From 6e95fcaa42e5078ac265964deebed597f9eae07a Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 30 Oct 2013 11:50:49 +0100 Subject: lib: crc32: add functionality to combine two crc32{, c}s in GF(2) This patch adds a combinator to merge two or more crc32{,c}s into a new one. This is useful for checksum computations of fragmented skbs that use crc32/crc32c as checksums. The arithmetics for combining both in the GF(2) was taken and slightly modified from zlib. Only passing two crcs is insufficient as two crcs and the length of the second piece is needed for merging. The code is made generic, so that only polynomials need to be passed for crc32_le resp. crc32c_le. Signed-off-by: Daniel Borkmann Cc: linux-kernel@vger.kernel.org Signed-off-by: David S. Miller --- include/linux/crc32.h | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) (limited to 'include/linux') diff --git a/include/linux/crc32.h b/include/linux/crc32.h index 68267b64bb98..7d275c4fc011 100644 --- a/include/linux/crc32.h +++ b/include/linux/crc32.h @@ -11,8 +11,48 @@ extern u32 crc32_le(u32 crc, unsigned char const *p, size_t len); extern u32 crc32_be(u32 crc, unsigned char const *p, size_t len); +/** + * crc32_le_combine - Combine two crc32 check values into one. For two + * sequences of bytes, seq1 and seq2 with lengths len1 + * and len2, crc32_le() check values were calculated + * for each, crc1 and crc2. + * + * @crc1: crc32 of the first block + * @crc2: crc32 of the second block + * @len2: length of the second block + * + * Return: The crc32_le() check value of seq1 and seq2 concatenated, + * requiring only crc1, crc2, and len2. Note: If seq_full denotes + * the concatenated memory area of seq1 with seq2, and crc_full + * the crc32_le() value of seq_full, then crc_full == + * crc32_le_combine(crc1, crc2, len2) when crc_full was seeded + * with the same initializer as crc1, and crc2 seed was 0. See + * also crc32_combine_test(). + */ +extern u32 crc32_le_combine(u32 crc1, u32 crc2, size_t len2); + extern u32 __crc32c_le(u32 crc, unsigned char const *p, size_t len); +/** + * __crc32c_le_combine - Combine two crc32c check values into one. For two + * sequences of bytes, seq1 and seq2 with lengths len1 + * and len2, __crc32c_le() check values were calculated + * for each, crc1 and crc2. + * + * @crc1: crc32c of the first block + * @crc2: crc32c of the second block + * @len2: length of the second block + * + * Return: The __crc32c_le() check value of seq1 and seq2 concatenated, + * requiring only crc1, crc2, and len2. Note: If seq_full denotes + * the concatenated memory area of seq1 with seq2, and crc_full + * the __crc32c_le() value of seq_full, then crc_full == + * __crc32c_le_combine(crc1, crc2, len2) when crc_full was + * seeded with the same initializer as crc1, and crc2 seed + * was 0. See also crc32c_combine_test(). + */ +extern u32 __crc32c_le_combine(u32 crc1, u32 crc2, size_t len2); + #define crc32(seed, data, length) crc32_le(seed, (unsigned char const *)(data), length) /* -- cgit v1.2.3 From 2817a336d4d533fb8b68719723cd60ea7dd7c09e Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 30 Oct 2013 11:50:51 +0100 Subject: 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 Signed-off-by: David S. Miller --- include/linux/skbuff.h | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 2c154976394b..44727b5d4981 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -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) { -- cgit v1.2.3