send_message
t->vtbl->send_message(NULL, t);
t->virtual->vtbl->send_message(msg, 0);
int (*send_message) (struct message *, struct transport *);
return v->encap->vtbl->send_message(msg, v->encap);
return v->main->vtbl->send_message(msg, v->main);
send_message(&ibuf, &msg, sizeof msg, fd);
send_message(&ibuf, &ack, sizeof ack, -1);
static void send_message(struct imsgbuf *, void *, size_t, int);