceful socket closings.
- */
- if (net_ratelimit())
- printk(KERN_INFO "TCP: time wait bucket table overflow\n");
- }
- tcp_update_metrics(sk);
- tcp_done(sk);
- }
- /* Kill off TIME_WAIT sockets once their lifetime has expired. */
- static int tcp_tw_death_row_slot;
- static void tcp_twkill(unsigned long);
- /* TIME_WAIT reaping mechanism. */
- #define TCP_TWKILL_SLOTS 8 /* Please keep this a power of 2. */
- #define TCP_TWKILL_PERIOD (TCP_TIMEWAIT_LEN/TCP_TWKILL_SLOTS)
- #define TCP_TWKILL_QUOTA 100
- static struct hlist_head tcp_tw_death_row[TCP_TWKILL_SLOTS];
- static DEFINE_SPINLOCK(tw_death_lock);
- static struct timer_list tcp_tw_timer = TIMER_INITIALIZER(tcp_twkill, 0, 0);
- static void twkill_work(void *);
- static DECLARE_WORK(tcp_twkill_work, twkill_work, NULL);
- static u32 twkill_thread_slots;
- /* Returns non-zero if quota exceeded. */
- static int tcp_do_twkill_work(int slot, unsigned int quota)
- {
- struct tcp_tw_bucket *tw;
- struct hlist_node *node;
- unsigned int killed;
- int ret;
- /* NOTE: compare this to previous version where lock
- * was released after detaching chain. It was racy,
- * because tw buckets are scheduled in not serialized context
- * in 2.3 (with netfilter), and with softnet it is common, because
- * soft irqs are not sequenced.
- */
- killed = 0;
- ret = 0;
- rescan:
- tw_for_each_inmate(tw, node, &tcp_tw_death_row[slot]) {
- __tw_del_dead_node(tw);
- spin_unlock(&tw_death_lock);
- tcp_timewait_kill(tw);
- tcp_tw_put(tw);
- killed++;
- spin_lock(&tw_death_lock);
- if (killed > quota) {
- ret = 1;
- break;
- }
- /* While we dropped tw_death_lock, another cpu may have
- * killed off the next TW bucket in the list, therefore
- * do a fresh re-read of the hlist head node with the
- * lock reacquired. We still use the hlist traversal
- * macro in order to get the prefetches.
- */
- goto rescan;
- }
- tcp_tw_count -= killed;
- NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed);
- return ret;
- }
- static void tcp_twkill(unsigned long dummy)
- {
- int need_timer, ret;
- spin_lock(&tw_death_lock);
- if (tcp_tw_count == 0)
- goto out;
- need_timer = 0;
- ret = tcp_do_twkill_work(tcp_tw_death_row_slot, TCP_TWKILL_QUOTA);
- if (ret) {
- twkill_thread_slots |= (1 << tcp_tw_death_row_slot);
- mb();
- schedule_work(&tcp_twkill_work);
- need_timer = 1;
- } else {
- /* We purged the entire slot, anything left? */
- if (tcp_tw_count)
- need_timer = 1;
- }
- tcp_tw_death_row_slot =
- ((tcp_tw_death_row_slot + 1) & (TCP_TWKILL_SLOTS - 1));
- if (need_timer)
- mod_timer(&tcp_tw_timer, jiffies + TCP_TWKILL_PERIOD);
- out:
- spin_unlock(&tw_death_lock);
- }
- extern void twkill_slots_invalid(void);
- static void twkill_work(void *dummy)
- {
- int i;
- if ((TCP_TWKILL_SLOTS - 1) > (sizeof(twkill_thread_slots) * 8))
- twkill_slots_invalid();
- while (twkill_thread_slots) {
- spin_lock_bh(&tw_death_lock);
- for (i = 0; i < TCP_TWKILL_SLOTS; i++) {
- if (!(twkill_thread_slots & (1 << i)))
- continue;
- while (tcp_do_twkill_work(i, TCP_TWKILL_QUOTA) != 0) {
- if (need_resched()) {
- spin_unlock_bh(&tw_death_lock);
- schedule();
- spin_lock_bh(&tw_death_lock);
- }
- }
- twkill_thread_slots &= ~(1 << i);
- }
- spin_unlock_bh(&tw_death_lock);
- }
- }
- /* These are always called from BH context. See callers in
- * tcp_input.c to verify this.
