Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
new file mode 100644
index 0000000..fd70509
--- /dev/null
+++ b/net/ipv4/tcp_minisocks.c
@@ -0,0 +1,1077 @@
+/*
+ * 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, <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/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 tcp_ehash_bucket *ehead;
+ struct tcp_bind_hashbucket *bhead;
+ struct tcp_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[tcp_bhashfn(tw->tw_num)];
+ spin_lock(&bhead->lock);
+ tb = tw->tw_tb;
+ __hlist_del(&tw->tw_bind_node);
+ tw->tw_tb = NULL;
+ tcp_bucket_destroy(tb);
+ spin_unlock(&bhead->lock);
+
+#ifdef INET_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)
+{
+ struct tcp_ehash_bucket *ehead = &tcp_ehash[sk->sk_hashent];
+ struct tcp_bind_hashbucket *bhead;
+
+ /* Step 1: Put TW into bind hash. Original socket stays there too.
+ Note, that any socket with inet_sk(sk)->num != 0 MUST be bound in
+ binding cache, even if it is closed.
+ */
+ bhead = &tcp_bhash[tcp_bhashfn(inet_sk(sk)->num)];
+ spin_lock(&bhead->lock);
+ tw->tw_tb = tcp_sk(sk)->bind_hash;
+ BUG_TRAP(tcp_sk(sk)->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 open_request *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 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);
+ tcp_sk(newsk)->bind_hash = NULL;
+
+ /* Clone the TCP header template */
+ inet_sk(newsk)->dport = req->rmt_port;
+
+ sock_lock_init(newsk);
+ bh_lock_sock(newsk);
+
+ rwlock_init(&newsk->sk_dst_lock);
+ 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 = 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_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->frto_counter = 0;
+ newtp->frto_highmark = 0;
+
+ 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 = 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->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;
+ 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->sk_err = 0;
+ newsk->sk_priority = 0;
+ atomic_set(&newsk->sk_refcnt, 2);
+#ifdef INET_REFCNT_DEBUG
+ atomic_inc(&inet_sock_nr);
+#endif
+ 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 = req->tstamp_ok;
+ if((newtp->rx_opt.sack_ok = req->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 = req->wscale_ok;
+ if (newtp->rx_opt.wscale_ok) {
+ newtp->rx_opt.snd_wscale = req->snd_wscale;
+ newtp->rx_opt.rcv_wscale = req->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_ca_init(newtp);
+
+ TCP_INC_STATS_BH(TCP_MIB_PASSIVEOPENS);
+ }
+ 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_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 == 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.
+
+ 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 != 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,
+ 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(LINUX_MIB_PAWSESTABREJECTED);
+ return NULL;
+ }
+
+ /* In sequence, PAWS is OK. */
+
+ if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, req->rcv_isn+1))
+ req->ts_recent = tmp_opt.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;
+
+ /* 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 == 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(LINUX_MIB_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->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);