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Commit 61df10c8 authored by chenbruce's avatar chenbruce
Browse files

Set UNICAST-RESPONSE bit for mDNS 

The field is used to minimize unnecessary broadcasts on the network.

Bug: 140857615
Test: cd packages/modules/DnsResolver && atest
Change-Id: I54bc6f7cd41ff9687d4de8c9e87780ce805df050
parent 95450851

getaddrinfo.cpp

+5 −0
Original line number Diff line number Diff line
@@ -1439,6 +1439,11 @@ static int dns_getaddrinfo(const char* name, const addrinfo* pai, 


    setMdnsFlag(name, &(res.flags));



    if (isMdnsResolution(res.flags)) {

        q.qclass |= C_UNICAST;

        q2.qclass |= C_UNICAST;

    }



    int he;

    if (res_searchN(name, &q, &res, &he) < 0) {

        // Return h_errno (he) to catch more detailed errors rather than EAI_NODATA.

gethnamaddr.cpp

+2 −1
Original line number Diff line number Diff line
@@ -631,7 +631,8 @@ static int dns_gethtbyname(ResState* res, const char* name, int addr_type, getna 
    auto buf = std::make_unique<querybuf>();



    int he;

    n = res_nsearch(res, name, C_IN, type, buf->buf, (int)sizeof(buf->buf), &he);

    const unsigned qclass = isMdnsResolution(res->flags) ? C_IN | C_UNICAST : C_IN;

    n = res_nsearch(res, name, qclass, type, buf->buf, (int)sizeof(buf->buf), &he);

    if (n < 0) {

        LOG(DEBUG) << __func__ << ": res_nsearch failed (" << n << ")";

        // Return h_errno (he) to catch more detailed errors rather than EAI_NODATA.

res_cache.cpp

+3 −1
Original line number Diff line number Diff line
@@ -260,6 +260,7 @@ static time_t _time_now(void) { 
#define DNS_TYPE_ALL "\00\0377" /* big-endian decimal 255 */



#define DNS_CLASS_IN "\00\01" /* big-endian decimal 1 */

#define MDNS_CLASS_UNICAST_IN "\200\01" /* big-endian decimal 32769 */



struct DnsPacket {

    const uint8_t* base;
@@ -374,7 +375,8 @@ static int _dnsPacket_checkQR(DnsPacket* packet) { 
        return 0;

    }

    /* CLASS must be IN */

    if (!_dnsPacket_checkBytes(packet, 2, DNS_CLASS_IN)) {

    if (!_dnsPacket_checkBytes(packet, 2, DNS_CLASS_IN) &&

        !_dnsPacket_checkBytes(packet, 2, MDNS_CLASS_UNICAST_IN)) {

        LOG(INFO) << __func__ << ": unsupported CLASS";

        return 0;

    }

resolv_private.h

+2 −0
Original line number Diff line number Diff line
@@ -88,6 +88,8 @@ union sockaddr_union { 
};

constexpr int MAXPACKET = 8 * 1024;



const unsigned C_UNICAST = 0x8000;  // unicast-response bit for MDNS



struct ResState {

    ResState(const android_net_context* netcontext, android::net::NetworkDnsEventReported* dnsEvent)

        : netid(netcontext->dns_netid),

tests/dns_responder/dns_responder.cpp

+3 −1
Original line number Diff line number Diff line
@@ -979,8 +979,10 @@ bool DNSResponder::makeResponse(DNSHeader* header, int protocol, char* response, 


bool DNSResponder::makeResponseFromAddressOrHostname(DNSHeader* header, char* response,

                                                     size_t* response_len) const {

    const unsigned unicast_bit = 0x8000;  // unicast-response bit for MDNS

    for (const DNSQuestion& question : header->questions) {

        if (question.qclass != ns_class::ns_c_in && question.qclass != ns_class::ns_c_any) {

        if (question.qclass != ns_class::ns_c_in && question.qclass != ns_class::ns_c_any &&

            question.qclass != (unicast_bit | ns_class::ns_c_in)) {

            LOG(INFO) << "unsupported question class " << question.qclass;

            return makeErrorResponse(header, ns_rcode::ns_r_notimpl, response, response_len);

        }