// SPDX-License-Identifier: GPL-2.0-or-later
/*
* inet fragments management
*
* Authors: Pavel Emelyanov <[email protected]>
* 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 <linux/rhashtable.h>
#include <net/sock.h>
#include <net/inet_frag.h>
#include <net/inet_ecn.h>
#include <net/ip.h>
#include <net/ipv6.h>
#include "../core/sock_destructor.h"
/* Use skb->cb to track consecutive/adjacent fragments coming at
* the end of the queue. Nodes in the rb-tree queue will
* contain "runs" of one or more adjacent fragments.
*
* Invariants:
* - next_frag is NULL at the tail of a "run";
* - the head of a "run" has the sum of all fragment lengths in frag_run_len.
*/
struct ipfrag_skb_cb {
union {
struct inet_skb_parm h4;
struct inet6_skb_parm h6;
};
struct sk_buff *next_frag;
int frag_run_len;
int ip_defrag_offset;
};
#define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb))
static void fragcb_clear(struct sk_buff *skb)
{
RB_CLEAR_NODE(&skb->rbnode);
FRAG_CB(skb)->next_frag = NULL;
FRAG_CB(skb)->frag_run_len = skb->len;
}
/* Append skb to the last "run". */
static void fragrun_append_to_last(struct inet_frag_queue *q,
struct sk_buff *skb)
{
fragcb_clear(skb);
FRAG_CB(q->last_run_head)->frag_run_len += skb->len;
FRAG_CB(q->fragments_tail)->next_frag = skb;
q->fragments_tail = skb;
}
/* Create a new "run" with the skb. */
static void fragrun_create(struct inet_frag_queue *q, struct sk_buff *skb)
{
BUILD_BUG_ON(sizeof(struct ipfrag_skb_cb) > sizeof(skb->cb));
fragcb_clear(skb);
if (q->last_run_head)
rb_link_node(&skb->rbnode, &q->last_run_head->rbnode,
&q->last_run_head->rbnode.rb_right);
else
rb_link_node(&skb->rbnode, NULL, &q->rb_fragments.rb_node);
rb_insert_color(&skb->rbnode, &q->rb_fragments);
q->fragments_tail = skb;
q->last_run_head = skb;
}
/* 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);
int inet_frags_init(struct inet_frags *f)
{
f->frags_cachep = kmem_cache_create(f->frags_cache_name, f->qsize, 0, 0,
NULL);
if (!f->frags_cachep)
return -ENOMEM;
refcount_set(&f->refcnt, 1);
init_completion(&f->completion);
return 0;
}
EXPORT_SYMBOL(inet_frags_init);
void inet_frags_fini(struct inet_frags *f)
{
if (refcount_dec_and_test(&f->refcnt))
complete(&f->completion);
wait_for_completion(&f->completion);
kmem_cache_destroy(f->frags_cachep);
f->frags_cachep = NULL;
}
EXPORT_SYMBOL(inet_frags_fini);
/* called from rhashtable_free_and_destroy() at netns_frags dismantle */
static void inet_frags_free_cb(void *ptr, void *arg)
{
struct inet_frag_queue *fq = ptr;
int count;
count = del_timer_sync(&fq->timer) ? 1 : 0;
spin_lock_bh(&fq->lock);
fq->flags |= INET_FRAG_DROP;
if (!(fq->flags & INET_FRAG_COMPLETE)) {
fq->flags |= INET_FRAG_COMPLETE;
count++;
} else if (fq->flags & INET_FRAG_HASH_DEAD) {
count++;
}
spin_unlock_bh(&fq->lock);
if (refcount_sub_and_test(count, &fq->refcnt))
inet_frag_destroy(fq);
}
static LLIST_HEAD(fqdir_free_list);
static void fqdir_free_fn(struct work_struct *work)
{
struct llist_node *kill_list;
struct fqdir *fqdir, *tmp;
struct inet_frags *f;
/* Atomically snapshot the list of fqdirs to free */
kill_list = llist_del_all(&fqdir_free_list);
/* We need to make sure all ongoing call_rcu(..., inet_frag_destroy_rcu)
* have completed, since they need to dereference fqdir.
