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rlp: Add support for 576bit RLP frames 

The code so far only supported 240bit RLP frames; Add support for
576bit in this patch.  We still only support versions 0+1 and not
version 2.

Change-Id: Idfdcabb19fe8733fb9c5ee76a39b0bf4cdf60c2c
This commit is contained in:
Harald Welte 2023-11-26 18:53:30 +01:00 committed by laforge
parent ca540be807
commit 7f2b22b5fc
1 changed files with 26 additions and 21 deletions
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47
src/gsm/rlp.c
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@ -57,19 +57,21 @@ const struct value_string osmo_rlp_ftype_s_vals[] = {
{ 0, NULL }
};
/* number of bytes used up by FCS */
#define FCS_SIZE_BYTES 3
/*! decode a RLP frame into its abstract representation. Doesn't check FCS correctness.
* \param[out] out caller-allocated memory for output of decoded frame
* \param[in] version RLP version number to use when decoding
* \param[in] data raw RLP frame input data
* \param[in] data_len length of data (in octets)
* \param[in] data_len length of data (in octets); must be 30 (240bit) or 72 (576bit)
* \returns 0 in case of success; negative on error */
int osmo_rlp_decode(struct osmo_rlp_frame_decoded *out, uint8_t version, const uint8_t *data, size_t data_len)
{
const uint8_t hdr_len = 2; /* will become a variable when we introduce v2 support */
uint8_t n_s, n_r;
/* we only support 240 bit so far */
if (data_len != 240/8)
if (data_len != 240/8 && data_len != 576/8)
return -EINVAL;
/* we only support version 0+1 so far */
@ -82,7 +84,7 @@ int osmo_rlp_decode(struct osmo_rlp_frame_decoded *out, uint8_t version, const u
out->c_r = data[0] & 1;
n_s = (data[0] >> 3) | (data[1] & 1) << 5;
n_r = (data[1] >> 2);
out->fcs = (data[240/8-1] << 16) | (data[240/8-2]) << 8 | (data[240/8-3] << 0);
out->fcs = (data[data_len-1] << 16) | (data[data_len-2]) << 8 | (data[data_len-3] << 0);
out->p_f = (data[1] >> 1) & 1;
switch (n_s) {
@ -90,8 +92,8 @@ int osmo_rlp_decode(struct osmo_rlp_frame_decoded *out, uint8_t version, const u
out->ftype = OSMO_RLP_FT_U;
out->u_ftype = n_r & 0x1f;
if (out->u_ftype == OSMO_RLP_U_FT_XID) {
memcpy(out->info, data+2, 240/8 - 5);
out->info_len = 240/8 - 5;
memcpy(out->info, data + hdr_len, data_len - (hdr_len + FCS_SIZE_BYTES));
out->info_len = data_len - (hdr_len + FCS_SIZE_BYTES);
}
break;
case 0x3e:
@ -104,8 +106,8 @@ int osmo_rlp_decode(struct osmo_rlp_frame_decoded *out, uint8_t version, const u
out->s_ftype = (data[0] >> 1) & 3;
out->n_s = n_s;
out->n_r = n_r;
memcpy(out->info, data+2, 240/8 - 5);
out->info_len = 240/8 - 5;
memcpy(out->info, data + hdr_len, data_len - (hdr_len + FCS_SIZE_BYTES));
out->info_len = data_len - (2 + 3);
break;
}
@ -114,12 +116,12 @@ int osmo_rlp_decode(struct osmo_rlp_frame_decoded *out, uint8_t version, const u
/*! encode a RLP frame from its abstract representation. Generates FCS.
* \param[out] out caller-allocated output buffer
* \param[in] out_size size of output buffer (in octets)
* \param[in] out_size size of output buffer (in octets); must be 30 (240bit) or 72 (576bit)
* \param[in] in decoded RLP frame which is to be encoded
* \returns number of output bytes used; negative on error */
int osmo_rlp_encode(uint8_t *out, size_t out_size, const struct osmo_rlp_frame_decoded *in)
{
uint8_t out_len = 240/8;
const uint8_t hdr_len = 2; /* will become a variable when we introduce v2 support */
uint8_t n_s, n_r, s_bits;
uint32_t fcs;
@ -127,10 +129,10 @@ int osmo_rlp_encode(uint8_t *out, size_t out_size, const struct osmo_rlp_frame_d
if (in->version >= 2)
return -ENOTSUP;
if (out_size < out_len)
if (out_size != 240/8 && out_size != 576/8)
return -EINVAL;
memset(out, 0, out_len);
memset(out, 0, out_size);
if (in->c_r)
out[0] |= 0x01;
@ -142,8 +144,11 @@ int osmo_rlp_encode(uint8_t *out, size_t out_size, const struct osmo_rlp_frame_d
n_s = 0x3f;
n_r = in->u_ftype;
s_bits = 0;
if (in->u_ftype == OSMO_RLP_U_FT_XID)
memcpy(out+2, in->info, in->info_len);
if (in->u_ftype == OSMO_RLP_U_FT_XID) {
if (in->info_len > out_size - (hdr_len + FCS_SIZE_BYTES))
return -EINVAL;
memcpy(out+hdr_len, in->info, in->info_len);
}
break;
case OSMO_RLP_FT_S:
n_s = 0x3e;
@ -152,12 +157,12 @@ int osmo_rlp_encode(uint8_t *out, size_t out_size, const struct osmo_rlp_frame_d
break;
case OSMO_RLP_FT_IS:
/* we only support 240 bit so far */
if (in->info_len != 240/8 - 5)
if (in->info_len > out_size - (hdr_len + FCS_SIZE_BYTES))
return -EINVAL;
n_s = in->n_s;
n_r = in->n_r;
s_bits = in->s_ftype;
memcpy(out+2, in->info, in->info_len);
memcpy(out+hdr_len, in->info, in->info_len);
break;
default:
return -EINVAL;
@ -174,12 +179,12 @@ int osmo_rlp_encode(uint8_t *out, size_t out_size, const struct osmo_rlp_frame_d
out[0] |= (s_bits & 3) << 1;
/* compute FCS + add it to end of frame */
fcs = osmo_rlp_fcs_compute(out, out_len - 3);
out[out_len - 3] = (fcs >> 0) & 0xff;
out[out_len - 2] = (fcs >> 8) & 0xff;
out[out_len - 1] = (fcs >> 16) & 0xff;
fcs = osmo_rlp_fcs_compute(out, out_size - FCS_SIZE_BYTES);
out[out_size - 3] = (fcs >> 0) & 0xff;
out[out_size - 2] = (fcs >> 8) & 0xff;
out[out_size - 1] = (fcs >> 16) & 0xff;
return out_len;
return out_size;
}