- */
- /* This is for handling early-kills of TIME_WAIT sockets. */
- void tcp_tw_deschedule(struct tcp_tw_bucket *tw)
- {
- spin_lock(&tw_death_lock);
- if (tw_del_dead_node(tw)) {
- tcp_tw_put(tw);
- if (--tcp_tw_count == 0)
- del_timer(&tcp_tw_timer);
- }
- spin_unlock(&tw_death_lock);
- tcp_timewait_kill(tw);
- }
- /* Short-time timewait calendar */
- static int tcp_twcal_hand = -1;
- static int tcp_twcal_jiffie;
- static void tcp_twcal_tick(unsigned long);
- static struct timer_list tcp_twcal_timer =
- TIMER_INITIALIZER(tcp_twcal_tick, 0, 0);
- static struct hlist_head tcp_twcal_row[TCP_TW_RECYCLE_SLOTS];
- static void tcp_tw_schedule(struct tcp_tw_bucket *tw, int timeo)
- {
- struct hlist_head *list;
- int slot;
- /* timeout := RTO * 3.5
- *
- * 3.5 = 1+2+0.5 to wait for two retransmits.
- *
- * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
- * our ACK acking that FIN can be lost. If N subsequent retransmitted
- * FINs (or previous seqments) are lost (probability of such event
- * is p^(N+1), where p is probability to lose single packet and
- * time to detect the loss is about RTO*(2^N - 1) with exponential
- * backoff). Normal timewait length is calculated so, that we
- * waited at least for one retransmitted FIN (maximal RTO is 120sec).
- * [ BTW Linux. following BSD, violates this requirement waiting
- * only for 60sec, we should wait at least for 240 secs.
- * Well, 240 consumes too much of resources 8)
- * ]
- * This interval is not reduced to catch old duplicate and
- * responces to our wandering segments living for two MSLs.
- * However, if we use PAWS to detect
- * old duplicates, we can reduce the interval to bounds required
- * by RTO, rather than MSL. So, if peer understands PAWS, we
- * kill tw bucket after 3.5*RTO (it is important that this number
- * is greater than TS tick!) and detect old duplicates with help
- * of PAWS.
- */
- slot = (timeo + (1<<TCP_TW_RECYCLE_TICK) - 1) >> TCP_TW_RECYCLE_TICK;
- spin_lock(&tw_death_lock);
- /* Unlink it, if it was scheduled */
- if (tw_del_dead_node(tw))
- tcp_tw_count--;
- else
- atomic_inc(&tw->tw_refcnt);
- if (slot >= TCP_TW_RECYCLE_SLOTS) {
- /* Schedule to slow timer */
- if (timeo >= TCP_TIMEWAIT_LEN) {
- slot = TCP_TWKILL_SLOTS-1;
- } else {
- slot = (timeo + TCP_TWKILL_PERIOD-1) / TCP_TWKILL_PERIOD;
- if (slot >= TCP_TWKILL_SLOTS)
- slot = TCP_TWKILL_SLOTS-1;
- }
- tw->tw_ttd = jiffies + timeo;
- slot = (tcp_tw_death_row_slot + slot) & (TCP_TWKILL_SLOTS - 1);
- list = &tcp_tw_death_row[slot];
- } else {
- tw->tw_ttd = jiffies + (slot << TCP_TW_RECYCLE_TICK);
- if (tcp_twcal_hand < 0) {
- tcp_twcal_hand = 0;
- tcp_twcal_jiffie = jiffies;
- tcp_twcal_timer.expires = tcp_twcal_jiffie + (slot<<TCP_TW_RECYCLE_TICK);
- add_timer(&tcp_twcal_timer);
- } else {
- if (time_after(tcp_twcal_timer.expires, jiffies + (slot<<TCP_TW_RECYCLE_TICK)))
- mod_timer(&tcp_twcal_timer, jiffies + (slot<<TCP_TW_RECYCLE_TICK));
- slot = (tcp_twcal_hand + slot)&(TCP_TW_RECYCLE_SLOTS-1);
- }
- list = &tcp_twcal_row[slot];
- }
- hlist_add_head(&tw->tw_death_node, list);
- if (tcp_tw_count++ == 0)
- mod_timer(&tcp_tw_timer, jiffies+TCP_TWKILL_PERIOD);
- spin_unlock(&tw_death_lock);
- }
- void tcp_twcal_tick(unsigned long dummy)
- {
- int n, slot;
- unsigned long j;
- unsigned long now = jiffies;
- int killed = 0;
- int adv = 0;
- spin_lock(&tw_death_lock);
