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iw_scan.c
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iw_scan.c
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/*
* Auxiliary declarations and functions imported from iwlib in order to
* process and parse scan events. This code is copied with little change
* from wireless tools 30. It remains here until the wext code will be
* replaced by corresponding netlink calls.
*/
#include "iw_if.h"
#include <search.h> /* lsearch(3) */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include "ie_id.h"
#include "iw_nl80211.h"
/* GLOBAL VARIABLES */
static struct nl_sock *scan_wait_sk;
/*
* Ordering functions for scan results: all return true for a < b.
*/
/* Order by frequency. */
static bool cmp_freq(const struct scan_entry *a, const struct scan_entry *b)
{
return a->freq < b->freq;
}
/* Order by signal strength. */
static bool cmp_sig(const struct scan_entry *a, const struct scan_entry *b)
{
if (!a->bss_signal && !b->bss_signal)
return a->bss_signal_qual < b->bss_signal_qual;
return a->bss_signal < b->bss_signal;
}
/* Order by ESSID, organize entries with same ESSID by frequency and signal. */
static bool cmp_essid(const struct scan_entry *a, const struct scan_entry *b)
{
int res = strncmp(a->essid, b->essid, IW_ESSID_MAX_SIZE);
return res == 0 ? (a->freq == b->freq ? cmp_sig(a, b) : cmp_freq(a, b))
: res < 0;
}
/* Order by MAC address */
static bool cmp_mac(const struct scan_entry *a, const struct scan_entry *b)
{
return memcmp(&a->ap_addr, &b->ap_addr, sizeof(a->ap_addr)) < 0;
}
/* Order by frequency, grouping channels by ESSID. */
static bool cmp_chan(const struct scan_entry *a, const struct scan_entry *b)
{
return a->freq == b->freq ? cmp_essid(a, b) : cmp_freq(a, b);
}
/* Order by frequency first, then by signal strength. */
static bool cmp_chan_sig(const struct scan_entry *a, const struct scan_entry *b)
{
return a->freq == b->freq ? cmp_sig(a, b) : cmp_chan(a, b);
}
/* Order by openness (open access points frist). */
static bool cmp_open(const struct scan_entry *a, const struct scan_entry *b)
{
return a->has_key < b->has_key;
}
/* Sort (open) access points by signal strength. */
static bool cmp_open_sig(const struct scan_entry *a, const struct scan_entry *b)
{
return a->has_key == b->has_key ? cmp_sig(a, b) : cmp_open(a, b);
}
static bool (*scan_cmp[])(const struct scan_entry *, const struct scan_entry *) = {
[SO_CHAN] = cmp_chan,
[SO_SIGNAL] = cmp_sig,
[SO_MAC] = cmp_mac,
[SO_ESSID] = cmp_essid,
[SO_OPEN] = cmp_open,
[SO_CHAN_SIG] = cmp_chan_sig,
[SO_OPEN_SIG] = cmp_open_sig
};
/*
* Scan event handling
*/
/* Callback event handler */
static int wait_event(struct nl_msg *msg, void *arg)
{
struct wait_event *wait = arg;
struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
int i;
for (i = 0; i < wait->n_cmds; i++) {
if (gnlh->cmd == wait->cmds[i])
wait->cmd = gnlh->cmd;
}
return NL_SKIP;
}
/**
* Wait for scan result notification sent by the kernel
* Returns true if scan results are available, false if scan was aborted.
