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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /net/ipv4/inetpeer.c
downloadlinux-dev-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz
linux-dev-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip
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!
Diffstat (limited to 'net/ipv4/inetpeer.c')
-rw-r--r--net/ipv4/inetpeer.c460
1 files changed, 460 insertions, 0 deletions
diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
new file mode 100644
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+++ b/net/ipv4/inetpeer.c
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+/*
+ * 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);