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USBLL: Code commenting and alignment 

Following changes in the file:
1. Explain usbll_address_t and usbll_data_t.
2. Grouping header fields belonging to the same type of packets.
3. Removed unnecessary condition check for usbll_data pointer
   in dissect_usbll_data function.
4. Brief comments on the Macros.
5. Correct code indentation at a few places.

Signed-off-by: Ameya Deshpande <ameyanrd@outlook.com>
This commit is contained in:
Ameya Deshpande 2020-09-18 17:19:47 +05:30 committed by AndersBroman
parent ddd3910709
commit 3ec16de87b
1 changed files with 104 additions and 64 deletions
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168
epan/dissectors/packet-usbll.c
View File

@ -142,10 +142,11 @@ static const value_string usb_endpoint_type_vals[] = {
{0, NULL}
};
/* Macros for Token Packets. */
#define TOKEN_BITS_GET_ADDRESS(bits) (bits & 0x007F)
#define TOKEN_BITS_GET_ENDPOINT(bits) ((bits & 0x0780) >> 7)
/* Macros for Split Packets. */
#define SPLIT_BITS_GET_HUB_ADDRESS(bits) (guint8)(bits & 0x007F)
#define SPLIT_BITS_GET_HUB_PORT(bits) (guint8)((bits & 0x7F00) >> 8)
#define SPLIT_BITS_GET_ENDPOINT_TYPE(bits) ((bits & 0x060000) >> 17)
@ -153,6 +154,9 @@ static const value_string usb_endpoint_type_vals[] = {
#define SPLIT_BIT_E_U 0x10000
#define SPLIT_BIT_START_COMPLETE 0x0080
/* Bitmasks definitions for usbll_address_t flags
* and 'flags' parameter of usbll_set_address function.
*/
#define USBLL_ADDRESS_STANDARD 0
#define USBLL_ADDRESS_HOST 0x01
#define USBLL_ADDRESS_HUB_PORT 0x02
@ -166,16 +170,41 @@ static const value_string usb_endpoint_type_vals[] = {
#define USBLL_ADDRESS_IS_HOST_TO_DEV(flags) \
(!USBLL_ADDRESS_IS_DEV_TO_HOST(flags))
/* usbll_address_t represents the address
* of Host, Hub and Devices.
*/
typedef struct {
guint8 flags;
guint8 device;
guint8 endpoint;
guint8 flags; /* flags - Contains information if address is
* Host, Hub, Device or Broadcast.
*/
guint8 device; /* device - Device or Hub Address */
guint8 endpoint; /* endpoint - It represents endpoint number for
* Device and port number for Hub.
*/
} usbll_address_t;
/* USB is a stateful protocol. The addresses of Data Packets
* and Handshake Packets depend on the packets before them.
*
* For every packet, we need to store it's source address and
* destination address. We also need to store a reference to
* previous and next packet.
*
* We maintain a static global pointer of the type usbll_data_t.
* Maintaining a pointer instead of a conversation helps in reducing
* memory usage, taking the following advantages:
* 1. Packets are always ordered.
* 2. Addresses of packets only up to last 3 packets are required.
*
* Previous pointer is used in the initial pass to decide the
* source and destination addresses for Data and Handshake packets.
*
* Previous and Next pointers help to idenitfy the transactions and
* invalid sequences. Next pointer is used in the later passes.
*/
typedef struct usbll_data {
guint32 pid;
/* TRUE if Split Complete, FALSE for Split Start */
gboolean is_split_complete;
gboolean is_split_complete; /* TRUE if Split Complete, FALSE for Split Start. */
usbll_address_t src;
usbll_address_t dst;
struct usbll_data *prev;
@ -194,13 +223,13 @@ static int usbll_addr_to_str(const address* addr, gchar *buf, int buf_len)
g_strlcpy(buf, "broadcast", buf_len);
} else if (addrp->flags & USBLL_ADDRESS_HUB_PORT) {
/*
* in split transaction we use : to mark that the last part is port not
* endpoint
* In split transaction we use : to mark that the last part is port not
* endpoint.