- if (tcp_twcal_hand < 0)
- goto out;
- slot = tcp_twcal_hand;
- j = tcp_twcal_jiffie;
- for (n=0; n<TCP_TW_RECYCLE_SLOTS; n++) {
- if (time_before_eq(j, now)) {
- struct hlist_node *node, *safe;
- struct tcp_tw_bucket *tw;
- tw_for_each_inmate_safe(tw, node, safe,
- &tcp_twcal_row[slot]) {
- __tw_del_dead_node(tw);
- tcp_timewait_kill(tw);
- tcp_tw_put(tw);
- killed++;
- }
- } else {
- if (!adv) {
- adv = 1;
- tcp_twcal_jiffie = j;
- tcp_twcal_hand = slot;
- }
- if (!hlist_empty(&tcp_twcal_row[slot])) {
- mod_timer(&tcp_twcal_timer, j);
- goto out;
- }
- }
- j += (1<<TCP_TW_RECYCLE_TICK);
- slot = (slot+1)&(TCP_TW_RECYCLE_SLOTS-1);
- }
- tcp_twcal_hand = -1;
- out:
- if ((tcp_tw_count -= killed) == 0)
- del_timer(&tcp_tw_timer);
- NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed);
- spin_unlock(&tw_death_lock);
- }
- /* This is not only more efficient than what we used to do, it eliminates
- * a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
- *
- * Actually, we could lots of memory writes here. tp of listening
- * socket contains all necessary default parameters.
- */
- struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, struct sk_buff *skb)
- {
- /* allocate the newsk from the same slab of the master sock,
- * if not, at sk_free time we'll try to free it from the wrong
- * slabcache (i.e. is it TCPv4 or v6?), this is handled thru sk->sk_prot -acme */
- struct sock *newsk = sk_alloc(PF_INET, GFP_ATOMIC, sk->sk_prot, 0);
- if(newsk != NULL) {
- struct inet_request_sock *ireq = inet_rsk(req);
- struct tcp_request_sock *treq = tcp_rsk(req);
- struct inet_sock *newinet = inet_sk(newsk);
- struct tcp_sock *newtp;
- struct sk_filter *filter;
- memcpy(newsk, sk, sizeof(struct tcp_sock));
- newsk->sk_state = TCP_SYN_RECV;
- /* SANITY */
- sk_node_init(&newsk->sk_node);
- newinet->bind_hash = NULL;
- /* Clone the TCP header template */
- newinet->dport = ireq->rmt_port;
- sock_lock_init(newsk);
- bh_lock_sock(newsk);
- rwlock_init(&newsk->sk_dst_lock);
- newsk->sk_dst_cache = NULL;
- atomic_set(&newsk->sk_rmem_alloc, 0);
- skb_queue_head_init(&newsk->sk_receive_queue);
- atomic_set(&newsk->sk_wmem_alloc, 0);
- skb_queue_head_init(&newsk->sk_write_queue);
- atomic_set(&newsk->sk_omem_alloc, 0);
- newsk->sk_wmem_queued = 0;
- newsk->sk_forward_alloc = 0;
- sock_reset_flag(newsk, SOCK_DONE);
- newsk->sk_userlocks = sk->sk_userlocks & ~SOCK_BINDPORT_LOCK;
- newsk->sk_backlog.head = newsk->sk_backlog.tail = NULL;
- newsk->sk_send_head = NULL;
- rwlock_init(&newsk->sk_callback_lock);
- skb_queue_head_init(&newsk->sk_error_queue);
- newsk->sk_write_space = sk_stream_write_space;
- if ((filter = newsk->sk_filter) != NULL)
- sk_filter_charge(newsk, filter);
- if (unlikely(xfrm_sk_clone_policy(newsk))) {
- /* It is still raw copy of parent, so invalidate
- * destructor and make plain sk_free() */
- newsk->sk_destruct = NULL;
- sk_free(newsk);
- return NULL;
- }
- /* Now setup tcp_sock */
- newtp = tcp_sk(newsk);
- newtp->pred_flags = 0;
- newtp->rcv_nxt = treq->rcv_isn + 1;
- newtp->snd_nxt = treq->snt_isn + 1;
- newtp->snd_una = treq->snt_isn + 1;
- newtp->snd_sml = treq->snt_isn + 1;
- tcp_prequeue_init(newtp);
- tcp_init_wl(newtp, treq->snt_isn, treq->rcv_isn);
- newtp->retransmits = 0;
- newtp->backoff = 0;
- newtp->srtt = 0;
- newtp->mdev = TCP_TIMEOUT_INIT;
- newtp->rto = TCP_TIMEOUT_INIT;
