Philipp | 91df16c | 2016-08-26 17:00:21 +0200 | [diff] [blame] | 1 | /* GPRS SNDCP header compression handler */ |
| 2 | |
| 3 | /* (C) 2016 by Sysmocom s.f.m.c. GmbH |
| 4 | * All Rights Reserved |
| 5 | * |
| 6 | * Author: Philipp Maier |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or modify |
| 9 | * it under the terms of the GNU Affero General Public License as published by |
| 10 | * the Free Software Foundation; either version 3 of the License, or |
| 11 | * (at your option) any later version. |
| 12 | * |
| 13 | * This program is distributed in the hope that it will be useful, |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | * GNU Affero General Public License for more details. |
| 17 | * |
| 18 | * You should have received a copy of the GNU Affero General Public License |
| 19 | * along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 20 | * |
| 21 | */ |
| 22 | |
| 23 | #include <stdio.h> |
| 24 | #include <string.h> |
| 25 | #include <stdint.h> |
| 26 | #include <math.h> |
| 27 | #include <errno.h> |
| 28 | #include <stdbool.h> |
| 29 | |
| 30 | #include <osmocom/core/utils.h> |
| 31 | #include <osmocom/core/msgb.h> |
| 32 | #include <osmocom/core/linuxlist.h> |
| 33 | #include <osmocom/core/talloc.h> |
| 34 | #include <osmocom/gsm/tlv.h> |
| 35 | |
| 36 | #include <openbsc/gprs_llc.h> |
| 37 | #include <openbsc/sgsn.h> |
| 38 | #include <openbsc/gprs_sndcp_xid.h> |
| 39 | #include <openbsc/slhc.h> |
| 40 | #include <openbsc/debug.h> |
| 41 | #include <openbsc/gprs_sndcp_comp.h> |
| 42 | #include <openbsc/gprs_sndcp_pcomp.h> |
| 43 | |
| 44 | /* Initalize header compression */ |
| 45 | int gprs_sndcp_pcomp_init(const void *ctx, struct gprs_sndcp_comp *comp_entity, |
| 46 | const struct gprs_sndcp_comp_field *comp_field) |
| 47 | { |
| 48 | /* Note: This function is automatically called from |
| 49 | * gprs_sndcp_comp.c when a new header compression |
| 50 | * entity is created by gprs_sndcp.c */ |
| 51 | |
| 52 | OSMO_ASSERT(comp_entity); |
| 53 | OSMO_ASSERT(comp_field); |
| 54 | |
| 55 | if (comp_entity->compclass == SNDCP_XID_PROTOCOL_COMPRESSION |
| 56 | && comp_entity->algo == RFC_1144) { |
| 57 | comp_entity->state = |
| 58 | slhc_init(ctx, comp_field->rfc1144_params->s01 + 1, |
| 59 | comp_field->rfc1144_params->s01 + 1); |
| 60 | LOGP(DSNDCP, LOGL_INFO, |
| 61 | "RFC1144 header compression initalized.\n"); |
| 62 | return 0; |
| 63 | } |
| 64 | |
| 65 | /* Just in case someone tries to initalize an unknown or unsupported |
| 66 | * header compresson. Since everything is checked during the SNDCP |
| 67 | * negotiation process, this should never happen! */ |
| 68 | OSMO_ASSERT(false); |
| 69 | } |
| 70 | |
| 71 | /* Terminate header compression */ |
| 72 | void gprs_sndcp_pcomp_term(struct gprs_sndcp_comp *comp_entity) |
| 73 | { |
| 74 | /* Note: This function is automatically called from |
| 75 | * gprs_sndcp_comp.c when a header compression |
| 76 | * entity is deleted by gprs_sndcp.c */ |
| 77 | |
| 78 | OSMO_ASSERT(comp_entity); |
| 79 | |
| 80 | if (comp_entity->compclass == SNDCP_XID_PROTOCOL_COMPRESSION |
| 81 | && comp_entity->algo == RFC_1144) { |
| 82 | if (comp_entity->state) { |
| 83 | slhc_free((struct slcompress *)comp_entity->state); |
| 84 | comp_entity->state = NULL; |
| 85 | } |
| 86 | LOGP(DSNDCP, LOGL_INFO, |
| 87 | "RFC1144 header compression terminated.\n"); |
| 88 | return; |
| 89 | } |
| 90 | |
| 91 | /* Just in case someone tries to terminate an unknown or unsupported |
