Change in libosmo-gprs[master]: llc: implement Exchange Identification (XID) codec - gerrit-log

28 Sep 2022

fixeria has submitted this change. ( https://gerrit.osmocom.org/c/libosmo-gprs/+/29482 )
Change subject: llc: implement Exchange Identification (XID) codec
......................................................................
llc: implement Exchange Identification (XID) codec
Change-Id: I16b3f7ab82c489144098aad0dccc4c67d8382c67
---
M include/osmocom/gprs/llc/llc.h
M src/llc/llc_xid.c
M tests/llc/pdu_codec_test.c
M tests/llc/pdu_codec_test.ok
4 files changed, 403 insertions(+), 0 deletions(-)
Approvals:
  Jenkins Builder: Verified
  fixeria: Looks good to me, approved

diff --git a/include/osmocom/gprs/llc/llc.h b/include/osmocom/gprs/llc/llc.h
index 0e4531e..e27fb8a 100644
--- a/include/osmocom/gprs/llc/llc.h
+++ b/include/osmocom/gprs/llc/llc.h
@@ -95,6 +95,17 @@
    return get_value_string(osmo_gprs_llc_xid_type_names, val);
 }
+struct osmo_gprs_llc_xid_field {
+	enum osmo_gprs_llc_xid_type type;
+	/* Fixed-length value */
+	uint32_t val;
+	/* Variable-length value */
+	struct {
+		const uint8_t *val;
+		uint8_t val_len;
+	} var;
+};
+
 /* Section 4.5.2 Logical Link States + Annex C.2 */
 enum osmo_gprs_llc_lle_state {
    OSMO_GPRS_LLC_LLES_UNASSIGNED	= 1,	/* No TLLI yet */
@@ -158,4 +169,12 @@
uint32_t osmo_gprs_llc_fcs(const uint8_t *data, size_t len);
+bool osmo_gprs_llc_xid_field_is_valid(const struct osmo_gprs_llc_xid_field *field);
+int osmo_gprs_llc_xid_decode(struct osmo_gprs_llc_xid_field *fields,
+			     unsigned int max_fields,
+			     const uint8_t *data, size_t data_len);
+int osmo_gprs_llc_xid_encode(struct msgb *msg,
+			     const struct osmo_gprs_llc_xid_field *fields,
+			     unsigned int num_fields);
+
 void osmo_gprs_llc_set_log_cat(int cat);
diff --git a/src/llc/llc_xid.c b/src/llc/llc_xid.c
index fb84137..a787e1a 100644
--- a/src/llc/llc_xid.c
+++ b/src/llc/llc_xid.c
@@ -20,10 +20,17 @@
  *
  */
+#include <errno.h>
+#include <stdint.h>
+
+#include <osmocom/core/msgb.h>
 #include <osmocom/core/utils.h>
+#include <osmocom/core/logging.h>
#include <osmocom/gprs/llc/llc.h>
+extern int g_log_cat;
+
 const struct value_string osmo_gprs_llc_xid_type_names[] = {
    { OSMO_GPRS_LLC_XID_T_VERSION,		"LLC-Version" },
    { OSMO_GPRS_LLC_XID_T_IOV_UI,		"IOV-UI" },
@@ -43,3 +50,212 @@
    { OSMO_GPRS_LLC_XID_T_MAC_IOV_UI,	"MAC-IOV-UI" },
    { 0, NULL }
 };
+
+/* Table 6: LLC layer parameter negotiation */
+static const struct {
+	bool var_len;
+	uint8_t len;
+	unsigned int min;
+	unsigned int max;
+	bool allow_zero;
+} gprs_llc_xid_desc[] = {
+	[OSMO_GPRS_LLC_XID_T_VERSION] = { .len = 1, .min = 0, .max = 15 },
+	[OSMO_GPRS_LLC_XID_T_IOV_UI] = { .len = 4, .min = 0, .max = UINT32_MAX },
+	[OSMO_GPRS_LLC_XID_T_IOV_I] = { .len = 4, .min = 0, .max = UINT32_MAX },
+	[OSMO_GPRS_LLC_XID_T_T200] = { .len = 2, .min = 0, .max = 4095 },
+	[OSMO_GPRS_LLC_XID_T_N200] = { .len = 1, .min = 1, .max = 15 },
+	[OSMO_GPRS_LLC_XID_T_N201_U] = { .len = 2, .min = 140, .max = 1520 },
+	[OSMO_GPRS_LLC_XID_T_N201_I] = { .len = 2, .min = 140, .max = 1520 },
