SNDCP: add V.42bis data compression functionality
- Add compression control for V.42bis Add code to handle compression
(gprs_sndcp_dcomp.c/h)
- Add Adjustments in SNDCP
- Add VTY commands
Change-Id: I6d36cbdf2f5c5f83ca9ba57c70452f02b8582e7e
diff --git a/openbsc/src/gprs/gprs_sndcp_dcomp.c b/openbsc/src/gprs/gprs_sndcp_dcomp.c
new file mode 100644
index 0000000..489106b
--- /dev/null
+++ b/openbsc/src/gprs/gprs_sndcp_dcomp.c
@@ -0,0 +1,357 @@
+/* GPRS SNDCP data compression handler */
+
+/* (C) 2016 by Sysmocom s.f.m.c. GmbH
+ * All Rights Reserved
+ *
+ * Author: Philipp Maier
+ *
+ * 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 <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <math.h>
+#include <errno.h>
+#include <stdbool.h>
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/gsm/tlv.h>
+
+#include <openbsc/gprs_llc.h>
+#include <openbsc/sgsn.h>
+#include <openbsc/gprs_sndcp_xid.h>
+#include <openbsc/v42bis.h>
+#include <openbsc/v42bis_private.h>
+#include <openbsc/debug.h>
+#include <openbsc/gprs_sndcp_comp.h>
+#include <openbsc/gprs_sndcp_dcomp.h>
+
+/* A struct to capture the output data of compressor and decompressor */
+struct v42bis_output_buffer {
+ uint8_t *buf;
+ uint8_t *buf_pointer;
+ int len;
+};
+
+/* Handler to capture the output data from the compressor */
+void tx_v42bis_frame_handler(void *user_data, const uint8_t *pkt, int len)
+{
+ struct v42bis_output_buffer *output_buffer =
+ (struct v42bis_output_buffer *)user_data;
+ memcpy(output_buffer->buf_pointer, pkt, len);
+ output_buffer->buf_pointer += len;
+ output_buffer->len += len;
+ return;
+}
+
+/* Handler to capture the output data from the decompressor */
+void rx_v42bis_data_handler(void *user_data, const uint8_t *buf, int len)
+{
+ struct v42bis_output_buffer *output_buffer =
+ (struct v42bis_output_buffer *)user_data;
+ memcpy(output_buffer->buf_pointer, buf, len);
+ output_buffer->buf_pointer += len;
+ output_buffer->len += len;
+ return;
+}
+
+/* Initalize data compression */
+int gprs_sndcp_dcomp_init(const void *ctx, struct gprs_sndcp_comp *comp_entity,
+ const struct gprs_sndcp_comp_field *comp_field)
+{
+ /* Note: This function is automatically called from
+ * gprs_sndcp_comp.c when a new data compression
+ * entity is created by gprs_sndcp.c */
+
+ OSMO_ASSERT(comp_entity);
+ OSMO_ASSERT(comp_field);
+
+ if (comp_entity->compclass == SNDCP_XID_DATA_COMPRESSION
+ && comp_entity->algo == V42BIS) {
+ comp_entity->state =
+ v42bis_init(ctx, NULL, comp_field->v42bis_params->p0,
+ comp_field->v42bis_params->p1,
+ comp_field->v42bis_params->p2,
+ &tx_v42bis_frame_handler, NULL,
+ V42BIS_MAX_OUTPUT_LENGTH,
+ &rx_v42bis_data_handler, NULL,
+ V42BIS_MAX_OUTPUT_LENGTH);
+ LOGP(DSNDCP, LOGL_INFO,
+ "V.42bis data compression initalized.\n");
+ return 0;
+ }
+
+ /* Just in case someone tries to initalize an unknown or unsupported
+ * data compresson. Since everything is checked during the SNDCP
+ * negotiation process, this should never happen! */
+ OSMO_ASSERT(false);
+}
+
+/* Terminate data compression */
+void gprs_sndcp_dcomp_term(struct gprs_sndcp_comp *comp_entity)
+{
+ /* Note: This function is automatically called from
+ * gprs_sndcp_comp.c when a data compression
+ * entity is deleted by gprs_sndcp.c */
+
+ OSMO_ASSERT(comp_entity);
+
+ if (comp_entity->compclass == SNDCP_XID_DATA_COMPRESSION
+ && comp_entity->algo == V42BIS) {
