Linux-2.6.12-rc2v2.6.12-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!

1 files changed, 460 insertions, 0 deletions

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
new file mode 100644
index 000000000000..95473953c406
--- /dev/null
+++ b/net/ipv4/inetpeer.c
@@ -0,0 +1,460 @@
+/*
+ *              INETPEER - A storage for permanent information about peers
+ *
+ *  This source is covered by the GNU GPL, the same as all kernel sources.
+ *
+ *  Version:    $Id: inetpeer.c,v 1.7 2001/09/20 21:22:50 davem Exp $
+ *
+ *  Authors:    Andrey V. Savochkin <saw@msu.ru>
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/random.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/time.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/net.h>
+#include <net/inetpeer.h>
+
+/*
+ *  Theory of operations.
+ *  We keep one entry for each peer IP address.  The nodes contains long-living
+ *  information about the peer which doesn't depend on routes.
+ *  At this moment this information consists only of ID field for the next
+ *  outgoing IP packet.  This field is incremented with each packet as encoded
+ *  in inet_getid() function (include/net/inetpeer.h).
+ *  At the moment of writing this notes identifier of IP packets is generated
+ *  to be unpredictable using this code only for packets subjected
+ *  (actually or potentially) to defragmentation.  I.e. DF packets less than
+ *  PMTU in size uses a constant ID and do not use this code (see
+ *  ip_select_ident() in include/net/ip.h).
+ *
+ *  Route cache entries hold references to our nodes.
+ *  New cache entries get references via lookup by destination IP address in
+ *  the avl tree.  The reference is grabbed only when it's needed i.e. only
+ *  when we try to output IP packet which needs an unpredictable ID (see
+ *  __ip_select_ident() in net/ipv4/route.c).
+ *  Nodes are removed only when reference counter goes to 0.
+ *  When it's happened the node may be removed when a sufficient amount of
+ *  time has been passed since its last use.  The less-recently-used entry can
+ *  also be removed if the pool is overloaded i.e. if the total amount of
+ *  entries is greater-or-equal than the threshold.
+ *
+ *  Node pool is organised as an AVL tree.
+ *  Such an implementation has been chosen not just for fun.  It's a way to
+ *  prevent easy and efficient DoS attacks by creating hash collisions.  A huge
+ *  amount of long living nodes in a single hash slot would significantly delay
+ *  lookups performed with disabled BHs.
+ *
+ *  Serialisation issues.
+ *  1.  Nodes may appear in the tree only with the pool write lock held.
+ *  2.  Nodes may disappear from the tree only with the pool write lock held
+ *      AND reference count being 0.
+ *  3.  Nodes appears and disappears from unused node list only under
+ *      "inet_peer_unused_lock".
+ *  4.  Global variable peer_total is modified under the pool lock.
+ *  5.  struct inet_peer fields modification:
+ *              avl_left, avl_right, avl_parent, avl_height: pool lock
+ *              unused_next, unused_prevp: unused node list lock
+ *              refcnt: atomically against modifications on other CPU;
+ *                 usually under some other lock to prevent node disappearing
+ *              dtime: unused node list lock
+ *              v4daddr: unchangeable
+ *              ip_id_count: idlock
+ */
+
+/* Exported for inet_getid inline function.  */
+DEFINE_SPINLOCK(inet_peer_idlock);
+
+static kmem_cache_t *peer_cachep;
+
+#define node_height(x) x->avl_height
+static struct inet_peer peer_fake_node = {
+        .avl_left       = &peer_fake_node,
+        .avl_right      = &peer_fake_node,
+        .avl_height     = 0
+};
+#define peer_avl_empty (&peer_fake_node)
+static struct inet_peer *peer_root = peer_avl_empty;
+static DEFINE_RWLOCK(peer_pool_lock);
+#define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
+
+static volatile int peer_total;
+/* Exported for sysctl_net_ipv4.  */
+int inet_peer_threshold = 65536 + 128;  /* start to throw entries more
+                                         * aggressively at this stage */
+int inet_peer_minttl = 120 * HZ;        /* TTL under high load: 120 sec */
+int inet_peer_maxttl = 10 * 60 * HZ;    /* usual time to live: 10 min */
+
+static struct inet_peer *inet_peer_unused_head;
+/* Exported for inet_putpeer inline function.  */
+struct inet_peer **inet_peer_unused_tailp = &inet_peer_unused_head;
+DEFINE_SPINLOCK(inet_peer_unused_lock);
+#define PEER_MAX_CLEANUP_WORK 30
+
+static void peer_check_expire(unsigned long dummy);
+static struct timer_list peer_periodic_timer =
+        TIMER_INITIALIZER(peer_check_expire, 0, 0);
+
+/* Exported for sysctl_net_ipv4.  */
+int inet_peer_gc_mintime = 10 * HZ,
+    inet_peer_gc_maxtime = 120 * HZ;
+
+/* Called from ip_output.c:ip_init  */
+void __init inet_initpeers(void)
+{
+        struct sysinfo si;
+
+        /* Use the straight interface to information about memory. */
+        si_meminfo(&si);
+        /* The values below were suggested by Alexey Kuznetsov
+         * <kuznet@ms2.inr.ac.ru>.  I don't have any opinion about the values
+         * myself.  --SAW
+         */
+        if (si.totalram <= (32768*1024)/PAGE_SIZE)
+                inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
+        if (si.totalram <= (16384*1024)/PAGE_SIZE)
+                inet_peer_threshold >>= 1; /* about 512KB */
+        if (si.totalram <= (8192*1024)/PAGE_SIZE)
+                inet_peer_threshold >>= 2; /* about 128KB */
+
+        peer_cachep = kmem_cache_create("inet_peer_cache",
+                        sizeof(struct inet_peer),
+                        0, SLAB_HWCACHE_ALIGN,
+                        NULL, NULL);
+
+        if (!peer_cachep)
+                panic("cannot create inet_peer_cache");
+
+        /* All the timers, started at system startup tend
+           to synchronize. Perturb it a bit.
