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Diffstat (limited to 'lib/route/pktloc.c')
-rw-r--r-- | lib/route/pktloc.c | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/lib/route/pktloc.c b/lib/route/pktloc.c new file mode 100644 index 0000000..f0d0155 --- /dev/null +++ b/lib/route/pktloc.c @@ -0,0 +1,168 @@ +/* + * 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; +} |