Android 8 wifi blakclist
2024-09-20 16:07:01
在连接wifi的时候，认证或者关联失败，有时会加入黑名单中。记录wpa_supplicant中blacklist的原理。
分析可以看到，如果是机器自己断开，是不会把AP加入黑名单的，只有AP侧出了问题，才有可能加入黑名单。
首先看一下blacklist的结构体。
external\wpa_supplicant_8\wpa_supplicant\blacklist.h
struct wpa_blacklist {
struct wpa_blacklist *next;
u8 bssid[ETH_ALEN];
int count;
};
external\wpa_supplicant_8\wpa_supplicant\blacklist.c
/**
* wpa_blacklist_get - Get the blacklist entry for a BSSID
* @wpa_s: Pointer to wpa_supplicant data
* @bssid: BSSID
* Returns: Matching blacklist entry for the BSSID or %NULL if not found
*/
struct wpa_blacklist * wpa_blacklist_get(struct wpa_supplicant *wpa_s,
const u8 *bssid)
{
struct wpa_blacklist *e;
if (wpa_s == NULL || bssid == NULL)
return NULL;
e = wpa_s->blacklist;
while (e) {
if (os_memcmp(e->bssid, bssid, ETH_ALEN) == 0)
return e;
e = e->next;
}
return NULL;
}
/**
* wpa_blacklist_add - Add an BSSID to the blacklist
* @wpa_s: Pointer to wpa_supplicant data
* @bssid: BSSID to be added to the blacklist
* Returns: Current blacklist count on success, -1 on failure
*
* This function adds the specified BSSID to the blacklist or increases the
* blacklist count if the BSSID was already listed. It should be called when
* an association attempt fails either due to the selected BSS rejecting
* association or due to timeout.
*
* This blacklist is used to force %wpa_supplicant to go through all available
* BSSes before retrying to associate with an BSS that rejected or timed out
* association. It does not prevent the listed BSS from being used; it only
* changes the order in which they are tried.
*/
int wpa_blacklist_add(struct wpa_supplicant *wpa_s, const u8 *bssid)
{
struct wpa_blacklist *e;
if (wpa_s == NULL || bssid == NULL)
return -1;
e = wpa_blacklist_get(wpa_s, bssid);
if (e) { // 如果blacklist中已经存在这个ssid，，count++
e->count++;
wpa_printf(MSG_DEBUG, "BSSID " MACSTR " blacklist count "
"incremented to %d",
MAC2STR(bssid), e->count);
return e->count;
}
// 不存在就添加到blacklist链表中
e = os_zalloc(sizeof(*e));
if (e == NULL)
return -1;
// 这个插入方式应该是从链表头插入
os_memcpy(e->bssid, bssid, ETH_ALEN);
e->count = 1;
e->next = wpa_s->blacklist;
wpa_s->blacklist = e;
wpa_printf(MSG_DEBUG, "Added BSSID " MACSTR " into blacklist",
MAC2STR(bssid));
return e->count;
}
/**
* wpa_blacklist_del - Remove an BSSID from the blacklist
* @wpa_s: Pointer to wpa_supplicant data
* @bssid: BSSID to be removed from the blacklist
* Returns: 0 on success, -1 on failure
*/
int wpa_blacklist_del(struct wpa_supplicant *wpa_s, const u8 *bssid)
{
struct wpa_blacklist *e, *prev = NULL;
if (wpa_s == NULL || bssid == NULL)
return -1;
e = wpa_s->blacklist;
while (e) {
if (os_memcmp(e->bssid, bssid, ETH_ALEN) == 0) {
if (prev == NULL) {
wpa_s->blacklist = e->next;
} else {
prev->next = e->next;
}
wpa_printf(MSG_DEBUG, "Removed BSSID " MACSTR " from "
"blacklist", MAC2STR(bssid));
os_free(e);
return 0;
}
prev = e;
e = e->next;
}
return -1;
}
/**
* wpa_blacklist_clear - Clear the blacklist of all entries
* @wpa_s: Pointer to wpa_supplicant data
*/
void wpa_blacklist_clear(struct wpa_supplicant *wpa_s)
{
struct wpa_blacklist *e, *prev;
int max_count = 0;
e = wpa_s->blacklist;
wpa_s->blacklist = NULL;
while (e) {
// 获取count的最大值
if (e->count > max_count)
max_count = e->count;
prev = e;
e = e->next;
wpa_printf(MSG_DEBUG, "Removed BSSID " MACSTR " from "
"blacklist (clear)", MAC2STR(prev->bssid));
os_free(prev);
}
// 临时的计数，判断删除最后一条blacklist是否有失败。
wpa_s->extra_blacklist_count += max_count;
}
wpa_supplicant.c
void wpas_connection_failed(struct wpa_supplicant *wpa_s, const u8 *bssid)
{
int timeout;
int count;
int *freqs = NULL;
wpas_connect_work_done(wpa_s);
/*
* Remove possible authentication timeout since the connection failed.