- newtp->packets_out = 0;
- newtp->left_out = 0;
- newtp->retrans_out = 0;
- newtp->sacked_out = 0;
- newtp->fackets_out = 0;
- newtp->snd_ssthresh = 0x7fffffff;
- /* So many TCP implementations out there (incorrectly) count the
- * initial SYN frame in their delayed-ACK and congestion control
- * algorithms that we must have the following bandaid to talk
- * efficiently to them. -DaveM
- */
- newtp->snd_cwnd = 2;
- newtp->snd_cwnd_cnt = 0;
- newtp->frto_counter = 0;
- newtp->frto_highmark = 0;
- newtp->ca_ops = &tcp_reno;
- tcp_set_ca_state(newtp, TCP_CA_Open);
- tcp_init_xmit_timers(newsk);
- skb_queue_head_init(&newtp->out_of_order_queue);
- newtp->rcv_wup = treq->rcv_isn + 1;
- newtp->write_seq = treq->snt_isn + 1;
- newtp->pushed_seq = newtp->write_seq;
- newtp->copied_seq = treq->rcv_isn + 1;
- newtp->rx_opt.saw_tstamp = 0;
- newtp->rx_opt.dsack = 0;
- newtp->rx_opt.eff_sacks = 0;
- newtp->probes_out = 0;
- newtp->rx_opt.num_sacks = 0;
- newtp->urg_data = 0;
- /* Deinitialize accept_queue to trap illegal accesses. */
- memset(&newtp->accept_queue, 0, sizeof(newtp->accept_queue));
- /* Back to base struct sock members. */
- newsk->sk_err = 0;
- newsk->sk_priority = 0;
- atomic_set(&newsk->sk_refcnt, 2);
- /*
- * Increment the counter in the same struct proto as the master
- * sock (sk_refcnt_debug_inc uses newsk->sk_prot->socks, that
- * is the same as sk->sk_prot->socks, as this field was copied
- * with memcpy), same rationale as the first comment in this
- * function.
- *
- * This _changes_ the previous behaviour, where
- * tcp_create_openreq_child always was incrementing the
- * equivalent to tcp_prot->socks (inet_sock_nr), so this have
- * to be taken into account in all callers. -acme
- */
- sk_refcnt_debug_inc(newsk);
- atomic_inc(&tcp_sockets_allocated);
- if (sock_flag(newsk, SOCK_KEEPOPEN))
- tcp_reset_keepalive_timer(newsk,
- keepalive_time_when(newtp));
- newsk->sk_socket = NULL;
- newsk->sk_sleep = NULL;
- newtp->rx_opt.tstamp_ok = ireq->tstamp_ok;
- if((newtp->rx_opt.sack_ok = ireq->sack_ok) != 0) {
- if (sysctl_tcp_fack)
- newtp->rx_opt.sack_ok |= 2;
- }
- newtp->window_clamp = req->window_clamp;
- newtp->rcv_ssthresh = req->rcv_wnd;
- newtp->rcv_wnd = req->rcv_wnd;
- newtp->rx_opt.wscale_ok = ireq->wscale_ok;
- if (newtp->rx_opt.wscale_ok) {
- newtp->rx_opt.snd_wscale = ireq->snd_wscale;
- newtp->rx_opt.rcv_wscale = ireq->rcv_wscale;
- } else {
- newtp->rx_opt.snd_wscale = newtp->rx_opt.rcv_wscale = 0;
- newtp->window_clamp = min(newtp->window_clamp, 65535U);
- }
- newtp->snd_wnd = ntohs(skb->h.th->window) << newtp->rx_opt.snd_wscale;
- newtp->max_window = newtp->snd_wnd;
- if (newtp->rx_opt.tstamp_ok) {
- newtp->rx_opt.ts_recent = req->ts_recent;
- newtp->rx_opt.ts_recent_stamp = xtime.tv_sec;
- newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
- } else {
- newtp->rx_opt.ts_recent_stamp = 0;
- newtp->tcp_header_len = sizeof(struct tcphdr);
- }
- if (skb->len >= TCP_MIN_RCVMSS+newtp->tcp_header_len)
- newtp->ack.last_seg_size = skb->len-newtp->tcp_header_len;
- newtp->rx_opt.mss_clamp = req->mss;
- TCP_ECN_openreq_child(newtp, req);
- if (newtp->ecn_flags&TCP_ECN_OK)
- sock_set_flag(newsk, SOCK_NO_LARGESEND);
- TCP_INC_STATS_BH(TCP_MIB_PASSIVEOPENS);
- }
- return newsk;
- }
- /*
- * Process an incoming packet for SYN_RECV sockets represented
- * as a request_sock.