+	[OSMO_GPRS_LLC_XID_T_mD] = { .len = 2, .min = 9, .max = 24320, .allow_zero = true },
+	[OSMO_GPRS_LLC_XID_T_mU] = { .len = 2, .min = 9, .max = 24320, .allow_zero = true },
+	[OSMO_GPRS_LLC_XID_T_kD] = { .len = 1, .min = 1, .max = 255 },
+	[OSMO_GPRS_LLC_XID_T_kU] = { .len = 1, .min = 1, .max = 255 },
+	[OSMO_GPRS_LLC_XID_T_L3_PAR] = { .var_len = true },
+	[OSMO_GPRS_LLC_XID_T_RESET] = { .len = 0 },
+	[OSMO_GPRS_LLC_XID_T_IIOV_UI] = { .len = 4, .min = 0, .max = UINT32_MAX },
+	[OSMO_GPRS_LLC_XID_T_IIOV_UI_CNT] = { .len = 1, .min = 1, .max = 255 },
+	[OSMO_GPRS_LLC_XID_T_MAC_IOV_UI] = { .len = 4, .min = 0, .max = UINT32_MAX },
+};
+
+bool osmo_gprs_llc_xid_field_is_valid(const struct osmo_gprs_llc_xid_field *field)
+{
+	if (field->type >= ARRAY_SIZE(gprs_llc_xid_desc)) {
+		LOGP(g_log_cat, LOGL_ERROR,
+		     "Unknown XID field type 0x%02x\n", field->type);
+		return false;
+	}
+
+	if (gprs_llc_xid_desc[field->type].var_len)
+		return true;
+
+	/* For mU and mD, the value range (9 .. 24320) also includes 0 */
+	if (gprs_llc_xid_desc[field->type].allow_zero && field->val == 0)
+		return true;
+
+	if (field->val < gprs_llc_xid_desc[field->type].min) {
+		LOGP(g_log_cat, LOGL_ERROR,
+		     "XID field %s value=%u < min=%u\n",
+		     osmo_gprs_llc_xid_type_name(field->type),
+		     field->val, gprs_llc_xid_desc[field->type].min);
+		return false;
+	}
+
+	if (field->val > gprs_llc_xid_desc[field->type].max) {
+		LOGP(g_log_cat, LOGL_ERROR,
+		     "XID field %s value=%u > max=%u\n",
+		     osmo_gprs_llc_xid_type_name(field->type),
+		     field->val, gprs_llc_xid_desc[field->type].max);
+		return false;
+	}
+
+	return true;
+}
+
+int osmo_gprs_llc_xid_encode(struct msgb *msg,
+			     const struct osmo_gprs_llc_xid_field *fields,
+			     unsigned int num_fields)
+{
+	for (unsigned int i = 0; i < num_fields; i++) {
+		const struct osmo_gprs_llc_xid_field *field = &fields[i];
+		uint8_t *hdr, len;
+
+		if (!osmo_gprs_llc_xid_field_is_valid(field))
+			return -EINVAL;
+
+		/* XID field type */
+		hdr = msgb_put(msg, 1);
+		hdr[0] = (field->type & 0x1f) << 2;
+
+		/* XID field length */
+		if (gprs_llc_xid_desc[field->type].var_len)
+			len = field->var.val_len;
+		else
+			len = gprs_llc_xid_desc[field->type].len;
+
+		if (len == 0)
+			continue;
+		if (len < 4) {
+			hdr[0] |= len;
+		} else {
+			msgb_put(msg, 1);
+			hdr[0] |= (1 << 7); /* XL=1 */
+			hdr[0] |= (len >> 6) & 0x03;
+			hdr[1]  = (len << 2) & 0xff;
+		}
+
+		/* XID field value (variable length) */
+		if (gprs_llc_xid_desc[field->type].var_len) {
+			memcpy(msgb_put(msg, len), field->var.val, len);
+		} else {
+			switch (len) {
+			case 1:
+				msgb_put_u8(msg, field->val);
+				break;
+			case 2:
+				osmo_store16be(field->val, msgb_put(msg, 2));
+				break;
+			case 4:
+				osmo_store32be(field->val, msgb_put(msg, 4));
+				break;
+			default:
+				/* Shall not happen */
+				OSMO_ASSERT(0);
+			}
+		}
+	}
+
+	return 0;
+}
+
+int osmo_gprs_llc_xid_decode(struct osmo_gprs_llc_xid_field *fields,
+			     unsigned int max_fields,
+			     const uint8_t *data, size_t data_len)
+{
+	const uint8_t *ptr = &data[0];
+	unsigned int num_fields = 0;
