fpp: Fix mCRC calculation
Conversations start at SMD-S and are continued with SMD-C frames Added CRC information to proto_data of conversation for mCRC calculation Continue checksum calculation for faulty fragments Reassembly information added to info column Reworked packet_direction
This commit is contained in:
Benedikt Heumüller
A Wireshark GitLab Utility
parent
83959f77e3
commit
90c784bd97
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@ -126,6 +126,12 @@ typedef enum {
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CRC_FALSE
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} fpp_crc_t;
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typedef enum {
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PACKET_DIRECTION_INBOUND = 0x1,
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PACKET_DIRECTION_OUTBOUND = 0x2,
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PACKET_DIRECTION_UNKNOWN = 0x0,
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} packet_direction_enum;
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/* Packets with correct CRC sum */
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static const value_string preemptive_delim_desc[] = {
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{ SMD_PP_Start_0, "[Non-fragmented packet: SMD-S0]" },
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@ -144,6 +150,15 @@ static const value_string initial_delim_desc[] = {
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{ 0x0, NULL }
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};
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/* Packets with incorrect checksum */
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static const value_string corrupted_delim_desc[] = {
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{ SMD_PP_Start_0, "[Corrupted fragment: SMD-S0]" },
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{ SMD_PP_Start_1, "[Corrupted fragment: SMD-S1]" },
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{ SMD_PP_Start_2, "[Corrupted fragment: SMD-S2]" },
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{ SMD_PP_Start_3, "[Corrupted fragment: SMD-S3]" },
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{ 0x0, NULL }
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};
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static const value_string continuation_delim_desc[] = {
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{ SMD_PP_ContFrag_0, "[Continuation fragment: SMD-C0]" },
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{ SMD_PP_ContFrag_1, "[Continuation fragment: SMD-C1]" },
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@ -227,6 +242,19 @@ get_crc_stat(tvbuff_t *tvb, guint32 crc, guint32 mcrc) {
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return crc_val;
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}
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static fpp_crc_t
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get_express_crc_stat(tvbuff_t *tvb, guint32 express_crc) {
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fpp_crc_t crc_val;
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guint32 received_crc = tvb_get_guint32(tvb, tvb_reported_length(tvb) - FPP_CRC_LENGTH, ENC_BIG_ENDIAN);
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if (received_crc == express_crc) {
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crc_val = CRC_CRC;
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} else {
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crc_val = CRC_FALSE;
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}
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return crc_val;
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}
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static fpp_packet_t
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get_packet_type(tvbuff_t *tvb) {
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/* function analyze a packet based on preamble and ignore crc */
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@ -294,10 +322,12 @@ col_fstr_process(tvbuff_t *tvb, packet_info *pinfo, fpp_crc_t crc_val) {
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col_add_str(pinfo->cinfo, COL_INFO, "[Respond]");
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break;
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case FPP_Packet_Init:
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if ((crc_val == CRC_CRC) || (crc_val == CRC_FALSE))
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col_add_fstr(pinfo->cinfo, COL_INFO, "%s", try_val_to_str(tvb_get_guint8(tvb, preamble_length-1), preemptive_delim_desc));
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if (crc_val == CRC_CRC)
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col_add_fstr(pinfo->cinfo, COL_INFO, "%s", try_val_to_str(tvb_get_guint8(tvb, preamble_length-1), preemptive_delim_desc));
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else if (crc_val == CRC_mCRC)
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col_add_fstr(pinfo->cinfo, COL_INFO, "%s", try_val_to_str(tvb_get_guint8(tvb, preamble_length-1), initial_delim_desc));
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else
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col_add_fstr(pinfo->cinfo, COL_INFO, "%s", try_val_to_str(tvb_get_guint8(tvb, preamble_length-1), initial_delim_desc));
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col_add_fstr(pinfo->cinfo, COL_INFO, "%s", try_val_to_str(tvb_get_guint8(tvb, preamble_length-1), corrupted_delim_desc));
