dns: switch from ares_gethostbyname to ares_getaddrinfo

bazel/repository_locations.bzl

@@ -27,9 +27,13 @@ REPOSITORY_LOCATIONS = dict(
         urls = ["https://files.pythonhosted.org/packages/c6/b4/510617906f8e0c5660e7d96fbc5585113f83ad547a3989b80297ac72a74c/thrift-0.11.0.tar.gz"],
     ),
     com_github_c_ares_c_ares = dict(
-        sha256 = "7deb7872cbd876c29036d5f37e30c4cbc3cc068d59d8b749ef85bb0736649f04",
-        strip_prefix = "c-ares-cares-1_15_0",
-        urls = ["https://github.com/c-ares/c-ares/archive/cares-1_15_0.tar.gz"],
+        sha256 = "96edccdb19d79f6bc48c2c0e5916346c8f0507efa72e76bd146a1b9d05f93c2a",
+        strip_prefix = "c-ares-5dd3629bc93449840c36dd635ea6cce606b8c366",
+        # 2019-06-19
+        # 21 new commits from release-1.15.0. Upgrade for commit 7d3591ee8a1a63e7748e68e6d880bd1763a32885 "getaddrinfo enhancements"
+        # Use getaddrinfo to query DNS record and TTL.
+        # TODO(crazyxy): Update to release-1.16.0 when it is released.
+        urls = ["https://github.com/c-ares/c-ares/archive/5dd3629bc93449840c36dd635ea6cce606b8c366.tar.gz"],
     ),
     com_github_circonus_labs_libcircllhist = dict(
         sha256 = "8165aa25e529d7d4b9ae849d3bf30371255a99d6db0421516abcff23214cdc2c",

source/common/network/dns_impl.cc

@@ -67,8 +67,8 @@ void DnsResolverImpl::initializeChannel(ares_options* options, int optmask) {
   ares_init_options(&channel_, options, optmask | ARES_OPT_SOCK_STATE_CB);
 }
 
-void DnsResolverImpl::PendingResolution::onAresHostCallback(int status, int timeouts,
-                                                            hostent* hostent) {
+void DnsResolverImpl::PendingResolution::onAresGetAddrInfoCallback(int status, int timeouts,
+                                                                   ares_addrinfo* addrinfo) {
   // We receive ARES_EDESTRUCTION when destructing with pending queries.
   if (status == ARES_EDESTRUCTION) {
     ASSERT(owned_);
@@ -81,30 +81,34 @@ void DnsResolverImpl::PendingResolution::onAresHostCallback(int status, int time
 
   std::list<Address::InstanceConstSharedPtr> address_list;
   if (status == ARES_SUCCESS) {
-    if (hostent->h_addrtype == AF_INET) {
-      for (int i = 0; hostent->h_addr_list[i] != nullptr; ++i) {
-        ASSERT(hostent->h_length == sizeof(in_addr));
-        sockaddr_in address;
-        memset(&address, 0, sizeof(address));
-        address.sin_family = AF_INET;
-        address.sin_port = 0;
-        address.sin_addr = *reinterpret_cast<in_addr*>(hostent->h_addr_list[i]);
-        address_list.emplace_back(new Address::Ipv4Instance(&address));
-      }
-    } else if (hostent->h_addrtype == AF_INET6) {
-      for (int i = 0; hostent->h_addr_list[i] != nullptr; ++i) {
-        ASSERT(hostent->h_length == sizeof(in6_addr));
-        sockaddr_in6 address;
-        memset(&address, 0, sizeof(address));
-        address.sin6_family = AF_INET6;
-        address.sin6_port = 0;
-        address.sin6_addr = *reinterpret_cast<in6_addr*>(hostent->h_addr_list[i]);
-        address_list.emplace_back(new Address::Ipv6Instance(address));
+    if (addrinfo != nullptr && addrinfo->nodes != nullptr) {
+      if (addrinfo->nodes->ai_family == AF_INET) {
+        for (const ares_addrinfo_node* ai = addrinfo->nodes; ai != nullptr; ai = ai->ai_next) {
+          sockaddr_in address;
+          memset(&address, 0, sizeof(address));
+          address.sin_family = AF_INET;
+          address.sin_port = 0;
+          address.sin_addr = reinterpret_cast<sockaddr_in*>(ai->ai_addr)->sin_addr;
+          address_list.emplace_back(new Address::Ipv4Instance(&address));
+        }
+      } else if (addrinfo->nodes->ai_family == AF_INET6) {
+        for (const ares_addrinfo_node* ai = addrinfo->nodes; ai != nullptr; ai = ai->ai_next) {
+          sockaddr_in6 address;
+          memset(&address, 0, sizeof(address));
+          address.sin6_family = AF_INET6;
+          address.sin6_port = 0;
+          address.sin6_addr = reinterpret_cast<sockaddr_in6*>(ai->ai_addr)->sin6_addr;
+          address_list.emplace_back(new Address::Ipv6Instance(address));
+        }
       }
     }
+
     if (!address_list.empty()) {
       completed_ = true;
     }
+
+    ASSERT(addrinfo != nullptr);
+    ares_freeaddrinfo(addrinfo);
   }
 