+         */
+        peer_periodic_timer.expires = jiffies
+                + net_random() % inet_peer_gc_maxtime
+                + inet_peer_gc_maxtime;
+        add_timer(&peer_periodic_timer);
+}
+
+/* Called with or without local BH being disabled. */
+static void unlink_from_unused(struct inet_peer *p)
+{
+        spin_lock_bh(&inet_peer_unused_lock);
+        if (p->unused_prevp != NULL) {
+                /* On unused list. */
+                *p->unused_prevp = p->unused_next;
+                if (p->unused_next != NULL)
+                        p->unused_next->unused_prevp = p->unused_prevp;
+                else
+                        inet_peer_unused_tailp = p->unused_prevp;
+                p->unused_prevp = NULL; /* mark it as removed */
+        }
+        spin_unlock_bh(&inet_peer_unused_lock);
+}
+
+/* Called with local BH disabled and the pool lock held. */
+#define lookup(daddr)                                           \
+({                                                              \
+        struct inet_peer *u, **v;                               \
+        stackptr = stack;                                       \
+        *stackptr++ = &peer_root;                               \
+        for (u = peer_root; u != peer_avl_empty; ) {            \
+                if (daddr == u->v4daddr)                        \
+                        break;                                  \
+                if (daddr < u->v4daddr)                         \
+                        v = &u->avl_left;                       \
+                else                                            \
+                        v = &u->avl_right;                      \
+                *stackptr++ = v;                                \
+                u = *v;                                         \
+        }                                                       \
+        u;                                                      \
+})
+
+/* Called with local BH disabled and the pool write lock held. */
+#define lookup_rightempty(start)                                \
+({                                                              \
+        struct inet_peer *u, **v;                               \
+        *stackptr++ = &start->avl_left;                         \
+        v = &start->avl_left;                                   \
+        for (u = *v; u->avl_right != peer_avl_empty; ) {        \
+                v = &u->avl_right;                              \
+                *stackptr++ = v;                                \
+                u = *v;                                         \
+        }                                                       \
+        u;                                                      \
+})
+
+/* Called with local BH disabled and the pool write lock held.
+ * Variable names are the proof of operation correctness.
