/* * inet fragments management * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * Authors: Pavel Emelyanov <xemul@openvz.org> * Started as consolidation of ipv4/ip_fragment.c, * ipv6/reassembly. and ipv6 nf conntrack reassembly */ #include <linux/list.h> #include <linux/spinlock.h> #include <linux/module.h> #include <linux/timer.h> #include <linux/mm.h> #include <linux/random.h> #include <linux/skbuff.h> #include <linux/rtnetlink.h> #include <linux/slab.h> #include <net/sock.h> #include <net/inet_frag.h> #include <net/inet_ecn.h> #define INETFRAGS_EVICT_BUCKETS 128 #define INETFRAGS_EVICT_MAX 512 /* don't rebuild inetfrag table with new secret more often than this */ #define INETFRAGS_MIN_REBUILD_INTERVAL (5 * HZ) /* Given the OR values of all fragments, apply RFC 3168 5.3 requirements * Value : 0xff if frame should be dropped. * 0 or INET_ECN_CE value, to be ORed in to final iph->tos field */ const u8 ip_frag_ecn_table[16] = { /* at least one fragment had CE, and others ECT_0 or ECT_1 */ [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = INET_ECN_CE, [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = INET_ECN_CE, [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = INET_ECN_CE, /* invalid combinations : drop frame */ [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff, [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff, [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff, [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff, [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff, [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff, [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff, }; EXPORT_SYMBOL(ip_frag_ecn_table); static unsigned int inet_frag_hashfn(const struct inet_frags *f, const struct inet_frag_queue *q) { return f->hashfn(q) & (INETFRAGS_HASHSZ - 1); } static bool inet_frag_may_rebuild(struct inet_frags *f) { return time_after(jiffies, f->last_rebuild_jiffies + INETFRAGS_MIN_REBUILD_INTERVAL); } static void inet_frag_secret_rebuild(struct inet_frags *f) { int i; write_seqlock_bh(&f->rnd_seqlock); if (!inet_frag_may_rebuild(f)) goto out; get_random_bytes(&f->rnd, sizeof(u32)); for (i = 0; i < INETFRAGS_HASHSZ; i++) { struct inet_frag_bucket *hb; struct inet_frag_queue *q; struct hlist_node *n; hb = &f->hash[i]; spin_lock(&hb->chain_lock); hlist_for_each_entry_safe(q, n, &hb->chain, list) { unsigned int hval = inet_frag_hashfn(f, q); if (hval != i) { struct inet_frag_bucket *hb_dest; hlist_del(&q->list); /* Relink to new hash chain. */ hb_dest = &f->hash[hval]; /* This is the only place where we take * another chain_lock while already holding * one. As this will not run concurrently, * we cannot deadlock on hb_dest lock below, if its * already locked it will be released soon since * other caller cannot be waiting for hb lock * that we've taken above. */ spin_lock_nested(&hb_dest->chain_lock, SINGLE_DEPTH_NESTING); hlist_add_head(&q->list, &hb_dest->chain); spin_unlock(&hb_dest->chain_lock); } } spin_unlock(&hb->chain_lock); } f->rebuild = false; f->last_rebuild_jiffies = jiffies; out: write_sequnlock_bh(&f->rnd_seqlock); } static bool inet_fragq_should_evict(const struct inet_frag_queue *q) { return q->net->low_thresh == 0 || frag_mem_limit(q->net) >= q->net->low_thresh; } static unsigned int inet_evict_bucket(struct inet_frags *f, struct inet_frag_bucket *hb) { struct inet_frag_queue *fq; struct hlist_node *n; unsigned int evicted = 0; HLIST_HEAD(expired); evict_again: spin_lock(&hb->chain_lock); hlist_for_each_entry_safe(fq, n, &hb->chain, list) { if (!inet_fragq_should_evict(fq)) continue; if (!del_timer(&fq->timer)) { /* q expiring right now thus increment its refcount so * it won't be freed under us and wait until the timer * has finished executing then destroy it */ atomic_inc(&fq->refcnt); spin_unlock(&hb->chain_lock); del_timer_sync(&fq->timer); inet_frag_put(fq, f); goto evict_again; } fq->flags |= INET_FRAG_EVICTED; hlist_del(&fq->list); hlist_add_head(&fq->list, &expired); ++evicted; } spin_unlock(&hb->chain_lock); hlist_for_each_entry_safe(fq, n, &expired, list) f->frag_expire((unsigned long) fq); return evicted; } static void inet_frag_worker(struct work_struct *work) { unsigned int budget = INETFRAGS_EVICT_BUCKETS; unsigned int i, evicted = 0; struct inet_frags *f; f = container_of(work, struct inet_frags, frags_work); BUILD_BUG_ON(INETFRAGS_EVICT_BUCKETS >= INETFRAGS_HASHSZ); local_bh_disable(); for (i = ACCESS_ONCE(f->next_bucket); budget; --budget) { evicted += inet_evict_bucket(f, &f->hash[i]); i = (i + 1) & (INETFRAGS_HASHSZ - 1); if (evicted > INETFRAGS_EVICT_MAX) break; } f->next_bucket = i; local_bh_enable(); if (f->rebuild && inet_frag_may_rebuild(f)) inet_frag_secret_rebuild(f); } static void inet_frag_schedule_worker(struct inet_frags *f) { if (unlikely(!work_pending(&f->frags_work))) schedule_work(&f->frags_work); } int inet_frags_init(struct inet_frags *f) { int i; INIT_WORK(&f->frags_work, inet_frag_worker); for (i = 0; i < INETFRAGS_HASHSZ; i++) { struct inet_frag_bucket *hb = &f->hash[i]; spin_lock_init(&hb->chain_lock); INIT_HLIST_HEAD(&hb->chain); } seqlock_init(&f->rnd_seqlock); f->last_rebuild_jiffies = 0; f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0, NULL); if (!f->frags_cachep) return -ENOMEM; return 0; } EXPORT_SYMBOL(inet_frags_init); void inet_frags_init_net(struct netns_frags *nf) { init_frag_mem_limit(nf); } EXPORT_SYMBOL(inet_frags_init_net); void inet_frags_fini(struct inet_frags *f) { cancel_work_sync(&f->frags_work); kmem_cache_destroy(f->frags_cachep); } EXPORT_SYMBOL(inet_frags_fini); void inet_frags_exit_net(struct netns_frags *nf, struct inet_frags *f) { unsigned int seq; int i; nf->low_thresh = 0; local_bh_disable(); evict_again: seq = read_seqbegin(&f->rnd_seqlock); for (i = 0; i < INETFRAGS_HASHSZ ; i++) inet_evict_bucket(f, &f->hash[i]); if (read_seqretry(&f->rnd_seqlock, seq)) goto evict_again; local_bh_enable(); percpu_counter_destroy(&nf->mem); } EXPORT_SYMBOL(inet_frags_exit_net); static struct inet_frag_bucket * get_frag_bucket_locked(struct inet_frag_queue *fq, struct inet_frags *f) __acquires(hb->chain_lock) { struct inet_frag_bucket *hb; unsigned int seq, hash; restart: seq = read_seqbegin(&f->rnd_seqlock); hash = inet_frag_hashfn(f, fq); hb = &f->hash[hash]; spin_lock(&hb->chain_lock); if (read_seqretry(&f->rnd_seqlock, seq)) { spin_unlock(&hb->chain_lock); goto restart; } return hb; } static inline void fq_unlink(struct inet_frag_queue *fq, struct inet_frags *f) { struct inet_frag_bucket *hb; hb = get_frag_bucket_locked(fq, f); if (!(fq->flags & INET_FRAG_EVICTED)) hlist_del(&fq->list); spin_unlock(&hb->chain_lock); } void inet_frag_kill(struct inet_frag_queue *fq, struct inet_frags *f) { if (del_timer(&fq->timer)) atomic_dec(&fq->refcnt); if (!