Function sbuf_set_drain

freebsd/kern/subr_sbuf.c:371–381

* Set up a drain function and argument on an sbuf to flush data to * when the sbuf buffer overflows. */

 * when the sbuf buffer overflows.
 */
void
sbuf_set_drain(struct sbuf *s, sbuf_drain_func *func, void *ctx)
{

	assert_sbuf_state(s, 0);
	assert_sbuf_integrity(s);
	KASSERT(func == s->s_drain_func || s->s_len == 0,
	    ("Cannot change drain to %p on non-empty sbuf %p", func, s));
	s->s_drain_func = func;
	s->s_drain_arg = ctx;
}

/*
 * Call the drain and process the return.