* Taken from iw:event.c:__do_listen_events
*/
static bool wait_for_scan_events(void)
{
static const uint32_t cmds[] = {
NL80211_CMD_NEW_SCAN_RESULTS,
NL80211_CMD_SCAN_ABORTED,
};
struct wait_event wait_ev = {
.cmds = cmds,
.n_cmds = ARRAY_SIZE(cmds),
.cmd = 0
};
struct nl_cb *cb;
if (!scan_wait_sk)
scan_wait_sk = alloc_nl_mcast_sk("scan");
cb = nl_cb_alloc(IW_NL_CB_DEBUG ? NL_CB_DEBUG : NL_CB_DEFAULT);
if (!cb)
err_sys("failed to allocate netlink callbacks");
/* no sequence checking for multicast messages */
nl_cb_set(cb, NL_CB_SEQ_CHECK, NL_CB_CUSTOM, no_seq_check, NULL);
nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, wait_event, &wait_ev);
while (!wait_ev.cmd)
nl_recvmsgs(scan_wait_sk, cb);
nl_cb_put(cb);
return wait_ev.cmd == NL80211_CMD_NEW_SCAN_RESULTS;
}
/**
* Scan result handler. Stolen from iw:scan.c
* This also updates the scan-result statistics.
*/
int scan_dump_handler(struct nl_msg *msg, void *arg)
{
struct scan_result *sr = (struct scan_result *)arg;
struct scan_entry *new;
struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
struct nlattr *tb[NL80211_ATTR_MAX + 1];
struct nlattr *bss[NL80211_BSS_MAX + 1];
static struct nla_policy bss_policy[NL80211_BSS_MAX + 1] = {
[NL80211_BSS_TSF] = { .type = NLA_U64 },
[NL80211_BSS_FREQUENCY] = { .type = NLA_U32 },
[NL80211_BSS_BSSID] = { },
[NL80211_BSS_BEACON_INTERVAL] = { .type = NLA_U16 },
[NL80211_BSS_CAPABILITY] = { .type = NLA_U16 },
[NL80211_BSS_INFORMATION_ELEMENTS] = { },
[NL80211_BSS_SIGNAL_MBM] = { .type = NLA_U32 },
[NL80211_BSS_SIGNAL_UNSPEC] = { .type = NLA_U8 },
[NL80211_BSS_STATUS] = { .type = NLA_U32 },
[NL80211_BSS_SEEN_MS_AGO] = { .type = NLA_U32 },
[NL80211_BSS_BEACON_IES] = { },
};
nla_parse(tb, NL80211_ATTR_MAX, genlmsg_attrdata(gnlh, 0),
genlmsg_attrlen(gnlh, 0), NULL);
if (!tb[NL80211_ATTR_BSS])
return NL_SKIP;
if (nla_parse_nested(bss, NL80211_BSS_MAX,
tb[NL80211_ATTR_BSS],
bss_policy))
return NL_SKIP;
if (!bss[NL80211_BSS_BSSID])
return NL_SKIP;
new = calloc(1, sizeof(*new));
if (!new)
err_sys("failed to allocate scan entry");
memcpy(&new->ap_addr, nla_data(bss[NL80211_BSS_BSSID]), sizeof(new->ap_addr));
if (bss[NL80211_BSS_FREQUENCY]) {
new->freq = nla_get_u32(bss[NL80211_BSS_FREQUENCY]);
new->chan = ieee80211_frequency_to_channel(new->freq);
}
if (bss[NL80211_BSS_SIGNAL_UNSPEC])
new->bss_signal_qual = nla_get_u8(bss[NL80211_BSS_SIGNAL_UNSPEC]);
if (bss[NL80211_BSS_SIGNAL_MBM]) {
int s = nla_get_u32(bss[NL80211_BSS_SIGNAL_MBM]);
new->bss_signal = s / 100;
}
if (bss[NL80211_BSS_CAPABILITY]) {
new->bss_capa = nla_get_u16(bss[NL80211_BSS_CAPABILITY]);
new->has_key = (new->bss_capa & WLAN_CAPABILITY_PRIVACY) != 0;
}
if (bss[NL80211_BSS_SEEN_MS_AGO])
new->last_seen = nla_get_u32(bss[NL80211_BSS_SEEN_MS_AGO]);
if (bss[NL80211_BSS_TSF])
new->tsf = nla_get_u64(bss[NL80211_BSS_TSF]);
if (bss[NL80211_BSS_INFORMATION_ELEMENTS]) {
uint8_t *ie = nla_data(bss[NL80211_BSS_INFORMATION_ELEMENTS]);
int ielen = nla_len(bss[NL80211_BSS_INFORMATION_ELEMENTS]);
