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Commit 418cfb6c authored by cken's avatar cken Committed by Ken Chen
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Add resolv_has_nameserver() to replace getHasDns() 

getHasDns() returns the value assigned from networkCreateVpn(). It causes
issues when DNS configuration is changed without triggering VPN reconnection.
For example, first established vpn has no DNS server, then switch to the one
with DNS server, the system continues to use the DNS servers from the default
network in addition to the ones assigned from the VPN server, resulting in a
DNS leak. In the reverse case it causes DNS resolution fails. New API
resolv_has_nameserver() get DNS information from the DNS resolver directly.

Bug: 116539103
Test: verify patch via unmerged CTS test case aosp/658122 (with
little modification)

Change-Id: Ie01814435f4361c258c4ba96a47eb917f5441274
parent a26cc2a2

include/netd_resolv/resolv.h

+2 −0
Original line number Diff line number Diff line
@@ -110,6 +110,8 @@ LIBNETD_RESOLV_PUBLIC int android_getaddrinfofornetcontext(const char*, const ch 
                                                           const addrinfo*,

                                                           const android_net_context*, addrinfo**);



LIBNETD_RESOLV_PUBLIC bool resolv_has_nameservers(unsigned netid);



// Query dns with raw msg

// TODO: Add a way to control query parameter, like flags, or maybe res_options or even res_state.

LIBNETD_RESOLV_PUBLIC int resolv_res_nsend(const android_net_context* netContext, const u_char* msg,

libnetd_resolv.map.txt

+1 −0
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ LIBNETD_RESOLV { 
    resolv_delete_cache_for_net;

    resolv_delete_private_dns_for_net;

    resolv_get_private_dns_status_for_net;

    resolv_has_nameservers;

    resolv_register_private_dns_callback;

    resolv_res_nsend;

    resolv_set_nameservers_for_net;

res_cache.cpp

+28 −19
Original line number Diff line number Diff line
@@ -1154,8 +1154,6 @@ struct resolv_cache_info { 
    int dnsrch_offset[MAXDNSRCH + 1];  // offsets into defdname

};



#define HTABLE_VALID(x) ((x) != NULL && (x) != HTABLE_DELETED)



static pthread_once_t _res_cache_once = PTHREAD_ONCE_INIT;

static void res_cache_init(void);
@@ -1267,7 +1265,7 @@ void _resolv_cache_query_failed(unsigned netid, const void* query, int querylen) 
    pthread_mutex_unlock(&res_cache_list_lock);

}



static struct resolv_cache_info* _find_cache_info_locked(unsigned netid);

static resolv_cache_info* find_cache_info_locked(unsigned netid);



static void _cache_flush_locked(Cache* cache) {

    int nn;
@@ -1619,21 +1617,21 @@ Exit: 
// Head of the list of caches.  Protected by _res_cache_list_lock.

static struct resolv_cache_info res_cache_list;



/* insert resolv_cache_info into the list of resolv_cache_infos */

// insert resolv_cache_info into the list of resolv_cache_infos

static void insert_cache_info_locked(resolv_cache_info* cache_info);

/* creates a resolv_cache_info */

// creates a resolv_cache_info

static resolv_cache_info* create_cache_info();

/* gets a resolv_cache_info associated with a network, or NULL if not found */

static struct resolv_cache_info* _find_cache_info_locked(unsigned netid);

/* empty the named cache */

// gets a resolv_cache_info associated with a network, or NULL if not found

static resolv_cache_info* find_cache_info_locked(unsigned netid);

// empty the named cache

static void flush_cache_for_net_locked(unsigned netid);

/* empty the nameservers set for the named cache */

// empty the nameservers set for the named cache

static void free_nameservers_locked(resolv_cache_info* cache_info);

// return 1 if the provided list of name servers differs from the list of name servers

// currently attached to the provided cache_info

static int resolv_is_nameservers_equal_locked(resolv_cache_info* cache_info, const char** servers,

                                              int numservers);

/* clears the stats samples contained withing the given cache_info */

// clears the stats samples contained withing the given cache_info

static void res_cache_clear_stats_locked(resolv_cache_info* cache_info);



static void res_cache_init(void) {
@@ -1641,7 +1639,18 @@ static void res_cache_init(void) { 
    pthread_mutex_init(&res_cache_list_lock, NULL);

