[PATCH net-next 06/10] net: fold __skb_checksum() into skb_checksum()

Eric Biggers
2025-05-11T00:41:35Z

From: Eric Biggers <ebiggers@google.com>

Now that the only remaining caller of __skb_checksum() is
skb_checksum(), fold __skb_checksum() into skb_checksum(). This makes
struct skb_checksum_ops unnecessary, so remove that too and simply do
the "regular" net checksum. It also makes the wrapper functions
csum_partial_ext() and csum_block_add_ext() unnecessary, so remove those
too and just use the underlying functions.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
include/linux/skbuff.h | 9 -------
include/net/checksum.h | 12 ---------
net/core/skbuff.c | 59 +++++-------------------------------------
3 files changed, 7 insertions(+), 73 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 33b33bb18aa6..eac5c8dde4a5 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -4181,19 +4181,10 @@ static inline int memcpy_from_msg(void *data, struct msghdr *msg, int len)
static inline int memcpy_to_msg(struct msghdr *msg, void *data, int len)
{
return copy_to_iter(data, len, &msg->msg_iter) == len ? 0 : -EFAULT;
}

-struct skb_checksum_ops {
- __wsum (*update)(const void *mem, int len, __wsum wsum);
- __wsum (*combine)(__wsum csum, __wsum csum2, int offset, int len);
-};
-
-extern const struct skb_checksum_ops *crc32c_csum_stub __read_mostly;
-
-__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);
u32 skb_crc32c(const struct sk_buff *skb, int offset, int len, u32 crc);

static inline void * __must_check
diff --git a/include/net/checksum.h b/include/net/checksum.h
index 243f972267b8..e57986b173f8 100644
--- a/include/net/checksum.h
+++ b/include/net/checksum.h
@@ -96,16 +96,10 @@ static __always_inline __wsum
csum_block_add(__wsum csum, __wsum csum2, int offset)
{
return csum_add(csum, csum_shift(csum2, offset));
}

-static __always_inline __wsum
-csum_block_add_ext(__wsum csum, __wsum csum2, int offset, int len)
-{
- return csum_block_add(csum, csum2, offset);
-}
-
static __always_inline __wsum
csum_block_sub(__wsum csum, __wsum csum2, int offset)
{
return csum_block_add(csum, ~csum2, offset);
}
@@ -113,16 +107,10 @@ csum_block_sub(__wsum csum, __wsum csum2, int offset)
static __always_inline __wsum csum_unfold(__sum16 n)
{
return (__force __wsum)n;
}

-static __always_inline
-__wsum csum_partial_ext(const void *buff, int len, __wsum sum)
-{
- return csum_partial(buff, len, sum);
-}
-
#define CSUM_MANGLED_0 ((__force __sum16)0xffff)

static __always_inline void csum_replace_by_diff(__sum16 *sum, __wsum diff)
{
*sum = csum_fold(csum_add(diff, ~csum_unfold(*sum)));
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b9900cc16a24..bfa892ccc7f7 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3438,24 +3438,22 @@ int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len)
return -EFAULT;
}
EXPORT_SYMBOL(skb_store_bits);

/* Checksum skb data. */
-__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)
{
int start = skb_headlen(skb);
int i, copy = start - offset;
struct sk_buff *frag_iter;
int pos = 0;

/* Checksum header. */
if (copy > 0) {
if (copy > len)
copy = len;
- csum = INDIRECT_CALL_1(ops->update, csum_partial_ext,
- skb->data + offset, copy, csum);
+ csum = csum_partial(skb->data + offset, copy, csum);
if ((len -= copy) == 0)
return csum;
offset += copy;
pos = copy;
}
@@ -3481,17 +3479,13 @@ __wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,

skb_frag_foreach_page(frag,
skb_frag_off(frag) + offset - start,
copy, p, p_off, p_len, copied) {
vaddr = kmap_atomic(p);
- csum2 = INDIRECT_CALL_1(ops->update,
- csum_partial_ext,
- vaddr + p_off, p_len, 0);
+ csum2 = csum_partial(vaddr + p_off, p_len, 0);
kunmap_atomic(vaddr);
- csum = INDIRECT_CALL_1(ops->combine,
- csum_block_add_ext, csum,
- csum2, pos, p_len);
+ csum = csum_block_add(csum, csum2, pos);
pos += p_len;
}

if (!(len -= copy))
return csum;
@@ -3508,14 +3502,13 @@ __wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,
end = start + frag_iter->len;
if ((copy = end - offset) > 0) {
__wsum csum2;
if (copy > len)
copy = len;
- csum2 = __skb_checksum(frag_iter, offset - start,
- copy, 0, ops);
- csum = INDIRECT_CALL_1(ops->combine, csum_block_add_ext,
- csum, csum2, pos, copy);
+ csum2 = skb_checksum(frag_iter, offset - start, copy,
+ 0);
+ csum = csum_block_add(csum, csum2, pos);
if ((len -= copy) == 0)
return csum;
offset += copy;
pos += copy;
}
@@ -3523,22 +3516,10 @@ __wsum __skb_checksum(const struct sk_buff *skb, int offset, int len,
}
BUG_ON(len);

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_ext,
- .combine = csum_block_add_ext,
- };
-
- return __skb_checksum(skb, offset, len, csum, &ops);
-}
EXPORT_SYMBOL(skb_checksum);

/* Both of above in one bottle. */

__wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset,
@@ -3758,36 +3739,10 @@ __sum16 __skb_checksum_complete(struct sk_buff *skb)

return sum;
}
EXPORT_SYMBOL(__skb_checksum_complete);

-static __wsum warn_crc32c_csum_update(const void *buff, int len, __wsum sum)
-{
- net_warn_ratelimited(
- "%s: attempt to compute crc32c without libcrc32c.ko\n",
- __func__);
- return 0;
-}
-
-static __wsum warn_crc32c_csum_combine(__wsum csum, __wsum csum2,
- int offset, int len)
-{
- net_warn_ratelimited(
- "%s: attempt to compute crc32c without libcrc32c.ko\n",
- __func__);
- return 0;
-}
-
-static const struct skb_checksum_ops default_crc32c_ops = {
- .update = warn_crc32c_csum_update,
- .combine = warn_crc32c_csum_combine,
-};
-
-const struct skb_checksum_ops *crc32c_csum_stub __read_mostly =
- &default_crc32c_ops;
-EXPORT_SYMBOL(crc32c_csum_stub);
-
/**
* skb_zerocopy_headlen - Calculate headroom needed for skb_zerocopy()
* @from: source buffer
*
* Calculates the amount of linear headroom needed in the 'to' skb passed
--
2.49.0