   if (timeouts > 0) {
@@ -134,7 +138,7 @@ void DnsResolverImpl::PendingResolution::onAresHostCallback(int status, int time
 
   if (!completed_ && fallback_if_failed_) {
     fallback_if_failed_ = false;
-    getHostByName(AF_INET);
+    getAddrInfo(AF_INET);
     // Note: Nothing can follow this call to getHostByName due to deletion of this
     // object upon synchronous resolution.
     return;
@@ -195,9 +199,9 @@ ActiveDnsQuery* DnsResolverImpl::resolve(const std::string& dns_name,
   }
 
   if (dns_lookup_family == DnsLookupFamily::V4Only) {
-    pending_resolution->getHostByName(AF_INET);
+    pending_resolution->getAddrInfo(AF_INET);
   } else {
-    pending_resolution->getHostByName(AF_INET6);
+    pending_resolution->getAddrInfo(AF_INET6);
   }
 
   if (pending_resolution->completed_) {
@@ -215,11 +219,20 @@ ActiveDnsQuery* DnsResolverImpl::resolve(const std::string& dns_name,
   }
 }
 
-void DnsResolverImpl::PendingResolution::getHostByName(int family) {
-  ares_gethostbyname(
-      channel_, dns_name_.c_str(), family,
-      [](void* arg, int status, int timeouts, hostent* hostent) {
-        static_cast<PendingResolution*>(arg)->onAresHostCallback(status, timeouts, hostent);
+void DnsResolverImpl::PendingResolution::getAddrInfo(int family) {
+  struct ares_addrinfo_hints hints = {};
+  hints.ai_family = family;
+
+  /**
+   * ARES_AI_NOSORT result addresses will not be sorted and no connections to resolved addresses
+   * will be attempted
+   */
+  hints.ai_flags = ARES_AI_NOSORT;
+
+  ares_getaddrinfo(
+      channel_, dns_name_.c_str(), /* service */ nullptr, &hints,
+      [](void* arg, int status, int timeouts, ares_addrinfo* addrinfo) {
+        static_cast<PendingResolution*>(arg)->onAresGetAddrInfoCallback(status, timeouts, addrinfo);
       },
       this);
 }

source/common/network/dns_impl.h

@@ -50,17 +50,17 @@ class DnsResolverImpl : public DnsResolver, protected Logger::Loggable<Logger::I
     }
 
     /**
-     * c-ares ares_gethostbyname() query callback.
-     * @param status return status of call to ares_gethostbyname.
+     * ares_getaddrinfo query callback.
+     * @param status return status of call to ares_getaddrinfo.
      * @param timeouts the number of times the request timed out.
-     * @param hostent structure that stores information about a given host.
+     * @param addrinfo structure to store address info.
      */
-    void onAresHostCallback(int status, int timeouts, hostent* hostent);
+    void onAresGetAddrInfoCallback(int status, int timeouts, ares_addrinfo* addrinfo);
     /**
-     * wrapper function of call to ares_gethostbyname.
+     * wrapper function of call to ares_getaddrinfo.
      * @param family currently AF_INET and AF_INET6 are supported.
      */
-    void getHostByName(int family);
+    void getAddrInfo(int family);
 
     // Caller supplied callback to invoke on query completion or error.
     const ResolveCb callback_;

tools/spelling_dictionary.txt

@@ -164,6 +164,7 @@ NOAUTH
 NOLINT
 NOLINTNEXTLINE
 NONCES
+NOSORT
 NS
 NUL
 Nilsson
@@ -289,6 +290,7 @@ WS
 Welford's
 Werror
 XDS
+getaddrinfo
 sendto
 vip
 xDSes