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deflate.c

/* 
 * Cryptographic API.
 *
 * Deflate algorithm (RFC 1951), implemented here primarily for use
 * by IPCOMP (RFC 3173 & RFC 2394).
 *
 * Copyright (c) 2003 James Morris <jmorris@intercode.com.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.
 *
 * FIXME: deflate transforms will require up to a total of about 436k of kernel
 * memory on i386 (390k for compression, the rest for decompression), as the
 * current zlib kernel code uses a worst case pre-allocation system by default.
 * This needs to be fixed so that the amount of memory required is properly
 * related to the  winbits and memlevel parameters.
 *
 * The default winbits of 11 should suit most packets, and it may be something
 * to configure on a per-tfm basis in the future.
 *
 * Currently, compression history is not maintained between tfm calls, as
 * it is not needed for IPCOMP and keeps the code simpler.  It can be
 * implemented if someone wants it.
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/zlib.h>
#include <linux/vmalloc.h>
#include <linux/interrupt.h>
#include <linux/mm.h>
#include <linux/net.h>
#include <linux/slab.h>

#define DEFLATE_DEF_LEVEL           Z_DEFAULT_COMPRESSION
#define DEFLATE_DEF_WINBITS         11
#define DEFLATE_DEF_MEMLEVEL        MAX_MEM_LEVEL

struct deflate_ctx {
      struct z_stream_s comp_stream;
      struct z_stream_s decomp_stream;
};

static int deflate_comp_init(struct deflate_ctx *ctx)
{
      int ret = 0;
      struct z_stream_s *stream = &ctx->comp_stream;

      stream->workspace = vmalloc(zlib_deflate_workspacesize());
      if (!stream->workspace ) {
            ret = -ENOMEM;
            goto out;
      }
      memset(stream->workspace, 0, zlib_deflate_workspacesize());
      ret = zlib_deflateInit2(stream, DEFLATE_DEF_LEVEL, Z_DEFLATED,
                              -DEFLATE_DEF_WINBITS, DEFLATE_DEF_MEMLEVEL,
                              Z_DEFAULT_STRATEGY);
      if (ret != Z_OK) {
            ret = -EINVAL;
            goto out_free;
      }
out:  
      return ret;
out_free:
      vfree(stream->workspace);
      goto out;
}

static int deflate_decomp_init(struct deflate_ctx *ctx)
{
      int ret = 0;
      struct z_stream_s *stream = &ctx->decomp_stream;

      stream->workspace = kzalloc(zlib_inflate_workspacesize(), GFP_KERNEL);
      if (!stream->workspace ) {
            ret = -ENOMEM;
            goto out;
      }
      ret = zlib_inflateInit2(stream, -DEFLATE_DEF_WINBITS);
      if (ret != Z_OK) {
            ret = -EINVAL;
            goto out_free;
      }
out:
      return ret;
out_free:
      kfree(stream->workspace);
      goto out;
}

static void deflate_comp_exit(struct deflate_ctx *ctx)
{
      zlib_deflateEnd(&ctx->comp_stream);
      vfree(ctx->comp_stream.workspace);
}

static void deflate_decomp_exit(struct deflate_ctx *ctx)
{
      zlib_inflateEnd(&ctx->decomp_stream);
      kfree(ctx->decomp_stream.workspace);
}

static int deflate_init(struct crypto_tfm *tfm)
{
      struct deflate_ctx *ctx = crypto_tfm_ctx(tfm);
      int ret;
      
      ret = deflate_comp_init(ctx);
      if (ret)
            goto out;
      ret = deflate_decomp_init(ctx);
      if (ret)
            deflate_comp_exit(ctx);
out:
      return ret;
}

static void deflate_exit(struct crypto_tfm *tfm)
{
      struct deflate_ctx *ctx = crypto_tfm_ctx(tfm);

      deflate_comp_exit(ctx);
      deflate_decomp_exit(ctx);
}

static int deflate_compress(struct crypto_tfm *tfm, const u8 *src,
                      unsigned int slen, u8 *dst, unsigned int *dlen)
{
      int ret = 0;
      struct deflate_ctx *dctx = crypto_tfm_ctx(tfm);
      struct z_stream_s *stream = &dctx->comp_stream;

      ret = zlib_deflateReset(stream);
      if (ret != Z_OK) {
            ret = -EINVAL;
            goto out;
      }

      stream->next_in = (u8 *)src;
      stream->avail_in = slen;
      stream->next_out = (u8 *)dst;
      stream->avail_out = *dlen;

      ret = zlib_deflate(stream, Z_FINISH);
      if (ret != Z_STREAM_END) {
            ret = -EINVAL;
            goto out;
      }
      ret = 0;
      *dlen = stream->total_out;
out:
      return ret;
}
 
static int deflate_decompress(struct crypto_tfm *tfm, const u8 *src,
                        unsigned int slen, u8 *dst, unsigned int *dlen)
{
      
      int ret = 0;
      struct deflate_ctx *dctx = crypto_tfm_ctx(tfm);
      struct z_stream_s *stream = &dctx->decomp_stream;

      ret = zlib_inflateReset(stream);
      if (ret != Z_OK) {
            ret = -EINVAL;
            goto out;
      }

      stream->next_in = (u8 *)src;
      stream->avail_in = slen;
      stream->next_out = (u8 *)dst;
      stream->avail_out = *dlen;

      ret = zlib_inflate(stream, Z_SYNC_FLUSH);
      /*
       * Work around a bug in zlib, which sometimes wants to taste an extra
       * byte when being used in the (undocumented) raw deflate mode.
       * (From USAGI).
       */
      if (ret == Z_OK && !stream->avail_in && stream->avail_out) {
            u8 zerostuff = 0;
            stream->next_in = &zerostuff;
            stream->avail_in = 1; 
            ret = zlib_inflate(stream, Z_FINISH);
      }
      if (ret != Z_STREAM_END) {
            ret = -EINVAL;
            goto out;
      }
      ret = 0;
      *dlen = stream->total_out;
out:
      return ret;
}

static struct crypto_alg alg = {
      .cra_name         = "deflate",
      .cra_flags        = CRYPTO_ALG_TYPE_COMPRESS,
      .cra_ctxsize            = sizeof(struct deflate_ctx),
      .cra_module       = THIS_MODULE,
      .cra_list         = LIST_HEAD_INIT(alg.cra_list),
      .cra_init         = deflate_init,
      .cra_exit         = deflate_exit,
      .cra_u                  = { .compress = {
      .coa_compress           = deflate_compress,
      .coa_decompress   = deflate_decompress } }
};

static int __init init(void)
{
      return crypto_register_alg(&alg);
}

static void __exit fini(void)
{
      crypto_unregister_alg(&alg);
}

module_init(init);
module_exit(fini);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Deflate Compression Algorithm for IPCOMP");
MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");


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