+ if (comp_entity->state) {
+ v42bis_free((v42bis_state_t *) comp_entity->state);
+ comp_entity->state = NULL;
+ }
+ LOGP(DSNDCP, LOGL_INFO,
+ "V.42bis data compression terminated.\n");
+ return;
+ }
+
+ /* Just in case someone tries to terminate an unknown or unsupported
+ * data compresson. Since everything is checked during the SNDCP
+ * negotiation process, this should never happen! */
+ OSMO_ASSERT(false);
+}
+
+/* Perform a full reset of the V.42bis compression state */
+static void v42bis_reset(v42bis_state_t *comp)
+{
+ /* This function performs a complete reset of the V.42bis compression
+ * state by reinitalizing the state withe the previously negotiated
+ * parameters. */
+
+ int p0, p1, p2;
+ p0 = comp->decompress.v42bis_parm_p0 | comp->compress.v42bis_parm_p0;
+ p1 = comp->decompress.v42bis_parm_n2;
+ p2 = comp->decompress.v42bis_parm_n7;
+
+ DEBUGP(DSNDCP, "Resetting compression state: %p, p0=%d, p1=%d, p2=%d\n",
+ comp, p0, p1, p2);
+
+ v42bis_init(NULL, comp, p0, p1, p2, &tx_v42bis_frame_handler, NULL,
+ V42BIS_MAX_OUTPUT_LENGTH, &rx_v42bis_data_handler, NULL,
+ V42BIS_MAX_OUTPUT_LENGTH);
+}
+
+/* Compress a packet using V.42bis data compression */
+static int v42bis_compress_unitdata(uint8_t *pcomp_index, uint8_t *data,
+ unsigned int len, v42bis_state_t *comp)
+{
+ /* Note: This implementation may only be used to compress SN_UNITDATA
+ * packets, since it resets the compression state for each NPDU. */
+
+ uint8_t *data_o;
+ int rc;
+ int skip = 0;
+ struct v42bis_output_buffer compressed_data;
+
+ /* Don't bother with short packets */
+ if (len < MIN_COMPR_PAYLOAD)
+ skip = 1;
+
+ /* Skip if compression is not enabled for TX direction */
+ if (!comp->compress.v42bis_parm_p0)
+ skip = 1;
+
+ /* Skip compression */
+ if (skip) {
+ *pcomp_index = 0;
+ return len;
+ }
+
+ /* Reset V.42bis compression state */
+ v42bis_reset(comp);
+
+ /* Run compressor */
+ data_o = talloc_zero_size(comp, len * MAX_DATADECOMPR_FAC);
+ compressed_data.buf = data_o;
+ compressed_data.buf_pointer = data_o;
+ compressed_data.len = 0;
+ comp->compress.user_data = (&compressed_data);
+ rc = v42bis_compress(comp, data, len);
+ if (rc < 0) {
+ LOGP(DSNDCP, LOGL_ERROR,
+ "Data compression failed, skipping...\n");
+ skip = 1;
+ }
+ rc = v42bis_compress_flush(comp);
+ if (rc < 0) {
+ LOGP(DSNDCP, LOGL_ERROR,
+ "Data compression failed, skipping...\n");
+ skip = 1;
+ }
+
+ /* The compressor might yield negative compression gain, in
+ * this case, we just decide to send the packat as normal,
+ * uncompressed payload => skip compresssion */
+ if (compressed_data.len >= len) {
+ LOGP(DSNDCP, LOGL_ERROR,
+ "Data compression ineffective, skipping...\n");
+ skip = 1;
+ }
+
+ /* Skip compression */
+ if (skip) {
+ *pcomp_index = 0;
+ talloc_free(data_o);
+ return len;
+ }
+
+ *pcomp_index = 1;
+ memcpy(data, data_o, compressed_data.len);
+ talloc_free(data_o);
+
+ return compressed_data.len;
+}
+
+/* Expand a packet using V.42bis data compression */
+static int v42bis_expand_unitdata(uint8_t *data, unsigned int len,
+ uint8_t pcomp_index, v42bis_state_t *comp)
+{
+ /* Note: This implementation may only be used to compress SN_UNITDATA
+ * packets, since it resets the compression state for each NPDU. */
+
+ int rc;
+ struct v42bis_output_buffer uncompressed_data;
+ uint8_t *data_i;
+
+ /* Skip when the packet is marked as uncompressed */