+ * Look into mm/map_avl.c for more detail description of the ideas.  */
+static void peer_avl_rebalance(struct inet_peer **stack[],
+                struct inet_peer ***stackend)
+{
+        struct inet_peer **nodep, *node, *l, *r;
+        int lh, rh;
+
+        while (stackend > stack) {
+                nodep = *--stackend;
+                node = *nodep;
+                l = node->avl_left;
+                r = node->avl_right;
+                lh = node_height(l);
+                rh = node_height(r);
+                if (lh > rh + 1) { /* l: RH+2 */
+                        struct inet_peer *ll, *lr, *lrl, *lrr;
+                        int lrh;
+                        ll = l->avl_left;
+                        lr = l->avl_right;
+                        lrh = node_height(lr);
+                        if (lrh <= node_height(ll)) {   /* ll: RH+1 */
+                                node->avl_left = lr;    /* lr: RH or RH+1 */
+                                node->avl_right = r;    /* r: RH */
+                                node->avl_height = lrh + 1; /* RH+1 or RH+2 */
+                                l->avl_left = ll;       /* ll: RH+1 */
+                                l->avl_right = node;    /* node: RH+1 or RH+2 */
+                                l->avl_height = node->avl_height + 1;
+                                *nodep = l;
+                        } else { /* ll: RH, lr: RH+1 */
+                                lrl = lr->avl_left;     /* lrl: RH or RH-1 */
+                                lrr = lr->avl_right;    /* lrr: RH or RH-1 */
+                                node->avl_left = lrr;   /* lrr: RH or RH-1 */
+                                node->avl_right = r;    /* r: RH */
+                                node->avl_height = rh + 1; /* node: RH+1 */
+                                l->avl_left = ll;       /* ll: RH */
+                                l->avl_right = lrl;     /* lrl: RH or RH-1 */
+                                l->avl_height = rh + 1; /* l: RH+1 */
+                                lr->avl_left = l;       /* l: RH+1 */
+                                lr->avl_right = node;   /* node: RH+1 */
+                                lr->avl_height = rh + 2;
+                                *nodep = lr;
+                        }
+                } else if (rh > lh + 1) { /* r: LH+2 */
+                        struct inet_peer *rr, *rl, *rlr, *rll;
+                        int rlh;
+                        rr = r->avl_right;
+                        rl = r->avl_left;
+                        rlh = node_height(rl);
+                        if (rlh <= node_height(rr)) {   /* rr: LH+1 */
+                                node->avl_right = rl;   /* rl: LH or LH+1 */
+                                node->avl_left = l;     /* l: LH */
+                                node->avl_height = rlh + 1; /* LH+1 or LH+2 */
+                                r->avl_right = rr;      /* rr: LH+1 */
+                                r->avl_left = node;     /* node: LH+1 or LH+2 */
+                                r->avl_height = node->avl_height + 1;
+                                *nodep = r;
+                        } else { /* rr: RH, rl: RH+1 */
+                                rlr = rl->avl_right;    /* rlr: LH or LH-1 */
+                                rll = rl->avl_left;     /* rll: LH or LH-1 */
+                                node->avl_right = rll;  /* rll: LH or LH-1 */
+                                node->avl_left = l;     /* l: LH */
+                                node->avl_height = lh + 1; /* node: LH+1 */
+                                r->avl_right = rr;      /* rr: LH */
+                                r->avl_left = rlr;      /* rlr: LH or LH-1 */
+                                r->avl_height = lh + 1; /* r: LH+1 */
+                                rl->avl_right = r;      /* r: LH+1 */
+                                rl->avl_left = node;    /* node: LH+1 */
+                                rl->avl_height = lh + 2;
+                                *nodep = rl;
+                        }
+                } else {
+                        node->avl_height = (lh > rh ? lh : rh) + 1;
+                }
+        }
+}
+
+/* Called with local BH disabled and the pool write lock held. */
+#define link_to_pool(n)                                         \
+do {                                                            \
+        n->avl_height = 1;                                      \
+        n->avl_left = peer_avl_empty;                           \
+        n->avl_right = peer_avl_empty;                          \
+        **--stackptr = n;                                       \
+        peer_avl_rebalance(stack, stackptr);                    \
+} while(0)
+
+/* May be called with local BH enabled. */
+static void unlink_from_pool(struct inet_peer *p)
+{
+        int do_free;
+
+        do_free = 0;
+
+        write_lock_bh(&peer_pool_lock);
+        /* Check the reference counter.  It was artificially incremented by 1
+         * in cleanup() function to prevent sudden disappearing.  If the
+         * reference count is still 1 then the node is referenced only as `p'
+         * here and from the pool.  So under the exclusive pool lock it's safe
+         * to remove the node and free it later. */
+        if (atomic_read(&p->refcnt) == 1) {
+                struct inet_peer **stack[PEER_MAXDEPTH];
+                struct inet_peer ***stackptr, ***delp;
+                if (lookup(p->v4daddr) != p)
+                        BUG();
+                delp = stackptr - 1; /* *delp[0] == p */
+                if (p->avl_left == peer_avl_empty) {
+                        *delp[0] = p->avl_right;
+                        --stackptr;
+                } else {
+                        /* look for a node to insert instead of p */
+                        struct inet_peer *t;
+                        t = lookup_rightempty(p);
+                        if (*stackptr[-1] != t)
+                                BUG();
+                        **--stackptr = t->avl_left;
+                        /* t is removed, t->v4daddr > x->v4daddr for any
+                         * x in p->avl_left subtree.
