libnl  3.5.0
pktloc.c
1 /* SPDX-License-Identifier: LGPL-2.1-only */
2 /*
3  * lib/route/pktloc.c Packet Location Aliasing
4  *
5  * This library is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU Lesser General Public
7  * License as published by the Free Software Foundation version 2.1
8  * of the License.
9  *
10  * Copyright (c) 2008-2013 Thomas Graf <tgraf@suug.ch>
11  */
12 
13 /**
14  * @ingroup tc
15  * @defgroup pktloc Packet Location Aliasing
16  * Packet Location Aliasing
17  *
18  * The packet location aliasing interface eases the use of offset definitions
19  * inside packets by allowing them to be referenced by name. Known positions
20  * of protocol fields are stored in a configuration file and associated with
21  * a name for later reference. The configuration file is distributed with the
22  * library and provides a well defined set of definitions for most common
23  * protocol fields.
24  *
25  * @section pktloc_examples Examples
26  * @par Example 1.1 Looking up a packet location
27  * @code
28  * struct rtnl_pktloc *loc;
29  *
30  * rtnl_pktloc_lookup("ip.src", &loc);
31  * @endcode
32  * @{
33  */
34 
35 #include <netlink-private/netlink.h>
36 #include <netlink-private/tc.h>
37 #include <netlink/netlink.h>
38 #include <netlink/utils.h>
39 #include <netlink/route/pktloc.h>
40 
41 #include "pktloc_syntax.h"
42 #include "pktloc_grammar.h"
43 
44 /** @cond SKIP */
45 #define PKTLOC_NAME_HT_SIZ 256
46 
47 static struct nl_list_head pktloc_name_ht[PKTLOC_NAME_HT_SIZ];
48 
49 /* djb2 */
50 static unsigned int pktloc_hash(const char *str)
51 {
52  unsigned long hash = 5381;
53  int c;
54 
55  while ((c = *str++))
56  hash = ((hash << 5) + hash) + c; /* hash * 33 + c */
57 
58  return hash % PKTLOC_NAME_HT_SIZ;
59 }
60 
61 static int __pktloc_lookup(const char *name, struct rtnl_pktloc **result)
62 {
63  struct rtnl_pktloc *loc;
64  int hash;
65 
66  hash = pktloc_hash(name);
67  nl_list_for_each_entry(loc, &pktloc_name_ht[hash], list) {
68  if (!strcasecmp(loc->name, name)) {
69  loc->refcnt++;
70  *result = loc;
71  return 0;
72  }
73  }
74 
75  return -NLE_OBJ_NOTFOUND;
76 }
77 
78 extern int pktloc_parse(void *scanner);
79 
80 static void rtnl_pktloc_free(struct rtnl_pktloc *loc)
81 {
82  if (!loc)
83  return;
84 
85  free(loc->name);
86  free(loc);
87 }
88 
89 static int read_pktlocs(void)
90 {
91  YY_BUFFER_STATE buf = NULL;
92  yyscan_t scanner = NULL;
93  static time_t last_read;
94  struct stat st;
95  char *path;
96  int i, err;
97  FILE *fd;
98 
99  if (build_sysconf_path(&path, "pktloc") < 0)
100  return -NLE_NOMEM;
101 
102  /* if stat fails, just try to read the file */
103  if (stat(path, &st) == 0) {
104  /* Don't re-read file if file is unchanged */
105  if (last_read == st.st_mtime) {
106  err = 0;
107  goto errout;
108  }
109  }
110 
111  NL_DBG(2, "Reading packet location file \"%s\"\n", path);
112 
113  if (!(fd = fopen(path, "re"))) {
114  err = -NLE_PKTLOC_FILE;
115  goto errout;
116  }
117 
118  for (i = 0; i < PKTLOC_NAME_HT_SIZ; i++) {
119  struct rtnl_pktloc *loc, *n;
120 
121  nl_list_for_each_entry_safe(loc, n, &pktloc_name_ht[i], list)
122  rtnl_pktloc_put(loc);
123 
124  nl_init_list_head(&pktloc_name_ht[i]);
125  }
126 
127  if ((err = pktloc_lex_init(&scanner)) < 0) {
128  err = -NLE_FAILURE;
129  goto errout_close;
130  }
131 
132  buf = pktloc__create_buffer(fd, YY_BUF_SIZE, scanner);
133  pktloc__switch_to_buffer(buf, scanner);
134 
135  if ((err = pktloc_parse(scanner)) != 0) {
136  pktloc__delete_buffer(buf, scanner);
137  err = -NLE_PARSE_ERR;
138  goto errout_scanner;
139  }
140 
141  last_read = st.st_mtime;
142 
143 errout_scanner:
144  pktloc_lex_destroy(scanner);
145 errout_close:
146  fclose(fd);
147 errout:
148  free(path);
149 
150  return err;
151 }
152 
153 /** @endcond */
154 
155 /**
156  * Lookup packet location alias
157  * @arg name Name of packet location.