*/
eloop_cancel_timeout(wpa_supplicant_timeout, wpa_s, NULL);
// 如果断开连接是机器自己产生的，就不会把AP加入到blacklist中，直接返回。
/*
* There is no point in blacklisting the AP if this event is
* generated based on local request to disconnect.
*/
if (wpa_s->own_disconnect_req) {
wpa_s->own_disconnect_req = 0;
wpa_dbg(wpa_s, MSG_DEBUG,
"Ignore connection failure due to local request to disconnect");
return;
}
if (wpa_s->disconnected) {
wpa_dbg(wpa_s, MSG_DEBUG, "Ignore connection failure "
"indication since interface has been put into "
"disconnected state");
return;
}
// 将BSSID加入blacklist中，加速扫描其他可以连接并且关联过的AP。
// 并且对这个BSSID的扫描间隔增加延时，避免连续多次扫描。
/*
* Add the failed BSSID into the blacklist and speed up next scan
* attempt if there could be other APs that could accept association.
* The current blacklist count indicates how many times we have tried
* connecting to this AP and multiple attempts mean that other APs are
* either not available or has already been tried, so that we can start
* increasing the delay here to avoid constant scanning.
*/
// 加入黑名单，并获取在黑名单的计数
count = wpa_blacklist_add(wpa_s, bssid);
if (count == 1 && wpa_s->current_bss) {
//这个BSS以前没有在blacklist中，如果在同一个ESS中有另外的BSS，
// 那么另外一个BSS我们也要进行尝试
// 并且在这之前，对这个BSS进行在进行一个尝试，不过还不行，count再加一。
/*
* This BSS was not in the blacklist before. If there is
* another BSS available for the same ESS, we should try that
* next. Otherwise, we may as well try this one once more
* before allowing other, likely worse, ESSes to be considered.
*/
freqs = get_bss_freqs_in_ess(wpa_s);
if (freqs) {
wpa_dbg(wpa_s, MSG_DEBUG, "Another BSS in this ESS "
"has been seen; try it next");
wpa_blacklist_add(wpa_s, bssid);
/*
* On the next scan, go through only the known channels
* used in this ESS based on previous scans to speed up
* common load balancing use case.
*/
os_free(wpa_s->next_scan_freqs);
wpa_s->next_scan_freqs = freqs;
}
}
/*
* Add previous failure count in case the temporary blacklist was
* cleared due to no other BSSes being available.
*/
count += wpa_s->extra_blacklist_count;
// count大于3，直接设置认证失败。
if (count > 3 && wpa_s->current_ssid) {
wpa_printf(MSG_DEBUG, "Continuous association failures - "
"consider temporary network disabling");
wpas_auth_failed(wpa_s, "CONN_FAILED");
}
switch (count) {
case 1:
timeout = 100;
break;
case 2:
timeout = 500;
break;
case 3:
timeout = 1000;
break;
case 4:
timeout = 5000;
break;
default:
timeout = 10000;
break;
}
wpa_dbg(wpa_s, MSG_DEBUG, "Blacklist count %d --> request scan in %d "
"ms", count, timeout);
// 进行下一次扫描，后面两个参数是扫描的时间
/*
* TODO: if more than one possible AP is available in scan results,
* could try the other ones before requesting a new scan.
*/
// 例如timeout=10000, 那么再次扫描的时间10000/1000+1000*(10000%1000) = 10s
wpa_supplicant_req_scan(wpa_s, timeout / 1000,
1000 * (timeout % 1000));
}
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