Commit af2806f8 authored by Thomas Graf's avatar Thomas Graf Committed by Jesse Gross
Browse files

net: Export skb_zerocopy() to zerocopy from one skb to another 



Make the skb zerocopy logic written for nfnetlink queue available for
use by other modules.

Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
Reviewed-by: default avatarDaniel Borkmann <dborkman@redhat.com>
Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarJesse Gross <jesse@nicira.com>
parent 5f03f47c

include/linux/skbuff.h

+3 −0
Original line number Diff line number Diff line
@@ -2345,6 +2345,9 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset, 
		    struct pipe_inode_info *pipe, unsigned int len,

		    unsigned int flags);

void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);

unsigned int skb_zerocopy_headlen(const struct sk_buff *from);

void skb_zerocopy(struct sk_buff *to, const struct sk_buff *from,

		  int len, int hlen);

void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len);

int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);

void skb_scrub_packet(struct sk_buff *skb, bool xnet);

net/core/skbuff.c

+85 −0
Original line number Diff line number Diff line
@@ -2122,6 +2122,91 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, 
}

EXPORT_SYMBOL(skb_copy_and_csum_bits);



 /**

 *	skb_zerocopy_headlen - Calculate headroom needed for skb_zerocopy()

 *	@from: source buffer

 *

 *	Calculates the amount of linear headroom needed in the 'to' skb passed

 *	into skb_zerocopy().

 */

unsigned int

skb_zerocopy_headlen(const struct sk_buff *from)

{

	unsigned int hlen = 0;



	if (!from->head_frag ||

	    skb_headlen(from) < L1_CACHE_BYTES ||

	    skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS)

		hlen = skb_headlen(from);



	if (skb_has_frag_list(from))

		hlen = from->len;



	return hlen;

}

EXPORT_SYMBOL_GPL(skb_zerocopy_headlen);



/**

 *	skb_zerocopy - Zero copy skb to skb

 *	@to: destination buffer

 *	@source: source buffer

 *	@len: number of bytes to copy from source buffer

 *	@hlen: size of linear headroom in destination buffer

 *

 *	Copies up to `len` bytes from `from` to `to` by creating references

 *	to the frags in the source buffer.

 *

 *	The `hlen` as calculated by skb_zerocopy_headlen() specifies the

 *	headroom in the `to` buffer.

 */

void

skb_zerocopy(struct sk_buff *to, const struct sk_buff *from, int len, int hlen)

{

	int i, j = 0;

	int plen = 0; /* length of skb->head fragment */

	struct page *page;

	unsigned int offset;



	BUG_ON(!from->head_frag && !hlen);



	/* dont bother with small payloads */

	if (len <= skb_tailroom(to)) {

		skb_copy_bits(from, 0, skb_put(to, len), len);

		return;

	}



	if (hlen) {

		skb_copy_bits(from, 0, skb_put(to, hlen), hlen);

		len -= hlen;

	} else {

		plen = min_t(int, skb_headlen(from), len);

		if (plen) {

			page = virt_to_head_page(from->head);

			offset = from->data - (unsigned char *)page_address(page);

			__skb_fill_page_desc(to, 0, page, offset, plen);

			get_page(page);

			j = 1;

			len -= plen;

		}

	}



	to->truesize += len + plen;

	to->len += len + plen;

	to->data_len += len + plen;



	for (i = 0; i < skb_shinfo(from)->nr_frags; i++) {

		if (!len)

			break;

		skb_shinfo(to)->frags[j] = skb_shinfo(from)->frags[i];

		skb_shinfo(to)->frags[j].size = min_t(int, skb_shinfo(to)->frags[j].size, len);

		len -= skb_shinfo(to)->frags[j].size;

		skb_frag_ref(to, j);

		j++;

	}

	skb_shinfo(to)->nr_frags = j;

}

EXPORT_SYMBOL_GPL(skb_zerocopy);



void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to)

{

	__wsum csum;

net/netfilter/nfnetlink_queue_core.c

+4 −55
Original line number Diff line number Diff line
@@ -235,51 +235,6 @@ nfqnl_flush(struct nfqnl_instance *queue, nfqnl_cmpfn cmpfn, unsigned long data) 
	spin_unlock_bh(&queue->lock);

}



static void

nfqnl_zcopy(struct sk_buff *to, const struct sk_buff *from, int len, int hlen)

{

	int i, j = 0;

	int plen = 0; /* length of skb->head fragment */

	struct page *page;

	unsigned int offset;



	/* dont bother with small payloads */

	if (len <= skb_tailroom(to)) {

		skb_copy_bits(from, 0, skb_put(to, len), len);

		return;

	}



	if (hlen) {

		skb_copy_bits(from, 0, skb_put(to, hlen), hlen);

		len -= hlen;

	} else {

		plen = min_t(int, skb_headlen(from), len);

		if (plen) {

			page = virt_to_head_page(from->head);

			offset = from->data - (unsigned char *)page_address(page);

			__skb_fill_page_desc(to, 0, page, offset, plen);

			get_page(page);

			j = 1;

			len -= plen;

		}

	}



	to->truesize += len + plen;

	to->len += len + plen;

	to->data_len += len + plen;



	for (i = 0; i < skb_shinfo(from)->nr_frags; i++) {

		if (!len)

			break;

		skb_shinfo(to)->frags[j] = skb_shinfo(from)->frags[i];

		skb_shinfo(to)->frags[j].size = min_t(int, skb_shinfo(to)->frags[j].size, len);

		len -= skb_shinfo(to)->frags[j].size;

		skb_frag_ref(to, j);

		j++;

	}

	skb_shinfo(to)->nr_frags = j;

}



static int

nfqnl_put_packet_info(struct sk_buff *nlskb, struct sk_buff *packet,

		      bool csum_verify)
@@ -304,7 +259,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue, 
{

	size_t size;

	size_t data_len = 0, cap_len = 0;

	int hlen = 0;

	unsigned int hlen = 0;

	struct sk_buff *skb;

	struct nlattr *nla;

	struct nfqnl_msg_packet_hdr *pmsg;
@@ -356,14 +311,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue, 
		if (data_len > entskb->len)

			data_len = entskb->len;



		if (!entskb->head_frag ||

		    skb_headlen(entskb) < L1_CACHE_BYTES ||

		    skb_shinfo(entskb)->nr_frags >= MAX_SKB_FRAGS)

			hlen = skb_headlen(entskb);



		if (skb_has_frag_list(entskb))

			hlen = entskb->len;

		hlen = min_t(int, data_len, hlen);

		hlen = skb_zerocopy_headlen(entskb);

		hlen = min_t(unsigned int, hlen, data_len);

		size += sizeof(struct nlattr) + hlen;

		cap_len = entskb->len;

		break;
@@ -504,7 +453,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue, 
		nla->nla_type = NFQA_PAYLOAD;

		nla->nla_len = nla_attr_size(data_len);



		nfqnl_zcopy(skb, entskb, data_len, hlen);

		skb_zerocopy(skb, entskb, data_len, hlen);

	}



	nlh->nlmsg_len = skb->len;