gsm: Add APN conversion functions

These functions are currently part of openbsc but also needed by
other projects.

The function have been renamed as follows:

  gprs_apn_to_str -> osmo_apn_to_str
  gprs_str_to_apn -> osmo_apn_from_str

Sponsored-by: On-Waves ehf

7 files changed, 216 insertions, 3 deletions

diff --git a/include/osmocom/gsm/apn.h b/include/osmocom/gsm/apn.h
index a256d973..b4ece3a2 100644
--- a/include/osmocom/gsm/apn.h
+++ b/include/osmocom/gsm/apn.h
@@ -14,3 +14,6 @@ char *osmo_apn_qualify(unsigned int mcc, unsigned int mnc, const char *ni);
  * static buffer. */
 char *osmo_apn_qualify_from_imsi(const char *imsi,
 				 const char *ni, int have_3dig_mnc);
+
+int osmo_apn_from_str(uint8_t *apn_enc, size_t max_apn_enc_len, const char *str);
+char * osmo_apn_to_str(char *out_str, const uint8_t *apn_enc, size_t apn_enc_len);
diff --git a/src/gsm/apn.c b/src/gsm/apn.c
index 413130aa..ccf36b99 100644
--- a/src/gsm/apn.c
+++ b/src/gsm/apn.c
@@ -36,3 +36,78 @@ char *osmo_apn_qualify_from_imsi(const char *imsi,
 	}
 	return osmo_apn_qualify(atoi(cbuf), atoi(nbuf), ni);
 }
+
+/**
+ * Convert an encoded APN into a dot-separated string.
+ *
+ * \param out_str      the destination buffer (size must be >= max(app_enc_len,1))
+ * \param apn_enc      the encoded APN
+ * \param apn_enc_len  the length of the encoded APN
+ *
+ * \returns out_str on success and NULL otherwise
+ */
+char * osmo_apn_to_str(char *out_str, const uint8_t *apn_enc, size_t apn_enc_len)
+{
+	char *str = out_str;
+	size_t rest_chars = apn_enc_len;
+
+	while (rest_chars > 0 && apn_enc[0]) {
+		size_t label_size = apn_enc[0];
+		if (label_size + 1 > rest_chars)
+			return NULL;
+
+		memmove(str, apn_enc + 1, label_size);
+		str += label_size;
+		rest_chars -= label_size + 1;
+		apn_enc += label_size + 1;
+
+		if (rest_chars)
+			*(str++) = '.';
+	}
+	str[0] = '\0';
+
+	return out_str;
+}
+
+/**
+ * Convert a dot-separated string into an encoded APN.
+ *
+ * \param apn_enc          the encoded APN
+ * \param max_apn_enc_len  the size of the apn_enc buffer
+ * \param str              the source string
+ *
+ * \returns out_str on success and NULL otherwise
+ */
+int osmo_apn_from_str(uint8_t *apn_enc, size_t max_apn_enc_len, const char *str)
+{
+	uint8_t *last_len_field;
+	int len;
+
+	/* Can we even write the length field to the output? */
+	if (max_apn_enc_len == 0)
+		return -1;
+
+	/* Remember where we need to put the length once we know it */
+	last_len_field = apn_enc;
+	len = 1;
+	apn_enc += 1;
+
+	while (str[0]) {
+		if (len >= max_apn_enc_len)
+			return -1;
+
+		if (str[0] == '.') {
+			*last_len_field = (apn_enc - last_len_field) - 1;
+			last_len_field = apn_enc;
+		} else {
+			*apn_enc = str[0];
+		}
+		apn_enc += 1;
+		str += 1;
+		len += 1;
+	}
+
+	*last_len_field = (apn_enc - last_len_field) - 1;
+
+	return len;
+}
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 917a77d2..7eebe7f1 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -270,6 +270,8 @@ ipa_send;
 
 osmo_apn_qualify;
 osmo_apn_qualify_from_imsi;
+osmo_apn_to_str;
+osmo_apn_from_str;
 