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break;
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case FPP_Packet_Cont:
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col_add_fstr(pinfo->cinfo, COL_INFO, "%s %s", try_val_to_str(tvb_get_guint8(tvb, preamble_length-2), continuation_delim_desc),
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@ -313,16 +343,32 @@ struct _fpp_ctx_t {
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guint8 frame_cnt;
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guint8 frag_cnt;
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guint32 size;
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guint32 crc;
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wmem_map_t *crc_history;
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};
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typedef struct _fpp_ctx_t fpp_ctx_t;
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static packet_direction_enum
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get_packet_direction(packet_info *pinfo) {
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switch (pinfo->p2p_dir) {
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case P2P_DIR_RECV:
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return PACKET_DIRECTION_INBOUND;
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case P2P_DIR_SENT:
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return PACKET_DIRECTION_OUTBOUND;
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default:
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return PACKET_DIRECTION_UNKNOWN;
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}
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}
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static void
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init_fpp_ctx(struct _fpp_ctx_t *ctx, guint8 frame_cnt) {
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init_fpp_ctx(struct _fpp_ctx_t *ctx, guint8 frame_cnt, guint32 crc) {
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ctx->preemption = TRUE;
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ctx->frame_cnt = frame_cnt;
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ctx->frag_cnt = FragCount_3;
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ctx->size = 0;
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ctx->crc = crc;
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ctx->crc_history = wmem_map_new(wmem_epan_scope(), g_int_hash, g_int_equal);
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}
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static guint8
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@ -375,26 +421,12 @@ static void
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drop_fragments(packet_info *pinfo) {
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tvbuff_t *tvbuf;
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guint interface_id;
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guint packet_direction;
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switch (pinfo->p2p_dir) {
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case P2P_DIR_RECV:
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packet_direction = 0x1;
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break;
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case P2P_DIR_SENT:
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packet_direction = 0x2;
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break;
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case P2P_DIR_UNKNOWN:
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packet_direction = 0x0;
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break;
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default:
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packet_direction = 0x0;
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}
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packet_direction_enum packet_direction = get_packet_direction(pinfo);
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if (pinfo->rec->presence_flags & WTAP_HAS_INTERFACE_ID)
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interface_id = pinfo->rec->rec_header.packet_header.interface_id;
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interface_id = pinfo->rec->rec_header.packet_header.interface_id;
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else
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interface_id = 0;
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interface_id = 0;
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interface_id = interface_id << 0x2;
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tvbuf = fragment_delete(&fpp_reassembly_table, pinfo, interface_id | packet_direction, NULL);
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@ -403,21 +435,17 @@ drop_fragments(packet_info *pinfo) {
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}
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}
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static tvbuff_t *
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dissect_preemption(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32 crc, fpp_crc_t crc_val) {
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static tvbuff_t*
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dissect_preemption(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) {
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fpp_packet_t pck_type;
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guint preamble_length = get_preamble_length( tvb );