| 92 | * data compresson. Since everything is checked during the SNDCP |
| 93 | * negotiation process, this should never happen! */ |
| 94 | OSMO_ASSERT(false); |
| 95 | } |
| 96 | |
| 97 | /* Compress a packet using Van Jacobson RFC1144 header compression */ |
| 98 | static int rfc1144_compress(uint8_t *pcomp_index, uint8_t *data, |
| 99 | unsigned int len, struct slcompress *comp) |
| 100 | { |
| 101 | uint8_t *comp_ptr; |
| 102 | int compr_len; |
| 103 | uint8_t *data_o; |
| 104 | |
| 105 | /* Create a working copy of the incoming data */ |
| 106 | data_o = talloc_zero_size(comp, len); |
| 107 | memcpy(data_o, data, len); |
| 108 | |
| 109 | /* Run compressor */ |
| 110 | compr_len = slhc_compress(comp, data, len, data_o, &comp_ptr, 0); |
| 111 | |
| 112 | /* Generate pcomp_index */ |
| 113 | if (data_o[0] & SL_TYPE_COMPRESSED_TCP) { |
| 114 | *pcomp_index = 2; |
| 115 | data_o[0] &= ~SL_TYPE_COMPRESSED_TCP; |
| 116 | memcpy(data, data_o, compr_len); |
| 117 | } else if ((data_o[0] & SL_TYPE_UNCOMPRESSED_TCP) == |
| 118 | SL_TYPE_UNCOMPRESSED_TCP) { |
| 119 | *pcomp_index = 1; |
| 120 | data_o[0] &= 0x4F; |
| 121 | memcpy(data, data_o, compr_len); |
| 122 | } else |
| 123 | *pcomp_index = 0; |
| 124 | |
| 125 | talloc_free(data_o); |
| 126 | return compr_len; |
| 127 | } |
| 128 | |
| 129 | /* Expand a packet using Van Jacobson RFC1144 header compression */ |
| 130 | static int rfc1144_expand(uint8_t *data, unsigned int len, uint8_t pcomp_index, |
| 131 | struct slcompress *comp) |
| 132 | { |
| 133 | int data_decompressed_len; |
| 134 | int type; |
| 135 | |
| 136 | /* Note: this function should never be called with pcomp_index=0, |
| 137 | * since this condition is already filtered |
| 138 | * out by gprs_sndcp_pcomp_expand() */ |
| 139 | |
| 140 | /* Determine the data type by the PCOMP index */ |
| 141 | switch (pcomp_index) { |
| 142 | case 0: |
| 143 | type = SL_TYPE_IP; |
Philipp | 3c175ed | 2016-09-28 15:10:14 +0200 | [diff] [blame] | 144 | break; |
Philipp | 91df16c | 2016-08-26 17:00:21 +0200 | [diff] [blame] | 145 | case 1: |
| 146 | type = SL_TYPE_UNCOMPRESSED_TCP; |
| 147 | break; |
| 148 | case 2: |
| 149 | type = SL_TYPE_COMPRESSED_TCP; |
| 150 | break; |
| 151 | default: |
| 152 | LOGP(DSNDCP, LOGL_ERROR, |
| 153 | "rfc1144_expand() Invalid pcomp_index value (%d) detected, assuming no compression!\n", |
| 154 | pcomp_index); |
| 155 | type = SL_TYPE_IP; |
| 156 | break; |
| 157 | } |
| 158 | |
| 159 | /* Restore the original version nibble on |
| 160 | * marked uncompressed packets */ |
| 161 | if (type == SL_TYPE_UNCOMPRESSED_TCP) { |
| 162 | /* Just in case the phone tags uncompressed tcp-data |
| 163 | * (normally this is handled by pcomp so there is |
| 164 | * no need for tagging the data) */ |
| 165 | data[0] &= 0x4F; |
| 166 | data_decompressed_len = slhc_remember(comp, data, len); |
| 167 | return data_decompressed_len; |
| 168 | } |
| 169 | |
| 170 | /* Uncompress compressed packets */ |
| 171 | else if (type == SL_TYPE_COMPRESSED_TCP) { |
| 172 | data_decompressed_len = slhc_uncompress(comp, data, len); |
| 173 | return data_decompressed_len; |
| 174 | } |
| 175 | |
| 176 | /* Regular or unknown packets will not be touched */ |
| 177 | return len; |
| 178 | } |
| 179 | |
| 180 | /* Expand packet header */ |
| 181 | int gprs_sndcp_pcomp_expand(uint8_t *data, unsigned int len, uint8_t pcomp, |
| 182 | const struct llist_head *comp_entities) |
| 183 | { |
| 184 | int rc; |
| 185 | uint8_t pcomp_index = 0; |
| 186 | struct gprs_sndcp_comp *comp_entity; |
| 187 | |