*/
g_snprintf(buf, buf_len, "%d:%d", addrp->device,
addrp->endpoint);
} else {
/* Just a standard address.endpoint notation */
/* Just a standard address.endpoint notation. */
g_snprintf(buf, buf_len, "%d.%d", addrp->device,
addrp->endpoint);
}
@ -210,7 +239,7 @@ static int usbll_addr_to_str(const address* addr, gchar *buf, int buf_len)
static int usbll_addr_str_len(const address* addr _U_)
{
return 50; /* The same as for usb */
return 50; /* The same as for usb. */
}
static void
@ -289,7 +318,7 @@ static gint
dissect_usbll_sof(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, gint offset)
{
guint32 frame;
/* SOF Packets are broadcasted from Host to all devices. */
usbll_set_address(tree, tvb, pinfo, 0, 0, USBLL_ADDRESS_HOST_TO_DEV | USBLL_ADDRESS_BROADCAST,
NULL, NULL);
@ -319,7 +348,7 @@ dissect_usbll_token(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, gint of
address_bits = tvb_get_letohs(tvb, offset);
device_address = TOKEN_BITS_GET_ADDRESS(address_bits);
endpoint = TOKEN_BITS_GET_ENDPOINT(address_bits);
/* Tokens SETUP, IN, OUT and PING (special packet) are sent from Host to Device. */
usbll_set_address(tree, tvb, pinfo, device_address, endpoint, USBLL_ADDRESS_HOST_TO_DEV,
&usbll_data_ptr->src, &usbll_data_ptr->dst);
@ -350,17 +379,16 @@ dissect_usbll_data(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int offs
ENC_LITTLE_ENDIAN, PROTO_CHECKSUM_VERIFY);
offset += 2;
if (!usbll_data_ptr)
return offset;
if (usbll_data_ptr->prev) {
if(usbll_data_ptr->prev->pid == USB_PID_TOKEN_IN) {
/* Data packet goes from Device to Host. */
usbll_set_address(tree, tvb, pinfo,
usbll_data_ptr->prev->dst.device,
usbll_data_ptr->prev->dst.endpoint,
USBLL_ADDRESS_DEV_TO_HOST,
&usbll_data_ptr->src, &usbll_data_ptr->dst);
} else {
/* Data packet goes from Host to Device. */
usbll_set_address(tree, tvb, pinfo,
usbll_data_ptr->prev->dst.device,
usbll_data_ptr->prev->dst.endpoint,
@ -405,10 +433,12 @@ dissect_usbll_split(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, gint of
expert_add_info(pinfo, split_e_u, &ei_invalid_e_u);
} else {
usbll_data_ptr->is_split_complete = FALSE;
/* S/E fields have special meaning for Isochronous OUT transfers */
/* S/E fields have special meaning for Isochronous OUT transfers. */
if (SPLIT_BITS_GET_ENDPOINT_TYPE(tmp) == USB_EP_TYPE_ISOCHRONOUS) {
split_se = proto_tree_add_uint(tree, hf_usbll_split_iso_se, tvb, offset, 3, tmp);
/* Check if S = 0 and E = 0 if
* IN packet comes after Split Start.
*/
if( usbll_data_ptr->next &&
usbll_data_ptr->next->pid == USB_PID_TOKEN_IN &&
(tmp & SPLIT_BIT_SPEED ||
@ -489,7 +519,7 @@ usbll_restore_data(packet_info *pinfo)
static usbll_data_t*
usbll_create_data(packet_info *pinfo, guint32 pid)
{
/* allocate a data structure, as it is the first call on this frame */
/* allocate a data structure, as it is the first call on this frame. */
usbll_data_t *n_data_ptr = wmem_new0(wmem_file_scope(), usbll_data_t);
p_add_proto_data(wmem_file_scope(), pinfo, proto_usbll, pinfo->num, n_data_ptr);
@ -536,46 +566,47 @@ dissect_usbll_packet(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
usbll_data_ptr = usbll_restore_data(pinfo);
else {
usbll_data_ptr = usbll_create_data(pinfo, pid);
/* Set the next pointer for the previous packet. */
if (usbll_data_ptr->prev)
usbll_data_ptr->prev->next = usbll_data_ptr;
}
switch (pid)
{
case USB_PID_TOKEN_SETUP:
case USB_PID_TOKEN_OUT:
case USB_PID_TOKEN_IN:
case USB_PID_SPECIAL_PING:
offset = dissect_usbll_token(tvb, pinfo, tree, offset);
break;
case USB_PID_TOKEN_SETUP:
case USB_PID_TOKEN_OUT:
case USB_PID_TOKEN_IN:
