/**
* @brief Decode the add-CID byte of a ROHC packet (if the add-CID byte is
* present)
*
* @param data The ROHC packet with a possible add-CID byte
* @param len The length of the ROHC packet
* @return UINT8_MAX if no add-CID byte is present, the CID value otherwise
*/
uint8_t rohc_add_cid_decode(const uint8_t *const data, const size_t len)
{
uint8_t cid;
if(rohc_add_cid_is_present(data, len))
{
cid = GET_BIT_0_3(data);
}
else
{
cid = UINT8_MAX;
}
return cid;
}
/**
* @brief Process the insertion scheme of the list compression
*
* @param decomp The list decompressor
* @param packet The ROHC packet to decompress
* @param packet_len The length (in bytes) of the packet to decompress
* @param ps The PS bit
* @param xi_1 The XI 1 field if PS = 1 (4-bit XI)
* @param items_nr The number of items in the initial list
* @param ref_list The list to use as reference
* @param[out] ins_list The list with new items added
* @return \li In case of success, the number of bytes read in the
* given packet, ie. the length of the insertion mask
* \li -1 in case of failure
*/
static int rohc_list_parse_insertion_scheme(struct list_decomp *const decomp,
const uint8_t *packet,
size_t packet_len,
const int ps,
const int xi_1,
const size_t items_nr,
const struct rohc_list *const ref_list,
struct rohc_list *const ins_list)
{
size_t packet_read_len = 0;
uint8_t mask[2]; /* removal bit mask on 1-2 bytes */
size_t mask_len; /* length (in bits) of the removal mask */
size_t item_read_len; /* the amount of bytes currently read in the item field */
size_t ref_list_cur_pos; /* current position in reference list */
size_t xi_index; /* the index of the current XI in XI list */
size_t xi_len; /* the length (in bytes) of the XI list */
size_t k; /* the number of ones in insertion mask and the number of elements in XI list */
size_t i;
int ret;
assert(ps == 0 || ps == 1);
/* parse the insertion bit mask */
ret = rohc_list_decode_mask(decomp, "insertion", packet, packet_len,
mask, &mask_len);
if(ret < 0)
{
rd_list_warn(decomp, "failed to parse the insertion bit mask");
goto error;
}
packet += ret;
packet_read_len += ret;
packet_len -= ret;
/* determine the number of indexes in the XI list */
k = rohc_list_get_xi_nr(mask, mask_len);
/* determine the length (in bytes) of the XI list */
xi_len = rohc_list_get_xi_len(k, ps);
if(packet_len < xi_len)
{
rd_list_warn(decomp, "packet too small for k = %zu XI items (only %zu "
"bytes while at least %zu bytes are required)", k,
packet_len, xi_len);
goto error;
}
/* will the decompressed list contain too many items? */
if((items_nr + k) > ROHC_LIST_ITEMS_MAX)
{
rd_list_warn(decomp, "failed to decompress list based on reference list "
"with %zu existing items and %zu additional new items: too "
"many items for list (%u items max)", items_nr, k,
ROHC_LIST_ITEMS_MAX);
goto error;
}
/* create current list with reference list and new provided items */
xi_index = 0;
item_read_len = 0;
ref_list_cur_pos = 0;
for(i = 0; i < mask_len; i++)
{
uint8_t new_item_to_insert;
/* retrieve the corresponding bit in the insertion mask */
if(i < 7)
{
/* bit is located in first byte of insertion mask */
new_item_to_insert = rohc_get_bit(mask[0], 6 - i);
}
else
{
/* bit is located in 2nd byte of insertion mask */
new_item_to_insert = rohc_get_bit(mask[1], 14 - i);
}
/* insert item if required */
if(!new_item_to_insert)
{
/* take the next item from reference list (if there no more item in
reference list, do nothing) */
if(ref_list_cur_pos < ref_list->items_nr)
{
/* new list, insert the item from reference list */
rd_list_debug(decomp, "use item from reference list (index %zu) into "
"current list (index %zu)", ref_list_cur_pos, i);
/* use next item from reference list */
ins_list->items[i] = ref_list->items[ref_list_cur_pos];
ins_list->items_nr++;
/* skip item in removal list */
ref_list_cur_pos++;
}
}
else
{
unsigned int xi_x_value; /* the value of the X field in one XI field */
unsigned int xi_index_value; /* the value of the Index field in one XI field */
