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net: IP defrag: encapsulate rbtree defrag code into callable functions

Browse Source 
This is a refactoring patch: without changing runtime behavior,
it moves rbtree-related code from IPv4-specific files/functions
into .h/.c defrag files shared with IPv6 defragmentation code.

Signed-off-by: Peter Oskolkov <posk@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Cc: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Peter Oskolkov 2019-01-22 10:02:50 -08:00 committed by David S. Miller
parent ccaceadc4e
commit c23f35d19d
3 changed files with 334 additions and 264 deletions
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16
include/net/inet_frag.h
View File

@ -77,8 +77,8 @@ struct inet_frag_queue {
struct timer_list timer;
spinlock_t lock;
refcount_t refcnt;
struct sk_buff *fragments; /* Used in IPv6. */
struct rb_root rb_fragments; /* Used in IPv4. */
struct sk_buff *fragments; /* used in 6lopwpan IPv6. */
struct rb_root rb_fragments; /* Used in IPv4/IPv6. */
struct sk_buff *fragments_tail;
struct sk_buff *last_run_head;
ktime_t stamp;
@ -153,4 +153,16 @@ static inline void add_frag_mem_limit(struct netns_frags *nf, long val)
extern const u8 ip_frag_ecn_table[16];
/* Return values of inet_frag_queue_insert() */
#define IPFRAG_OK 0
#define IPFRAG_DUP 1
#define IPFRAG_OVERLAP 2
int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb,
int offset, int end);
void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb,
struct sk_buff *parent);
void inet_frag_reasm_finish(struct inet_frag_queue *q, struct sk_buff *head,
void *reasm_data);
struct sk_buff *inet_frag_pull_head(struct inet_frag_queue *q);
#endif

293
net/ipv4/inet_fragment.c
View File

@ -25,6 +25,62 @@
#include <net/sock.h>
#include <net/inet_frag.h>
#include <net/inet_ecn.h>
#include <net/ip.h>
#include <net/ipv6.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;
};
#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.
@ -123,6 +179,28 @@ static void inet_frag_destroy_rcu(struct rcu_head *head)
kmem_cache_free(f->frags_cachep, q);
}
unsigned int inet_frag_rbtree_purge(struct rb_root *root)
{
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(skb);
skb = next;
}
}
return sum;
}
EXPORT_SYMBOL(inet_frag_rbtree_purge);
void inet_frag_destroy(struct inet_frag_queue *q)
{
struct sk_buff *fp;
@ -224,3 +302,218 @@ struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, void *key)
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 (last->ip_defrag_offset + last->len < end) {
/* This is the common case: skb goes to the end. */
/* Detect and discard overlaps. */
if (offset < last->ip_defrag_offset + last->len)
return IPFRAG_OVERLAP;
if (offset == 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 = curr->ip_defrag_offset +
FRAG_CB(curr)->frag_run_len;
if (end <= curr->ip_defrag_offset)
rbn = &parent->rb_left;
else if (offset >= curr_run_end)
rbn = &parent->rb_right;
else if (offset >= 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);
}
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);
struct sk_buff **nextp;
int delta;
if (head != skb) {
fp = skb_clone(skb, GFP_ATOMIC);
if (!fp)
return NULL;
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;
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(head->ip_defrag_offset != 0);
delta = -head->truesize;
/* Head of list must not be cloned. */
if (skb_unclone(head, GFP_ATOMIC))
return NULL;
delta += head->truesize;
if (delta)
add_frag_mem_limit(q->net, 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)
return NULL;
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->net, clone->truesize);
skb_shinfo(head)->frag_list = clone;
nextp = &clone->next;
} else {
nextp = &skb_shinfo(head)->frag_list;
}
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)
{
struct sk_buff **nextp = (struct sk_buff **)reasm_data;
struct rb_node *rbn;
struct sk_buff *fp;
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);
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) {
*nextp = fp;
nextp = &fp->next;
fp->prev = NULL;
memset(&fp->rbnode, 0, sizeof(fp->rbnode));
fp->sk = NULL;
head->data_len += fp->len;
head->len += fp->len;
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);
head->truesize += fp->truesize;
fp = FRAG_CB(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->net, head->truesize);
*nextp = NULL;
skb_mark_not_on_list(head);
head->prev = NULL;
head->tstamp = q->stamp;
}
EXPORT_SYMBOL(inet_frag_reasm_finish);
struct sk_buff *inet_frag_pull_head(struct inet_frag_queue *q)
{
struct sk_buff *head;
if (q->fragments) {
head = q->fragments;
q->fragments = head->next;
} else {
struct sk_buff *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->net, head->truesize);
return head;
}
EXPORT_SYMBOL(inet_frag_pull_head);