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guint preamble_bit_length = preamble_length * 8;
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gboolean preamble_unaligned = FALSE;
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guint8 smd1 = tvb_get_guint8(tvb, preamble_length - 2);
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guint8 smd2 = tvb_get_guint8(tvb, preamble_length - 1);
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guint32 mcrc = crc ^ 0xffff0000;
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guint crc_offset = tvb_reported_length(tvb) - FPP_CRC_LENGTH;
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gint frag_size = tvb_reported_length(tvb) - preamble_length - FPP_CRC_LENGTH;
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@ -428,31 +456,17 @@ dissect_preemption(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32
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conversation_t *conv;
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fpp_ctx_t *ctx;
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guint interface_id;
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guint packet_direction;
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packet_direction_enum packet_direction = get_packet_direction(pinfo);
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fpp_crc_t crc_val;
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switch (pinfo->p2p_dir) {
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case P2P_DIR_RECV:
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packet_direction = 0x1;
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break;
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case P2P_DIR_SENT:
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packet_direction = 0x2;
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break;
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case P2P_DIR_UNKNOWN:
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packet_direction = 0x0;
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break;
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default:
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packet_direction = 0x0;
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}
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/* mCRC calculations needs previous crc */
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guint32 crc, mcrc, prev_crc;
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if (pinfo->rec->presence_flags & WTAP_HAS_INTERFACE_ID)
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interface_id = pinfo->rec->rec_header.packet_header.interface_id;
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interface_id = pinfo->rec->rec_header.packet_header.interface_id;
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else
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interface_id = 0;
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interface_id = 0;
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interface_id = interface_id << 0x2;
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conv = find_conversation_by_id(pinfo->num, ENDPOINT_NONE, interface_id | packet_direction, 0);
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if (!conv) {
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conv = conversation_new_by_id(pinfo->num, ENDPOINT_NONE, interface_id | packet_direction, 0);
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}
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/* Create a tree for the preamble. */
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proto_item *ti_preamble = proto_tree_add_item(tree, hf_fpp_preamble, tvb, 0, preamble_length, ENC_NA);
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@ -480,7 +494,9 @@ dissect_preemption(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32
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proto_tree_add_item(fpp_preamble_tree, hf_fpp_preamble_pad, tvb, 0, 1, ENC_BIG_ENDIAN);
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}
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if(get_packet_type(tvb) == FPP_Packet_Cont)
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pck_type = get_packet_type(tvb);
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if(pck_type == FPP_Packet_Cont)
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{
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proto_item *ti_smd = proto_tree_add_item(fpp_preamble_tree, hf_fpp_preamble_smd, tvb, preamble_length - 2, 1, ENC_BIG_ENDIAN);
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proto_item *ti_fragcnt = proto_tree_add_item(fpp_preamble_tree, hf_fpp_preamble_frag_count, tvb, preamble_length - 1, 1, ENC_BIG_ENDIAN);
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@ -493,10 +509,58 @@ dissect_preemption(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32
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proto_item_append_text(ti_smd, " %s", try_val_to_str(tvb_get_guint8(tvb, preamble_length-1), delim_desc) );
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}
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pck_type = get_packet_type(tvb);
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prev_crc = 0;
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conv = find_conversation_by_id(pinfo->num, ENDPOINT_NONE, interface_id | packet_direction, 0);
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/* Create a conversation at every SMD-S fragment.
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Find the conversation for every SMD-C fragment.*/