while (ielen >= 2 && ielen >= ie[1]) {
uint8_t len = ie[1];
switch (ie[0]) {
case IE_SSID:
if (len > 0 && len <= 32)
print_ssid_escaped(new->essid, sizeof(new->essid),
ie+2, len);
break;
case IE_BSS_LOAD:
if (len >= 5) {
new->bss_sta_count = ie[3] << 8 | ie[2];
new->bss_chan_usage = ie[4];
}
break;
case IE_EXT_CAPABILITIES:
if (len >= sizeof(new->ext_capa)) {
memcpy(new->ext_capa, &ie[2], sizeof(new->ext_capa));
}
break;
}
// Point to next ie
ielen -= ie[1] + 2;
ie += ie[1] + 2;
}
}
/* Update stats */
new->next = sr->head;
sr->head = new;
if (str_is_ascii(new->essid))
sr->max_essid_len = clamp(strlen(new->essid),
sr->max_essid_len,
IW_ESSID_MAX_SIZE);
if (new->freq > 45000) /* 802.11ad 60GHz spectrum */
err_quit("FIXME: can not handle %d MHz spectrum yet", new->freq);
else if (new->freq >= 5000)
sr->num.five_gig++;
else if (new->freq >= 2000)
sr->num.two_gig++;
sr->num.entries += 1;
sr->num.open += !new->has_key;
return NL_SKIP;
}
static int iw_nl80211_scan_trigger(void)
{
static struct cmd cmd_trigger_scan = {
.cmd = NL80211_CMD_TRIGGER_SCAN,
};
return handle_cmd(&cmd_trigger_scan);
}
static int iw_nl80211_get_scan_data(struct scan_result *sr)
{
static struct cmd cmd_scan_dump = {
.cmd = NL80211_CMD_GET_SCAN,
.flags = NLM_F_DUMP,
.handler = scan_dump_handler
};
memset(sr, 0, sizeof(*sr));
cmd_scan_dump.handler_arg = sr;
return handle_cmd(&cmd_scan_dump);
}
/*
* Simple sort routine.
* FIXME: use hash or tree to store entries, a list to display them.
*/
void sort_scan_list(struct scan_entry **headp)
{
struct scan_entry *head = NULL, *cur, *new = *headp, **prev;
while (new) {
for (cur = head, prev = &head; cur &&
conf.scan_sort_asc == scan_cmp[conf.scan_sort_order](cur, new);
prev = &cur->next, cur = cur->next)
;
*prev = new;
new = new->next;
(*prev)->next = cur;
}
*headp = head;
}
/** De-allocate list. Use after all threads are terminated. */
void free_scan_list(struct scan_entry *head)
{
if (head) {
free_scan_list(head->next);
free(head);
}
}
/** Initialize scan results. Requires lock to be taken. */
void init_scan_list(struct scan_result *sr)
{
free_scan_list(sr->head);
free(sr->channel_stats);
sr->head = NULL;
sr->channel_stats = NULL;
sr->msg[0] = '\0';
sr->max_essid_len = MAX_ESSID_LEN;
memset(&(sr->num), 0, sizeof(sr->num));
sr->mutex = (pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;
}
/*
* Channel statistics shown at the bottom of scan screen.
*/
/*
* For lsearch, it compares key value with array member, needs to
* return 0 if they are the same, non-0 otherwise.
*/
static int cmp_key(const void *a, const void *b)
{
return ((struct cnt *)a)->val - ((struct cnt *)b)->val;
}
/* For quick-sorting the array in descending order of counts */
static int cmp_cnt(const void *a, const void *b)
{
if (conf.scan_sort_order == SO_CHAN && !conf.scan_sort_asc)
return ((struct cnt *)a)->count - ((struct cnt *)b)->count;
return ((struct cnt *)b)->count - ((struct cnt *)a)->count;
}
/**
* Fill in sr->channel_stats (must not have been allocated yet).