283
net/ipv4/ip_fragment.c
View File

@ -57,57 +57,6 @@
*/
static const char ip_frag_cache_name[] = "ip4-frags";
/* 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 {
struct inet_skb_parm h;
struct sk_buff *next_frag;
int frag_run_len;
};
#define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb))
static void ip4_frag_init_run(struct sk_buff *skb)
{
BUILD_BUG_ON(sizeof(struct ipfrag_skb_cb) > sizeof(skb->cb));
FRAG_CB(skb)->next_frag = NULL;
FRAG_CB(skb)->frag_run_len = skb->len;
}
/* Append skb to the last "run". */
static void ip4_frag_append_to_last_run(struct inet_frag_queue *q,
struct sk_buff *skb)
{
RB_CLEAR_NODE(&skb->rbnode);
FRAG_CB(skb)->next_frag = NULL;
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 ip4_frag_create_run(struct inet_frag_queue *q, struct sk_buff *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);
ip4_frag_init_run(skb);
q->fragments_tail = skb;
q->last_run_head = skb;
}
/* Describe an entry in the "incomplete datagrams" queue. */
struct ipq {
struct inet_frag_queue q;
@ -212,27 +161,9 @@ static void ip_expire(struct timer_list *t)
* pull the head out of the tree in order to be able to
* deal with head->dev.
*/
if (qp->q.fragments) {
head = qp->q.fragments;
qp->q.fragments = head->next;
} else {
head = skb_rb_first(&qp->q.rb_fragments);
head = inet_frag_pull_head(&qp->q);
if (!head)
goto out;
if (FRAG_CB(head)->next_frag)
rb_replace_node(&head->rbnode,
&FRAG_CB(head)->next_frag->rbnode,
&qp->q.rb_fragments);
else
rb_erase(&head->rbnode, &qp->q.rb_fragments);
memset(&head->rbnode, 0, sizeof(head->rbnode));
barrier();
}
if (head == qp->q.fragments_tail)
qp->q.fragments_tail = NULL;
sub_frag_mem_limit(qp->q.net, head->truesize);
head->dev = dev_get_by_index_rcu(net, qp->iif);
if (!head->dev)
goto out;
@ -344,12 +275,10 @@ static int ip_frag_reinit(struct ipq *qp)
static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
{
struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
struct rb_node **rbn, *parent;
struct sk_buff *skb1, *prev_tail;
int ihl, end, skb1_run_end;
int ihl, end, flags, offset;
struct sk_buff *prev_tail;
struct net_device *dev;
unsigned int fragsize;
int flags, offset;
int err = -ENOENT;
u8 ecn;
@ -413,62 +342,13 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
/* Makes sure compiler wont do silly aliasing games */
barrier();
/* 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.
*
* We do the same here for IPv4 (and increment an snmp counter) but
* we do not want to drop the whole queue in response to a duplicate
* fragment.
*/
err = -EINVAL;
/* Find out where to put this fragment. */
prev_tail = qp->q.fragments_tail;
if (!prev_tail)
ip4_frag_create_run(&qp->q, skb); /* First fragment. */
else if (prev_tail->ip_defrag_offset + prev_tail->len < end) {
/* This is the common case: skb goes to the end. */
/* Detect and discard overlaps. */
if (offset < prev_tail->ip_defrag_offset + prev_tail->len)
goto overlap;
if (offset == prev_tail->ip_defrag_offset + prev_tail->len)
ip4_frag_append_to_last_run(&qp->q, skb);
else
ip4_frag_create_run(&qp->q, skb);
} else {
/* Binary search. Note that skb can become the first fragment,
* but not the last (covered above).
*/
rbn = &qp->q.rb_fragments.rb_node;
do {
parent = *rbn;
skb1 = rb_to_skb(parent);
skb1_run_end = skb1->ip_defrag_offset +
FRAG_CB(skb1)->frag_run_len;
if (end <= skb1->ip_defrag_offset)
rbn = &parent->rb_left;
else if (offset >= skb1_run_end)
rbn = &parent->rb_right;
else if (offset >= skb1->ip_defrag_offset &&
end <= skb1_run_end)
goto err; /* No new data, potential duplicate */
else
goto overlap; /* Found an overlap */
} while (*rbn);
/* Here we have parent properly set, and rbn pointing to
* one of its NULL left/right children. Insert skb.
*/
ip4_frag_init_run(skb);
rb_link_node(&skb->rbnode, parent, rbn);
rb_insert_color(&skb->rbnode, &qp->q.rb_fragments);
}
err = inet_frag_queue_insert(&qp->q, skb, offset, end);
if (err)
goto insert_error;
if (dev)
qp->iif = dev->ifindex;
