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Commit db04a2bd authored by Mike Yu's avatar Mike Yu
Browse files

Retry binding sockets in DNSResponder if errno is EADDRNOTAVAIL 

Tests fail in DNSResponder::startServer() when DNSResponder is binding
the socket while the address is still being set up. This change provides
a simple fix to address this problem because the tests are unaware of
onInterfaceAddressUpdated.

Below is a real failure log:

// device log
04-22 00:29:07.854  root   802   802 I netd    : interfaceAddAddress("testtun10002", "2001:db8:2::202", 128) <1.51ms>
04-22 00:29:07.855  root  6745  6745 E DNSResponder: failed to bind UDP 2001:db8:2::202:53: Cannot assign requested address

// dumpsys netd
04-22 00:29:07.857 onInterfaceAddressUpdated(2001:db8:2::202/128, testtun10002, 128, 0) (0.04ms)

Bug: 186181084
Bug: 175269391
Test: run ResolverMultinetworkTest.GetAddrInfo_AI_ADDRCONFIG 100 times
Change-Id: I8e8824c9056bd298e0e689adfbc720abaa45fcd4
parent 82ae84b9

tests/dns_responder/dns_responder.cpp

+31 −1
Original line number Diff line number Diff line
@@ -36,13 +36,16 @@ 
#define LOG_TAG "DNSResponder"

#include <android-base/logging.h>

#include <android-base/strings.h>

#include <netdutils/BackoffSequence.h>

#include <netdutils/InternetAddresses.h>

#include <netdutils/Slice.h>

#include <netdutils/SocketOption.h>



using android::netdutils::BackoffSequence;

using android::netdutils::enableSockopt;

using android::netdutils::ScopedAddrinfo;

using android::netdutils::Slice;

using std::chrono::milliseconds;



namespace test {
@@ -71,6 +74,33 @@ std::string addr2str(const sockaddr* sa, socklen_t sa_len) { 
    return std::string();

}



// Because The address might still being set up (b/186181084), This is a wrapper function

// that retries bind() if errno is EADDRNOTAVAIL

int bindSocket(int socket, const sockaddr* address, socklen_t address_len) {

    // Set the wrapper to try bind() at most 6 times with backoff time

    // (100 ms, 200 ms, ..., 1600 ms).

    auto backoff = BackoffSequence<milliseconds>::Builder()

                           .withInitialRetransmissionTime(milliseconds(100))

                           .withMaximumRetransmissionCount(5)

                           .build();



    while (true) {

        int ret = bind(socket, address, address_len);

        if (ret == 0 || errno != EADDRNOTAVAIL) {

            return ret;

        }



        if (!backoff.hasNextTimeout()) break;



        LOG(WARNING) << "Retry to bind " << addr2str(address, address_len);

        std::this_thread::sleep_for(backoff.getNextTimeout());

    }



    // Set errno before return since it might have been changed somewhere.

    errno = EADDRNOTAVAIL;

    return -1;

}



/* DNS struct helpers */



const char* dnstype2str(unsigned dnstype) {
@@ -1206,7 +1236,7 @@ android::base::unique_fd DNSResponder::createListeningSocket(int socket_type) { 
        const std::string host_str = addr2str(ai->ai_addr, ai->ai_addrlen);

        const char* socket_str = (socket_type == SOCK_STREAM) ? "TCP" : "UDP";



        if (bind(fd.get(), ai->ai_addr, ai->ai_addrlen)) {

        if (bindSocket(fd.get(), ai->ai_addr, ai->ai_addrlen)) {

            PLOG(ERROR) << "failed to bind " << socket_str << " " << host_str << ":"

                        << listen_service_;

            continue;