(fq->flags & INET_FRAG_COMPLETE)) { fq_unlink(fq, f); atomic_dec(&fq->refcnt); fq->flags |= INET_FRAG_COMPLETE; } } EXPORT_SYMBOL(inet_frag_kill); static inline void frag_kfree_skb(struct netns_frags *nf, struct inet_frags *f, struct sk_buff *skb) { if (f->skb_free) f->skb_free(skb); kfree_skb(skb); } void inet_frag_destroy(struct inet_frag_queue *q, struct inet_frags *f) { struct sk_buff *fp; struct netns_frags *nf; unsigned int sum, sum_truesize = 0; WARN_ON(!(q->flags & INET_FRAG_COMPLETE)); WARN_ON(del_timer(&q->timer) != 0); /* Release all fragment data. */ fp = q->fragments; nf = q->net; while (fp) { struct sk_buff *xp = fp->next; sum_truesize += fp->truesize; frag_kfree_skb(nf, f, fp); fp = xp; } sum = sum_truesize + f->qsize; sub_frag_mem_limit(q, sum); if (f->destructor) f->destructor(q); kmem_cache_free(f->frags_cachep, q); } EXPORT_SYMBOL(inet_frag_destroy); static struct inet_frag_queue *inet_frag_intern(struct netns_frags *nf, struct inet_frag_queue *qp_in, struct inet_frags *f, void *arg) { struct inet_frag_bucket *hb = get_frag_bucket_locked(qp_in, f); struct inet_frag_queue *qp; #ifdef CONFIG_SMP /* With SMP race we have to recheck hash table, because * such entry could have been created on other cpu before * we acquired hash bucket lock. */ hlist_for_each_entry(qp, &hb->chain, list) { if (qp->net == nf && f->match(qp, arg)) { atomic_inc(&qp->refcnt); spin_unlock(&hb->chain_lock); qp_in->flags |= INET_FRAG_COMPLETE; inet_frag_put(qp_in, f); return qp; } } #endif qp = qp_in; if (!mod_timer(&qp->timer, jiffies + nf->timeout)) atomic_inc(&qp->refcnt); atomic_inc(&qp->refcnt); hlist_add_head(&qp->list, &hb->chain); spin_unlock(&hb->chain_lock); return qp; } static struct inet_frag_queue *inet_frag_alloc(struct netns_frags *nf, struct inet_frags *f, void *arg) { struct inet_frag_queue *q; if (frag_mem_limit(nf) > nf->high_thresh) { inet_frag_schedule_worker(f); return NULL; } q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC); if (q == NULL) return NULL; q->net = nf; f->constructor(q, arg); add_frag_mem_limit(q, f->qsize); setup_timer(&q->timer, f->frag_expire, (unsigned long)q); spin_lock_init(&q->lock); atomic_set(&q->refcnt, 1); return q; } static struct inet_frag_queue *inet_frag_create(struct netns_frags *nf, struct inet_frags *f, void *arg) { struct inet_frag_queue *q; q = inet_frag_alloc(nf, f, arg); if (q == NULL) return NULL; return inet_frag_intern(nf, q, f, arg); } struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, struct inet_frags *f, void *key, unsigned int hash) { struct inet_frag_bucket *hb; struct inet_frag_queue *q; int depth = 0; if (frag_mem_limit(nf) > nf->low_thresh) inet_frag_schedule_worker(f); hash &= (INETFRAGS_HASHSZ - 1); hb = &f->hash[hash]; spin_lock(&hb->chain_lock); hlist_for_each_entry(q, &hb->chain, list) { if (q->net == nf && f->match(q, key)) { atomic_inc(&q->refcnt); spin_unlock(&hb->chain_lock); return q; } depth++; } spin_unlock(&hb->chain_lock); if (depth <= INETFRAGS_MAXDEPTH) return inet_frag_create(nf, f, key); if (inet_frag_may_rebuild(f)) { if (!f->rebuild) f->rebuild = true; inet_frag_schedule_worker(f); } return ERR_PTR(-ENOBUFS); } EXPORT_SYMBOL(inet_frag_find); void inet_frag_maybe_warn_overflow(struct inet_frag_queue *q, const char *prefix) { static const char msg[] = "inet_frag_find: Fragment hash bucket" " list length grew over limit " __stringify(INETFRAGS_MAXDEPTH) ". Dropping fragment.\n"; if (PTR_ERR(q) == -ENOBUFS) LIMIT_NETDEBUG(KERN_WARNING "%s%s", prefix, msg); } EXPORT_SYMBOL(inet_frag_maybe_warn_overflow);