Document the local (unix) address family

3 files changed, 75 insertions, 18 deletions

diff --git a/lib/kernel/doc/src/gen_tcp.xml b/lib/kernel/doc/src/gen_tcp.xml
index b75d42d198..88135ea43d 100644
--- a/lib/kernel/doc/src/gen_tcp.xml
+++ b/lib/kernel/doc/src/gen_tcp.xml
@@ -153,17 +153,17 @@ do_recv(Sock, Bs) ->
           <c><anno>Address</anno></c> can be a hostname or an IP address.</p>
         <p>The following options are available:</p>
         <taglist>
-          <tag><c>{ip, ip_address()}</c></tag>
+          <tag><c>{ip, Address}</c></tag>
           <item><p>If the host has many network interfaces, this option
             specifies which one to use.</p></item>
-          <tag><c>{ifaddr, ip_address()}</c></tag>
-          <item><p>Same as <c>{ip, ip_address()}</c>. If the host has many
+          <tag><c>{ifaddr, Address}</c></tag>
+          <item><p>Same as <c>{ip, Address}</c>. If the host has many
             network interfaces, this option specifies which one to use.</p>
           </item>
           <tag><c>{fd, integer() >= 0}</c></tag>
           <item><p>If a socket has somehow been connected without using
             <c>gen_tcp</c>, use this option to pass the file descriptor
-            for it. If <c>{ip, ip_address()}</c> and/or
+            for it. If <c>{ip, Address}</c> and/or
             <c>{port, port_number()}</c> is combined with this option,  the
             <c>fd</c> is bound to the specified interface and port before
             connecting. If these options are not specified, it is assumed that
@@ -175,9 +175,10 @@ do_recv(Sock, Bs) ->
 	  <tag><c>local</c></tag>
 	  <item>
             <p>
-	      Sets up the socket for local address family. This option is only
-              valid together with <c>{fd, integer()}</c> when the file descriptor
-              is of local address family (e.g. a Unix Domain Socket)
+	      Sets up a Unix Domain Socket. See
+	      <seealso marker="inet#type-local_address">
+		<c>inet:local_address()</c>
+	      </seealso>
 	    </p>
           </item>
           <tag><c>{port, Port}</c></tag>
@@ -254,7 +255,7 @@ do_recv(Sock, Bs) ->
           <item><p><c>B</c> is an integer &gt;= <c>0</c>. The backlog value
             defines the maximum length that the queue of pending connections
             can grow to. Defaults to <c>5</c>.</p></item>
-          <tag><c>{ip, ip_address()}</c></tag>
+          <tag><c>{ip, Address}</c></tag>
           <item><p>If the host has many network interfaces, this option
             specifies which one to listen on.</p></item>
           <tag><c>{port, Port}</c></tag>
@@ -263,8 +264,8 @@ do_recv(Sock, Bs) ->
           <item><p>If a socket has somehow been connected without using
             <c>gen_tcp</c>, use this option to pass the file
             descriptor for it.</p></item>
-          <tag><c>{ifaddr, ip_address()}</c></tag>
-          <item><p>Same as <c>{ip, ip_address()}</c>. If the host has many
+          <tag><c>{ifaddr, Address}</c></tag>
+          <item><p>Same as <c>{ip, Address}</c>. If the host has many
             network interfaces, this option specifies which one to use.</p>
           </item>
           <tag><c>inet6</c></tag>
diff --git a/lib/kernel/doc/src/gen_udp.xml b/lib/kernel/doc/src/gen_udp.xml
index ca9d9c978c..3f88a0272d 100644
--- a/lib/kernel/doc/src/gen_udp.xml
+++ b/lib/kernel/doc/src/gen_udp.xml
@@ -85,11 +85,11 @@
           <item><p>Received <c>Packet</c> is delivered as a list.</p></item>
           <tag><c>binary</c></tag>
           <item><p>Received <c>Packet</c> is delivered as a binary.</p></item>
