nat: Introduce a prefix lookup tree (trie) for number rewriting
* It is a trie. The max depth of the trie is the length of the
longest prefix. The lookup is O(lookuped_prefix), but as the prefix
length is limited, the lookup time is constant.
* Each node can hold the entire prefix, has place for the rewrite
rule with up to three digits.
* A trie with 20k entries will take about 3MB ram.
* Filling the trie 100 times takes ~800ms on my i7 laptop
* 10.000.000 lookups take 315ms.. (for the same prefix).
* 93/99 lines are tested, 6/6 functions are tested, 49 of 54 branches
are tested. Only memory allocation failures are not covered
* A late addition is to handle the '+' sign and to increase the number
of chars in the rewrite prefix. The timing/line coverage has not
been updated after this change.
diff --git a/openbsc/src/osmo-bsc_nat/Makefile.am b/openbsc/src/osmo-bsc_nat/Makefile.am
index e2ba551..aae6d69 100644
--- a/openbsc/src/osmo-bsc_nat/Makefile.am
+++ b/openbsc/src/osmo-bsc_nat/Makefile.am
@@ -7,7 +7,7 @@
osmo_bsc_nat_SOURCES = bsc_filter.c bsc_mgcp_utils.c bsc_nat.c bsc_nat_utils.c \
bsc_nat_vty.c bsc_sccp.c bsc_ussd.c bsc_nat_ctrl.c \
- bsc_nat_rewrite.c bsc_nat_filter.c
+ bsc_nat_rewrite.c bsc_nat_filter.c bsc_nat_rewrite_trie.c
osmo_bsc_nat_LDADD = $(top_builddir)/src/libcommon/libcommon.a \
$(top_builddir)/src/libmgcp/libmgcp.a \
$(top_builddir)/src/libbsc/libbsc.a \
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat.c b/openbsc/src/osmo-bsc_nat/bsc_nat.c
index 1237339..897c657 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat.c
@@ -1480,6 +1480,7 @@
.is_config_node = bsc_vty_is_config_node,
};
+
int main(int argc, char **argv)
{
int rc;
@@ -1526,6 +1527,8 @@
/* seed the PRNG */
srand(time(NULL));
+
+
/*
* Setup the MGCP code..
*/
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite_trie.c b/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite_trie.c
new file mode 100644
index 0000000..57043ac
--- /dev/null
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite_trie.c
@@ -0,0 +1,240 @@
+/* Handling for loading a re-write file/database */
+/*
+ * (C) 2013 by On-Waves
+ * (C) 2013 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <openbsc/nat_rewrite_trie.h>
+#include <openbsc/debug.h>
+
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/utils.h>
+
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+
+#define CHECK_IS_DIGIT_OR_FAIL(prefix, pos) \
+ if (!isdigit(prefix[pos]) && prefix[pos] != '+') { \
+ LOGP(DNAT, LOGL_ERROR, \
+ "Prefix(%s) contains non ascii text at(%d=%c)\n", \
+ prefix, pos, prefix[pos]); \
+ goto fail; \
+ }
+#define TO_INT(c) \
+ ((c) == '+' ? 10 : ((c - '0') % 10))
+
+static void insert_rewrite_node(struct nat_rewrite_rule *rule, struct nat_rewrite *root)
+{
+ struct nat_rewrite_rule *new = &root->rule;
+
+ const size_t len = strlen(rule->prefix);
+ int i;
+
+ if (len == 0) {
+ LOGP(DNAT, LOGL_ERROR, "An empty prefix does not make sense.\n");
+ goto fail;
+ }
+
+ for (i = 0; i < len - 1; ++i) {
+ int pos;
+
+ /* check if the input is valid */
+ CHECK_IS_DIGIT_OR_FAIL(rule->prefix, i);
+
+ /* check if the next node is already valid */
+ pos = TO_INT(rule->prefix[i]);
+ if (!new->rules[pos]) {
+ new->rules[pos] = talloc_zero(root, struct nat_rewrite_rule);
+ if (!new->rules[pos]) {
+ LOGP(DNAT, LOGL_ERROR,
+ "Failed to allocate memory.\n");
+ goto fail;
+ }
+
+ new->rules[pos]->empty = 1;
+ }
+
+ /* we continue here */
+ new = new->rules[pos];
+ }
+
+ /* new now points to the place where we want to add it */
+ int pos;
+
+ /* check if the input is valid */
