/*
   * Cryptographic API.
   *
   * CRC32C chksum
   *
   *@Article{castagnoli-crc,
   * author =       { Guy Castagnoli and Stefan Braeuer and Martin Herrman},
   * title =        {{Optimization of Cyclic Redundancy-Check Codes with 24
   *                 and 32 Parity Bits}},
   * journal =      IEEE Transactions on Communication,
   * year =         {1993},
   * volume =       {41},
   * number =       {6},
   * pages =        {},
   * month =        {June},
   *}
   * Used by the iSCSI driver, possibly others, and derived from the
   * the iscsi-crc.c module of the linux-iscsi driver at
   * http://linux-iscsi.sourceforge.net.
   *
   * Following the example of lib/crc32, this function is intended to be
   * flexible and useful for all users.  Modules that currently have their
   * own crc32c, but hopefully may be able to use this one are:
   *  net/sctp (please add all your doco to here if you change to
   *            use this one!)
   *  <endoflist>
   *
   * Copyright (c) 2004 Cisco Systems, Inc.
   * Copyright (c) 2008 Herbert Xu <herbert@gondor.apana.org.au>
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License as published by the Free
   * Software Foundation; either version 2 of the License, or (at your option)
   * any later version.
   *
   */
  
  #include <crypto/internal/hash.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/string.h>
  #include <linux/kernel.h>
  #include <linux/crc32.h>
  
  #define CHKSUM_BLOCK_SIZE	1
  #define CHKSUM_DIGEST_SIZE	4
  
  struct chksum_ctx {
  	u32 key;
  };
  
  struct chksum_desc_ctx {
  	u32 crc;
  };
  
  /*
   * Steps through buffer one byte at at time, calculates reflected
   * crc using table.
   */
  
  static int chksum_init(struct shash_desc *desc)
  {
  	struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
  	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
  
  	ctx->crc = mctx->key;
  
  	return 0;
  }
  
  /*
   * Setting the seed allows arbitrary accumulators and flexible XOR policy
   * If your algorithm starts with ~0, then XOR with ~0 before you set
   * the seed.
   */
  static int chksum_setkey(struct crypto_shash *tfm, const u8 *key,
  			 unsigned int keylen)
  {
  	struct chksum_ctx *mctx = crypto_shash_ctx(tfm);
  
  	if (keylen != sizeof(mctx->key)) {
  		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
  		return -EINVAL;
  	}
  	mctx->key = le32_to_cpu(*(__le32 *)key);
  	return 0;
  }
  
  static int chksum_update(struct shash_desc *desc, const u8 *data,
  			 unsigned int length)
  {
  	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
  
  	ctx->crc = __crc32c_le(ctx->crc, data, length);
  	return 0;
  }
  
  static int chksum_final(struct shash_desc *desc, u8 *out)
  {
  	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
  
  	*(__le32 *)out = ~cpu_to_le32p(&ctx->crc);
  	return 0;
  }
  
  static int __chksum_finup(u32 *crcp, const u8 *data, unsigned int len, u8 *out)
  {
  	*(__le32 *)out = ~cpu_to_le32(__crc32c_le(*crcp, data, len));
  	return 0;
  }
  
  static int chksum_finup(struct shash_desc *desc, const u8 *data,
  			unsigned int len, u8 *out)
  {
  	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
  
  	return __chksum_finup(&ctx->crc, data, len, out);
  }
  
  static int chksum_digest(struct shash_desc *desc, const u8 *data,
  			 unsigned int length, u8 *out)
  {
  	struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
  
  	return __chksum_finup(&mctx->key, data, length, out);
  }
  
  static int crc32c_cra_init(struct crypto_tfm *tfm)
  {
  	struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
  
  	mctx->key = ~0;
  	return 0;
  }
  
  static struct shash_alg alg = {
  	.digestsize		=	CHKSUM_DIGEST_SIZE,
  	.setkey			=	chksum_setkey,
  	.init		=	chksum_init,
  	.update		=	chksum_update,
  	.final		=	chksum_final,
  	.finup		=	chksum_finup,
  	.digest		=	chksum_digest,
  	.descsize		=	sizeof(struct chksum_desc_ctx),
  	.base			=	{
  		.cra_name		=	"crc32c",
  		.cra_driver_name	=	"crc32c-generic",
  		.cra_priority		=	100,
  		.cra_blocksize		=	CHKSUM_BLOCK_SIZE,
  		.cra_alignmask		=	3,
  		.cra_ctxsize		=	sizeof(struct chksum_ctx),
  		.cra_module		=	THIS_MODULE,
  		.cra_init		=	crc32c_cra_init,
  	}
  };
  
  static int __init crc32c_mod_init(void)
  {
  	return crypto_register_shash(&alg);
  }
  
  static void __exit crc32c_mod_fini(void)
  {
  	crypto_unregister_shash(&alg);
  }
  
  module_init(crc32c_mod_init);
  module_exit(crc32c_mod_fini);
  
  MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
  MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
  MODULE_LICENSE("GPL");