/* new item to insert in list, parse the related XI field */
if(!ps)
{
/* ROHC header contains 4-bit XIs */
/* which type of XI do we parse ? first one, odd one or even one ? */
if(xi_index == 0)
{
/* first XI is stored in the first byte of the header */
xi_x_value = GET_BIT_3(&xi_1);
xi_index_value = GET_BIT_0_2(&xi_1);
}
else if((xi_index % 2) != 0)
{
/* handle odd XI, ie. XI stored in MSB */
xi_x_value = GET_BIT_7(packet + (xi_index - 1) / 2);
xi_index_value = GET_BIT_4_6(packet + (xi_index - 1) / 2);
}
else
{
/* handle even XI, ie. XI stored in LSB */
xi_x_value = GET_BIT_3(packet + (xi_index - 1) / 2);
xi_index_value = GET_BIT_0_2(packet + (xi_index - 1) / 2);
}
}
else
{
/* ROHC header contains 8-bit XIs */
xi_x_value = GET_BIT_7(packet + xi_index);
xi_index_value = GET_BIT_0_6(packet + xi_index);
}
/* is the XI index valid? */
if(!decomp->check_item(decomp, xi_index_value))
{
rd_list_warn(decomp, "XI #%zu got invalid index %u", xi_index,
xi_index_value);
goto error;
}
/* parse the corresponding item if present */
if(xi_x_value)
{
const uint8_t *const xi_item = packet + xi_len + item_read_len;
const size_t xi_item_max_len = packet_len - xi_len - item_read_len;
size_t item_len;
rd_list_debug(decomp, "handle XI item #%zu", xi_index);
/* create (or update if it already exists) the corresponding
* item with the item transmitted in the ROHC header */
if(!rohc_decomp_list_create_item(decomp, xi_index, xi_index_value,
xi_item, xi_item_max_len,
&item_len))
{
rd_list_warn(decomp, "failed to create XI item #%zu from "
"packet", xi_index);
goto error;
}
/* skip the item in ROHC header */
item_read_len += item_len;
}
else
{
/* X bit not set in XI, so item is not provided in ROHC header,
* it must already be known by decompressor */
if(!decomp->trans_table[xi_index_value].known)
{
rd_list_warn(decomp, "list item with index #%u referenced by "
"XI #%zu is not known yet", xi_index_value,
xi_index);
goto error;
}
}
/* use new item from packet */
rd_list_debug(decomp, "use new item #%zu into current list (index "
"%zu)", xi_index, i);
ins_list->items[i] = &(decomp->trans_table[xi_index_value]);
ins_list->items_nr++;
/* skip the XI we have just parsed */
xi_index++;
}
}
/* ensure that in case of an even number of 4-bit XIs, the 4 bits of
* padding are set to 0 */
if(ps == 0 && (k % 2) == 0)
{
const uint8_t xi_padding = GET_BIT_0_3(packet + xi_len - 1);
if(xi_padding != 0)
{
rd_list_warn(decomp, "sender does not conform to ROHC standards: "
"when an even number of 4-bit XIs is used, the last 4 "
"bits of the XI list should be set to 0, not 0x%x",
xi_padding);
#ifdef ROHC_RFC_STRICT_DECOMPRESSOR
goto error;
#endif
}
}
/* skip the XI list and the item list */
packet_read_len += xi_len + item_read_len;
#ifndef __clang_analyzer__ /* silent warning about dead in/decrement */
packet_len -= xi_len + item_read_len;
#endif
return packet_read_len;
error:
return -1;
}
/**
* @brief Decode an extension list type 0
*
* @param decomp The list decompressor
* @param packet The ROHC packet to decompress
* @param packet_len The length (in bytes) of the packet to decompress
* @param gen_id The id of the current list,
* maybe ROHC_LIST_GEN_ID_ANON if not defined
* @param ps The ps field
* @param m The m field
* @return \li In case of success, the number of bytes read in the given
* packet, ie. the length of the compressed list
* \li -1 in case of failure
*/
static int rohc_list_decode_type_0(struct list_decomp *const decomp,
const unsigned char *packet,
size_t packet_len,
const unsigned int gen_id,
const int ps,
const uint8_t m)
{
size_t packet_read_len = 0;
size_t xi_len; /* the length (in bytes) of the XI list */
unsigned int xi_index; /* the index of the current XI in XI list */
size_t item_read_len; /* the amount of bytes currently read in the item field */
assert(decomp != NULL);
assert(packet != NULL);
assert(gen_id != ROHC_LIST_GEN_ID_NONE);
assert(ps == 0 || ps == 1);
assert(m <= ROHC_LIST_ITEMS_MAX);
/* determine the length (in bytes) of the XI list */
