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Commit 0feca619 authored by Pablo Neira Ayuso's avatar Pablo Neira Ayuso Committed by David S. Miller
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net: ipv6: add skbuff fraglist splitter 



This patch adds the skbuff fraglist split iterator. This API provides an
iterator to transform the fraglist into single skbuff objects, it
consists of:

* ip6_fraglist_init(), that initializes the internal state of the
  fraglist iterator.
* ip6_fraglist_prepare(), that restores the IPv6 header on the fragment.
* ip6_fraglist_next(), that retrieves the fragment from the fraglist and
  updates the internal state of the iterator to point to the next
  fragment in the fraglist.

The ip6_fraglist_iter object stores the internal state of the iterator.

This code has been extracted from ip6_fragment(). Symbols are also
exported to allow to reuse this iterator from the bridge codepath to
build its own refragmentation routine by reusing the existing codebase.

Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c8b17be0

include/net/ipv6.h

+25 −0
Original line number Diff line number Diff line
@@ -154,6 +154,31 @@ struct frag_hdr { 
#define	IP6_MF		0x0001

#define	IP6_OFFSET	0xFFF8



struct ip6_fraglist_iter {

	struct ipv6hdr	*tmp_hdr;

	struct sk_buff	*frag_list;

	struct sk_buff	*frag;

	int		offset;

	unsigned int	hlen;

	__be32		frag_id;

	u8		nexthdr;

};



int ip6_fraglist_init(struct sk_buff *skb, unsigned int hlen, u8 *prevhdr,

		      u8 nexthdr, __be32 frag_id,

		      struct ip6_fraglist_iter *iter);

void ip6_fraglist_prepare(struct sk_buff *skb, struct ip6_fraglist_iter *iter);



static inline struct sk_buff *ip6_fraglist_next(struct ip6_fraglist_iter *iter)

{

	struct sk_buff *skb = iter->frag;



	iter->frag = skb->next;

	skb_mark_not_on_list(skb);



	return skb;

}



#define IP6_REPLY_MARK(net, mark) \

	((net)->ipv6.sysctl.fwmark_reflect ? (mark) : 0)

net/ipv6/ip6_output.c

+77 −55
Original line number Diff line number Diff line
@@ -592,6 +592,73 @@ static void ip6_copy_metadata(struct sk_buff *to, struct sk_buff *from) 
	skb_copy_secmark(to, from);

}



int ip6_fraglist_init(struct sk_buff *skb, unsigned int hlen, u8 *prevhdr,

		      u8 nexthdr, __be32 frag_id,

		      struct ip6_fraglist_iter *iter)

{

	unsigned int first_len;

	struct frag_hdr *fh;



	/* BUILD HEADER */

	*prevhdr = NEXTHDR_FRAGMENT;

	iter->tmp_hdr = kmemdup(skb_network_header(skb), hlen, GFP_ATOMIC);

	if (!iter->tmp_hdr)

		return -ENOMEM;



	iter->frag_list = skb_shinfo(skb)->frag_list;

	iter->frag = iter->frag_list;

	skb_frag_list_init(skb);



	iter->offset = 0;

	iter->hlen = hlen;

	iter->frag_id = frag_id;

	iter->nexthdr = nexthdr;



	__skb_pull(skb, hlen);

	fh = __skb_push(skb, sizeof(struct frag_hdr));

	__skb_push(skb, hlen);

	skb_reset_network_header(skb);

	memcpy(skb_network_header(skb), iter->tmp_hdr, hlen);



	fh->nexthdr = nexthdr;

	fh->reserved = 0;

	fh->frag_off = htons(IP6_MF);

	fh->identification = frag_id;



	first_len = skb_pagelen(skb);

	skb->data_len = first_len - skb_headlen(skb);

	skb->len = first_len;

	ipv6_hdr(skb)->payload_len = htons(first_len - sizeof(struct ipv6hdr));



	return 0;

}

EXPORT_SYMBOL(ip6_fraglist_init);



void ip6_fraglist_prepare(struct sk_buff *skb,

			  struct ip6_fraglist_iter *iter)

{

	struct sk_buff *frag = iter->frag;

	unsigned int hlen = iter->hlen;

	struct frag_hdr *fh;



	frag->ip_summed = CHECKSUM_NONE;

	skb_reset_transport_header(frag);

	fh = __skb_push(frag, sizeof(struct frag_hdr));