case USB_PID_SPECIAL_PING:
offset = dissect_usbll_token(tvb, pinfo, tree, offset);
break;
case USB_PID_DATA_DATA0:
case USB_PID_DATA_DATA1:
case USB_PID_DATA_DATA2:
case USB_PID_DATA_MDATA:
offset = dissect_usbll_data(tvb, pinfo, tree, offset);
break;
case USB_PID_DATA_DATA0:
case USB_PID_DATA_DATA1:
case USB_PID_DATA_DATA2:
case USB_PID_DATA_MDATA:
offset = dissect_usbll_data(tvb, pinfo, tree, offset);
break;
case USB_PID_HANDSHAKE_ACK:
case USB_PID_HANDSHAKE_NAK:
case USB_PID_HANDSHAKE_NYET:
case USB_PID_HANDSHAKE_STALL:
offset = dissect_usbll_handshake(tvb, pinfo, tree, offset);
break;
case USB_PID_HANDSHAKE_ACK:
case USB_PID_HANDSHAKE_NAK:
case USB_PID_HANDSHAKE_NYET:
case USB_PID_HANDSHAKE_STALL:
offset = dissect_usbll_handshake(tvb, pinfo, tree, offset);
break;
case USB_PID_TOKEN_SOF:
offset = dissect_usbll_sof(tvb, pinfo, tree, offset);
break;
case USB_PID_TOKEN_SOF:
offset = dissect_usbll_sof(tvb, pinfo, tree, offset);
break;
case USB_PID_SPECIAL_SPLIT:
offset = dissect_usbll_split(tvb, pinfo, tree, offset);
break;
case USB_PID_SPECIAL_PRE_OR_ERR:
break;
case USB_PID_SPECIAL_RESERVED:
break;
default:
break;
case USB_PID_SPECIAL_SPLIT:
offset = dissect_usbll_split(tvb, pinfo, tree, offset);
break;
case USB_PID_SPECIAL_PRE_OR_ERR:
break;
case USB_PID_SPECIAL_RESERVED:
break;
default:
break;
}
if (tvb_reported_length_remaining(tvb, offset) > 0) {
@ -592,11 +623,25 @@ proto_register_usbll(void)
expert_module_t *expert_module;
static hf_register_info hf[] = {
/* Common header fields */
{ &hf_usbll_pid,
{ "PID", "usbll.pid",
FT_UINT8, BASE_HEX|BASE_EXT_STRING, &usb_packetid_vals_ext, 0x00,
"USB Packet ID", HFILL }},
{ &hf_usbll_src,
{ "Source", "usbll.src",
FT_STRING, STR_ASCII, NULL, 0x0,
NULL, HFILL }},
{ &hf_usbll_dst,
{ "Destination", "usbll.dst",
FT_STRING, STR_ASCII, NULL, 0x0,
NULL, HFILL }},
{ &hf_usbll_addr,
{ "Source or Destination", "usbll.addr",
FT_STRING, STR_ASCII, NULL, 0x0,
NULL, HFILL }},
/* Token header fields */
{ &hf_usbll_device_addr,
{ "Address", "usbll.device_addr",
FT_UINT16, BASE_DEC, NULL, 0x007F,
@ -605,6 +650,14 @@ proto_register_usbll(void)
{ "Endpoint", "usbll.endp",
FT_UINT16, BASE_DEC, NULL, 0x0780,
NULL, HFILL }},
/*SOF header field */
{ &hf_usbll_sof_framenum,
{ "Frame Number", "usbll.frame_num",
FT_UINT16, BASE_DEC, NULL, 0x07FF,
NULL, HFILL }},
/* Token and SOF header fields */
{ &hf_usbll_crc5,
{ "CRC5", "usbll.crc5",
FT_UINT16, BASE_HEX, NULL, 0xF800,
@ -613,6 +666,8 @@ proto_register_usbll(void)
{ "CRC5 Status", "usbll.crc5.status",
FT_UINT8, BASE_NONE, VALS(proto_checksum_vals), 0,
NULL, HFILL }},
/* Data header fields */
{ &hf_usbll_data,
{ "Data", "usbll.data",
FT_BYTES, BASE_NONE, NULL, 0,
@ -625,11 +680,8 @@ proto_register_usbll(void)
{ "CRC Status", "usbll.crc16.status",
FT_UINT8, BASE_NONE, VALS(proto_checksum_vals), 0,
NULL, HFILL }},
{ &hf_usbll_sof_framenum,
{ "Frame Number", "usbll.frame_num",
FT_UINT16, BASE_DEC, NULL, 0x07FF,
NULL, HFILL }},
/* Split header fields */
{ &hf_usbll_split_hub_addr,
{ "Hub Address", "usbll.split_hub_addr",
FT_UINT24, BASE_DEC, NULL, 0x00007F,
@ -670,18 +722,6 @@ proto_register_usbll(void)
{ "CRC5 Status", "usbll.split_crc5.status",
FT_UINT8, BASE_NONE, VALS(proto_checksum_vals), 0,
NULL, HFILL }},
{ &hf_usbll_src,
{ "Source", "usbll.src",
FT_STRING, STR_ASCII, NULL, 0x0,
NULL, HFILL }},
{ &hf_usbll_dst,
{ "Destination", "usbll.dst",
FT_STRING, STR_ASCII, NULL, 0x0,
NULL, HFILL }},
{ &hf_usbll_addr,
{ "Source or Destination", "usbll.addr",
FT_STRING, STR_ASCII, NULL, 0x0,
NULL, HFILL }}
};
static ei_register_info ei[] = {