Function sta_pick_bss

freebsd/net80211/ieee80211_scan_sta.c:1258–1320

* Pick an ap or ibss network to join or find a channel * to use to start an ibss network. */

 * to use to start an ibss network.
 */
static int
sta_pick_bss(struct ieee80211_scan_state *ss, struct ieee80211vap *vap)
{
	struct sta_table *st = ss->ss_priv;
	struct sta_entry *selbs;
	struct ieee80211_channel *chan;

	KASSERT(vap->iv_opmode == IEEE80211_M_STA,
		("wrong mode %u", vap->iv_opmode));

	if (st->st_newscan) {
		sta_update_notseen(st);
		st->st_newscan = 0;
	}
	if (ss->ss_flags & IEEE80211_SCAN_NOPICK) {
		/*
		 * Manual/background scan, don't select+join the
		 * bss, just return.  The scanning framework will
		 * handle notification that this has completed.
		 */
		ss->ss_flags &= ~IEEE80211_SCAN_NOPICK;
		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
		    "%s: nopick; return 1\n", __func__);
		return 1;
	}
	/*
	 * Automatic sequencing; look for a candidate and
	 * if found join the network.
	 */
	/* NB: unlocked read should be ok */
	if (TAILQ_FIRST(&st->st_entry) == NULL) {
		IEEE80211_DPRINTF(vap, IEEE80211_MSG_SCAN,
			"%s: no scan candidate, join=%d, return 0\n",
			__func__,
			!! (ss->ss_flags & IEEE80211_SCAN_NOJOIN));
		if (ss->ss_flags & IEEE80211_SCAN_NOJOIN)
			return 0;
notfound:
		/*
		 * If nothing suitable was found decrement
		 * the failure counts so entries will be
		 * reconsidered the next time around.  We
		 * really want to do this only for sta's
		 * where we've previously had some success.
		 */
		sta_dec_fails(st);
		st->st_newscan = 1;
		return 0;			/* restart scan */
	}
	selbs = select_bss(ss, vap, IEEE80211_MSG_SCAN);
	if (ss->ss_flags & IEEE80211_SCAN_NOJOIN)
		return (selbs != NULL);
	if (selbs == NULL)
		goto notfound;
	chan = selbs->base.se_chan;
	if (selbs->se_flags & STA_DEMOTE11B)
		chan = demote11b(vap, chan);
	if (!ieee80211_sta_join(vap, chan, &selbs->base))