+ if (pcomp_index == 0) {
+ return len;
+ }
+
+ /* Reset V.42bis compression state */
+ v42bis_reset(comp);
+
+ /* Decompress packet */
+ data_i = talloc_zero_size(comp, len);
+ memcpy(data_i, data, len);
+ uncompressed_data.buf = data;
+ uncompressed_data.buf_pointer = data;
+ uncompressed_data.len = 0;
+ comp->decompress.user_data = (&uncompressed_data);
+ rc = v42bis_decompress(comp, data_i, len);
+ talloc_free(data_i);
+ if (rc < 0)
+ return -EINVAL;
+ rc = v42bis_decompress_flush(comp);
+ if (rc < 0)
+ return -EINVAL;
+
+ return uncompressed_data.len;
+}
+
+/* Expand packet */
+int gprs_sndcp_dcomp_expand(uint8_t *data, unsigned int len, uint8_t pcomp,
+ const struct llist_head *comp_entities)
+{
+ int rc;
+ uint8_t pcomp_index = 0;
+ struct gprs_sndcp_comp *comp_entity;
+
+ OSMO_ASSERT(data);
+ OSMO_ASSERT(comp_entities);
+
+ LOGP(DSNDCP, LOGL_DEBUG,
+ "Data compression entity list: comp_entities=%p\n", comp_entities);
+
+ LOGP(DSNDCP, LOGL_DEBUG, "Data compression mode: dcomp=%d\n", pcomp);
+
+ /* Skip on pcomp=0 */
+ if (pcomp == 0) {
+ return len;
+ }
+
+ /* Find out which compression entity handles the data */
+ comp_entity = gprs_sndcp_comp_by_comp(comp_entities, pcomp);
+
+ /* Skip compression if no suitable compression entity can be found */
+ if (!comp_entity) {
+ return len;
+ }
+
+ /* Note: Only data compression entities may appear in
+ * data compression context */
+ OSMO_ASSERT(comp_entity->compclass == SNDCP_XID_DATA_COMPRESSION);
+
+ /* Note: Currently V42BIS is the only compression method we
+ * support, so the only allowed algorithm is V42BIS */
+ OSMO_ASSERT(comp_entity->algo == V42BIS);
+
+ /* Find pcomp_index */
+ pcomp_index = gprs_sndcp_comp_get_idx(comp_entity, pcomp);
+
+ /* Run decompression algo */
+ rc = v42bis_expand_unitdata(data, len, pcomp_index, comp_entity->state);
+
+ LOGP(DSNDCP, LOGL_DEBUG,
+ "Data expansion done, old length=%d, new length=%d, entity=%p\n",
+ len, rc, comp_entity);
+
+ return rc;
+}
+
+/* Compress packet */
+int gprs_sndcp_dcomp_compress(uint8_t *data, unsigned int len, uint8_t *pcomp,
+ const struct llist_head *comp_entities,
+ uint8_t nsapi)
+{
+ int rc;
+ uint8_t pcomp_index = 0;
+ struct gprs_sndcp_comp *comp_entity;
+
+ OSMO_ASSERT(data);
+ OSMO_ASSERT(pcomp);
+ OSMO_ASSERT(comp_entities);
+
+ LOGP(DSNDCP, LOGL_DEBUG,
+ "Data compression entity list: comp_entities=%p\n", comp_entities);
+
+ /* Find out which compression entity handles the data */
+ comp_entity = gprs_sndcp_comp_by_nsapi(comp_entities, nsapi);
+
+ /* Skip compression if no suitable compression entity can be found */
+ if (!comp_entity) {
+ *pcomp = 0;
+ return len;
+ }
+
+ /* Note: Only data compression entities may appear in
+ * data compression context */
+ OSMO_ASSERT(comp_entity->compclass == SNDCP_XID_DATA_COMPRESSION);
+
+ /* Note: Currently V42BIS is the only compression method we
+ * support, so the only allowed algorithm is V42BIS */
+ OSMO_ASSERT(comp_entity->algo == V42BIS);
+
+ /* Run compression algo */
+ rc = v42bis_compress_unitdata(&pcomp_index, data, len,
+ comp_entity->state);
+
+ /* Find pcomp value */
+ *pcomp = gprs_sndcp_comp_get_comp(comp_entity, pcomp_index);
+
+ LOGP(DSNDCP, LOGL_DEBUG, "Data compression mode: dcomp=%d\n", *pcomp);
+
+ LOGP(DSNDCP, LOGL_DEBUG,
+ "Data compression done, old length=%d, new length=%d, entity=%p\n",
+ len, rc, comp_entity);
+
+ return rc;
+}