hostapd: account for subseconds when checking rule rates

[Scott Cheloha]

Hi,

You need to account for subsecond differences when evaluating
a rule rate, otherwise you'll reset f_rate_cnt prematurely in
some cases.

e.g.:

        t_now = { .tv_sec = 100, .tv_usec = 250000 };
        frame->f_last = { .tv_sec = 99, .tv_usec = 750000 };
        frame->f_rate_intval = 1;

        /* true */
        t_now.tv_sec - frame->f_last.tv_sec >= frame->f_rate_intval

        /* and yet ... */
        struct timeval t_diff;
        timersub(&t_now, &frame->f_last, &t_diff);

        /* also true */
        t_diff.tv_sec < frame->f_rate_intval

ok?

--
Scott Cheloha

Index: usr.sbin/hostapd/handle.c
===================================================================
RCS file: /cvs/src/usr.sbin/hostapd/handle.c,v
retrieving revision 1.12
diff -u -p -r1.12 handle.c
--- usr.sbin/hostapd/handle.c   16 Jan 2015 06:40:17 -0000      1.12
+++ usr.sbin/hostapd/handle.c   14 Feb 2018 19:34:49 -0000
@@ -114,7 +114,7 @@ hostapd_handle_frame(struct hostapd_apme
        struct hostapd_ieee80211_frame *mh;
        struct hostapd_radiotap rtap;
        u_int8_t *wfrom, *wto, *wbssid;
-       struct timeval t_now;
+       struct timeval t_diff, t_now;
        u_int32_t flags;
        int offset, min_rate = 0, val;
 
@@ -247,7 +247,8 @@ hostapd_handle_frame(struct hostapd_apme
 
        /* Handle optional minimal rate */
        if (frame->f_rate && frame->f_rate_intval) {
-               frame->f_rate_delay = t_now.tv_sec - frame->f_last.tv_sec;
+               timersub(&t_now, &frame->f_last, &t_diff);
+               frame->f_rate_delay = t_diff.tv_sec;
                if (frame->f_rate_delay < frame->f_rate_intval) {
                        frame->f_rate_cnt++;
                        if (frame->f_rate_cnt < frame->f_rate)