	__skb_push(frag, hlen);

	skb_reset_network_header(frag);

	memcpy(skb_network_header(frag), iter->tmp_hdr, hlen);

	iter->offset += skb->len - hlen - sizeof(struct frag_hdr);

	fh->nexthdr = iter->nexthdr;

	fh->reserved = 0;

	fh->frag_off = htons(iter->offset);

	if (frag->next)

		fh->frag_off |= htons(IP6_MF);

	fh->identification = iter->frag_id;

	ipv6_hdr(frag)->payload_len = htons(frag->len - sizeof(struct ipv6hdr));

	ip6_copy_metadata(frag, skb);

}

EXPORT_SYMBOL(ip6_fraglist_prepare);



int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,

		 int (*output)(struct net *, struct sock *, struct sk_buff *))

{
@@ -599,7 +666,6 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, 
	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);

	struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?

				inet6_sk(skb->sk) : NULL;

	struct ipv6hdr *tmp_hdr;

	struct frag_hdr *fh;

	unsigned int mtu, hlen, left, len, nexthdr_offset;

	int hroom, troom;
@@ -651,6 +717,7 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, 
	hroom = LL_RESERVED_SPACE(rt->dst.dev);

	if (skb_has_frag_list(skb)) {

		unsigned int first_len = skb_pagelen(skb);

		struct ip6_fraglist_iter iter;

		struct sk_buff *frag2;



		if (first_len - hlen > mtu ||
@@ -678,74 +745,29 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, 
			skb->truesize -= frag->truesize;

		}



		err = 0;

		offset = 0;

		/* BUILD HEADER */



		*prevhdr = NEXTHDR_FRAGMENT;

		tmp_hdr = kmemdup(skb_network_header(skb), hlen, GFP_ATOMIC);

		if (!tmp_hdr) {

			err = -ENOMEM;

		err = ip6_fraglist_init(skb, hlen, prevhdr, nexthdr, frag_id,

					&iter);

		if (err < 0)

			goto fail;

		}

		frag = skb_shinfo(skb)->frag_list;

		skb_frag_list_init(skb);



		__skb_pull(skb, hlen);

		fh = __skb_push(skb, sizeof(struct frag_hdr));

		__skb_push(skb, hlen);

		skb_reset_network_header(skb);

		memcpy(skb_network_header(skb), tmp_hdr, hlen);



		fh->nexthdr = nexthdr;

		fh->reserved = 0;

		fh->frag_off = htons(IP6_MF);

		fh->identification = frag_id;



		first_len = skb_pagelen(skb);

		skb->data_len = first_len - skb_headlen(skb);

		skb->len = first_len;

		ipv6_hdr(skb)->payload_len = htons(first_len -

						   sizeof(struct ipv6hdr));



		for (;;) {

			/* Prepare header of the next frame,

			 * before previous one went down. */

			if (frag) {

				frag->ip_summed = CHECKSUM_NONE;

				skb_reset_transport_header(frag);

				fh = __skb_push(frag, sizeof(struct frag_hdr));

				__skb_push(frag, hlen);

				skb_reset_network_header(frag);

				memcpy(skb_network_header(frag), tmp_hdr,

				       hlen);

				offset += skb->len - hlen - sizeof(struct frag_hdr);

				fh->nexthdr = nexthdr;

				fh->reserved = 0;

				fh->frag_off = htons(offset);

				if (frag->next)

					fh->frag_off |= htons(IP6_MF);

				fh->identification = frag_id;

				ipv6_hdr(frag)->payload_len =

						htons(frag->len -

						      sizeof(struct ipv6hdr));

				ip6_copy_metadata(frag, skb);

			}

			if (iter.frag)

				ip6_fraglist_prepare(skb, &iter);



			err = output(net, sk, skb);

			if (!err)

				IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),

					      IPSTATS_MIB_FRAGCREATES);



			if (err || !frag)

			if (err || !iter.frag)

				break;



			skb = frag;

			frag = skb->next;

			skb_mark_not_on_list(skb);

			skb = ip6_fraglist_next(&iter);

		}



		kfree(tmp_hdr);

		kfree(iter.tmp_hdr);



		if (err == 0) {

			IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),
@@ -753,7 +775,7 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb, 
			return 0;

		}



		kfree_skb_list(frag);

		kfree_skb_list(iter.frag_list);



		IP6_INC_STATS(net, ip6_dst_idev(&rt->dst),

			      IPSTATS_MIB_FRAGFAILS);