if(!ps)
{
/* 4-bit XIs */
if((m % 2) == 0)
{
/* even number of XI fields */
xi_len = m / 2;
}
else
{
/* odd number of XI fields, there are 4 bits of padding */
xi_len = (m + 1) / 2;
}
}
else
{
/* 8-bit XIs */
xi_len = m;
}
/* is there enough room in packet for all the XI list ? */
if(packet_len < xi_len)
{
rd_list_warn(decomp, "packet too small for m = %d XI items (only %zu "
"bytes while at least %zu bytes are required)", m,
packet_len, xi_len);
goto error;
}
/* creation of the list from the m XI items */
item_read_len = 0;
for(xi_index = 0; xi_index < m; xi_index++)
{
unsigned int xi_x_value; /* the value of the X field in one XI field */
unsigned int xi_index_value; /* the value of the Index field in one XI field */
/* extract the value of the XI index */
if(!ps)
{
/* 4-bit XI */
if((xi_index % 2) == 0)
{
/* 4-bit XI is stored in MSB */
xi_x_value = GET_BIT_7(packet + xi_index / 2);
xi_index_value = GET_BIT_4_6(packet + xi_index / 2);
}
else
{
/* 4-bit XI is stored in LSB */
xi_x_value = GET_BIT_3(packet + xi_index / 2);
xi_index_value = GET_BIT_0_2(packet + xi_index / 2);
}
rd_list_debug(decomp, "0x%02x: XI #%u got index %u",
packet[xi_index / 2], xi_index, xi_index_value);
}
else
{
/* 8-bit XI */
xi_x_value = GET_BIT_7(packet + xi_index);
xi_index_value = GET_BIT_0_6(packet + xi_index);
rd_list_debug(decomp, "0x%02x: XI #%u got index %u",
packet[xi_index], xi_index, xi_index_value);
}
/* is the XI index valid? */
if(!decomp->check_item(decomp, xi_index_value))
{
rd_list_warn(decomp, "XI #%u got invalid index %u", xi_index,
xi_index_value);
goto error;
}
/* is there a corresponding item in packet after the XI list? */
if(xi_x_value)
{
const uint8_t *const xi_item = packet + xi_len + item_read_len;
const size_t xi_item_max_len = packet_len - xi_len - item_read_len;
size_t item_len;
rd_list_debug(decomp, "handle XI item #%u", xi_index);
/* create (or update if it already exists) the corresponding item
* with the item transmitted in the ROHC header */
if(!rohc_decomp_list_create_item(decomp, xi_index, xi_index_value,
xi_item, xi_item_max_len, &item_len))
{
rd_list_warn(decomp, "failed to create XI item #%u from packet",
xi_index);
goto error;
}
/* skip the item in ROHC header */
item_read_len += item_len;
}
else
{
/* X bit not set in XI, so item is not provided in ROHC header,
* it must already be known by decompressor */
if(!decomp->trans_table[xi_index_value].known)
{
rd_list_warn(decomp, "list item with index #%u referenced by XI "
"#%d is not known yet", xi_index_value, xi_index);
goto error;
}
}
/* record the structure of the list of the current packet */
assert(decomp->pkt_list.items_nr < ROHC_LIST_ITEMS_MAX);
decomp->pkt_list.items[decomp->pkt_list.items_nr] =
&decomp->trans_table[xi_index_value];
decomp->pkt_list.items_nr++;
rd_list_debug(decomp, " XI #%u: use item of type 0x%02x (index %u in "
"translation table) in list", xi_index,
decomp->trans_table[xi_index_value].type, xi_index_value);
}
/* ensure that in case of an odd number of 4-bit XIs, the 4 bits of padding
are set to 0 */
if(ps == 0 && (m % 2) != 0)
{
const uint8_t xi_padding = GET_BIT_0_3(packet + xi_len - 1);
if(xi_padding != 0)
{
rd_list_warn(decomp, "sender does not conform to ROHC standards: "
"when an odd number of 4-bit XIs is used, the last 4 "
"bits of the XI list should be set to 0, not 0x%x",
xi_padding);
#ifdef ROHC_RFC_STRICT_DECOMPRESSOR
goto error;
#endif
}
}
/* skip the XI list and the item list */
packet_read_len += xi_len + item_read_len;
#ifndef __clang_analyzer__ /* silent warning about dead in/decrement */
packet_len -= xi_len + item_read_len;
#endif
return packet_read_len;
error:
return -1;
}
/**
* @brief Decompress the compressed list in given packet
*
* @param decomp The list decompressor
* @param packet The ROHC packet to decompress
* @param packet_len The remaining length of the packet to decode (in bytes)
* @return The size of the compressed list in packet in case of
* success, -1 in case of failure
*/
