README.md

   1 # udebug - OpenWrt debugging infrastructure
   2
   3 udebug assists whole-system debugging by making it easy to provide ring buffers
   4 with debug data and make them accessible through a unified API.
   5 Through the CLI, you can either create snapshots of data with a specific duration,
   6 or stream data in real time. The data itself is stored in .pcapng files, which can
   7 contain a mix of packets and log messages.
   8
   9 ## libudebug C API
  10
  11 #### `void udebug_init(struct udebug *ctx)`
  12
  13 Initializes the udebug context. Must be called before adding buffers.
  14
  15 #### `int udebug_connect(struct udebug *ctx, const char *path)`
  16
  17 Connect to udebugd and submit any buffers that were added using `udebug_buf_add`.
  18
  19 #### `void udebug_auto_connect(struct udebug *ctx, const char *path)`
  20
  21 Connects and automatically reconnects to udebugd. Uses uloop and calls `udebug_add_uloop`.
  22
  23 #### `void udebug_free(struct udebug *ctx)`
  24
  25 Frees the udebug context and all added created buffers.
  26
  27 #### `int udebug_buf_init(struct udebug_buf *buf, size_t entries, size_t size)`
  28
  29 Allocates a buffer with a given size. Entries and size are rounded up internally to the
  30 nearest power-of-2.
  31
  32 #### `int udebug_buf_add(struct udebug *ctx, struct udebug_buf *buf, const struct udebug_buf_meta *meta);`
  33
  34 Submits the buffer to udebugd and makes it visible.
  35
  36 #### `void udebug_buf_free(struct udebug_buf *buf)`
  37
  38 Removes the buffer from udebugd and frees it.
  39
  40 #### `void udebug_entry_init(struct udebug_buf *buf)`
  41
  42 Initializes a new entry on the ring buffer.
  43
  44 #### `void *udebug_entry_append(struct udebug_buf *buf, const void *data, uint32_t len)`
  45
  46 Appends data to the ring buffer. When called with data == NULL, space is only
  47 reserved, and the return value provides a pointer with len bytes that can be
  48 written to.
  49
  50 #### `int udebug_entry_printf(struct udebug_buf *buf, const char *fmt, ...)`
  51
  52 Appends a string to the buffer, based on format string + arguments (like printf)
  53
  54 #### `int udebug_entry_vprintf(struct udebug_buf *buf, const char *fmt, va_list ap)`
  55
  56 Like `udebug_entry_printf()`
  57
  58 #### `void udebug_entry_add(struct udebug_buf *buf)`
  59
  60 Finalizes and publishes the entry on the ring buffer.
  61
  62 ### Simple example
  63
  64 ```
  65 static struct udebug ud;
  66 static struct udebug_buf udb;
  67
  68 /* ... */
  69
  70 uloop_init();
  71 udebug_init(&ud);
  72 udebug_auto_connect(&ud, NULL);
  73
  74 static const struct udebug_buf_meta buf_meta = {
  75         .name = "counter",
  76         .format = UDEBUG_FORMAT_STRING,
  77 };
  78
  79 int entries = 128;
  80 int data_size = 1024;
  81
  82 udebug_buf_init(&udb, entries, data_size);
  83 udebug_buf_add(&ud, &udb, &buf_meta);
  84
  85 /* ... */
  86
  87 udebug_entry_init(&udb); // initialize entry
  88 udebug_entry_printf(&udb, "count=%d", count++);
  89 udebug_entry_add(&udb); // finalize the entry
  90
  91 ```
  92
  93 ## udebug CLI
  94
  95 ```
  96 Usage: udebug-cli [<options>] <command> [<args>]
  97
  98   Options:
  99     -f                          Ignore errors on opening rings
 100     -d <duration>:              Only fetch data up to <duration> seconds old
 101     -o <file>|-                 Set output file for snapshot/stream (or '-' for stdout)
 102     -i <process>[:<name>]       Select debug buffer for snapshot/stream
 103     -s <path>                   Use udebug socket <path>
 104     -q                          Suppress warnings/error messages
 105
 106   Commands:
 107     list:                       List available debug buffers
 108     snapshot:                   Create a pcapng snapshot of debug buffers
 109     set_flag [<name>=0|1 ...]   Set ring buffer flags
 110     get_flags                   Get ring buffer flags
 111
 112 ```
 113