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Commit 56a4c7fd authored by Ken Chen's avatar Ken Chen
Browse files

Code Health: Make OperationLimiter generic 

Aosp/2071247 read an experimental flag max_queries_global in
OperationLimiter::start(), making the generic class OperationLimiter
specific. This commit adds a wrapper function to pass the global
limiter, allowing OperationLimiter to remain generic.

Bug: 230284143
Test: atest resolv_unit_test:OperationLimiterTest
Change-Id: I7b14ace9d27a87b3832e1c807d762850feeab5fe
parent a2ca20db

DnsProxyListener.cpp

+24 −14
Original line number Diff line number Diff line
@@ -81,6 +81,16 @@ constexpr int MAX_QUERIES_PER_UID = 256; 


android::netdutils::OperationLimiter<uid_t> queryLimiter(MAX_QUERIES_PER_UID);



bool startQueryLimiter(uid_t uid) {

    const int globalLimit =

            android::net::Experiments::getInstance()->getFlag("max_queries_global", INT_MAX);

    return queryLimiter.start(uid, globalLimit);

}



void endQueryLimiter(uid_t uid) {

    queryLimiter.finish(uid);

}



void logArguments(int argc, char** argv) {

    if (!WOULD_LOG(VERBOSE)) return;

    for (int i = 0; i < argc; i++) {
@@ -788,14 +798,14 @@ void DnsProxyListener::GetAddrInfoHandler::doDns64Synthesis(int32_t* rv, addrinf 
    if (ipv6WantedButNoData) {

        // If caller wants IPv6 answers but no data, try to query IPv4 answers for synthesis

        const uid_t uid = mClient->getUid();

        if (queryLimiter.start(uid)) {

        if (startQueryLimiter(uid)) {

            const char* host = mHost.starts_with('^') ? nullptr : mHost.c_str();

            const char* service = mService.starts_with('^') ? nullptr : mService.c_str();

            mHints->ai_family = AF_INET;

            // Don't need to do freeaddrinfo(res) before starting new DNS lookup because previous

            // DNS lookup is failed with error EAI_NODATA.

            *rv = resolv_getaddrinfo(host, service, mHints.get(), &mNetContext, res, event);

            queryLimiter.finish(uid);

            endQueryLimiter(uid);

            if (*rv) {

                *rv = EAI_NODATA;  // return original error code

                return;
@@ -829,7 +839,7 @@ void DnsProxyListener::GetAddrInfoHandler::run() { 
    int32_t rv = 0;

    NetworkDnsEventReported event;

    initDnsEvent(&event, mNetContext);

    if (queryLimiter.start(uid)) {

    if (startQueryLimiter(uid)) {

        const char* host = mHost.starts_with('^') ? nullptr : mHost.c_str();

        const char* service = mService.starts_with('^') ? nullptr : mService.c_str();

        if (evaluate_domain_name(mNetContext, host)) {
@@ -837,7 +847,7 @@ void DnsProxyListener::GetAddrInfoHandler::run() { 
        } else {

            rv = EAI_SYSTEM;

        }

        queryLimiter.finish(uid);

        endQueryLimiter(uid);

    } else {

        // Note that this error code is currently not passed down to the client.

        // android_getaddrinfo_proxy() returns EAI_NODATA on any error.
@@ -1038,14 +1048,14 @@ void DnsProxyListener::ResNSendHandler::run() { 
    int ansLen = -1;

    NetworkDnsEventReported event;

    initDnsEvent(&event, mNetContext);

    if (queryLimiter.start(uid)) {

    if (startQueryLimiter(uid)) {

        if (evaluate_domain_name(mNetContext, rr_name.c_str())) {

            ansLen = resolv_res_nsend(&mNetContext, {msg.data(), msgLen}, ansBuf, &rcode,

                                      static_cast<ResNsendFlags>(mFlags), &event);

        } else {

            ansLen = -EAI_SYSTEM;

        }

        queryLimiter.finish(uid);

        endQueryLimiter(uid);

    } else {

        LOG(WARNING) << "ResNSendHandler::run: resnsend: from UID " << uid

                     << ", max concurrent queries reached";
@@ -1214,10 +1224,10 @@ void DnsProxyListener::GetHostByNameHandler::doDns64Synthesis(int32_t* rv, hoste 


    // If caller wants IPv6 answers but no data, try to query IPv4 answers for synthesis

    const uid_t uid = mClient->getUid();

    if (queryLimiter.start(uid)) {

    if (startQueryLimiter(uid)) {

        const char* name = mName.starts_with('^') ? nullptr : mName.c_str();

        *rv = resolv_gethostbyname(name, AF_INET, hbuf, buf, buflen, &mNetContext, hpp, event);

        queryLimiter.finish(uid);

        endQueryLimiter(uid);

        if (*rv) {

            *rv = EAI_NODATA;  // return original error code

            return;
@@ -1245,7 +1255,7 @@ void DnsProxyListener::GetHostByNameHandler::run() { 
    int32_t rv = 0;

