patch-2.4.0-test7 linux/net/ipv4/tcp_minisocks.c
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- Lines: 971
- Date:
Thu Aug 10 13:01:26 2000
- Orig file:
v2.4.0-test6/linux/net/ipv4/tcp_minisocks.c
- Orig date:
Wed Dec 31 16:00:00 1969
diff -u --recursive --new-file v2.4.0-test6/linux/net/ipv4/tcp_minisocks.c linux/net/ipv4/tcp_minisocks.c
@@ -0,0 +1,970 @@
+/*
+ * 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 1.1 2000/08/09 11:59:04 davem Exp $
+ *
+ * Authors: Ross Biro, <bir7@leland.Stanford.Edu>
+ * 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/sysctl.h>
+#include <net/tcp.h>
+#include <net/inet_common.h>
+
+#ifdef CONFIG_SYSCTL
+#define SYNC_INIT 0 /* let the user enable it */
+#else
+#define SYNC_INIT 1
+#endif
+
+int sysctl_tcp_tw_recycle = 0;
+int sysctl_tcp_max_tw_buckets = NR_FILE*2;
+
+int sysctl_tcp_syncookies = SYNC_INIT;
+int sysctl_tcp_abort_on_overflow = 0;
+
+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 = 0;
+
+
+/* Must be called with locally disabled BHs. */
+void tcp_timewait_kill(struct tcp_tw_bucket *tw)
+{
+ struct tcp_ehash_bucket *ehead;
+ struct tcp_bind_hashbucket *bhead;
+ struct tcp_bind_bucket *tb;
+
+ /* Unlink from established hashes. */
+ ehead = &tcp_ehash[tw->hashent];
+ write_lock(&ehead->lock);
+ if (!tw->pprev) {
+ write_unlock(&ehead->lock);
+ return;
+ }
+ if(tw->next)
+ tw->next->pprev = tw->pprev;
+ *(tw->pprev) = tw->next;
+ tw->pprev = NULL;
+ write_unlock(&ehead->lock);
+
+ /* Disassociate with bind bucket. */
+ bhead = &tcp_bhash[tcp_bhashfn(tw->num)];
+ spin_lock(&bhead->lock);
+ if ((tb = tw->tb) != NULL) {
+ if(tw->bind_next)
+ tw->bind_next->bind_pprev = tw->bind_pprev;
+ *(tw->bind_pprev) = tw->bind_next;
+ tw->tb = NULL;
+ if (tb->owners == NULL) {
+ if (tb->next)
+ tb->next->pprev = tb->pprev;
+ *(tb->pprev) = tb->next;
+ kmem_cache_free(tcp_bucket_cachep, tb);
+ }
+ }
+ spin_unlock(&bhead->lock);
+
+#ifdef INET_REFCNT_DEBUG
+ if (atomic_read(&tw->refcnt) != 1) {
+ printk(KERN_DEBUG "tw_bucket %p refcnt=%d\n", tw, atomic_read(&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 retransmision 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_opt tp;
+ int paws_reject = 0;
+
+ tp.saw_tstamp = 0;
+ if (th->doff > (sizeof(struct tcphdr)>>2) && tw->ts_recent_stamp) {
+ tcp_parse_options(skb, &tp);
+
+ if (tp.saw_tstamp) {
+ tp.ts_recent = tw->ts_recent;
+ tp.ts_recent_stamp = tw->ts_recent_stamp;
+ paws_reject = tcp_paws_check(&tp, th->rst);
+ }
+ }
+
+ if (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->rcv_nxt, tw->rcv_nxt + tw->rcv_wnd))
+ return TCP_TW_ACK;
+
+ if (th->rst)
+ goto kill;
+
+ if (th->syn && TCP_SKB_CB(skb)->seq != tw->syn_seq)
+ goto kill_with_rst;
+
+ /* Dup ACK? */
+ if (!after(TCP_SKB_CB(skb)->end_seq, 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->rcv_nxt+1) {
+kill_with_rst:
+ tcp_tw_deschedule(tw);
+ tcp_timewait_kill(tw);
+ tcp_tw_put(tw);
+ return TCP_TW_RST;
+ }
+
+ /* FIN arrived, enter true time-wait state. */
+ tw->substate = TCP_TIME_WAIT;
+ tw->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
+ if (tp.saw_tstamp) {
+ tw->ts_recent_stamp = xtime.tv_sec;
+ tw->ts_recent = tp.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->family == AF_INET &&
+ sysctl_tcp_tw_recycle && tw->ts_recent_stamp &&
+ tcp_v4_tw_remember_stamp(tw))
+ tcp_tw_schedule(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->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_timewait_kill(tw);
+ tcp_tw_put(tw);