* Would it not be nice to have kfree_rcu_barrier() ? :)
*/
rcu_barrier();
llist_for_each_entry_safe(fqdir, tmp, kill_list, free_list) {
f = fqdir->f;
if (refcount_dec_and_test(&f->refcnt))
complete(&f->completion);
kfree(fqdir);
}
}
static DECLARE_DELAYED_WORK(fqdir_free_work, fqdir_free_fn);
static void fqdir_work_fn(struct work_struct *work)
{
struct fqdir *fqdir = container_of(work, struct fqdir, destroy_work);
rhashtable_free_and_destroy(&fqdir->rhashtable, inet_frags_free_cb, NULL);
if (llist_add(&fqdir->free_list, &fqdir_free_list))
queue_delayed_work(system_wq, &fqdir_free_work, HZ);
}
int fqdir_init(struct fqdir **fqdirp, struct inet_frags *f, struct net *net)
{
struct fqdir *fqdir = kzalloc(sizeof(*fqdir), GFP_KERNEL);
int res;
if (!fqdir)
return -ENOMEM;
fqdir->f = f;
fqdir->net = net;
res = rhashtable_init(&fqdir->rhashtable, &fqdir->f->rhash_params);
if (res < 0) {
kfree(fqdir);
return res;
}
refcount_inc(&f->refcnt);
*fqdirp = fqdir;
return 0;
}
EXPORT_SYMBOL(fqdir_init);
static struct workqueue_struct *inet_frag_wq;
static int __init inet_frag_wq_init(void)
{
inet_frag_wq = create_workqueue("inet_frag_wq");
if (!inet_frag_wq)
panic("Could not create inet frag workq");
return 0;
}
pure_initcall(inet_frag_wq_init);
void fqdir_exit(struct fqdir *fqdir)
{
INIT_WORK(&fqdir->destroy_work, fqdir_work_fn);
queue_work(inet_frag_wq, &fqdir->destroy_work);
}
EXPORT_SYMBOL(fqdir_exit);
void inet_frag_kill(struct inet_frag_queue *fq)
{
if (del_timer(&fq->timer))
refcount_dec(&fq->refcnt);
if (!(fq->flags & INET_FRAG_COMPLETE)) {
struct fqdir *fqdir = fq->fqdir;
fq->flags |= INET_FRAG_COMPLETE;
rcu_read_lock();
/* The RCU read lock provides a memory barrier
* guaranteeing that if fqdir->dead is false then
* the hash table destruction will not start until
* after we unlock. Paired with fqdir_pre_exit().
*/
if (!READ_ONCE(fqdir->dead)) {
rhashtable_remove_fast(&fqdir->rhashtable, &fq->node,
fqdir->f->rhash_params);
refcount_dec(&fq->refcnt);
} else {
fq->flags |= INET_FRAG_HASH_DEAD;
}
rcu_read_unlock();
}
}
EXPORT_SYMBOL(inet_frag_kill);
static void inet_frag_destroy_rcu(struct rcu_head *head)
{
struct inet_frag_queue *q = container_of(head, struct inet_frag_queue,
rcu);
struct inet_frags *f = q->fqdir->f;
if (f->destructor)
f->destructor(q);
kmem_cache_free(f->frags_cachep, q);
}
unsigned int inet_frag_rbtree_purge(struct rb_root *root,
enum skb_drop_reason reason)
{
struct rb_node *p = rb_first(root);
unsigned int sum = 0;
while (p) {
struct sk_buff *skb = rb_entry(p, struct sk_buff, rbnode);
p = rb_next(p);
rb_erase(&skb->rbnode, root);
while (skb) {
struct sk_buff *next = FRAG_CB(skb)->next_frag;
sum += skb->truesize;
kfree_skb_reason(skb, reason);
skb = next;
}
}
return sum;
}
EXPORT_SYMBOL(inet_frag_rbtree_purge);
void inet_frag_destroy(struct inet_frag_queue *q)
{
unsigned int sum, sum_truesize = 0;
enum skb_drop_reason reason;
struct inet_frags *f;
struct fqdir *fqdir;
WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
reason = (q->flags & INET_FRAG_DROP) ?