+
+#define check_len(len, text) \
+	do { \
+		if (data_len < (len)) { \
+			LOGP(g_log_cat, LOGL_ERROR, "Failed to parse XID: %s\n", text); \
+			return -EINVAL; \
+		} \
+	} while (0)
+
+	while (data_len > 0) {
+		struct osmo_gprs_llc_xid_field *field = &fields[num_fields++];
+		uint8_t len;
+
+		if (num_fields > max_fields) {
+			LOGP(g_log_cat, LOGL_ERROR,
+			     "Failed to parse XID: too many fields\n");
+			return -ENOMEM;
+		}
+
+		check_len(1, "short read at XID header");
+		data_len -= 1;
+
+		/* XID field type */
+		field->type = (*ptr >> 2) & 0x1f;
+		if (field->type >= ARRAY_SIZE(gprs_llc_xid_desc)) {
+			LOGP(g_log_cat, LOGL_ERROR,
+			     "Failed to parse XID: unknown field type 0x%02x\n", field->type);
+			return -EINVAL;
+		}
+
+		/* XID field length */
+		if (*ptr & (1 << 7)) {
+			check_len(1, "short read");
+			data_len -= 1;
+			len  = (*(ptr++) & 0x07) << 6;
+			len |= (*(ptr++) >> 2);
+		} else {
+			len = *(ptr++) & 0x03;
+		}
+
+		check_len(len, "short read at XID payload");
+		data_len -= len;
+
+		/* XID field value (variable length) */
+		if (gprs_llc_xid_desc[field->type].var_len) {
+			field->var.val = len ? ptr : NULL;
+			field->var.val_len = len;
+		} else {
+			if (len != gprs_llc_xid_desc[field->type].len) {
+				LOGP(g_log_cat, LOGL_NOTICE,
+				     "XID field %s has unusual length=%u (expected %u)\n",
+				     osmo_gprs_llc_xid_type_name(field->type),
+				     len, gprs_llc_xid_desc[field->type].len);
+			}
+
+			switch (len) {
+			case 0:
+				field->val = 0;
+				break;
+			case 1:
+				field->val = *ptr;
+				break;
+			case 2:
+				field->val = osmo_load16be(ptr);
+				break;
+			case 4:
+				field->val = osmo_load32be(ptr);
+				break;
+			default:
+				LOGP(g_log_cat, LOGL_ERROR,
+				     "Failed to parse XID: unsupported field (%s) length=%u\n",
+				     osmo_gprs_llc_xid_type_name(field->type), len);
+				return -EINVAL;
+			}
+
+			if (!osmo_gprs_llc_xid_field_is_valid(field))
+				return -EINVAL;
+		}
+
+		ptr += len;
+	}
+
+#undef check_len
+
+	return num_fields;
+}
diff --git a/tests/llc/pdu_codec_test.c b/tests/llc/pdu_codec_test.c
index ed4e8bd..f2418fe 100644
--- a/tests/llc/pdu_codec_test.c
+++ b/tests/llc/pdu_codec_test.c
@@ -77,6 +77,109 @@
    printf("\n");
 }
+static void print_xid_fields(const struct osmo_gprs_llc_xid_field *fields,
+			     unsigned int num_fields)
+{
+	for (unsigned int i = 0; i < num_fields; i++) {
+		const struct osmo_gprs_llc_xid_field *field = &fields[i];
+
+		printf("  field[%02d]: type=0x%02x (%s)",
+		       i, field->type, osmo_gprs_llc_xid_type_name(field->type));
+		if (field->type == OSMO_GPRS_LLC_XID_T_L3_PAR) {
+			printf(" data[] (len=%u): %s\n", field->var.val_len,
+			       osmo_hexdump_nospc(field->var.val, field->var.val_len));
+		} else {
+			printf(" val=%u\n", field->val);
+		}
+	}
+}
+
+static void test_xid_dec_enc(void)
+{
+	static const char * const testData[] = {
+		/* TODO: more test vectors */
+		"25401602082c",
+		"16020825402c",
+		"01001601f41a05df",
+		"01001605f01a05f0ac18112233445566",
+		"01001601f41a02081e00002200002908",
+	};
+
+	struct msgb *msg = msgb_alloc(1024, "LLC-XID");