+ return TCP_TW_SUCCESS;
+ }
+ }
+ tcp_tw_schedule(tw, TCP_TIMEWAIT_LEN);
+
+ if (tp.saw_tstamp) {
+ tw->ts_recent = tp.rcv_tsval;
+ 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->rcv_nxt) ||
+ (tp.saw_tstamp && (s32)(tw->ts_recent - tp.rcv_tsval) < 0))) {
+ u32 isn = 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(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)
+{
+ struct tcp_ehash_bucket *ehead = &tcp_ehash[sk->hashent];
+ struct tcp_bind_hashbucket *bhead;
+ struct sock **head, *sktw;
+
+ write_lock(&ehead->lock);
+
+ /* Step 1: Remove SK from established hash. */
+ if (sk->pprev) {
+ if(sk->next)
+ sk->next->pprev = sk->pprev;
+ *sk->pprev = sk->next;
+ sk->pprev = NULL;
+ sock_prot_dec_use(sk->prot);
+ }
+
+ /* Step 2: Hash TW into TIMEWAIT half of established hash table. */
+ head = &(ehead + tcp_ehash_size)->chain;
+ sktw = (struct sock *)tw;
+ if((sktw->next = *head) != NULL)
+ (*head)->pprev = &sktw->next;
+ *head = sktw;
+ sktw->pprev = head;
+ atomic_inc(&tw->refcnt);
+
+ write_unlock(&ehead->lock);
+
+ /* Step 3: Put TW into bind hash. Original socket stays there too.
+ Note, that any socket with sk->num!=0 MUST be bound in binding
+ cache, even if it is closed.
+ */
+ bhead = &tcp_bhash[tcp_bhashfn(sk->num)];
+ spin_lock(&bhead->lock);
+ tw->tb = (struct tcp_bind_bucket *)sk->prev;
+ BUG_TRAP(sk->prev!=NULL);
+ if ((tw->bind_next = tw->tb->owners) != NULL)
+ tw->tb->owners->bind_pprev = &tw->bind_next;
+ tw->tb->owners = (struct sock*)tw;
+ tw->bind_pprev = &tw->tb->owners;
+ spin_unlock(&bhead->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_opt *tp = &(sk->tp_pinfo.af_tcp);
+ int recycle_ok = 0;
+
+ if (sysctl_tcp_tw_recycle && tp->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) {
+ int rto = (tp->rto<<2) - (tp->rto>>1);
+
+ /* Give us an identity. */
+ tw->daddr = sk->daddr;
+ tw->rcv_saddr = sk->rcv_saddr;
+ tw->bound_dev_if= sk->bound_dev_if;
+ tw->num = sk->num;
+ tw->state = TCP_TIME_WAIT;
+ tw->substate = state;
+ tw->sport = sk->sport;
+ tw->dport = sk->dport;
+ tw->family = sk->family;
+ tw->reuse = sk->reuse;
+ tw->rcv_wscale = tp->rcv_wscale;
+ atomic_set(&tw->refcnt, 0);
+
+ tw->hashent = sk->hashent;
+ tw->rcv_nxt = tp->rcv_nxt;
+ tw->snd_nxt = tp->snd_nxt;
+ tw->rcv_wnd = tcp_receive_window(tp);
+ tw->syn_seq = tp->syn_seq;
+ tw->ts_recent = tp->ts_recent;
+ tw->ts_recent_stamp= tp->ts_recent_stamp;
+ tw->pprev_death = NULL;
+
+#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
+ if(tw->family == PF_INET6) {
+ memcpy(&tw->v6_daddr,
+ &sk->net_pinfo.af_inet6.daddr,
+ sizeof(struct in6_addr));
+ memcpy(&tw->v6_rcv_saddr,
+ &sk->net_pinfo.af_inet6.rcv_saddr,
+ sizeof(struct in6_addr));
+ }
+#endif
+ /* Linkage updates. */
+ __tcp_tw_hashdance(sk, tw);
+
+ /* Get the TIME_WAIT timeout firing. */
+ if (timeo < rto)
+ timeo = rto;
+
+ if (recycle_ok) {
+ tw->timeout = rto;
+ } else {
+ tw->timeout = TCP_TIMEWAIT_LEN;
+ if (state == TCP_TIME_WAIT)
+ timeo = TCP_TIMEWAIT_LEN;
+ }
+
+ tcp_tw_schedule(tw, timeo);
+ } 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 = 0;
+
+static void tcp_twkill(unsigned long);
+
+static struct tcp_tw_bucket *tcp_tw_death_row[TCP_TWKILL_SLOTS];
+static spinlock_t tw_death_lock = SPIN_LOCK_UNLOCKED;
+static struct timer_list tcp_tw_timer = { function: tcp_twkill };
+
+static void SMP_TIMER_NAME(tcp_twkill)(unsigned long dummy)
+{
+ struct tcp_tw_bucket *tw;
+ int killed = 0;
+
+ /* 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.