SKB_DROP_REASON_FRAG_REASM_TIMEOUT :
SKB_CONSUMED;
WARN_ON(del_timer(&q->timer) != 0);
/* Release all fragment data. */
fqdir = q->fqdir;
f = fqdir->f;
sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments, reason);
sum = sum_truesize + f->qsize;
call_rcu(&q->rcu, inet_frag_destroy_rcu);
sub_frag_mem_limit(fqdir, sum);
}
EXPORT_SYMBOL(inet_frag_destroy);
static struct inet_frag_queue *inet_frag_alloc(struct fqdir *fqdir,
struct inet_frags *f,
void *arg)
{
struct inet_frag_queue *q;
q = kmem_cache_zalloc(f->frags_cachep, GFP_ATOMIC);
if (!q)
return NULL;
q->fqdir = fqdir;
f->constructor(q, arg);
add_frag_mem_limit(fqdir, f->qsize);
timer_setup(&q->timer, f->frag_expire, 0);
spin_lock_init(&q->lock);
refcount_set(&q->refcnt, 3);
return q;
}
static struct inet_frag_queue *inet_frag_create(struct fqdir *fqdir,
void *arg,
struct inet_frag_queue **prev)
{
struct inet_frags *f = fqdir->f;
struct inet_frag_queue *q;
q = inet_frag_alloc(fqdir, f, arg);
if (!q) {
*prev = ERR_PTR(-ENOMEM);
return NULL;
}
mod_timer(&q->timer, jiffies + fqdir->timeout);
*prev = rhashtable_lookup_get_insert_key(&fqdir->rhashtable, &q->key,
&q->node, f->rhash_params);
if (*prev) {
q->flags |= INET_FRAG_COMPLETE;
inet_frag_kill(q);
inet_frag_destroy(q);
return NULL;
}
return q;
}
/* TODO : call from rcu_read_lock() and no longer use refcount_inc_not_zero() */
struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key)
{
/* This pairs with WRITE_ONCE() in fqdir_pre_exit(). */
long high_thresh = READ_ONCE(fqdir->high_thresh);
struct inet_frag_queue *fq = NULL, *prev;
if (!high_thresh || frag_mem_limit(fqdir) > high_thresh)
return NULL;
rcu_read_lock();
prev = rhashtable_lookup(&fqdir->rhashtable, key, fqdir->f->rhash_params);
if (!prev)
fq = inet_frag_create(fqdir, key, &prev);
if (!IS_ERR_OR_NULL(prev)) {
fq = prev;
if (!refcount_inc_not_zero(&fq->refcnt))
fq = NULL;
}
rcu_read_unlock();
return fq;
}
EXPORT_SYMBOL(inet_frag_find);
int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb,
int offset, int end)
{
struct sk_buff *last = q->fragments_tail;
/* RFC5722, Section 4, amended by Errata ID : 3089
* When reassembling an IPv6 datagram, if
* one or more its constituent fragments is determined to be an
* overlapping fragment, the entire datagram (and any constituent
* fragments) MUST be silently discarded.
*
* Duplicates, however, should be ignored (i.e. skb dropped, but the
* queue/fragments kept for later reassembly).