- */
- struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb,
- struct request_sock *req,
- struct request_sock **prev)
- {
- struct tcphdr *th = skb->h.th;
- struct tcp_sock *tp = tcp_sk(sk);
- u32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
- int paws_reject = 0;
- struct tcp_options_received tmp_opt;
- struct sock *child;
- tmp_opt.saw_tstamp = 0;
- if (th->doff > (sizeof(struct tcphdr)>>2)) {
- tcp_parse_options(skb, &tmp_opt, 0);
- if (tmp_opt.saw_tstamp) {
- tmp_opt.ts_recent = req->ts_recent;
- /* We do not store true stamp, but it is not required,
- * it can be estimated (approximately)
- * from another data.
- */
- tmp_opt.ts_recent_stamp = xtime.tv_sec - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans);
- paws_reject = tcp_paws_check(&tmp_opt, th->rst);
- }
- }
- /* Check for pure retransmitted SYN. */
- if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn &&
- flg == TCP_FLAG_SYN &&
- !paws_reject) {
- /*
- * RFC793 draws (Incorrectly! It was fixed in RFC1122)
- * this case on figure 6 and figure 8, but formal
- * protocol description says NOTHING.
- * To be more exact, it says that we should send ACK,
- * because this segment (at least, if it has no data)
- * is out of window.
- *
- * CONCLUSION: RFC793 (even with RFC1122) DOES NOT
- * describe SYN-RECV state. All the description
- * is wrong, we cannot believe to it and should
- * rely only on common sense and implementation
- * experience.
- *
- * Enforce "SYN-ACK" according to figure 8, figure 6
- * of RFC793, fixed by RFC1122.
- */
- req->rsk_ops->rtx_syn_ack(sk, req, NULL);
- return NULL;
- }
- /* Further reproduces section "SEGMENT ARRIVES"
- for state SYN-RECEIVED of RFC793.
- It is broken, however, it does not work only
- when SYNs are crossed.
- You would think that SYN crossing is impossible here, since
- we should have a SYN_SENT socket (from connect()) on our end,
- but this is not true if the crossed SYNs were sent to both
- ends by a malicious third party. We must defend against this,
- and to do that we first verify the ACK (as per RFC793, page
- 36) and reset if it is invalid. Is this a true full defense?
- To convince ourselves, let us consider a way in which the ACK
- test can still pass in this 'malicious crossed SYNs' case.
- Malicious sender sends identical SYNs (and thus identical sequence
- numbers) to both A and B:
- A: gets SYN, seq=7
- B: gets SYN, seq=7
- By our good fortune, both A and B select the same initial
- send sequence number of seven :-)
- A: sends SYN|ACK, seq=7, ack_seq=8
- B: sends SYN|ACK, seq=7, ack_seq=8
- So we are now A eating this SYN|ACK, ACK test passes. So
- does sequence test, SYN is truncated, and thus we consider
- it a bare ACK.
- If tp->defer_accept, we silently drop this bare ACK. Otherwise,
- we create an established connection. Both ends (listening sockets)
- accept the new incoming connection and try to talk to each other. 8-)
- Note: This case is both harmless, and rare. Possibility is about the
- same as us discovering intelligent life on another plant tomorrow.
- But generally, we should (RFC lies!) to accept ACK
- from SYNACK both here and in tcp_rcv_state_process().
