Fix Addrinfo.new(String) to reliably find the address family

* By reading `sa_family` from the `struct sockaddr` (see `man 2 bind`).
  This is also what MRI does. Note that the `sa_family` is at a non-zero offset on macOS.
* Match MRI for error messages.
* Set family and socket_type for Socket.pair.

Author: eregon

lib/truffle/socket/addrinfo.rb

@@ -106,17 +106,14 @@ def initialize(sockaddr, pfamily = nil, socktype = 0, protocol = 0)
         pfamily = Socket::PF_INET6
       end
     else
-      if sockaddr.bytesize == Truffle::Socket::Foreign::SockaddrUn.size
+      @afamily = Truffle::Socket::Foreign::Sockaddr.family_of_string(sockaddr)
+      case @afamily
+      when Socket::AF_UNIX
         @unix_path = Socket.unpack_sockaddr_un(sockaddr)
-        @afamily   = Socket::AF_UNIX
-      else
+      when Socket::AF_INET
+        @ip_port, @ip_address = Socket.unpack_sockaddr_in(sockaddr)
+      when Socket::AF_INET6
         @ip_port, @ip_address = Socket.unpack_sockaddr_in(sockaddr)
-
-        if sockaddr.bytesize == Truffle::Socket::Foreign::SockaddrIn6.size
-          @afamily = Socket::AF_INET6
-        else
-          @afamily = Socket::AF_INET
-        end
       end
     end
 
@@ -203,17 +200,13 @@ def ip?
   end
 
   def ip_address
-    unless ip?
-      raise SocketError, 'An IPv4/IPv6 address is required'
-    end
+    raise SocketError, 'need IPv4 or IPv6 address' unless ip?
 
     @ip_address
   end
 
   def ip_port
-    unless ip?
-      raise SocketError, 'An IPv4/IPv6 address is required'
-    end
+    raise SocketError, 'need IPv4 or IPv6 address' unless ip?
 
     @ip_port
   end

lib/truffle/socket/socket.rb

@@ -251,9 +251,16 @@ def self.socketpair(family, type, protocol = 0)
     family = Truffle::Socket.address_family(family)
     type   = Truffle::Socket.socket_type(type)
 
-    fd0, fd1 = Truffle::Socket::Foreign.socketpair(family, type, protocol)
+    fd1, fd2 = Truffle::Socket::Foreign.socketpair(family, type, protocol)
 
-    [for_fd(fd0), for_fd(fd1)]
+    s1 = for_fd(fd1)
+    s2 = for_fd(fd2)
+
+    [s1, s2].map do |sock|
+      sock.instance_variable_set(:@family, family)
+      sock.instance_variable_set(:@socket_type, type)
+      sock
+    end
   end
 
   class << self

lib/truffle/socket/truffle/foreign.rb

@@ -304,7 +304,7 @@ def self.unpack_sockaddr_in(sockaddr, reverse_lookup)
 
         # On some systems this doesn't fail for families other than AF_INET(6)
         # so we raise manually here.
-        unless family =~ /AF_INET/
+        unless family.include?('AF_INET')
           raise ArgumentError, 'not an AF_INET/AF_INET6 sockaddr'
         end
 

lib/truffle/socket/truffle/foreign/sockaddr.rb

@@ -30,6 +30,20 @@ module Foreign
       class Sockaddr < Truffle::FFI::Struct
         config('platform.sockaddr', :sa_data, :sa_family)
 
+        SA_FAMILY_T = Truffle::Config['platform.typedef.sa_family_t'].to_sym
+        SA_FAMILY_OFFSET = Truffle::Config['platform.sockaddr.sa_family.offset']
+
+        def self.family_of_string(str)
+          case SA_FAMILY_T
+          when :ushort
+            str[SA_FAMILY_OFFSET..-1].unpack1('S')
+          when :uchar
+            str[SA_FAMILY_OFFSET..-1].unpack1('C')
+          else
+            raise "Unexpected type for sa_family_t: #{SA_FAMILY_T}"
+          end
+        end
+
         def data
           self[:sa_data]
         end