*/
if (!last)
fragrun_create(q, skb); /* First fragment. */
else if (FRAG_CB(last)->ip_defrag_offset + last->len < end) {
/* This is the common case: skb goes to the end. */
/* Detect and discard overlaps. */
if (offset < FRAG_CB(last)->ip_defrag_offset + last->len)
return IPFRAG_OVERLAP;
if (offset == FRAG_CB(last)->ip_defrag_offset + last->len)
fragrun_append_to_last(q, skb);
else
fragrun_create(q, skb);
} else {
/* Binary search. Note that skb can become the first fragment,
* but not the last (covered above).
*/
struct rb_node **rbn, *parent;
rbn = &q->rb_fragments.rb_node;
do {
struct sk_buff *curr;
int curr_run_end;
parent = *rbn;
curr = rb_to_skb(parent);
curr_run_end = FRAG_CB(curr)->ip_defrag_offset +
FRAG_CB(curr)->frag_run_len;
if (end <= FRAG_CB(curr)->ip_defrag_offset)
rbn = &parent->rb_left;
else if (offset >= curr_run_end)
rbn = &parent->rb_right;
else if (offset >= FRAG_CB(curr)->ip_defrag_offset &&
end <= curr_run_end)
return IPFRAG_DUP;
else
return IPFRAG_OVERLAP;
} while (*rbn);
/* Here we have parent properly set, and rbn pointing to
* one of its NULL left/right children. Insert skb.
*/
fragcb_clear(skb);
rb_link_node(&skb->rbnode, parent, rbn);
rb_insert_color(&skb->rbnode, &q->rb_fragments);
}
FRAG_CB(skb)->ip_defrag_offset = offset;
return IPFRAG_OK;
}
EXPORT_SYMBOL(inet_frag_queue_insert);
void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb,
struct sk_buff *parent)
{
struct sk_buff *fp, *head = skb_rb_first(&q->rb_fragments);
void (*destructor)(struct sk_buff *);
unsigned int orig_truesize = 0;
struct sk_buff **nextp = NULL;
struct sock *sk = skb->sk;
int delta;
if (sk && is_skb_wmem(skb)) {
/* TX: skb->sk might have been passed as argument to
* dst->output and must remain valid until tx completes.
*
* Move sk to reassembled skb and fix up wmem accounting.
*/
orig_truesize = skb->truesize;
destructor = skb->destructor;
}
if (head != skb) {
fp = skb_clone(skb, GFP_ATOMIC);
if (!fp) {
head = skb;
goto out_restore_sk;
}
FRAG_CB(fp)->next_frag = FRAG_CB(skb)->next_frag;
if (RB_EMPTY_NODE(&skb->rbnode))
FRAG_CB(parent)->next_frag = fp;
else
rb_replace_node(&skb->rbnode, &fp->rbnode,
&q->rb_fragments);
if (q->fragments_tail == skb)
q->fragments_tail = fp;
if (orig_truesize) {
/* prevent skb_morph from releasing sk */
skb->sk = NULL;
skb->destructor = NULL;
}
skb_morph(skb, head);
FRAG_CB(skb)->next_frag = FRAG_CB(head)->next_frag;
rb_replace_node(&head->rbnode, &skb->rbnode,
&q->rb_fragments);
consume_skb(head);
head = skb;
}
WARN_ON(FRAG_CB(head)->ip_defrag_offset != 0);
delta = -head->truesize;
/* Head of list must not be cloned. */
if (skb_unclone(head, GFP_ATOMIC))
goto out_restore_sk;
delta += head->truesize;
if (delta)
add_frag_mem_limit(q->fqdir, delta);
/* If the first fragment is fragmented itself, we split
* it to two chunks: the first with data and paged part
* and the second, holding only fragments.