+	OSMO_ASSERT(msg != NULL);
+
+	for (unsigned int i = 0; i < ARRAY_SIZE(testData); i++) {
+		struct osmo_gprs_llc_xid_field fields[16] = { 0 };
+		uint8_t xid[256];
+		size_t xid_len;
+		int rc;
+
+		printf("%s(): decoding testData[%u] = %s\n", __func__, i, testData[i]);
+
+		rc = osmo_hexparse(testData[i], &xid[0], sizeof(xid));
+		xid_len = strlen(testData[i]) / 2;
+		OSMO_ASSERT(rc == xid_len);
+
+		rc = osmo_gprs_llc_xid_decode(fields, ARRAY_SIZE(fields),
+					      &xid[0], xid_len);
+		printf("  osmo_gprs_llc_xid_decode() returns %d\n", rc);
+
+		if (rc > 0)
+			print_xid_fields(&fields[0], rc);
+		else
+			continue;
+
+		printf("%s(): encoding decoded testData[%u]\n", __func__, i);
+
+		msgb_reset(msg);
+		rc = osmo_gprs_llc_xid_encode(msg, fields, rc);
+		printf("  osmo_gprs_llc_xid_encode() returns %d\n", rc);
+		printf("  osmo_gprs_llc_xid_encode(): %s\n", osmo_hexdump_nospc(msg->data, msg->len));
+		printf("  memcmp() returns %d\n", memcmp(&xid, msg->data, xid_len));
+	}
+
+	msgb_free(msg);
+	printf("\n");
+}
+
+static void test_xid_enc_dec(void)
+{
+	struct osmo_gprs_llc_xid_field dec_fields[16] = { 0 };
+	int rc;
+
+	const uint8_t l3_params[] = { 0x11, 0x22, 0x33, 0x44, 0x55, 0x66 };
+	const struct osmo_gprs_llc_xid_field test_fields[] = {
+		{ .type = OSMO_GPRS_LLC_XID_T_VERSION,	.val = 0 },
+		{ .type = OSMO_GPRS_LLC_XID_T_T200,	.val = 4095 },
+		{ .type = OSMO_GPRS_LLC_XID_T_N200,	.val = 10 },
+		{ .type = OSMO_GPRS_LLC_XID_T_IOV_I,	.val = 0x42424242 },
+		{ .type = OSMO_GPRS_LLC_XID_T_IOV_UI,	.val = 0xdeadbeef },
+		{ .type = OSMO_GPRS_LLC_XID_T_L3_PAR,
+		  .var = { .val_len = sizeof(l3_params), .val = &l3_params[0] } },
+		{ .type = OSMO_GPRS_LLC_XID_T_RESET },
+	};
+
+	struct msgb *msg = msgb_alloc(1024, "LLC-XID");
+	OSMO_ASSERT(msg != NULL);
+
+	printf("%s(): encoding hand-crafted testData\n", __func__);
+
+	rc = osmo_gprs_llc_xid_encode(msg, &test_fields[0], ARRAY_SIZE(test_fields));
+	printf("  osmo_gprs_llc_xid_encode() returns %d\n", rc);
+	printf("  osmo_gprs_llc_xid_encode(): %s\n", osmo_hexdump_nospc(msg->data, msg->len));
+
+	printf("%s(): decoding encoded hand-crafted testData\n", __func__);
+
+	rc = osmo_gprs_llc_xid_decode(&dec_fields[0], ARRAY_SIZE(dec_fields),
+				      msg->data, msg->len);
+	printf("  osmo_gprs_llc_xid_decode() returns %d\n", rc);
+	if (rc > 0)
+		print_xid_fields(&dec_fields[0], rc);
+
+	msgb_free(msg);
+	printf("\n");
+}
+
 static const struct log_info_cat test_log_categories[] = { };
 static const struct log_info test_log_info = {
    .cat = test_log_categories,
@@ -97,6 +200,8 @@
    log_set_use_color(osmo_stderr_target, 0);
test_pdu_dec_enc();
+	test_xid_dec_enc();
+	test_xid_enc_dec();
talloc_free(tall_ctx);
 }
diff --git a/tests/llc/pdu_codec_test.ok b/tests/llc/pdu_codec_test.ok
index 691e983..664768a 100644
--- a/tests/llc/pdu_codec_test.ok
+++ b/tests/llc/pdu_codec_test.ok
@@ -38,3 +38,66 @@
   osmo_gprs_llc_pdu_encode(): 03fb1604d216f984
   memcmp() returns 0
+test_xid_dec_enc(): decoding testData[0] = 25401602082c
+  osmo_gprs_llc_xid_decode() returns 3
+  field[00]: type=0x09 (kD) val=64
