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/*
 * lib/route/pktloc.c     Packet Location Aliasing
 *
 *      This library 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 version 2 of the License.
 *
 * Copyright (c) 2008-2010 Thomas Graf <tgraf@suug.ch>
 */

/**
 * @ingroup tc
 * @defgroup pktloc Packet Location Aliasing
 * Packet Location Aliasing
 *
 * The packet location aliasing interface eases the use of offset definitions
 * inside packets by allowing them to be referenced by name. Known positions
 * of protocol fields are stored in a configuration file and associated with
 * a name for later reference. The configuration file is distributed with the
 * library and provides a well defined set of definitions for most common
 * protocol fields.
 *
 * @subsection pktloc_examples Examples
 * @par Example 1.1 Looking up a packet location
 * @code
 * struct rtnl_pktloc *loc;
 *
 * rtnl_pktloc_lookup("ip.src", &loc);
 * @endcode
 * @{
 */

#include <netlink-local.h>
#include <netlink-tc.h>
#include <netlink/netlink.h>
#include <netlink/utils.h>
#include <netlink/route/pktloc.h>

#include "pktloc_syntax.h"
#include "pktloc_grammar.h"

/** @cond */
#define PKTLOC_NAME_HT_SIZ 256

static struct nl_list_head pktloc_name_ht[PKTLOC_NAME_HT_SIZ];

/* djb2 */
unsigned int pktloc_hash(const char *str)
{
        unsigned long hash = 5381;
        int c;

        while ((c = *str++))
                hash = ((hash << 5) + hash) + c; /* hash * 33 + c */

        return hash % PKTLOC_NAME_HT_SIZ;
}


void rtnl_pktloc_add(struct rtnl_pktloc *loc)
{
        nl_list_add_tail(&loc->list, &pktloc_name_ht[pktloc_hash(loc->name)]);
}

extern int pktloc_parse(void *scanner);

/** @endcond */

static void rtnl_pktloc_free(struct rtnl_pktloc *loc)
{
        if (!loc)
                return;

        free(loc->name);
        free(loc);
}

static int read_pktlocs(void)
{
        YY_BUFFER_STATE buf;
        yyscan_t scanner = NULL;
        static time_t last_read;
        struct stat st = {0};
        char *path;
        int i, err;
        FILE *fd;

        asprintf(&path, "%s/pktloc", SYSCONFDIR);

        /* if stat fails, just try to read the file */
        if (stat(path, &st) == 0) {
                /* Don't re-read file if file is unchanged */
                if (last_read == st.st_mtime)
                        return 0;
        }

        if (!(fd = fopen(path, "r")))
                return -NLE_PKTLOC_FILE;

        for (i = 0; i < PKTLOC_NAME_HT_SIZ; i++) {
                struct rtnl_pktloc *loc, *n;

                nl_list_for_each_entry_safe(loc, n, &pktloc_name_ht[i], list)
                        rtnl_pktloc_free(loc);

                nl_init_list_head(&pktloc_name_ht[i]);
        }

        if ((err = pktloc_lex_init(&scanner)) < 0)
                return -NLE_FAILURE;

        buf = pktloc__create_buffer(fd, YY_BUF_SIZE, scanner);
        pktloc__switch_to_buffer(buf, scanner);

        if ((err = pktloc_parse(scanner)) < 0)
                return -NLE_FAILURE;

        if (scanner)
                pktloc_lex_destroy(scanner);

        free(path);
        last_read = st.st_mtime;

        return 0;
}

/**
 * Lookup packet location alias
 * @arg name            Name of packet location.
 *
 * Tries to find a matching packet location alias for the supplied
 * packet location name.
 *
 * The file containing the packet location definitions is automatically
 * re-read if its modification time has changed since the last call.
 *
 * @return 0 on success or a negative error code.
 * @retval NLE_PKTLOC_FILE Unable to open packet location file.
 * @retval NLE_OBJ_NOTFOUND No matching packet location alias found.
 */
int rtnl_pktloc_lookup(const char *name, struct rtnl_pktloc **result)
{
        struct rtnl_pktloc *loc;
        int hash, err;

        if ((err = read_pktlocs()) < 0)
                return err;

        hash = pktloc_hash(name);
        nl_list_for_each_entry(loc, &pktloc_name_ht[hash], list) {
                if (!strcasecmp(loc->name, name)) {
                        *result = loc;
                        return 0;
                }
        }

        return -NLE_OBJ_NOTFOUND;
}

static int __init pktloc_init(void)
{
        int i;

        for (i = 0; i < PKTLOC_NAME_HT_SIZ; i++)
                nl_init_list_head(&pktloc_name_ht[i]);
        
        return 0;
}