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if (pck_type == FPP_Packet_Init) {
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/* will be used for seeding the crc calculation */
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if (!PINFO_FD_VISITED(pinfo)) {
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conv = conversation_new_by_id(pinfo->num, ENDPOINT_NONE, interface_id | packet_direction, 0);
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find_conversation_pinfo(pinfo, 0);
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}
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}
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else if (pck_type == FPP_Packet_Cont) {
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if (conv) {
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ctx = (fpp_ctx_t *)conversation_get_proto_data(conv, proto_fpp);
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if (ctx) {
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if (!PINFO_FD_VISITED(pinfo)) {
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if ((ctx->preemption) && (ctx->frame_cnt == smd1) && (frag_cnt_next(ctx->frag_cnt) == smd2)) {
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prev_crc = ctx->crc;
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}
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/* create a copy of frame number and previous crc and store in crc_history */
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guint32 *copy_of_pinfo_num = wmem_new(wmem_epan_scope(), guint32);
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guint32 *copy_of_prev_crc = wmem_new(wmem_epan_scope(), guint32);
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*copy_of_pinfo_num = pinfo->num;
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*copy_of_prev_crc = prev_crc;
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wmem_map_insert(ctx->crc_history, copy_of_pinfo_num, copy_of_prev_crc);
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}
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else {
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prev_crc = *(guint32 *)wmem_map_lookup(ctx->crc_history, &pinfo->num);
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}
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}
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}
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}
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crc = GUINT32_SWAP_LE_BE(crc32_ccitt_tvb_offset_seed(tvb, preamble_length, frag_size, GUINT32_SWAP_LE_BE(prev_crc) ^ 0xffffffff));
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mcrc = crc ^ 0xffff0000;
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crc_val = get_crc_stat(tvb, crc, mcrc); /* might be crc if last part or mcrc if continuation */
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/* fill column Info */
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col_fstr_process(tvb, pinfo, crc_val);
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if (pck_type == FPP_Packet_Init) {
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/* Add data to this new conversation during first iteration*/
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if (!PINFO_FD_VISITED(pinfo)) {
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ctx = wmem_new(wmem_file_scope(), struct _fpp_ctx_t);
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init_fpp_ctx(ctx, get_cont_by_start(smd2), crc);
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ctx->size = frag_size;
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conversation_add_proto_data(conv, proto_fpp, ctx);
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}
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if (crc_val == CRC_CRC) {
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/* Non-fragmented packet */
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/* Non-fragmented packet
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end of continuation */
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drop_fragments(pinfo);
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if (!PINFO_FD_VISITED(pinfo)) {
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@ -506,20 +570,12 @@ dissect_preemption(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32
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proto_tree_add_checksum(tree, tvb, crc_offset, hf_fpp_crc32, hf_fpp_crc32_status, &ei_fpp_crc32, pinfo, crc, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
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return tvb_new_subset_length(tvb, preamble_length, frag_size);
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} else if (crc_val == CRC_mCRC) {
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/* Init frag */
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}
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else if (crc_val == CRC_mCRC) {
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/* First fragment */
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drop_fragments(pinfo);
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if (!PINFO_FD_VISITED(pinfo)) {
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// Fist delete previous conversation
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drop_conversation(conv);
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ctx = wmem_new(wmem_file_scope(), struct _fpp_ctx_t);
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init_fpp_ctx(ctx, get_cont_by_start(smd2));
