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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: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2013-10-30 11:50:51 +01:00 committed by David S. Miller
parent efba721f63
commit 2817a336d4
3 changed files with 37 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
include/linux/skbuff.h
View File

@ -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)
{

6
include/net/checksum.h
View File

@ -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)
{

31
net/core/skbuff.c
View File

@ -1928,9 +1928,8 @@ fault:
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 +
offset - start, copy, 0);
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. */