*/
if (skb_has_frag_list(head)) {
struct sk_buff *clone;
int i, plen = 0;
clone = alloc_skb(0, GFP_ATOMIC);
if (!clone)
goto out_restore_sk;
skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
skb_frag_list_init(head);
for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
clone->data_len = head->data_len - plen;
clone->len = clone->data_len;
head->truesize += clone->truesize;
clone->csum = 0;
clone->ip_summed = head->ip_summed;
add_frag_mem_limit(q->fqdir, clone->truesize);
skb_shinfo(head)->frag_list = clone;
nextp = &clone->next;
} else {
nextp = &skb_shinfo(head)->frag_list;
}
out_restore_sk:
if (orig_truesize) {
int ts_delta = head->truesize - orig_truesize;
/* if this reassembled skb is fragmented later,
* fraglist skbs will get skb->sk assigned from head->sk,
* and each frag skb will be released via sock_wfree.
*
* Update sk_wmem_alloc.
*/
head->sk = sk;
head->destructor = destructor;
refcount_add(ts_delta, &sk->sk_wmem_alloc);
}
return nextp;
}
EXPORT_SYMBOL(inet_frag_reasm_prepare);
void inet_frag_reasm_finish(struct inet_frag_queue *q, struct sk_buff *head,
void *reasm_data, bool try_coalesce)
{
struct sock *sk = is_skb_wmem(head) ? head->sk : NULL;
const unsigned int head_truesize = head->truesize;
struct sk_buff **nextp = reasm_data;
struct rb_node *rbn;
struct sk_buff *fp;
int sum_truesize;
skb_push(head, head->data - skb_network_header(head));
/* Traverse the tree in order, to build frag_list. */
fp = FRAG_CB(head)->next_frag;
rbn = rb_next(&head->rbnode);
rb_erase(&head->rbnode, &q->rb_fragments);
sum_truesize = head->truesize;
while (rbn || fp) {
/* fp points to the next sk_buff in the current run;
* rbn points to the next run.
*/
/* Go through the current run. */
while (fp) {
struct sk_buff *next_frag = FRAG_CB(fp)->next_frag;
bool stolen;
int delta;
sum_truesize += fp->truesize;
if (head->ip_summed != fp->ip_summed)
head->ip_summed = CHECKSUM_NONE;
else if (head->ip_summed == CHECKSUM_COMPLETE)
head->csum = csum_add(head->csum, fp->csum);
if (try_coalesce && skb_try_coalesce(head, fp, &stolen,
&delta)) {
kfree_skb_partial(fp, stolen);
} else {
fp->prev = NULL;
memset(&fp->rbnode, 0, sizeof(fp->rbnode));
fp->sk = NULL;
head->data_len += fp->len;
head->len += fp->len;
head->truesize += fp->truesize;
*nextp = fp;
nextp = &fp->next;
}
fp = next_frag;
}
/* Move to the next run. */
if (rbn) {
struct rb_node *rbnext = rb_next(rbn);
fp = rb_to_skb(rbn);
rb_erase(rbn, &q->rb_fragments);
rbn = rbnext;
}
}
sub_frag_mem_limit(q->fqdir, sum_truesize);
*nextp = NULL;
skb_mark_not_on_list(head);
head->prev = NULL;
head->tstamp = q->stamp;
head->tstamp_type = q->tstamp_type;
if (sk)
refcount_add(sum_truesize - head_truesize, &sk->sk_wmem_alloc);
}
EXPORT_SYMBOL(inet_frag_reasm_finish);
struct sk_buff *inet_frag_pull_head(struct inet_frag_queue *q)
{
struct sk_buff *head, *skb;
head = skb_rb_first(&q->rb_fragments);
if (!head)
return NULL;
skb = FRAG_CB(head)->next_frag;
if (skb)
rb_replace_node(&head->rbnode, &skb->rbnode,
&q->rb_fragments);
else
rb_erase(&head->rbnode, &q->rb_fragments);
memset(&head->rbnode, 0, sizeof(head->rbnode));
barrier();
if (head == q->fragments_tail)
q->fragments_tail = NULL;
sub_frag_mem_limit(q->fqdir, head->truesize);
return head;
}
EXPORT_SYMBOL(inet_frag_pull_head);
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