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ctx->size = frag_size;
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conversation_add_proto_data(conv, proto_fpp, ctx);
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}
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fragment_add_check(&fpp_reassembly_table,
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frag_data = fragment_add_check(&fpp_reassembly_table,
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tvb, preamble_length, pinfo, interface_id | packet_direction, NULL,
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0, frag_size, TRUE);
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@ -529,60 +585,64 @@ dissect_preemption(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32
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set_address_tvb(&pinfo->src, AT_ETHER, 6, tvb, 14);
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proto_tree_add_checksum(tree, tvb, crc_offset, hf_fpp_mcrc32, hf_fpp_mcrc32_status, &ei_fpp_mcrc32, pinfo, mcrc, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
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} else {
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/* Invalid packet */
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drop_fragments(pinfo);
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if (!PINFO_FD_VISITED(pinfo)) {
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drop_conversation(conv);
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if (frag_data != NULL) {
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col_append_frame_number(pinfo, COL_INFO, " [Reassembled in #%u]", frag_data->reassembled_in);
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process_reassembled_data(tvb, preamble_length, pinfo,
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"Reassembled FPP", frag_data, &fpp_frag_items,
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NULL, tree);
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}
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} else {
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/* Possibly first fragment */
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drop_fragments(pinfo);
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proto_tree_add_checksum(tree, tvb, crc_offset, hf_fpp_mcrc32, hf_fpp_mcrc32_status, &ei_fpp_mcrc32, pinfo, mcrc, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
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}
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} else if (pck_type == FPP_Packet_Cont) {
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if (crc_val == CRC_mCRC) {
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/* Continuation frag */
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/* Continuation fragment */
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/* Update data of this conversation */
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if (!PINFO_FD_VISITED(pinfo)) {
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ctx = (fpp_ctx_t*)conversation_get_proto_data(conv, proto_fpp);
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if ((ctx) && (ctx->preemption) && (ctx->frame_cnt == smd1) && (frag_cnt_next(ctx->frag_cnt) == smd2)) {
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if (ctx) {
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fpp_pdata_t *fpp_pdata = wmem_new(wmem_file_scope(), fpp_pdata_t);
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fpp_pdata->offset = ctx->size;
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p_add_proto_data(wmem_file_scope(), pinfo, proto_fpp, interface_id | packet_direction, fpp_pdata);
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ctx->size += frag_size;
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ctx->frag_cnt = smd2;
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} else {
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// There is no conversation or ctx is wrong
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drop_conversation(conv);
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ctx->crc = crc;
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}
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}
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proto_tree_add_checksum(tree, tvb, crc_offset, hf_fpp_mcrc32, hf_fpp_mcrc32_status, &ei_fpp_mcrc32, pinfo, mcrc, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
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fpp_pdata_t *fpp_pdata = (fpp_pdata_t *)p_get_proto_data(wmem_file_scope(), pinfo, proto_fpp, interface_id | packet_direction);
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if (fpp_pdata) {
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fragment_add_check(&fpp_reassembly_table,
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tvb, preamble_length, pinfo, interface_id | packet_direction, NULL,
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fpp_pdata->offset, frag_size, TRUE);
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frag_data = fragment_add_check(&fpp_reassembly_table,
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tvb, preamble_length, pinfo, interface_id | packet_direction, NULL,
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fpp_pdata->offset, frag_size, TRUE);
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if (frag_data != NULL) {
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col_append_frame_number(pinfo, COL_INFO, " [Reassembled in #%u]", frag_data->reassembled_in);
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process_reassembled_data(tvb, preamble_length, pinfo,
