feat: better non-blocking guarantees

when using crystal lang 1.19+

Author: stakach

shard.yml

@@ -1,5 +1,5 @@
 name: dns
-version: 1.2.0
+version: 1.3.0
 
 development_dependencies:
   ameba:

spec/dns_spec.cr

@@ -12,6 +12,22 @@ describe DNS do
     response.first.ip_address.address.should eq "127.0.0.1"
   end
 
+  it "should not perform queries for IP addresses" do
+    response = DNS.query("127.0.0.1", [DNS::RecordType::A])
+    response.size.should eq 1
+    response.first.ip_address.address.should eq "127.0.0.1"
+
+    response = DNS.query("::1", [DNS::RecordType::AAAA])
+    response.size.should eq 1
+    response.first.ip_address.address.should eq "::1"
+
+    response = DNS.query("127.0.0.1", [DNS::RecordType::AAAA])
+    response.size.should eq 0
+
+    response = DNS.query("::1", [DNS::RecordType::A])
+    response.size.should eq 0
+  end
+
   it "queries for A, AAAA and SVCB records" do
     response = DNS.query(
       "www.microsoft.com",

spec/ext_spec.cr

@@ -0,0 +1,22 @@
+describe DNS do
+  it "should resolve hostnames using the ext methods" do
+    client = TCPSocket.new("www.google.com", 80)
+    client.close
+  end
+
+  it "should resolve ips using the ext methods" do
+    channel = Channel(Nil).new(1)
+    server = TCPServer.new("127.0.0.1", 1234)
+    spawn do
+      channel.send(nil)
+      while server.accept?
+      end
+    end
+
+    channel.receive
+    client = TCPSocket.new("127.0.0.1", 1234)
+    client.close
+    server.close
+    channel.close
+  end
+end

src/dns.cr

@@ -98,7 +98,18 @@ module DNS
   #
   # NOTE:: A or AAAA answers may include cname and other records that are not directly relevent to the query.
   # It is up to the consumer to filter for the relevant results
+  # ameba:disable Metrics/CyclomaticComplexity
   def self.query(domain : String, query_records : Enumerable(RecordType | UInt16), &) : Nil
+    if Socket::IPAddress.valid?(domain)
+      record_type = Socket::IPAddress.valid_v4?(domain) ? RecordType::A : RecordType::AAAA
+      record_type_int = record_type.to_u16
+      if query_records.includes?(record_type) || query_records.includes?(record_type_int)
+        resource = record_type.a? ? Resource::A.new(domain) : Resource::AAAA.new(domain)
+        yield DNS::Packet::ResourceRecord.new(domain, record_type_int, ClassCode::Internet.to_u16, 1.day, resource)
+      end
+      return
+    end
+
     # RFC 3986 says:
     # > When a non-ASCII registered name represents an internationalized domain name
     # > intended for resolution via the DNS, the name must be transformed to the IDNA

src/dns/ext/addrinfo.cr

@@ -1,14 +1,19 @@
 require "socket"
 require "../../dns"
 
+{% begin %}
 struct Socket::Addrinfo
   QUERY_INET   = [DNS::Resource::A::RECORD_TYPE]
   QUERY_INET6  = [DNS::Resource::AAAA::RECORD_TYPE]
   QUERY_UNSPEC = [DNS::Resource::AAAA::RECORD_TYPE, DNS::Resource::A::RECORD_TYPE]
 
-  private def self.getaddrinfo(domain, service, family, type, protocol, timeout, &)
+  private def self.getaddrinfo(domain, service, family, type, protocol, timeout,
+    {% if compare_versions(Crystal::VERSION, "1.19.0") >= 0 %}
+      flags = 0,
+    {% end %}
+  &)
     # fallback to the original implementation in these cases
-    if family.unix? || Socket::IPAddress.valid?(domain) || domain.includes?('/') || DNS.select_resolver(domain).is_a?(DNS::Resolver::System)
+    if family.unix? || domain.includes?('/') || DNS.select_resolver(domain).is_a?(DNS::Resolver::System)
       domain = URI::Punycode.to_ascii domain
       Crystal::System::Addrinfo.getaddrinfo(domain, service, family, type, protocol, timeout) do |addrinfo|
         yield addrinfo
@@ -35,9 +40,12 @@ struct Socket::Addrinfo
         ip_address = record.ip_address.address
         found = true
 
-        # NOTE:: ideally we set AI_NUMERICHOST, supported on all platforms, to ensure no blocking takes place
-        # currently not possible in crystal as we don't have direct access to `ai_flags` field
-        Crystal::System::Addrinfo.getaddrinfo(ip_address, service, family, type, protocol, timeout) do |addrinfo|
+        # We set AI_NUMERICHOST, supported on all platforms, to ensure no blocking takes place
+        Crystal::System::Addrinfo.getaddrinfo(ip_address, service, family, type, protocol, timeout,
+          {% if compare_versions(Crystal::VERSION, "1.19.0") >= 0 %}
+            ::LibC::AI_NUMERICHOST
+          {% end %}
+        ) do |addrinfo|
           yield addrinfo
         end
       end
@@ -50,3 +58,4 @@ struct Socket::Addrinfo
     raise Socket::Addrinfo::Error.new(message: "Hostname lookup for #{domain} failed: No address found", cause: error)
   end
 end
+{% end %}