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net: IP defrag: encapsulate rbtree defrag code into callable functions
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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>
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Peter Oskolkov authored and David S. Miller committed Jan 26, 2019
1 parent ccacead commit c23f35d
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Showing 3 changed files with 334 additions and 264 deletions.
16 changes: 14 additions & 2 deletions include/net/inet_frag.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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 changes: 293 additions & 0 deletions net/ipv4/inet_fragment.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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.
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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);
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