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"Reassembled FPP", frag_data, &fpp_frag_items,
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NULL, tree);
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}
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} else {
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drop_fragments(pinfo);
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}
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proto_tree_add_checksum(tree, tvb, crc_offset, hf_fpp_mcrc32, hf_fpp_mcrc32_status, &ei_fpp_mcrc32, pinfo, mcrc, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
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} else {
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} else if (crc_val == CRC_CRC) {
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/* Suppose that the last fragment dissected
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1. preemption is active
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2. check frame count and frag count values
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After these steps check crc of entire reassembled frame
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*/
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if (!PINFO_FD_VISITED(pinfo)) {
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ctx = (fpp_ctx_t*)conversation_get_proto_data(conv, proto_fpp);
|
||||
if ((ctx) && (ctx->preemption) && (ctx->frame_cnt == smd1) && (frag_cnt_next(ctx->frag_cnt) == smd2)) {
|
||||
fpp_pdata_t *fpp_pdata = wmem_new(wmem_file_scope(), fpp_pdata_t);
|
||||
ctx = (fpp_ctx_t*)conversation_get_proto_data(conv, proto_fpp);
|
||||
if ((ctx) && (ctx->preemption) && (ctx->frame_cnt == smd1) && (frag_cnt_next(ctx->frag_cnt) == smd2)) {
|
||||
fpp_pdata_t *fpp_pdata = wmem_new(wmem_file_scope(), fpp_pdata_t);
|
||||
if (!PINFO_FD_VISITED(pinfo)) {
|
||||
fpp_pdata->offset = ctx->size;
|
||||
p_add_proto_data(wmem_file_scope(), pinfo, proto_fpp, interface_id | packet_direction, fpp_pdata);
|
||||
}
|
||||
|
||||
drop_conversation(conv);
|
||||
}
|
||||
|
||||
fpp_pdata_t *fpp_pdata = (fpp_pdata_t *)p_get_proto_data(wmem_file_scope(), pinfo, proto_fpp, interface_id | packet_direction);
|
||||
|
|
@ -614,9 +674,26 @@ dissect_preemption(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32
|
|||
/* Reassembly was unsuccessful; show this fragment. This may
|
||||
just mean that we don't yet have all the fragments, so
|
||||
we should not just continue dissecting. */
|
||||
proto_tree_add_checksum(tree, tvb, crc_offset, hf_fpp_mcrc32, hf_fpp_mcrc32_status, &ei_fpp_mcrc32, pinfo, crc, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
|
||||
return NULL;
|
||||
}
|
||||
} else {
|
||||
/* Invalid packet */
|
||||
if (!PINFO_FD_VISITED(pinfo)) {
|
||||
ctx = (fpp_ctx_t *)conversation_get_proto_data(conv, proto_fpp);
|
||||
if (ctx) {
|
||||
fpp_pdata_t *fpp_pdata = wmem_new(wmem_file_scope(), fpp_pdata_t);
|
||||
fpp_pdata->offset = ctx->size;
|
||||
p_add_proto_data(wmem_file_scope(), pinfo, proto_fpp, interface_id | packet_direction, fpp_pdata);
|
||||
|
||||
ctx->size += frag_size;
|
||||
ctx->frag_cnt = smd2;
|
||||
ctx->crc = crc;
|
||||
}
|
||||
}
|
||||
proto_tree_add_checksum(tree, tvb, crc_offset, hf_fpp_mcrc32, hf_fpp_mcrc32_status, &ei_fpp_mcrc32, pinfo, mcrc, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
|
||||
}
|
||||
|
||||
} else if (pck_type == FPP_Packet_Verify) {
|
||||
proto_tree_add_checksum(tree, tvb, crc_offset, hf_fpp_mcrc32, -1, &ei_fpp_mcrc32, pinfo, mcrc, ENC_BIG_ENDIAN, PROTO_CHECKSUM_VERIFY);
|
||||
} else if (pck_type == FPP_Packet_Response) {
|
||||
|
|
@ -677,7 +754,7 @@ dissect_express(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32 crc
|
|||
static int
|
||||
dissect_fpp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
|
||||
{
|
||||
guint32 crc, mcrc;
|
||||
guint32 express_crc;
|
||||
fpp_crc_t crc_val;
|
||||
tvbuff_t *next = tvb;
|
||||
guint preamble_length = get_preamble_length( tvb );
|
||||
|
|
@ -686,28 +763,28 @@ dissect_fpp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
|
|||
col_set_str(pinfo->cinfo, COL_PROTOCOL, "FPP");
|
||||
col_clear(pinfo->cinfo,COL_INFO);
|
||||
|
||||
crc = GUINT32_SWAP_LE_BE(crc32_ccitt_tvb_offset(tvb, preamble_length, pdu_data_len));
|
||||
mcrc = crc ^ 0xffff0000;
|
||||
|
||||
// get crc type
|
||||
crc_val = get_crc_stat(tvb, crc, mcrc);
|
||||
|
||||
// fill column Info
|
||||
col_fstr_process(tvb, pinfo, crc_val);
|
||||
|
||||
proto_item *ti = proto_tree_add_item(tree, proto_fpp, tvb, 0, -1, ENC_NA);
|
||||
|
||||
proto_tree *fpp_tree = proto_item_add_subtree(ti, ett_fpp);
|
||||
|
||||
switch (get_packet_type(tvb)) {
|
||||
case FPP_Packet_Expess:
|
||||
next = dissect_express(tvb, pinfo, fpp_tree, crc, crc_val);
|
||||
/* this is the old crc calculation which is only valid for express frames */
|
||||
express_crc = GUINT32_SWAP_LE_BE(crc32_ccitt_tvb_offset(tvb, preamble_length, pdu_data_len));
|
||||
|
||||
/* is express_crc valid */
|
||||
crc_val = get_express_crc_stat(tvb, express_crc);
|
||||
|
||||
/* fill column Info */
|
||||
col_fstr_process(tvb, pinfo, crc_val);
|
||||
|
||||
next = dissect_express(tvb, pinfo, fpp_tree, express_crc, crc_val);
|
||||
break;
|
||||
case FPP_Packet_Init:
|
||||
case FPP_Packet_Cont:
|
||||
case FPP_Packet_Verify:
|
||||
case FPP_Packet_Response:
|
||||
next = dissect_preemption(tvb, pinfo, fpp_tree, crc, crc_val);
|
||||
next = dissect_preemption(tvb, pinfo, fpp_tree);
|
||||
break;
|
||||
default:
|
||||
break;
|
||||
|
|
|
|||
Loading…
Reference in New Issue