The tnfctl_trace_attrs_get() function returns the trace attributes associated with hndl in attrs. The trace attributes can be changed by some of the other interfaces in libtnfctl(3TNF). It is the client's responsibility to use tnfctl_trace_attrs_get() to get the new trace attributes after use of interfaces that change them. Typically, a client will use tnfctl_trace_attrs_get() after a call to tnfctl_continue(3TNF) in order to make sure that tracing is still working. See the discussion of trace_buf_state that follows.

Trace attributes are represented by the struct tnfctl_trace_attrs structure defined in <tnf/tnfctl.h>:

struct tnfctl_trace_attrs {
pid_t              targ_pid;           /* not kernel mode */
const char         *trace_file_name;   /* not kernel mode */
size_t             trace_buf_size;
size_t             trace_min_size;
tnfctl_bufstate_t  trace_buf_state;
boolean_t          trace_state;
boolean_t          filter_state;       /* kernel mode only */
long               pad;
};

The semantics of the individual members of attrs are:

targ_pid

The process id of the target process. This is not valid for kernel tracing.

trace_file_name

The name of the trace file to which the target writes. trace_file_name will be NULL if no trace file exists or if kernel tracing is implemented. This pointer should not be used after calling other libtnfctl interfaces. The client should copy this string if it should be saved for the use of other libtnfctl interfaces.

trace_buf_size

The size of the trace buffer or file in bytes.

trace_min_size

The minimum size in bytes of the trace buffer that can be allocated by using the tnfctl_buffer_alloc(3TNF) interface.

trace_buf_state

The state of the trace buffer. TNFCTL_BUF_OK indicates that a trace buffer has been allocated. TNFCTL_BUF_NONE indicates that no buffer has been allocated. TNFCTL_BUF_BROKEN indicates that there is an internal error in the target for tracing. The target will continue to run correctly, but no trace records will be written. To fix tracing, restart the process. For kernel tracing, deallocate the existing buffer with tnfctl_buffer_dealloc(3TNF) and allocate a new one with tnfctl_buffer_alloc(3TNF).

trace_state

The global tracing state of the target. Probes that are enabled will not write out data unless this state is on. This state is off by default for the kernel and can be changed by tnfctl_trace_state_set(3TNF). For a process, this state is on by default and can only be changed by tnf_process_disable(3TNF) and tnf_process_enable(3TNF).

filter_state

The state of process filtering. For kernel probe control, it is possible to select a set of processes for which probes are enabled. See tnfctl_filter_list_get(3TNF), tnfctl_filter_list_add(3TNF), and tnfctl_filter_list_delete(3TNF). No trace output will be written when other processes traverse these probe points. By default process filtering is off, and all processes cause the generation of trace records when they hit an enabled probe. Use tnfctl_filter_state_set(3TNF) to change the filter state.

The tnfctl_trace_attrs_get() function returns TNFCTL_ERR_NONE upon success.

The tnfctl_trace_attrs_get() function will fail if:

TNFCTL_ERR_INTERNAL

An internal error occurred.

See attributes(5) for descriptions of the following attributes:

prex(1), TNF_PROBE(3TNF), libtnfctl(3TNF), tnfctl_buffer_alloc(3TNF), tnfctl_continue(3TNF), tnfctl_filter_list_get (3TNF), tnf_process_disable(3TNF), tracing(3TNF), attributes(5)