-          <tag><c>{ip, ip_address()}</c></tag>
+          <tag><c>{ip, Address}</c></tag>
           <item><p>If the host has many network interfaces, this option
             specifies which one to use.</p></item>
-          <tag><c>{ifaddr, ip_address()}</c></tag>
-          <item><p>Same as <c>{ip, ip_address()}</c>. If the host has many
+          <tag><c>{ifaddr, Address}</c></tag>
+          <item><p>Same as <c>{ip, Address}</c>. If the host has many
             network interfaces, this option specifies which one to
             use.</p></item>
           <tag><c>{fd, integer() >= 0}</c></tag>
@@ -107,9 +107,10 @@
 	  <tag><c>local</c></tag>
 	  <item>
             <p>
-	      Sets up the socket for local address family. This option is only
-              valid together with <c>{fd, integer()}</c> when the file descriptor
-              is of local address family (e.g. a Unix Domain Socket)
+	      Sets up a Unix Domain Socket. See
+	      <seealso marker="inet#type-local_address">
+		<c>inet:local_address()</c>
+	      </seealso>
 	    </p>
           </item>
           <tag><c>{udp_module, module()}</c></tag>
@@ -184,8 +185,10 @@
       <name name="send" arity="4"/>
       <fsummary>Send a packet.</fsummary>
       <desc>
-        <p>Sends a packet to the specified address and port. Argument
-          <c><anno>Address</anno></c> can be a hostname or an IP address.</p>
+        <p>
+	  Sends a packet to the specified address and port. Argument
+          <c><anno>Address</anno></c> can be a hostname or a socket address.
+	</p>
       </desc>
     </func>
   </funcs>
diff --git a/lib/kernel/doc/src/inet.xml b/lib/kernel/doc/src/inet.xml
index 5ff167bcb3..c0dce2f50c 100644
--- a/lib/kernel/doc/src/inet.xml
+++ b/lib/kernel/doc/src/inet.xml
@@ -118,6 +118,59 @@ fe80::204:acff:fe17:bf38
       <name name="port_number"/>
     </datatype>
     <datatype>
+      <name name="local_address"/>
+      <desc>
+	<p>
+	  This address family only works on Unix-like systems.
+	</p>
+	<p>
+	  <c><anno>File</anno></c> is normally a file pathname
+	  in a local filesystem.  It is limited in length by the
+	  operating system, traditionally to 108 bytes.
+	</p>
+	<p>
+	  A <c>binary()</c> is passed as is to the operating system,
+	  but a <c>string()</c> is encoded according to the
+	  <seealso marker="file#native_name_encoding/0">
+	    system filename encoding mode.
+	  </seealso>
+	</p>
+	<p>
+	  Other addresses are possible, for example Linux implements
+	  "Abstract Addresses".  See the documentation for
+	  Unix Domain Sockets on your system,
+	  normally <c>unix</c> in manual section 7.
+	</p>
+	<p>
+	  In most API functions where you can use
+	  this address family the port number must be <c>0</c>.
+	</p>
+      </desc>
+    </datatype>
+    <datatype>
+      <name name="socket_address"/>
+    </datatype>
+    <datatype>
+      <name name="returned_non_ip_address"/>
+      <desc>
+	<p>
+	  Addresses besides
+	  <seealso marker="#type-ip_address">
+	    <c>ip_address()</c>
+	  </seealso>
+	  ones that are returned from socket API functions.
+	  See in particular
+	  <seealso marker="#type-local_address">
+	    <c>local_address()</c>.
+	  </seealso>
+	  The <c>unspec</c> family corresponds to AF_UNSPEC and can
+	  occur if the other side has no socket address.
+	  The <c>undefined</c> family can only occur in the unlikely
+	  event of an address family that the VM does not recognize.
+	</p>
+      </desc>
+    </datatype>
+    <datatype>
       <name name="posix"/>
       <desc>
         <p>An atom that is named from the POSIX error codes used in Unix,