+ CHECK_IS_DIGIT_OR_FAIL(rule->prefix, (len - 1));
+
+ /* check if the next node is already valid */
+ pos = TO_INT(rule->prefix[len - 1]);
+ if (!new->rules[pos])
+ new->rules[pos] = rule;
+ else if (new->rules[pos]->empty) {
+ /* copy over entries */
+ new->rules[pos]->empty = 0;
+ memcpy(new->rules[pos]->prefix, rule->prefix, sizeof(rule->prefix));
+ memcpy(new->rules[pos]->rewrite, rule->rewrite, sizeof(rule->rewrite));
+ talloc_free(rule);
+ } else {
+ LOGP(DNAT, LOGL_ERROR,
+ "Prefix(%s) is already installed\n", rule->prefix);
+ goto fail;
+ }
+
+ root->prefixes += 1;
+ return;
+
+fail:
+ talloc_free(rule);
+ return;
+}
+
+static void handle_line(struct nat_rewrite *rewrite, char *line)
+{
+ char *split;
+ struct nat_rewrite_rule *rule;
+ size_t size_prefix, size_end, len;
+
+
+ /* Find the ',' in the line */
+ len = strlen(line);
+ split = strstr(line, ",");
+ if (!split) {
+ LOGP(DNAT, LOGL_ERROR, "Line doesn't contain ','\n");
+ return;
+ }
+
+ /* Check if there is space for the rewrite rule */
+ size_prefix = split - line;
+ if (len - size_prefix <= 2) {
+ LOGP(DNAT, LOGL_ERROR, "No rewrite available.\n");
+ return;
+ }
+
+ /* Continue after the ',' to the end */
+ split = &line[size_prefix + 1];
+ size_end = strlen(split) - 1;
+
+ /* Check if both strings can fit into the static array */
+ if (size_prefix > sizeof(rule->prefix) - 1) {
+ LOGP(DNAT, LOGL_ERROR,
+ "Prefix is too long with %zu\n", size_prefix);
+ return;
+ }
+
+ if (size_end > sizeof(rule->rewrite) - 1) {
+ LOGP(DNAT, LOGL_ERROR,
+ "Rewrite is too long with %zu on %s\n",
+ size_end, &line[size_prefix + 1]);
+ return;
+ }
+
+ /* Now create the entry and insert it into the trie */
+ rule = talloc_zero(rewrite, struct nat_rewrite_rule);
+ if (!rule) {
+ LOGP(DNAT, LOGL_ERROR, "Can not allocate memory\n");
+ return;
+ }
+
+ memcpy(rule->prefix, line, size_prefix);
+ assert(size_prefix < sizeof(rule->prefix));
+ rule->prefix[size_prefix] = '\0';
+
+ memcpy(rule->rewrite, split, size_end);
+ assert(size_end < sizeof(rule->rewrite));
+ rule->rewrite[size_end] = '\0';
+
+ /* now insert and balance the tree */
+ insert_rewrite_node(rule, rewrite);
+}
+
+struct nat_rewrite *nat_rewrite_parse(void *ctx, const char *filename)
+{
+ FILE *file;
+ char *line = NULL;
+ size_t n = 2342;
+ struct nat_rewrite *res;
+
+ file = fopen(filename, "r");
+ if (!file)
+ return NULL;
+
+ res = talloc_zero(ctx, struct nat_rewrite);
+ if (!res) {
+ fclose(file);
+ return NULL;
+ }
+
+ /* mark the root as empty */
+ res->rule.empty = 1;
+
+ while (getline(&line, &n, file) != -1) {
+ handle_line(res, line);
+ }
+
+ free(line);
+ fclose(file);
+ return res;
+}
+
+/**
+ * Simple find that tries to do a longest match...
+ */
+struct nat_rewrite_rule *nat_rewrite_lookup(struct nat_rewrite *rewrite,
+ const char *prefix)
+{
+ struct nat_rewrite_rule *rule = &rewrite->rule;
+ struct nat_rewrite_rule *last = NULL;
+ const int len = OSMO_MIN(strlen(prefix), (sizeof(rule->prefix) - 1));
+ int i;
+
+ for (i = 0; rule && i < len; ++i) {
+ int pos;
+
+ CHECK_IS_DIGIT_OR_FAIL(prefix, i);
+ pos = TO_INT(prefix[i]);
+
+ rule = rule->rules[pos];
+ if (rule && !rule->empty)
+ last = rule;
+ }
+
+ return last;
+
+fail:
+ return NULL;
+}
+
+static void nat_rewrite_dump_rec(struct nat_rewrite_rule *rule)
+{
+ int i;
+ if (!rule->empty)
+ printf("%s,%s\n", rule->prefix, rule->rewrite);
+
+ for (i = 0; i < ARRAY_SIZE(rule->rules); ++i) {
+ if (!rule->rules[i])
+ continue;
+ nat_rewrite_dump_rec(rule->rules[i]);
+ }
+}
+
+void nat_rewrite_dump(struct nat_rewrite *rewrite)
+{
+ nat_rewrite_dump_rec(&rewrite->rule);
+}