}



/* look up the named cache, and creates one if needed */

// public API for netd to query if name server is set on specific netid

bool resolv_has_nameservers(unsigned netid) {

    pthread_once(&_res_cache_once, res_cache_init);

    pthread_mutex_lock(&res_cache_list_lock);

    resolv_cache_info* info = find_cache_info_locked(netid);

    const bool ret = (info != nullptr) && (info->nscount > 0);

    pthread_mutex_unlock(&res_cache_list_lock);



    return ret;

}



// look up the named cache, and creates one if needed

static resolv_cache* get_res_cache_for_net_locked(unsigned netid) {

    resolv_cache* cache = find_named_cache_locked(netid);

    if (!cache) {
@@ -1676,7 +1685,7 @@ static void flush_cache_for_net_locked(unsigned netid) { 
    }



    // Also clear the NS statistics.

    resolv_cache_info* cache_info = _find_cache_info_locked(netid);

    resolv_cache_info* cache_info = find_cache_info_locked(netid);

    res_cache_clear_stats_locked(cache_info);

}
@@ -1716,12 +1725,12 @@ static void insert_cache_info_locked(struct resolv_cache_info* cache_info) { 
}



static resolv_cache* find_named_cache_locked(unsigned netid) {

    struct resolv_cache_info* info = _find_cache_info_locked(netid);

    resolv_cache_info* info = find_cache_info_locked(netid);

    if (info != NULL) return info->cache;

    return NULL;

}



static struct resolv_cache_info* _find_cache_info_locked(unsigned netid) {

static resolv_cache_info* find_cache_info_locked(unsigned netid) {

    struct resolv_cache_info* cache_info = res_cache_list.next;



    while (cache_info) {
@@ -1778,7 +1787,7 @@ int resolv_set_nameservers_for_net(unsigned netid, const char** servers, unsigne 
    // creates the cache if not created

    get_res_cache_for_net_locked(netid);



    struct resolv_cache_info* cache_info = _find_cache_info_locked(netid);

    resolv_cache_info* cache_info = find_cache_info_locked(netid);



    if (cache_info != NULL) {

        uint8_t old_max_samples = cache_info->params.max_samples;
@@ -1903,7 +1912,7 @@ void _resolv_populate_res_for_net(res_state statp) { 
    pthread_once(&_res_cache_once, res_cache_init);

    pthread_mutex_lock(&res_cache_list_lock);



    struct resolv_cache_info* info = _find_cache_info_locked(statp->netid);

    resolv_cache_info* info = find_cache_info_locked(statp->netid);

    if (info != NULL) {

        int nserv;

        struct addrinfo* ai;
@@ -1976,7 +1985,7 @@ int android_net_res_stats_get_info_for_net(unsigned netid, int* nscount, 
    int revision_id = -1;

    pthread_mutex_lock(&res_cache_list_lock);



    struct resolv_cache_info* info = _find_cache_info_locked(netid);

    resolv_cache_info* info = find_cache_info_locked(netid);

    if (info) {

        if (info->nscount > MAXNS) {

            pthread_mutex_unlock(&res_cache_list_lock);
@@ -2040,7 +2049,7 @@ int resolv_cache_get_resolver_stats(unsigned netid, __res_params* params, res_st 
    int revision_id = -1;

    pthread_mutex_lock(&res_cache_list_lock);



    struct resolv_cache_info* info = _find_cache_info_locked(netid);

    resolv_cache_info* info = find_cache_info_locked(netid);

    if (info) {

        memcpy(stats, info->nsstats, sizeof(info->nsstats));

        *params = info->params;
@@ -2057,7 +2066,7 @@ void _resolv_cache_add_resolver_stats_sample(unsigned netid, int revision_id, in 


    pthread_mutex_lock(&res_cache_list_lock);



    struct resolv_cache_info* info = _find_cache_info_locked(netid);

    resolv_cache_info* info = find_cache_info_locked(netid);



    if (info && info->revision_id == revision_id) {

        _res_cache_add_stats_sample_locked(&info->nsstats[ns], sample, max_samples);