+                         * Put t in the old place of p. */
+                        *delp[0] = t;
+                        t->avl_left = p->avl_left;
+                        t->avl_right = p->avl_right;
+                        t->avl_height = p->avl_height;
+                        if (delp[1] != &p->avl_left)
+                                BUG();
+                        delp[1] = &t->avl_left; /* was &p->avl_left */
+                }
+                peer_avl_rebalance(stack, stackptr);
+                peer_total--;
+                do_free = 1;
+        }
+        write_unlock_bh(&peer_pool_lock);
+
+        if (do_free)
+                kmem_cache_free(peer_cachep, p);
+        else
+                /* The node is used again.  Decrease the reference counter
+                 * back.  The loop "cleanup -> unlink_from_unused
+                 *   -> unlink_from_pool -> putpeer -> link_to_unused
+                 *   -> cleanup (for the same node)"
+                 * doesn't really exist because the entry will have a
+                 * recent deletion time and will not be cleaned again soon. */
+                inet_putpeer(p);
+}
+
+/* May be called with local BH enabled. */
+static int cleanup_once(unsigned long ttl)
+{
+        struct inet_peer *p;
+
+        /* Remove the first entry from the list of unused nodes. */
+        spin_lock_bh(&inet_peer_unused_lock);
+        p = inet_peer_unused_head;
+        if (p != NULL) {
+                if (time_after(p->dtime + ttl, jiffies)) {
+                        /* Do not prune fresh entries. */
+                        spin_unlock_bh(&inet_peer_unused_lock);
+                        return -1;
+                }
+                inet_peer_unused_head = p->unused_next;
+                if (p->unused_next != NULL)
+                        p->unused_next->unused_prevp = p->unused_prevp;
+                else
+                        inet_peer_unused_tailp = p->unused_prevp;
+                p->unused_prevp = NULL; /* mark as not on the list */
+                /* Grab an extra reference to prevent node disappearing
+                 * before unlink_from_pool() call. */
+                atomic_inc(&p->refcnt);
+        }
+        spin_unlock_bh(&inet_peer_unused_lock);
+
+        if (p == NULL)
+                /* It means that the total number of USED entries has
+                 * grown over inet_peer_threshold.  It shouldn't really
+                 * happen because of entry limits in route cache. */
+                return -1;
+
+        unlink_from_pool(p);
+        return 0;
+}
+
+/* Called with or without local BH being disabled. */
+struct inet_peer *inet_getpeer(__u32 daddr, int create)
+{
+        struct inet_peer *p, *n;
+        struct inet_peer **stack[PEER_MAXDEPTH], ***stackptr;
+
+        /* Look up for the address quickly. */
+        read_lock_bh(&peer_pool_lock);
+        p = lookup(daddr);
+        if (p != peer_avl_empty)
+                atomic_inc(&p->refcnt);
+        read_unlock_bh(&peer_pool_lock);
+
+        if (p != peer_avl_empty) {
+                /* The existing node has been found. */
+                /* Remove the entry from unused list if it was there. */
+                unlink_from_unused(p);
+                return p;
+        }
+
+        if (!create)
+                return NULL;
+
+        /* Allocate the space outside the locked region. */
+        n = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);
+        if (n == NULL)
+                return NULL;
+        n->v4daddr = daddr;
+        atomic_set(&n->refcnt, 1);
+        n->ip_id_count = secure_ip_id(daddr);
+        n->tcp_ts_stamp = 0;
+
+        write_lock_bh(&peer_pool_lock);
+        /* Check if an entry has suddenly appeared. */
+        p = lookup(daddr);
+        if (p != peer_avl_empty)
+                goto out_free;
+
+        /* Link the node. */
+        link_to_pool(n);
+        n->unused_prevp = NULL; /* not on the list */
+        peer_total++;
+        write_unlock_bh(&peer_pool_lock);
+
+        if (peer_total >= inet_peer_threshold)
+                /* Remove one less-recently-used entry. */
+                cleanup_once(0);
+
+        return n;
+
+out_free:
+        /* The appropriate node is already in the pool. */
+        atomic_inc(&p->refcnt);
+        write_unlock_bh(&peer_pool_lock);
+        /* Remove the entry from unused list if it was there. */
+        unlink_from_unused(p);
+        /* Free preallocated the preallocated node. */
+        kmem_cache_free(peer_cachep, n);
+        return p;
+}
+
+/* Called with local BH disabled. */
+static void peer_check_expire(unsigned long dummy)
+{
+        int i;
+        int ttl;
+
+        if (peer_total >= inet_peer_threshold)
+                ttl = inet_peer_minttl;
+        else
+                ttl = inet_peer_maxttl
+                                - (inet_peer_maxttl - inet_peer_minttl) / HZ *
+                                        peer_total / inet_peer_threshold * HZ;
+        for (i = 0; i < PEER_MAX_CLEANUP_WORK && !cleanup_once(ttl); i++);
+
+        /* Trigger the timer after inet_peer_gc_mintime .. inet_peer_gc_maxtime
+         * interval depending on the total number of entries (more entries,
+         * less interval). */
+        peer_periodic_timer.expires = jiffies
+                + inet_peer_gc_maxtime
+                - (inet_peer_gc_maxtime - inet_peer_gc_mintime) / HZ *
+                        peer_total / inet_peer_threshold * HZ;
+        add_timer(&peer_periodic_timer);
+}
+
+EXPORT_SYMBOL(inet_peer_idlock);