 local: *;
 };
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 3dc9bd91..9d14350f 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -7,7 +7,8 @@ check_PROGRAMS = timer/timer_test sms/sms_test ussd/ussd_test		\
                  conv/conv_test auth/milenage_test lapd/lapd_test	\
                  gsm0808/gsm0808_test gsm0408/gsm0408_test		\
 		 gb/bssgp_fc_test gb/gprs_bssgp_test gb/gprs_ns_test	\
-		 kasumi/kasumi_test logging/logging_test fr/fr_test	\
+		 gprs/gprs_test	kasumi/kasumi_test			\
+		 logging/logging_test fr/fr_test			\
 		 loggingrb/loggingrb_test strrb/strrb_test              \
 		 vty/vty_test comp128/comp128_test utils/utils_test	\
 		 smscb/gsm0341_test stats/stats_test
@@ -46,6 +47,9 @@ gsm0808_gsm0808_test_LDADD = $(top_builddir)/src/libosmocore.la $(top_builddir)/
 gsm0408_gsm0408_test_SOURCES = gsm0408/gsm0408_test.c
 gsm0408_gsm0408_test_LDADD = $(top_builddir)/src/libosmocore.la $(top_builddir)/src/gsm/libosmogsm.la
 
+gprs_gprs_test_SOURCES = gprs/gprs_test.c
+gprs_gprs_test_LDADD = $(top_builddir)/src/libosmocore.la $(top_builddir)/src/gsm/libosmogsm.la
+
 lapd_lapd_test_SOURCES = lapd/lapd_test.c
 lapd_lapd_test_LDADD = $(top_builddir)/src/libosmocore.la $(top_builddir)/src/gsm/libosmogsm.la
 