skb->ip_defrag_offset = offset;
qp->q.stamp = skb->tstamp;
qp->q.meat += skb->len;
@ -501,10 +381,16 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
skb_dst_drop(skb);
return -EINPROGRESS;
overlap:
insert_error:
if (err == IPFRAG_DUP) {
kfree_skb(skb);
return -EINVAL;
}
err = -EINVAL;
__IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
discard_qp:
inet_frag_kill(&qp->q);
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
err:
kfree_skb(skb);
return err;
@ -516,13 +402,8 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
{
struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
struct iphdr *iph;
struct sk_buff *fp, *head = skb_rb_first(&qp->q.rb_fragments);
struct sk_buff **nextp; /* To build frag_list. */
struct rb_node *rbn;
int len;
int ihlen;
int delta;
int err;
void *reasm_data;
int len, err;
u8 ecn;
ipq_kill(qp);
@ -532,117 +413,23 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
err = -EINVAL;
goto out_fail;
}
/* Make the one we just received the head. */
if (head != skb) {
fp = skb_clone(skb, GFP_ATOMIC);
if (!fp)
reasm_data = inet_frag_reasm_prepare(&qp->q, skb, prev_tail);
if (!reasm_data)
goto out_nomem;
FRAG_CB(fp)->next_frag = FRAG_CB(skb)->next_frag;
if (RB_EMPTY_NODE(&skb->rbnode))
FRAG_CB(prev_tail)->next_frag = fp;
else
rb_replace_node(&skb->rbnode, &fp->rbnode,
&qp->q.rb_fragments);
if (qp->q.fragments_tail == skb)
qp->q.fragments_tail = fp;
skb_morph(skb, head);
FRAG_CB(skb)->next_frag = FRAG_CB(head)->next_frag;
rb_replace_node(&head->rbnode, &skb->rbnode,
&qp->q.rb_fragments);
consume_skb(head);
head = skb;
}
WARN_ON(head->ip_defrag_offset != 0);
/* Allocate a new buffer for the datagram. */
ihlen = ip_hdrlen(head);
len = ihlen + qp->q.len;
len = ip_hdrlen(skb) + qp->q.len;
err = -E2BIG;
if (len > 65535)
goto out_oversize;
delta = - head->truesize;
inet_frag_reasm_finish(&qp->q, skb, reasm_data);
/* Head of list must not be cloned. */
if (skb_unclone(head, GFP_ATOMIC))
goto out_nomem;
skb->dev = dev;
IPCB(skb)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
delta += head->truesize;
if (delta)
add_frag_mem_limit(qp->q.net, 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_nomem;
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->len = clone->data_len = head->data_len - plen;
head->truesize += clone->truesize;
clone->csum = 0;
clone->ip_summed = head->ip_summed;
add_frag_mem_limit(qp->q.net, clone->truesize);
skb_shinfo(head)->frag_list = clone;
nextp = &clone->next;
} else {
nextp = &skb_shinfo(head)->frag_list;
}
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, &qp->q.rb_fragments);
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) {
*nextp = fp;
nextp = &fp->next;
fp->prev = NULL;
memset(&fp->rbnode, 0, sizeof(fp->rbnode));
fp->sk = NULL;
head->data_len += fp->len;
head->len += fp->len;
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);
head->truesize += fp->truesize;
fp = FRAG_CB(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, &qp->q.rb_fragments);
rbn = rbnext;
}
}
sub_frag_mem_limit(qp->q.net, head->truesize);
*nextp = NULL;
skb_mark_not_on_list(head);
head->prev = NULL;
head->dev = dev;
head->tstamp = qp->q.stamp;
IPCB(head)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
iph = ip_hdr(head);
iph = ip_hdr(skb);
iph->tot_len = htons(len);
iph->tos |= ecn;
@ -655,7 +442,7 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
* from one very small df-fragment and one large non-df frag.
*/
if (qp->max_df_size == qp->q.max_size) {
IPCB(head)->flags |= IPSKB_FRAG_PMTU;
IPCB(skb)->flags |= IPSKB_FRAG_PMTU;
iph->frag_off = htons(IP_DF);
} else {
iph->frag_off = 0;
@ -753,28 +540,6 @@ struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
}
EXPORT_SYMBOL(ip_check_defrag);
unsigned int inet_frag_rbtree_purge(struct rb_root *root)
{
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(skb);
skb = next;
}
}
return sum;
}
EXPORT_SYMBOL(inet_frag_rbtree_purge);
#ifdef CONFIG_SYSCTL
static int dist_min;