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Commit 353c9cb3 authored by Peter Oskolkov's avatar Peter Oskolkov Committed by David S. Miller
Browse files

ip: add helpers to process in-order fragments faster. 



This patch introduces several helper functions/macros that will be
used in the follow-up patch. No runtime changes yet.

The new logic (fully implemented in the second patch) is as follows:

* Nodes in the rb-tree will now contain not single fragments, but lists
  of consecutive fragments ("runs").

* At each point in time, the current "active" run at the tail is
  maintained/tracked. Fragments that arrive in-order, adjacent
  to the previous tail fragment, are added to this tail run without
  triggering the re-balancing of the rb-tree.

* If a fragment arrives out of order with the offset _before_ the tail run,
  it is inserted into the rb-tree as a single fragment.

* If a fragment arrives after the current tail fragment (with a gap),
  it starts a new "tail" run, as is inserted into the rb-tree
  at the end as the head of the new run.

skb->cb is used to store additional information
needed here (suggested by Eric Dumazet).

Reported-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarPeter Oskolkov <posk@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6a92ef08

include/net/inet_frag.h

+6 −0
Original line number Diff line number Diff line
@@ -57,7 +57,9 @@ struct frag_v6_compare_key { 
 * @lock: spinlock protecting this frag

 * @refcnt: reference count of the queue

 * @fragments: received fragments head

 * @rb_fragments: received fragments rb-tree root

 * @fragments_tail: received fragments tail

 * @last_run_head: the head of the last "run". see ip_fragment.c

 * @stamp: timestamp of the last received fragment

 * @len: total length of the original datagram

 * @meat: length of received fragments so far
@@ -78,6 +80,7 @@ struct inet_frag_queue { 
	struct sk_buff		*fragments;  /* Used in IPv6. */

	struct rb_root		rb_fragments; /* Used in IPv4. */

	struct sk_buff		*fragments_tail;

	struct sk_buff		*last_run_head;

	ktime_t			stamp;

	int			len;

	int			meat;
@@ -113,6 +116,9 @@ void inet_frag_kill(struct inet_frag_queue *q); 
void inet_frag_destroy(struct inet_frag_queue *q);

struct inet_frag_queue *inet_frag_find(struct netns_frags *nf, void *key);



/* Free all skbs in the queue; return the sum of their truesizes. */

unsigned int inet_frag_rbtree_purge(struct rb_root *root);



static inline void inet_frag_put(struct inet_frag_queue *q)

{

	if (refcount_dec_and_test(&q->refcnt))

net/ipv4/ip_fragment.c

+73 −0
Original line number Diff line number Diff line
@@ -57,6 +57,57 @@ 
 */

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;
@@ -654,6 +705,28 @@ 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;