+  field[01]: type=0x05 (N201-U) val=520
+  field[02]: type=0x0b (L3-Params) data[] (len=0): 
+test_xid_dec_enc(): encoding decoded testData[0]
+  osmo_gprs_llc_xid_encode() returns 0
+  osmo_gprs_llc_xid_encode(): 25401602082c
+  memcmp() returns 0
+test_xid_dec_enc(): decoding testData[1] = 16020825402c
+  osmo_gprs_llc_xid_decode() returns 3
+  field[00]: type=0x05 (N201-U) val=520
+  field[01]: type=0x09 (kD) val=64
+  field[02]: type=0x0b (L3-Params) data[] (len=0): 
+test_xid_dec_enc(): encoding decoded testData[1]
+  osmo_gprs_llc_xid_encode() returns 0
+  osmo_gprs_llc_xid_encode(): 16020825402c
+  memcmp() returns 0
+test_xid_dec_enc(): decoding testData[2] = 01001601f41a05df
+  osmo_gprs_llc_xid_decode() returns 3
+  field[00]: type=0x00 (LLC-Version) val=0
+  field[01]: type=0x05 (N201-U) val=500
+  field[02]: type=0x06 (N201-I) val=1503
+test_xid_dec_enc(): encoding decoded testData[2]
+  osmo_gprs_llc_xid_encode() returns 0
+  osmo_gprs_llc_xid_encode(): 01001601f41a05df
+  memcmp() returns 0
+test_xid_dec_enc(): decoding testData[3] = 01001605f01a05f0ac18112233445566
+  osmo_gprs_llc_xid_decode() returns 4
+  field[00]: type=0x00 (LLC-Version) val=0
+  field[01]: type=0x05 (N201-U) val=1520
+  field[02]: type=0x06 (N201-I) val=1520
+  field[03]: type=0x0b (L3-Params) data[] (len=6): 112233445566
+test_xid_dec_enc(): encoding decoded testData[3]
+  osmo_gprs_llc_xid_encode() returns 0
+  osmo_gprs_llc_xid_encode(): 01001605f01a05f0ac18112233445566
+  memcmp() returns 0
+test_xid_dec_enc(): decoding testData[4] = 01001601f41a02081e00002200002908
+  osmo_gprs_llc_xid_decode() returns 6
+  field[00]: type=0x00 (LLC-Version) val=0
+  field[01]: type=0x05 (N201-U) val=500
+  field[02]: type=0x06 (N201-I) val=520
+  field[03]: type=0x07 (mD) val=0
+  field[04]: type=0x08 (mU) val=0
+  field[05]: type=0x0a (kU) val=8
+test_xid_dec_enc(): encoding decoded testData[4]
+  osmo_gprs_llc_xid_encode() returns 0
+  osmo_gprs_llc_xid_encode(): 01001601f41a02081e00002200002908
+  memcmp() returns 0
+
+test_xid_enc_dec(): encoding hand-crafted testData
+  osmo_gprs_llc_xid_encode() returns 0
+  osmo_gprs_llc_xid_encode(): 01000e0fff110a8810424242428410deadbeefac1811223344556630
+test_xid_enc_dec(): decoding encoded hand-crafted testData
+  osmo_gprs_llc_xid_decode() returns 7
+  field[00]: type=0x00 (LLC-Version) val=0
+  field[01]: type=0x03 (T200) val=4095
+  field[02]: type=0x04 (N200) val=10
+  field[03]: type=0x02 (IOV-I) val=1111638594
+  field[04]: type=0x01 (IOV-UI) val=3735928559
+  field[05]: type=0x0b (L3-Params) data[] (len=6): 112233445566
+  field[06]: type=0x0c (Reset) val=0
+
-- 
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Gerrit-Project: libosmo-gprs
Gerrit-Branch: master
Gerrit-Change-Id: I16b3f7ab82c489144098aad0dccc4c67d8382c67
Gerrit-Change-Number: 29482
Gerrit-PatchSet: 5
Gerrit-Owner: fixeria vyanitskiy@sysmocom.de
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: fixeria vyanitskiy@sysmocom.de
Gerrit-Reviewer: laforge laforge@osmocom.org
Gerrit-Reviewer: osmith osmith@sysmocom.de
Gerrit-Reviewer: pespin pespin@sysmocom.de
Gerrit-MessageType: merged



    