*/
static void compute_channel_stats(struct scan_result *sr)
{
struct scan_entry *cur;
struct cnt *bin, key = {0, 0};
size_t n = 0;
if (!sr->num.entries)
return;
sr->channel_stats = calloc(sr->num.entries, sizeof(key));
for (cur = sr->head; cur; cur = cur->next) {
if (cur->chan >= 0) {
key.val = cur->chan;
bin = lsearch(&key, sr->channel_stats, &n, sizeof(key), cmp_key);
if (bin)
bin->count++;
}
}
if (n > 0) {
qsort(sr->channel_stats, n, sizeof(key), cmp_cnt);
} else {
free(sr->channel_stats);
sr->channel_stats = NULL;
}
sr->num.ch_stats = n < MAX_CH_STATS ? n : MAX_CH_STATS;
}
/** The actual scan thread. */
void *do_scan(void *sr_ptr)
{
struct scan_result *sr = sr_ptr;
sigset_t blockmask;
int ret = 0;
/* SIGWINCH is supposed to be handled in the main thread. */
sigemptyset(&blockmask);
sigaddset(&blockmask, SIGWINCH);
pthread_sigmask(SIG_BLOCK, &blockmask, NULL);
pthread_detach(pthread_self());
do {
ret = iw_nl80211_scan_trigger();
pthread_mutex_lock(&sr->mutex);
init_scan_list(sr);
switch(-ret) {
case 0:
case EBUSY:
/* Trigger returns -EBUSY if a scan request is pending or ready. */
pthread_mutex_unlock(&sr->mutex);
/* Do not hold the lock while awaiting results. */
if (!wait_for_scan_events()) {
pthread_mutex_lock(&sr->mutex);
snprintf(sr->msg, sizeof(sr->msg), "Waiting for scan data...");
pthread_mutex_unlock(&sr->mutex);
} else {
pthread_mutex_lock(&sr->mutex);
ret = iw_nl80211_get_scan_data(sr);
if (ret < 0) {
snprintf(sr->msg, sizeof(sr->msg),
"Scan failed on %s: %s", conf_ifname(), strerror(-ret));
} else if (!sr->head) {
snprintf(sr->msg, sizeof(sr->msg), "Empty scan results on %s", conf_ifname());
}
compute_channel_stats(sr);
pthread_mutex_unlock(&sr->mutex);
}
break;
case EPERM:
if (!has_net_admin_capability())
snprintf(sr->msg, sizeof(sr->msg), "This screen requires CAP_NET_ADMIN permissions");
pthread_mutex_unlock(&sr->mutex);
break;
case EFAULT:
/* EFAULT can occur after a window resizing event: temporary, fall through. */
case EINTR:
case EAGAIN:
/* Temporary errors. */
snprintf(sr->msg, sizeof(sr->msg), "Waiting for device to become ready ...");
pthread_mutex_unlock(&sr->mutex);
break;
case ENETDOWN:
if (!if_is_up(conf_ifname())) {
snprintf(sr->msg, sizeof(sr->msg), "Interface %s is down - setting it up ...", conf_ifname());
pthread_mutex_unlock(&sr->mutex);
if (if_set_up(conf_ifname()) < 0)
err_sys("Can not bring up interface '%s'", conf_ifname());
if (atexit(if_set_down_on_exit) < 0)
snprintf(sr->msg, sizeof(sr->msg), "Warning: unable to restore %s down state on exit", conf_ifname());
break;
}
/* fall through */
default:
snprintf(sr->msg, sizeof(sr->msg), "Scan trigger failed on %s: %s", conf_ifname(), strerror(-ret));
pthread_mutex_unlock(&sr->mutex);
}
} while (usleep(conf.stat_iv * 1000) == 0);
return NULL;
}