158  * @arg result Result pointer
159  *
160  * Tries to find a matching packet location alias for the supplied
161  * packet location name.
162  *
163  * The file containing the packet location definitions is automatically
164  * re-read if its modification time has changed since the last call.
165  *
166  * The returned packet location has to be returned after use by calling
167  * rtnl_pktloc_put() in order to allow freeing its memory after the last
168  * user has abandoned it.
169  *
170  * @return 0 on success or a negative error code.
171  * @retval NLE_PKTLOC_FILE Unable to open packet location file.
172  * @retval NLE_OBJ_NOTFOUND No matching packet location alias found.
173  */
174 int rtnl_pktloc_lookup(const char *name, struct rtnl_pktloc **result)
175 {
176  int err;
177 
178  if ((err = read_pktlocs()) < 0)
179  return err;
180 
181  return __pktloc_lookup(name, result);
182 }
183 
184 /**
185  * Allocate packet location object
186  */
188 {
189  struct rtnl_pktloc *loc;
190 
191  if (!(loc = calloc(1, sizeof(*loc))))
192  return NULL;
193 
194  loc->refcnt = 1;
195  nl_init_list_head(&loc->list);
196 
197  return loc;
198 }
199 
200 /**
201  * Return reference of a packet location
202  * @arg loc packet location object.
203  */
204 void rtnl_pktloc_put(struct rtnl_pktloc *loc)
205 {
206  if (!loc)
207  return;
208 
209  loc->refcnt--;
210  if (loc->refcnt <= 0)
211  rtnl_pktloc_free(loc);
212 }
213 
214 /**
215  * Add a packet location to the hash table
216  * @arg loc packet location object
217  *
218  * @return 0 on success or a negative error code.
219  */
220 int rtnl_pktloc_add(struct rtnl_pktloc *loc)
221 {
222  struct rtnl_pktloc *l;
223 
224  if (__pktloc_lookup(loc->name, &l) == 0) {
225  rtnl_pktloc_put(l);
226  return -NLE_EXIST;
227  }
228 
229  NL_DBG(2, "New packet location entry \"%s\" align=%u layer=%u "
230  "offset=%u mask=%#x shift=%u refnt=%u\n",
231  loc->name, loc->align, loc->layer, loc->offset,
232  loc->mask, loc->shift, loc->refcnt);
233 
234  nl_list_add_tail(&loc->list, &pktloc_name_ht[pktloc_hash(loc->name)]);
235 
236  return 0;
237 }
238 
239 void rtnl_pktloc_foreach(void (*cb)(struct rtnl_pktloc *, void *), void *arg)
240 {
241  struct rtnl_pktloc *loc;
242  int i;
243 
244  /* ignore errors */
245  read_pktlocs();
246 
247  for (i = 0; i < PKTLOC_NAME_HT_SIZ; i++)
248  nl_list_for_each_entry(loc, &pktloc_name_ht[i], list)
249  cb(loc, arg);
250 }
251 
252 static int __init pktloc_init(void)
253 {
254  int i;
255 
256  for (i = 0; i < PKTLOC_NAME_HT_SIZ; i++)
257  nl_init_list_head(&pktloc_name_ht[i]);
258 
259  return 0;
260 }
261 
262 /** @} */
struct rtnl_pktloc * rtnl_pktloc_alloc(void)
Allocate packet location object.
Definition: pktloc.c:187
void rtnl_pktloc_put(struct rtnl_pktloc *loc)
Return reference of a packet location.
Definition: pktloc.c:204
int rtnl_pktloc_lookup(const char *name, struct rtnl_pktloc **result)
Lookup packet location alias.
Definition: pktloc.c:174
int rtnl_pktloc_add(struct rtnl_pktloc *loc)
Add a packet location to the hash table.
Definition: pktloc.c:220