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Commit 2817a336 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

net: skb_checksum: allow custom update/combine for walking skb 



Currently, skb_checksum walks over 1) linearized, 2) frags[], and
3) frag_list data and calculats the one's complement, a 32 bit
result suitable for feeding into itself or csum_tcpudp_magic(),
but unsuitable for SCTP as we're calculating CRC32c there.

Hence, in order to not re-implement the very same function in
SCTP (and maybe other protocols) over and over again, use an
update() + combine() callback internally to allow for walking
over the skb with different algorithms.

Signed-off-by: default avatarDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent efba721f

include/linux/skbuff.h

+10 −3
Original line number Diff line number Diff line
@@ -2360,8 +2360,6 @@ int skb_copy_datagram_const_iovec(const struct sk_buff *from, int offset, 
void skb_free_datagram(struct sock *sk, struct sk_buff *skb);

void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb);

int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags);

__wsum skb_checksum(const struct sk_buff *skb, int offset, int len,

		    __wsum csum);

int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len);

int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len);

__wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, u8 *to,
@@ -2373,9 +2371,18 @@ void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to); 
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);



struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);



struct skb_checksum_ops {

	__wsum (*update)(const void *mem, int len, __wsum wsum);

	__wsum (*combine)(__wsum csum, __wsum csum2, int offset, int len);

};



__wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,

		      __wsum csum, const struct skb_checksum_ops *ops);

__wsum skb_checksum(const struct sk_buff *skb, int offset, int len,

		    __wsum csum);



static inline void *skb_header_pointer(const struct sk_buff *skb, int offset,

				       int len, void *buffer)

{

include/net/checksum.h

+6 −0
Original line number Diff line number Diff line
@@ -78,6 +78,12 @@ csum_block_add(__wsum csum, __wsum csum2, int offset) 
	return csum_add(csum, (__force __wsum)sum);

}



static inline __wsum

csum_block_add_ext(__wsum csum, __wsum csum2, int offset, int len)

{

	return csum_block_add(csum, csum2, offset);

}



static inline __wsum

csum_block_sub(__wsum csum, __wsum csum2, int offset)

{

net/core/skbuff.c

+21 −10
Original line number Diff line number Diff line
@@ -1928,9 +1928,8 @@ int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len) 
EXPORT_SYMBOL(skb_store_bits);



/* Checksum skb data. */



__wsum skb_checksum(const struct sk_buff *skb, int offset,

			  int len, __wsum csum)

__wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,

		      __wsum csum, const struct skb_checksum_ops *ops)

{

	int start = skb_headlen(skb);

	int i, copy = start - offset;
@@ -1941,7 +1940,7 @@ __wsum skb_checksum(const struct sk_buff *skb, int offset, 
	if (copy > 0) {

		if (copy > len)

			copy = len;

		csum = csum_partial(skb->data + offset, copy, csum);

		csum = ops->update(skb->data + offset, copy, csum);

		if ((len -= copy) == 0)

			return csum;

		offset += copy;
@@ -1962,10 +1961,10 @@ __wsum skb_checksum(const struct sk_buff *skb, int offset, 
			if (copy > len)

				copy = len;

			vaddr = kmap_atomic(skb_frag_page(frag));

			csum2 = csum_partial(vaddr + frag->page_offset +

			csum2 = ops->update(vaddr + frag->page_offset +

					    offset - start, copy, 0);

			kunmap_atomic(vaddr);

			csum = csum_block_add(csum, csum2, pos);

			csum = ops->combine(csum, csum2, pos, copy);

			if (!(len -= copy))

				return csum;

			offset += copy;
@@ -1984,9 +1983,9 @@ __wsum skb_checksum(const struct sk_buff *skb, int offset, 
			__wsum csum2;

			if (copy > len)

				copy = len;

			csum2 = skb_checksum(frag_iter, offset - start,

					     copy, 0);

			csum = csum_block_add(csum, csum2, pos);

			csum2 = __skb_checksum(frag_iter, offset - start,

					       copy, 0, ops);

			csum = ops->combine(csum, csum2, pos, copy);

			if ((len -= copy) == 0)

				return csum;

			offset += copy;
@@ -1998,6 +1997,18 @@ __wsum skb_checksum(const struct sk_buff *skb, int offset, 


	return csum;

}

EXPORT_SYMBOL(__skb_checksum);



__wsum skb_checksum(const struct sk_buff *skb, int offset,

		    int len, __wsum csum)

{

	const struct skb_checksum_ops ops = {

		.update  = csum_partial,

		.combine = csum_block_add_ext,

	};



	return __skb_checksum(skb, offset, len, csum, &ops);

}

EXPORT_SYMBOL(skb_checksum);



/* Both of above in one bottle. */