static int rohc_list_decode(struct list_decomp *decomp,
const unsigned char *packet,
size_t packet_len)
{
size_t read_length = 0;
uint8_t et; /* the type of list encoding */
bool gp; /* whether the gen_id field is present or not */
uint8_t ps; /* the type of XI field */
uint8_t m; /* the CC or Count field (share bits with XI 1) */
uint8_t xi_1; /* the XI 1 field (share bits with m) */
unsigned int gen_id; /* the gen_id if present,
ROHC_LIST_GEN_ID_ANON otherwise */
int ret;
/* reset the list of the current packet */
rohc_list_reset(&decomp->pkt_list);
/* is there enough data in packet for the ET, PS, m/XI1 and gen_id
* fields? */
if(packet_len < 2)
{
rd_list_warn(decomp, "packet too small for compressed list (only %zu "
"bytes while at least 2 bytes are required)", packet_len);
goto error;
}
/* parse ET, GP, PS, and m/XI1 fields */
et = GET_BIT_6_7(packet);
gp = !!GET_BIT_5(packet);
ps = GET_REAL(GET_BIT_4(packet));
m = GET_BIT_0_3(packet);
xi_1 = m; /* m and XI 1 are the same field */
packet++;
read_length++;
packet_len--;
rd_list_debug(decomp, "ET = %d, GP = %d, PS = %d, m = XI 1 = %d",
et, gp, ps, m);
assert(m <= ROHC_LIST_ITEMS_MAX);
/* parse gen_id if present */
if(gp == 1)
{
gen_id = GET_BIT_0_7(packet);
packet++;
read_length++;
packet_len--;
rd_list_debug(decomp, "gen_id = 0x%02x", gen_id);
}
else
{
gen_id = ROHC_LIST_GEN_ID_ANON;
rd_list_debug(decomp, "decode anonymous list");
}
decomp->pkt_list.id = gen_id;
/* decode the compressed list according to its type */
switch(et)
{
case 0:
ret = rohc_list_decode_type_0(decomp, packet, packet_len,
gen_id, ps, m);
break;
case 1:
ret = rohc_list_decode_type_1(decomp, packet, packet_len,
gen_id, ps, xi_1);
break;
case 2:
ret = rohc_list_decode_type_2(decomp, packet, packet_len, gen_id);
break;
case 3:
ret = rohc_list_decode_type_3(decomp, packet, packet_len,
gen_id, ps, xi_1);
break;
default:
/* should not happen */
rohc_error(decomp, ROHC_TRACE_DECOMP, decomp->profile_id,
"unknown type of compressed list (ET = %u)", et);
assert(0);
goto error;
}
if(ret < 0)
{
rd_list_warn(decomp, "failed to decode compressed list type %d", et);
goto error;
}
assert(((size_t) ret) <= packet_len);
#ifndef __clang_analyzer__ /* silent warning about dead in/decrement */
packet += ret;
packet_len -= ret;
#endif
read_length += ret;
/* RFC3095, section 5.8.2.1 reads:
* When the decompressor receives a compressed list, it retrieves the
* proper ref_list from the sliding window based on the ref_id, and
* decompresses the compressed list obtaining curr_list.
* In U/O-mode, curr_list is inserted into the sliding window
* together with its generation identifier if the compressed list had
* a generation identifier and the sliding window does not contain a
* list with that generation identifier. All lists with generations
* older than ref_id are removed from the sliding window. */
if(gen_id == ROHC_LIST_GEN_ID_ANON)
{
/* list is not identified by a gen_id, so do not update the sliding
* window of lists */
rd_list_debug(decomp, "anonymous list was received");
}
else if(decomp->lists[gen_id].counter > 0)
{
/* list is identified by a gen_id, but the sliding window of lists
* already contain a list with that generation identifier, so do
* not update the sliding window of lists */
decomp->lists[gen_id].counter++;
rd_list_debug(decomp, "list with gen_id %u is already present in "
"reference lists (received for the #%zu times)",
gen_id, decomp->lists[gen_id].counter);
}
else
{
/* list is identified by a gen_id and the sliding window of lists does
* not contain a list with that generation identifier yet, so update
* the sliding window of lists */
rd_list_debug(decomp, "list with gen_id %u is not present yet in "
"reference lists, add it", gen_id);
memcpy(decomp->lists[gen_id].items, decomp->pkt_list.items,
ROHC_LIST_ITEMS_MAX * sizeof(struct decomp_list *));
decomp->lists[gen_id].items_nr = decomp->pkt_list.items_nr;
decomp->lists[gen_id].counter = 1;
/* TODO: remove all lists with gen_id < ref_id */
}
return read_length;
error:
return -1;
}