    NetworkDnsEventReported event;

    initDnsEvent(&event, mNetContext);

    if (queryLimiter.start(uid)) {

    if (startQueryLimiter(uid)) {

        const char* name = mName.starts_with('^') ? nullptr : mName.c_str();

        if (evaluate_domain_name(mNetContext, name)) {

            rv = resolv_gethostbyname(name, mAf, &hbuf, tmpbuf, sizeof tmpbuf, &mNetContext, &hp,
@@ -1253,7 +1263,7 @@ void DnsProxyListener::GetHostByNameHandler::run() { 
        } else {

            rv = EAI_SYSTEM;

        }

        queryLimiter.finish(uid);

        endQueryLimiter(uid);

    } else {

        rv = EAI_MEMORY;

        LOG(ERROR) << "GetHostByNameHandler::run: from UID " << uid
@@ -1376,12 +1386,12 @@ void DnsProxyListener::GetHostByAddrHandler::doDns64ReverseLookup(hostent* hbuf, 
    }



    const uid_t uid = mClient->getUid();

    if (queryLimiter.start(uid)) {

    if (startQueryLimiter(uid)) {

        // Remove NAT64 prefix and do reverse DNS query

        struct in_addr v4addr = {.s_addr = v6addr.s6_addr32[3]};

        resolv_gethostbyaddr(&v4addr, sizeof(v4addr), AF_INET, hbuf, buf, buflen, &mNetContext, hpp,

                             event);

        queryLimiter.finish(uid);

        endQueryLimiter(uid);

        if (*hpp) {

            // Replace IPv4 address with original queried IPv6 address in place. The space has

            // reserved by dns_gethtbyaddr() and netbsd_gethostent_r() in
@@ -1407,7 +1417,7 @@ void DnsProxyListener::GetHostByAddrHandler::run() { 
    int32_t rv = 0;

    NetworkDnsEventReported event;

    initDnsEvent(&event, mNetContext);

    if (queryLimiter.start(uid)) {

    if (startQueryLimiter(uid)) {

        // From Android U, evaluate_domain_name() is not only for OEM customization, but also tells

        // DNS resolver whether the UID can send DNS on the specified network. The function needs

        // to be called even when there is no domain name to evaluate (GetHostByAddr). This is
@@ -1420,7 +1430,7 @@ void DnsProxyListener::GetHostByAddrHandler::run() { 
            rv = resolv_gethostbyaddr(&mAddress, mAddressLen, mAddressFamily, &hbuf, tmpbuf,

                                      sizeof tmpbuf, &mNetContext, &hp, &event);

        }

        queryLimiter.finish(uid);

        endQueryLimiter(uid);

    } else {

        rv = EAI_MEMORY;

        LOG(ERROR) << "GetHostByAddrHandler::run: from UID " << uid

OperationLimiter.h

+1 −3
Original line number Diff line number Diff line
@@ -56,10 +56,8 @@ class OperationLimiter { 
    //

    // Note: each successful start(key) must be matched by exactly one call to

    // finish(key).

    bool start(KeyType key) EXCLUDES(mMutex) {

    bool start(KeyType key, int globalLimit = INT_MAX) EXCLUDES(mMutex) {

        std::lock_guard lock(mMutex);

        int globalLimit =

                android::net::Experiments::getInstance()->getFlag("max_queries_global", INT_MAX);

        if (globalLimit < mLimitPerKey) {

            LOG(ERROR) << "Misconfiguration on max_queries_global " << globalLimit;

            globalLimit = INT_MAX;

OperationLimiterTest.cpp

+32 −0
Original line number Diff line number Diff line
@@ -74,5 +74,37 @@ TEST_F(OperationLimiterTest, destroyWithActiveOperations) { 
            "" /* "active operations */);

}



TEST_F(OperationLimiterTest, globalLimits) {

    OperationLimiter<int> limiter(1);



    EXPECT_TRUE(limiter.start(42, 2));



    // Calling with a different key is okay.

    EXPECT_TRUE(limiter.start(43, 2));



    // Global limit reached... calling with a different key should have no effect.

    EXPECT_FALSE(limiter.start(44, 2));



    // Global limit extended... calling with a different key is available again.

    EXPECT_TRUE(limiter.start(44, 4));



    // Per-key limit reached.

    EXPECT_FALSE(limiter.start(44, 4));



    // Global limit is still available.

    EXPECT_TRUE(limiter.start(45, 4));



    // Global limit reached again.

    EXPECT_FALSE(limiter.start(46, 4));



    // Shrink global limit.

    EXPECT_FALSE(limiter.start(46, 3));



    // Finish all pending operations

    for (const auto& key : {42, 43, 44, 45}) {

        limiter.finish(key);

    }

}



}  // namespace netdutils

}  // namespace android