| 188 | OSMO_ASSERT(data); |
| 189 | OSMO_ASSERT(comp_entities); |
| 190 | |
| 191 | LOGP(DSNDCP, LOGL_DEBUG, |
| 192 | "Header compression entity list: comp_entities=%p\n", |
| 193 | comp_entities); |
| 194 | |
| 195 | LOGP(DSNDCP, LOGL_DEBUG, "Header compression mode: pcomp=%d\n", pcomp); |
| 196 | |
| 197 | /* Skip on pcomp=0 */ |
| 198 | if (pcomp == 0) { |
| 199 | return len; |
| 200 | } |
| 201 | |
| 202 | /* Find out which compression entity handles the data */ |
| 203 | comp_entity = gprs_sndcp_comp_by_comp(comp_entities, pcomp); |
| 204 | |
| 205 | /* Skip compression if no suitable compression entity can be found */ |
| 206 | if (!comp_entity) { |
| 207 | return len; |
| 208 | } |
| 209 | |
| 210 | /* Note: Only protocol compression entities may appear in |
| 211 | * protocol compression context */ |
| 212 | OSMO_ASSERT(comp_entity->compclass == SNDCP_XID_PROTOCOL_COMPRESSION); |
| 213 | |
| 214 | /* Note: Currently RFC1144 is the only compression method we |
| 215 | * support, so the only allowed algorithm is RFC1144 */ |
| 216 | OSMO_ASSERT(comp_entity->algo == RFC_1144); |
| 217 | |
| 218 | /* Find pcomp_index */ |
| 219 | pcomp_index = gprs_sndcp_comp_get_idx(comp_entity, pcomp); |
| 220 | |
| 221 | /* Run decompression algo */ |
| 222 | rc = rfc1144_expand(data, len, pcomp_index, comp_entity->state); |
| 223 | slhc_i_status(comp_entity->state); |
| 224 | slhc_o_status(comp_entity->state); |
| 225 | |
| 226 | LOGP(DSNDCP, LOGL_DEBUG, |
| 227 | "Header expansion done, old length=%d, new length=%d, entity=%p\n", |
| 228 | len, rc, comp_entity); |
| 229 | |
| 230 | return rc; |
| 231 | } |
| 232 | |
| 233 | /* Compress packet header */ |
| 234 | int gprs_sndcp_pcomp_compress(uint8_t *data, unsigned int len, uint8_t *pcomp, |
| 235 | const struct llist_head *comp_entities, |
| 236 | uint8_t nsapi) |
| 237 | { |
| 238 | int rc; |
| 239 | uint8_t pcomp_index = 0; |
| 240 | struct gprs_sndcp_comp *comp_entity; |
| 241 | |
| 242 | OSMO_ASSERT(data); |
| 243 | OSMO_ASSERT(pcomp); |
| 244 | OSMO_ASSERT(comp_entities); |
| 245 | |
| 246 | LOGP(DSNDCP, LOGL_DEBUG, |
| 247 | "Header compression entity list: comp_entities=%p\n", |
| 248 | comp_entities); |
| 249 | |
| 250 | /* Find out which compression entity handles the data */ |
| 251 | comp_entity = gprs_sndcp_comp_by_nsapi(comp_entities, nsapi); |
| 252 | |
| 253 | /* Skip compression if no suitable compression entity can be found */ |
| 254 | if (!comp_entity) { |
| 255 | *pcomp = 0; |
| 256 | return len; |
| 257 | } |
| 258 | |
| 259 | /* Note: Only protocol compression entities may appear in |
| 260 | * protocol compression context */ |
| 261 | OSMO_ASSERT(comp_entity->compclass == SNDCP_XID_PROTOCOL_COMPRESSION); |
| 262 | |
| 263 | /* Note: Currently RFC1144 is the only compression method we |
| 264 | * support, so the only allowed algorithm is RFC1144 */ |
| 265 | OSMO_ASSERT(comp_entity->algo == RFC_1144); |
| 266 | |
| 267 | /* Run compression algo */ |
| 268 | rc = rfc1144_compress(&pcomp_index, data, len, comp_entity->state); |
| 269 | slhc_i_status(comp_entity->state); |
| 270 | slhc_o_status(comp_entity->state); |
| 271 | |
| 272 | /* Find pcomp value */ |
| 273 | *pcomp = gprs_sndcp_comp_get_comp(comp_entity, pcomp_index); |
| 274 | |
| 275 | LOGP(DSNDCP, LOGL_DEBUG, "Header compression mode: pcomp=%d\n", *pcomp); |
| 276 | |
| 277 | LOGP(DSNDCP, LOGL_DEBUG, |
| 278 | "Header compression done, old length=%d, new length=%d, entity=%p\n", |
| 279 | len, rc, comp_entity); |
| 280 | return rc; |
| 281 | } |