+ */
+ spin_lock(&tw_death_lock);
+
+ if (tcp_tw_count == 0)
+ goto out;
+
+ while((tw = tcp_tw_death_row[tcp_tw_death_row_slot]) != NULL) {
+ tcp_tw_death_row[tcp_tw_death_row_slot] = tw->next_death;
+ tw->pprev_death = NULL;
+ spin_unlock(&tw_death_lock);
+
+ tcp_timewait_kill(tw);
+ tcp_tw_put(tw);
+
+ killed++;
+
+ spin_lock(&tw_death_lock);
+ }
+ tcp_tw_death_row_slot =
+ ((tcp_tw_death_row_slot + 1) & (TCP_TWKILL_SLOTS - 1));
+
+ if ((tcp_tw_count -= killed) != 0)
+ mod_timer(&tcp_tw_timer, jiffies+TCP_TWKILL_PERIOD);
+ net_statistics[smp_processor_id()*2].TimeWaited += killed;
+out:
+ spin_unlock(&tw_death_lock);
+}
+
+SMP_TIMER_DEFINE(tcp_twkill, tcp_twkill_task);
+
+/* 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->pprev_death) {
+ if(tw->next_death)
+ tw->next_death->pprev_death = tw->pprev_death;
+ *tw->pprev_death = tw->next_death;
+ tw->pprev_death = NULL;
+ tcp_tw_put(tw);
+ if (--tcp_tw_count == 0)
+ del_timer(&tcp_tw_timer);
+ }
+ spin_unlock(&tw_death_lock);
+}
+
+/* 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 = {function: tcp_twcal_tick};
+static struct tcp_tw_bucket *tcp_twcal_row[TCP_TW_RECYCLE_SLOTS];
+
+void tcp_tw_schedule(struct tcp_tw_bucket *tw, int timeo)
+{
+ struct tcp_tw_bucket **tpp;
+ 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->pprev_death) {
+ if(tw->next_death)
+ tw->next_death->pprev_death = tw->pprev_death;
+ *tw->pprev_death = tw->next_death;
+ tw->pprev_death = NULL;
+ tcp_tw_count--;
+ } else
+ atomic_inc(&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->ttd = jiffies + timeo;
+ slot = (tcp_tw_death_row_slot + slot) & (TCP_TWKILL_SLOTS - 1);
+ tpp = &tcp_tw_death_row[slot];
+ } else {
+ 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 ((long)(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);
+ }
+ tpp = &tcp_twcal_row[slot];
+ }
+
+ if((tw->next_death = *tpp) != NULL)
+ (*tpp)->pprev_death = &tw->next_death;
+ *tpp = tw;
+ tw->pprev_death = tpp;
+
+ if (tcp_tw_count++ == 0)
+ mod_timer(&tcp_tw_timer, jiffies+TCP_TWKILL_PERIOD);
+ spin_unlock(&tw_death_lock);
+}
+
+void SMP_TIMER_NAME(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 ((long)(j - now) <= 0) {
+ struct tcp_tw_bucket *tw;
+
+ while((tw = tcp_twcal_row[slot]) != NULL) {
+ tcp_twcal_row[slot] = tw->next_death;
+ tw->pprev_death = NULL;
+
+ tcp_timewait_kill(tw);
+ tcp_tw_put(tw);
+ killed++;
+ }
+ } else {
+ if (!adv) {
+ adv = 1;
+ tcp_twcal_jiffie = j;
+ tcp_twcal_hand = slot;
+ }
+
+ if (tcp_twcal_row[slot] != NULL) {
+ 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_statistics[smp_processor_id()*2].TimeWaitKilled += killed;
+ spin_unlock(&tw_death_lock);
+}
+
+SMP_TIMER_DEFINE(tcp_twcal_tick, tcp_twcal_tasklet);
+
+
+/* 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 open_request *req, struct sk_buff *skb)
+{
+ struct sock *newsk = sk_alloc(PF_INET, GFP_ATOMIC, 0);
+
+ if(newsk != NULL) {
+ struct tcp_opt *newtp;
+#ifdef CONFIG_FILTER
+ struct sk_filter *filter;
