2015-07-17 1:04 GMT+03:00 Stefan Sperling <s...@stsp.name>:
> tcpdump currently prints country elements in 802.11 mgmt frames in hex:
>
> country 67 65 32 1 11 30,
>
> This diff makes tcpdump display the decoded form instead:
>
> country 'CA ', channels 1 2 3 4 5 6 7 8 9 10, max TX power 30dB
>
> Also show the power constraint which needs to be subtraced from
> max TX power to get the actual allowed TX power value.
>
> ok?
>
> Index: print-802_11.c
> ===================================================================
> RCS file: /cvs/src/usr.sbin/tcpdump/print-802_11.c,v
> retrieving revision 1.19
> diff -u -p -r1.19 print-802_11.c
> --- print-802_11.c 16 Jul 2015 20:57:13 -0000 1.19
> +++ print-802_11.c 16 Jul 2015 21:52:07 -0000
> @@ -78,6 +78,7 @@ int ieee80211_hdr(struct ieee80211_fram
> int ieee80211_data(struct ieee80211_frame *, u_int);
> void ieee80211_print_element(u_int8_t *, u_int);
> void ieee80211_print_essid(u_int8_t *, u_int);
> +void ieee80211_print_country(u_int8_t *, u_int);
> void ieee80211_print_htcaps(u_int8_t *, u_int);
> int ieee80211_elements(struct ieee80211_frame *, u_int);
> int ieee80211_frame(struct ieee80211_frame *, u_int);
> @@ -233,6 +234,36 @@ ieee80211_print_essid(u_int8_t *essid, u
>
> /* Caller checks len */
> void
> +ieee80211_print_country(u_int8_t *data, u_int len)
> +{
> + u_int8_t first_chan, nchan, maxpower;
> + int i;
> +
> + while (len > 0) {
> + if (len < 6)
> + break;
> +
> + /* ignore operating extension Id (values >= 201) */
> + if (data[3] >= 201 || data[4] >= 201)
> + continue;
> +
> + /* country string */
> + printf(" '%c%c%c'", data[0], data[1], data[2]);
> +
> + first_chan = data[3];
> + nchan = data[4];
> + maxpower = data[5];
> +
> + printf(", channels %d", first_chan);
> + for (i = first_chan + 1; i < nchan; i++)
> + printf(" %i", i);
It looks like you simply enumerate from first_chan till nchan; why not
to just print "channels %d-%d" then? Also, with this for loop, in case
of invalid data (nchan < first_chan) you won't have any data printed
at all.
> + printf(", max TX power %ddB", maxpower);
> +
> + len -= 6;
> + }
> +}
> +/* Caller checks len */
> +void
> ieee80211_print_htcaps(u_int8_t *data, u_int len)
> {
> u_int16_t htcaps;
> @@ -392,8 +423,7 @@ ieee80211_elements(struct ieee80211_fram
> break;
> case IEEE80211_ELEMID_COUNTRY:
> printf(", country");
> - for (i = len; i > 0; i--, data++)
> - printf(" %u", data[0]);
> + ieee80211_print_country(data, len);
> break;
> case IEEE80211_ELEMID_CHALLENGE:
> printf(", challenge");
> @@ -436,6 +466,9 @@ ieee80211_elements(struct ieee80211_fram
> printf(", htcaps");
> if (vflag)
> ieee80211_print_htcaps(data, len);
> + break;
> + case IEEE80211_ELEMID_POWER_CONSTRAINT:
> + printf(", power constraint %udB", data[0]);
> break;
> case IEEE80211_ELEMID_VENDOR:
> printf(", vendor");
>
--
WBR,
Vadim Zhukov
