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/*

 * 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 {

        int comp_initialized;

        int decomp_initialized;

        struct z_stream_s comp_stream;

        struct z_stream_s decomp_stream;

};

static inline int deflate_gfp(void)

{

        return in_softirq() ? GFP_ATOMIC : GFP_KERNEL;

}

static int deflate_init(void *ctx)

{

        return 0;

}

static void deflate_exit(void *ctx)

{

        struct deflate_ctx *dctx = ctx;

        if (dctx->comp_initialized)

                vfree(dctx->comp_stream.workspace);

        if (dctx->decomp_initialized)

                kfree(dctx->decomp_stream.workspace);

}

/*

 * Lazy initialization to make interface simple without allocating

 * un-needed workspaces.  Thus can be called in softirq context.

 */

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(),

                                      deflate_gfp()|__GFP_HIGHMEM,

                                      PAGE_KERNEL);

        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;

        }

        ctx->comp_initialized = 1;

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 = kmalloc(zlib_inflate_workspacesize(),

                                    deflate_gfp());

        if (!stream->workspace ) {

                ret = -ENOMEM;

                goto out;

        }

        memset(stream->workspace, 0, zlib_inflate_workspacesize());

        ret = zlib_inflateInit2(stream, -DEFLATE_DEF_WINBITS);

        if (ret != Z_OK) {

                ret = -EINVAL;

                goto out_free;

        }

        ctx->decomp_initialized = 1;

out:

        return ret;

out_free:

        kfree(stream->workspace);

        goto out;

}

static int deflate_compress(void *ctx, const u8 *src, unsigned int slen,

                            u8 *dst, unsigned int *dlen)

{

        int ret = 0;

        struct deflate_ctx *dctx = ctx;

        struct z_stream_s *stream = &dctx->comp_stream;

        if (!dctx->comp_initialized) {

                ret = deflate_comp_init(dctx);

                if (ret)

                        goto out;

        }

        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(void *ctx, const u8 *src, unsigned int slen,

                              u8 *dst, unsigned int *dlen)

{

        int ret = 0;

        struct deflate_ctx *dctx = ctx;

        struct z_stream_s *stream = &dctx->decomp_stream;

        if (!dctx->decomp_initialized) {

                ret = deflate_decomp_init(dctx);

                if (ret)

                        goto out;

        }

        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_u                  = { .compress = {

        .coa_init               = deflate_init,

        .coa_exit               = deflate_exit,

        .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>");