@@ -117,8 +121,8 @@ EXTRA_DIST = testsuite.at $(srcdir)/package.m4 $(TESTSUITE)		\
              lapd/lapd_test.ok gsm0408/gsm0408_test.ok			\
              gsm0808/gsm0808_test.ok gb/bssgp_fc_tests.err		\
              gb/bssgp_fc_tests.ok gb/bssgp_fc_tests.sh			\
-             gb/gprs_bssgp_test.ok					\
-             gb/gprs_ns_test.ok kasumi/kasumi_test.ok			\
+             gb/gprs_bssgp_test.ok gb/gprs_ns_test.ok			\
+             gprs/gprs_test.ok kasumi/kasumi_test.ok			\
              msgfile/msgfile_test.ok msgfile/msgconfig.cfg		\
              logging/logging_test.ok logging/logging_test.err		\
              fr/fr_test.ok loggingrb/logging_test.ok			\
diff --git a/tests/gprs/gprs_test.c b/tests/gprs/gprs_test.c
new file mode 100644
index 00000000..be80e5c0
--- /dev/null
+++ b/tests/gprs/gprs_test.c
@@ -0,0 +1,122 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <inttypes.h>
+
+#include <osmocom/core/application.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/gsm/apn.h>
+
+static void apn_round_trip(const uint8_t *input, size_t len, const char *wanted_output)
+{
+	char output[len ? len : 1];
+	uint8_t encoded[len + 50];
+	char *out_str;
+	int enc_len;
+
+	/* decode and verify we have what we want */
+	out_str = osmo_apn_to_str(output, input, len);
+	OSMO_ASSERT(out_str);
+	OSMO_ASSERT(out_str == &output[0]);
+	OSMO_ASSERT(strlen(out_str) == strlen(wanted_output));
+	OSMO_ASSERT(strcmp(out_str, wanted_output) == 0);
+
+	/* encode and verify it */
+	if (len != 0) {
+		enc_len = osmo_apn_from_str(encoded, ARRAY_SIZE(encoded), wanted_output);
+		OSMO_ASSERT(enc_len == len);
+		OSMO_ASSERT(memcmp(encoded, input, enc_len) == 0);
+	} else {
+		enc_len = osmo_apn_from_str(encoded, 0, wanted_output);
+		OSMO_ASSERT(enc_len == -1);
+	}
+}
+
+static void test_gsm_03_03_apn(void)
+{
+
+	{
+		/* test invalid writes */
+		const uint8_t ref[10] = { 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF };
+		uint8_t output[10];
+		int enc_len;
+
+		memcpy(output, ref, ARRAY_SIZE(output));
+		enc_len = osmo_apn_from_str(output, 0, "");
+		OSMO_ASSERT(enc_len == -1);
+		OSMO_ASSERT(memcmp(ref, output, ARRAY_SIZE(ref)) == 0);
+
+		memcpy(output, ref, ARRAY_SIZE(output));
+		enc_len = osmo_apn_from_str(output, 0, "foo");
+		OSMO_ASSERT(enc_len == -1);
+		OSMO_ASSERT(memcmp(ref, output, ARRAY_SIZE(ref)) == 0);
+
+		memcpy(output, ref, ARRAY_SIZE(output));
+		enc_len = osmo_apn_from_str(output, 1, "foo");
+		OSMO_ASSERT(enc_len == -1);
+		OSMO_ASSERT(memcmp(ref + 1, output + 1, ARRAY_SIZE(ref) - 1) == 0);
+
+		memcpy(output, ref, ARRAY_SIZE(output));
+		enc_len = osmo_apn_from_str(output, 2, "foo");
+		OSMO_ASSERT(enc_len == -1);
+		OSMO_ASSERT(memcmp(ref + 2, output + 2, ARRAY_SIZE(ref) - 2) == 0);
+
+		memcpy(output, ref, ARRAY_SIZE(output));
+		enc_len = osmo_apn_from_str(output, 3, "foo");
+		OSMO_ASSERT(enc_len == -1);
+		OSMO_ASSERT(memcmp(ref + 3, output + 3, ARRAY_SIZE(ref) - 3) == 0);
+	}
+
+	{
+		/* single empty label */
+		uint8_t input[] = { 0x0 };
+		const char *output = "";
+		apn_round_trip(input, ARRAY_SIZE(input), output);
+	}
+
+	{
+		/* no label */
+		uint8_t input[] = { };
+		const char *output = "";
+		apn_round_trip(input, ARRAY_SIZE(input), output);
+	}
+
+	{
+		/* single label with A */
+		uint8_t input[] = { 0x1, 65 };
+		const char *output = "A";
+		apn_round_trip(input, ARRAY_SIZE(input), output);
+		OSMO_ASSERT(osmo_apn_to_str(NULL, input, ARRAY_SIZE(input) - 1) == NULL);
+	}
+
+	{
+		uint8_t input[] = { 0x3, 65, 66, 67, 0x2, 90, 122 };
+		const char *output = "ABC.Zz";
+		char tmp[strlen(output) + 1];
+		apn_round_trip(input, ARRAY_SIZE(input), output);
+		OSMO_ASSERT(osmo_apn_to_str(tmp, input, ARRAY_SIZE(input) - 1) == NULL);
+		OSMO_ASSERT(osmo_apn_to_str(tmp, input, ARRAY_SIZE(input) - 2) == NULL);
+		OSMO_ASSERT(osmo_apn_to_str(tmp, input, ARRAY_SIZE(input) - 4) == NULL);
+		OSMO_ASSERT(osmo_apn_to_str(tmp, input, ARRAY_SIZE(input) - 5) == NULL);
+		OSMO_ASSERT(osmo_apn_to_str(tmp, input, ARRAY_SIZE(input) - 6) == NULL);
+	}
+}
+
+const struct log_info_cat default_categories[] = {
+};
+
+static struct log_info info = {
+	.cat = default_categories,
+	.num_cat = ARRAY_SIZE(default_categories),
+};
+
+int main(int argc, char **argv)
+{
+	osmo_init_logging(&info);
+
+	test_gsm_03_03_apn();
+
+	printf("Done.\n");
+	return EXIT_SUCCESS;
+}
diff --git a/tests/gprs/gprs_test.ok b/tests/gprs/gprs_test.ok
new file mode 100644
index 00000000..619c5618
--- /dev/null
+++ b/tests/gprs/gprs_test.ok
@@ -0,0 +1 @@
+Done.
diff --git a/tests/testsuite.at b/tests/testsuite.at
index a5427986..85c3e8bd 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -84,6 +84,12 @@ cat $abs_srcdir/gsm0408/gsm0408_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/gsm0408/gsm0408_test], [0], [expout], [ignore])
 AT_CLEANUP
 
+AT_SETUP([gprs])
+AT_KEYWORDS([gprs])
+cat $abs_srcdir/gprs/gprs_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/gprs/gprs_test], [0], [expout], [ignore])
+AT_CLEANUP
+
 AT_SETUP([logging])
 AT_KEYWORDS([logging])
 cat $abs_srcdir/logging/logging_test.ok > expout