+#endif
+
+ memcpy(newsk, sk, sizeof(*newsk));
+ newsk->state = TCP_SYN_RECV;
+
+ /* SANITY */
+ newsk->pprev = NULL;
+ newsk->prev = NULL;
+
+ /* Clone the TCP header template */
+ newsk->dport = req->rmt_port;
+
+ sock_lock_init(newsk);
+ bh_lock_sock(newsk);
+
+ atomic_set(&newsk->rmem_alloc, 0);
+ skb_queue_head_init(&newsk->receive_queue);
+ atomic_set(&newsk->wmem_alloc, 0);
+ skb_queue_head_init(&newsk->write_queue);
+ atomic_set(&newsk->omem_alloc, 0);
+ newsk->wmem_queued = 0;
+ newsk->forward_alloc = 0;
+
+ newsk->done = 0;
+ newsk->proc = 0;
+ newsk->backlog.head = newsk->backlog.tail = NULL;
+ skb_queue_head_init(&newsk->error_queue);
+ newsk->write_space = tcp_write_space;
+#ifdef CONFIG_FILTER
+ if ((filter = newsk->filter) != NULL)
+ sk_filter_charge(newsk, filter);
+#endif
+
+ /* Now setup tcp_opt */
+ newtp = &(newsk->tp_pinfo.af_tcp);
+ newtp->pred_flags = 0;
+ newtp->rcv_nxt = req->rcv_isn + 1;
+ newtp->snd_nxt = req->snt_isn + 1;
+ newtp->snd_una = req->snt_isn + 1;
+ newtp->snd_sml = req->snt_isn + 1;
+
+ tcp_delack_init(newtp);
+
+ tcp_prequeue_init(newtp);
+
+ tcp_init_wl(newtp, req->snt_isn, req->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->ca_state = TCP_CA_Open;
+ tcp_init_xmit_timers(newsk);
+ skb_queue_head_init(&newtp->out_of_order_queue);
+ newtp->send_head = NULL;
+ newtp->rcv_wup = req->rcv_isn + 1;
+ newtp->write_seq = req->snt_isn + 1;
+ newtp->pushed_seq = newtp->write_seq;
+ newtp->copied_seq = req->rcv_isn + 1;
+
+ newtp->saw_tstamp = 0;
+
+ newtp->dsack = 0;
+ newtp->eff_sacks = 0;
+
+ newtp->probes_out = 0;
+ newtp->num_sacks = 0;
+ newtp->syn_seq = req->rcv_isn;
+ newtp->fin_seq = req->rcv_isn;
+ newtp->urg_data = 0;
+ newtp->listen_opt = NULL;
+ newtp->accept_queue = newtp->accept_queue_tail = NULL;
+ /* Deinitialize syn_wait_lock to trap illegal accesses. */
+ memset(&newtp->syn_wait_lock, 0, sizeof(newtp->syn_wait_lock));
+
+ /* Back to base struct sock members. */
+ newsk->err = 0;
+ newsk->priority = 0;
+ atomic_set(&newsk->refcnt, 1);
+#ifdef INET_REFCNT_DEBUG
+ atomic_inc(&inet_sock_nr);
+#endif
+ atomic_inc(&tcp_sockets_allocated);
+
+ if (newsk->keepopen)
+ tcp_reset_keepalive_timer(newsk, keepalive_time_when(newtp));
+ newsk->socket = NULL;
+ newsk->sleep = NULL;
+
+ newtp->tstamp_ok = req->tstamp_ok;
+ if((newtp->sack_ok = req->sack_ok) != 0) {
+ if (sysctl_tcp_fack)
+ newtp->sack_ok |= 2;
+ }
+ newtp->window_clamp = req->window_clamp;
+ newtp->rcv_ssthresh = req->rcv_wnd;
+ newtp->rcv_wnd = req->rcv_wnd;
+ newtp->wscale_ok = req->wscale_ok;
+ if (newtp->wscale_ok) {
+ newtp->snd_wscale = req->snd_wscale;
+ newtp->rcv_wscale = req->rcv_wscale;
+ } else {
+ newtp->snd_wscale = newtp->rcv_wscale = 0;
+ newtp->window_clamp = min(newtp->window_clamp,65535);
+ }
+ newtp->snd_wnd = ntohs(skb->h.th->window) << newtp->snd_wscale;
+ newtp->max_window = newtp->snd_wnd;
+
+ if (newtp->tstamp_ok) {
+ newtp->ts_recent = req->ts_recent;
+ newtp->ts_recent_stamp = xtime.tv_sec;
+ newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
+ } else {
+ newtp->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->mss_clamp = req->mss;
+ TCP_ECN_openreq_child(newtp, req);
+ }
+ return newsk;
+}
+
+/*
+ * Process an incoming packet for SYN_RECV sockets represented
+ * as an open_request.
+ */
+
+struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb,
+ struct open_request *req,
+ struct open_request **prev)
+{
+ struct tcphdr *th = skb->h.th;
+ struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
+ u32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
+ int paws_reject = 0;
+ struct tcp_opt ttp;
+ struct sock *child;
+
+ ttp.saw_tstamp = 0;
+ if (th->doff > (sizeof(struct tcphdr)>>2)) {
+ tcp_parse_options(skb, &ttp);
+
+ if (ttp.saw_tstamp) {
+ ttp.ts_recent = req->ts_recent;
+ /* We do not store true stamp, but it is not required,
+ * it can be estimated (approximately)
+ * from another data.
+ */
+ ttp.ts_recent_stamp = xtime.tv_sec - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans);
+ paws_reject = tcp_paws_check(&ttp, th->rst);
+ }
+ }
+
+ /* Check for pure retransmited SYN. */
+ if (TCP_SKB_CB(skb)->seq == 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->class->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, which is impossible in our
+ case.
+
+ 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: "first check sequence number". */
+
+ if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
+ req->rcv_isn+1, req->rcv_isn+1+req->rcv_wnd)) {
+ /* Out of window: send ACK and drop. */
+ if (!(flg & TCP_FLAG_RST))
+ req->class->send_ack(skb, req);
+ if (paws_reject)
+ NET_INC_STATS_BH(PAWSEstabRejected);
+ return NULL;
+ }
+
+ /* In sequence, PAWS is OK. */
+
+ if (ttp.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, req->rcv_isn+1))
+ req->ts_recent = ttp.rcv_tsval;
+
+ if (TCP_SKB_CB(skb)->seq == req->rcv_isn) {
+ /* Truncate SYN, it is out of window starting
+ at 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;
+
+ /* RFC793: "fifth check the ACK field" */
+
+ if (!(flg & TCP_FLAG_ACK))
+ return NULL;
+
+ /* Invalid ACK: reset will be sent by listening socket */
+ if (TCP_SKB_CB(skb)->ack_seq != 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.
+ */
+
+ /* If TCP_DEFER_ACCEPT is set, drop bare ACK. */
+ if (tp->defer_accept && TCP_SKB_CB(skb)->end_seq == req->rcv_isn+1) {
+ 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) {
+ req->acked = 1;
+ return NULL;
+ }
+
+embryonic_reset:
+ NET_INC_STATS_BH(EmbryonicRsts);
+ if (!(flg & TCP_FLAG_RST))
+ req->class->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->state;
+
+ if (child->lock.users == 0) {
+ ret = tcp_rcv_state_process(child, skb, skb->h.th, skb->len);
+
+ /* Wakeup parent, send SIGIO */
+ if (state == TCP_SYN_RECV && child->state != state)
+ parent->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);
+ return ret;
+}
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)