- tcp_rcv_state_process() does not, hence, we do not too.
- Note that the case is absolutely generic:
- we cannot optimize anything here without
- violating protocol. All the checks must be made
- before attempt to create socket.
- */
- /* RFC793 page 36: "If the connection is in any non-synchronized state ...
- * and the incoming segment acknowledges something not yet
- * sent (the segment carries an unaccaptable ACK) ...
- * a reset is sent."
- *
- * Invalid ACK: reset will be sent by listening socket
- */
- if ((flg & TCP_FLAG_ACK) &&
- (TCP_SKB_CB(skb)->ack_seq != tcp_rsk(req)->snt_isn + 1))
- return sk;
- /* Also, it would be not so bad idea to check rcv_tsecr, which
- * is essentially ACK extension and too early or too late values
- * should cause reset in unsynchronized states.
- */
- /* RFC793: "first check sequence number". */
- if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
- tcp_rsk(req)->rcv_isn + 1, tcp_rsk(req)->rcv_isn + 1 + req->rcv_wnd)) {
- /* Out of window: send ACK and drop. */
- if (!(flg & TCP_FLAG_RST))
- req->rsk_ops->send_ack(skb, req);
- if (paws_reject)
- NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
- return NULL;
- }
- /* In sequence, PAWS is OK. */
- if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_isn + 1))
- req->ts_recent = tmp_opt.rcv_tsval;
- if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) {
- /* Truncate SYN, it is out of window starting
- at tcp_rsk(req)->rcv_isn + 1. */
- flg &= ~TCP_FLAG_SYN;
- }
- /* RFC793: "second check the RST bit" and
- * "fourth, check the SYN bit"
- */
- if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN))
- goto embryonic_reset;
- /* ACK sequence verified above, just make sure ACK is
- * set. If ACK not set, just silently drop the packet.
- */
- if (!(flg & TCP_FLAG_ACK))
- return NULL;
- /* If TCP_DEFER_ACCEPT is set, drop bare ACK. */
- if (tp->defer_accept && TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) {
- inet_rsk(req)->acked = 1;
- return NULL;
- }
- /* OK, ACK is valid, create big socket and
- * feed this segment to it. It will repeat all
- * the tests. THIS SEGMENT MUST MOVE SOCKET TO
- * ESTABLISHED STATE. If it will be dropped after
- * socket is created, wait for troubles.
- */
- child = tp->af_specific->syn_recv_sock(sk, skb, req, NULL);
- if (child == NULL)
- goto listen_overflow;
- tcp_synq_unlink(tp, req, prev);
- tcp_synq_removed(sk, req);
- tcp_acceptq_queue(sk, req, child);
- return child;
- listen_overflow:
- if (!sysctl_tcp_abort_on_overflow) {
- inet_rsk(req)->acked = 1;
- return NULL;
- }
- embryonic_reset:
- NET_INC_STATS_BH(LINUX_MIB_EMBRYONICRSTS);
- if (!(flg & TCP_FLAG_RST))
- req->rsk_ops->send_reset(skb);
- tcp_synq_drop(sk, req, prev);
- return NULL;
- }
- /*
- * Queue segment on the new socket if the new socket is active,
- * otherwise we just shortcircuit this and continue with
- * the new socket.
- */
- int tcp_child_process(struct sock *parent, struct sock *child,
- struct sk_buff *skb)
- {
- int ret = 0;
- int state = child->sk_state;
- if (!sock_owned_by_user(child)) {
- ret = tcp_rcv_state_process(child, skb, skb->h.th, skb->len);
- /* Wakeup parent, send SIGIO */
- if (state == TCP_SYN_RECV && child->sk_state != state)
- parent->sk_data_ready(parent, 0);
- } else {
- /* Alas, it is possible again, because we do lookup
- * in main socket hash table and lock on listening
- * socket does not protect us more.
- */
- sk_add_backlog(child, skb);
- }
- bh_unlock_sock(child);
- sock_put(child);
- return ret;
- }
- EXPORT_SYMBOL(tcp_check_req);
- EXPORT_SYMBOL(tcp_child_process);
- EXPORT_SYMBOL(tcp_create_openreq_child);
- EXPORT_SYMBOL(tcp_timewait_state_process);
- EXPORT_SYMBOL(tcp_tw_deschedule);
|