From: Oliver Hartkopp <socketcan@hartkopp.net>
To: Guy Harris <gharris@sonic.net>
Cc: wireshark-dev@wireshark.org,
	linux-can@vger.kernel.org,
	Oliver Hartkopp <socketcan@hartkopp.net>
Subject: [PATCH 3/4] socketcan: display len8dlc content for Classical CAN
Date: Mon, 18 Mar 2024 11:46:42 +0100
Message-ID: <20240318104643.24098-4-socketcan@hartkopp.net>
In-Reply-To: <20240318104643.24098-1-socketcan@hartkopp.net>
References: <20240318104643.24098-1-socketcan@hartkopp.net>
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While the Classical CAN frame can transport only 8 byte of data the
4 bit data length code (DLC) has the ability to have a value range
from 0 to 15. To be able to send and receive DLC values from 9 to 15
the struct can_frame contains an additional len8dlc element which
can have values from 9 to 15 when the data length value is 8.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
 epan/dissectors/packet-socketcan.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/epan/dissectors/packet-socketcan.c b/epan/dissectors/packet-socketcan.c
index 2e29484085..4ca0479f79 100644
--- a/epan/dissectors/packet-socketcan.c
+++ b/epan/dissectors/packet-socketcan.c
@@ -33,10 +33,11 @@ static int hf_can_infoent_ext;
 static int hf_can_infoent_std;
 static int hf_can_extflag;
 static int hf_can_rtrflag;
 static int hf_can_errflag;
 static int hf_can_reserved;
+static int hf_can_len8dlc;
 static int hf_can_padding;
 
 static int hf_can_err_tx_timeout;
 static int hf_can_err_lostarb;
 static int hf_can_err_ctrl;
@@ -720,11 +721,12 @@ dissect_socketcan_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, gu
 
         if (can_packet_type == PACKET_TYPE_CAN_FD) {
             proto_tree_add_bitmask_list(can_tree, tvb, CANFD_FLAG_OFFSET, 1, canfd_flag_fields, ENC_NA);
             proto_tree_add_item(can_tree, hf_can_reserved, tvb, CANFD_FLAG_OFFSET+1, 2, ENC_NA);
         } else {
-            proto_tree_add_item(can_tree, hf_can_reserved, tvb, CANFD_FLAG_OFFSET, 3, ENC_NA);
+            proto_tree_add_item(can_tree, hf_can_reserved, tvb, CANFD_FLAG_OFFSET, 2, ENC_NA);
+            proto_tree_add_item(can_tree, hf_can_len8dlc, tvb, CANFD_FLAG_OFFSET+2, 1, ENC_NA);
         }
 
         if (frame_type == LINUX_CAN_ERR) {
             int * const *flag;
             const char *sepa = ": ";
@@ -853,10 +855,12 @@ proto_register_socketcan(void) {
             "Remote Transmission Request Flag", "can.flags.rtr", FT_BOOLEAN, 32, NULL, CAN_RTR_FLAG, NULL, HFILL } },
         { &hf_can_errflag, {
             "Error Message Flag", "can.flags.err", FT_BOOLEAN, 32, NULL, CAN_ERR_FLAG, NULL, HFILL } },
         { &hf_can_len, {
             "Frame-Length", "can.len", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL } },
+        { &hf_can_len8dlc, {
+            "Len 8 DLC", "can.len8dlc", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL } },
         { &hf_can_reserved, {
             "Reserved", "can.reserved", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL } },
         { &hf_can_padding, {
             "Padding", "can.padding", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL } },
         { &hf_canfd_brsflag, {
-- 
2.43.0