Implement {netns,NS} option for inet:getifaddrs/1

Also implement the same option for the legacy undocumented functions
inet:getif/1,getiflist/1,ifget/2,ifset/2.

The arity 1 functions had before this change got signatures that
took a socket port that was used to do the needed syscall, so now
the signature was extended to also take an option list with the
only supported option {netns,Namespace}.  The Socket argument
variant remains unsupported.

For inet:getifaddrs/1 the documentation file was changed to old
style function name definition so be able to hide the Socket
argument variant that is visible in the type spec.

The arity 2 functions had got an option list as second argument.
This list had to be partitioned into one list for the namespace
option(s) and the other for the rest.

The namespace option list was then fed to the already existing
namespace support for socket opening, which places the socket
in a namespace and hence made all these functions that in
inet_drv.c used getsockopt() work without change.

The functions that used getifaddrs() in inet_drv.c had to be
changed in inet_drv.c to swap namespaces around the
getifaddrs() syscall.  This functionality was separated into
a new function call_getifaddrs().

2 files changed, 202 insertions, 62 deletions

diff --git a/lib/kernel/doc/src/inet.xml b/lib/kernel/doc/src/inet.xml
index ed775d67eb..127c110df4 100644
--- a/lib/kernel/doc/src/inet.xml
+++ b/lib/kernel/doc/src/inet.xml
@@ -198,6 +198,79 @@ fe80::204:acff:fe17:bf38
       </desc>
     </datatype>
     <datatype>
+      <name name="getifaddrs_ifopts"/>
+      <desc>
+	<p>
+	  Interface address description list returned from
+	  <seealso marker="#getifaddrs/0"><c>getifaddrs/0,1</c></seealso>
+	  for a named interface, translated from the returned
+	  data of the POSIX API function <c>getaddrinfo()</c>.
+	</p>
+        <p>
+	  <c><anno>Hwaddr</anno></c> is hardware dependent,
+	  for example, on Ethernet interfaces it is
+	the 6-byte Ethernet address (MAC address (EUI-48 address)).
+	</p>
+        <p>
+	  The tuples <c>{addr,<anno>Addr</anno>}</c>,
+	  <c>{netmask,<anno>Netmask</anno>}</c>, and possibly
+	  <c>{broadaddr,<anno>Broadaddr</anno>}</c> or
+	  <c>{dstaddr,<anno>Dstaddr</anno>}</c>
+	  are repeated in the list
+	  if the interface has got multiple addresses.
+	  An interface may have multiple <c>{flag,_}</c> tuples
+	  for example if it has different flags
+	  for different address families.
+	  Multiple <c>{hwaddr,<anno>Hwaddr</anno>}</c> tuples
+	  is hard to say anything definite about, though.
+	  The tuple <c>{flag,<anno>Flags</anno>}</c> is mandatory,
+	  all others are optional.
+	</p>
+        <p>
+	  Do not rely too much on the order
+	  of <c><anno>Flags</anno></c> atoms
+          or the <c><anno>Ifopt</anno></c> tuples.
+	  There are however some rules:
+	</p>
+        <list type="bulleted">
+	  <item><p>
+	    A <c>{flag,_}</c> tuple applies to all other tuples that follow.
+	  </p></item>
+          <item><p>
+	    Immediately after <c>{addr,_}</c> follows <c>{netmask,_}</c>.
+	  </p></item>
+          <item><p>
+	    Immediately thereafter may <c>{broadaddr,_}</c> follow
+	    if <c>broadcast</c> is member of <c><anno>Flags</anno></c>,
+	    or <c>{dstaddr,_}</c> if <c>pointtopoint</c>
+	    is member of <c><anno>Flags</anno></c>.
+	    Both <c>{dstaddr,_}</c> and <c>{broadaddr,_}</c>
+	    does not occur for the same <c>{addr,_}</c>.
+	  </p></item>
+          <item><p>
+	    Any <c>{netmask,_}</c>, <c>{broadaddr,_}</c>, or
+            <c>{dstaddr,_}</c> tuples that follow an
+	    <c>{addr,<anno>Addr</anno>}</c>
+            tuple concerns the address <c><anno>Addr</anno></c>.
+	  </p></item>
+        </list>
+        <p>
+	  The tuple <c>{hwaddr,_}</c> is not returned on Solaris, as the
+          hardware address historically belongs to the link layer
+	  and it is not returned by the Solaris API function
+	  <c>getaddrinfo()</c>.
+	</p>
+	<warning>
+	  <p>
+	    On Windows, the data is fetched from different
+	    OS API functions, so the <c><anno>Netmask</anno></c>
+	    and <c><anno>Broadaddr</anno></c> values may be calculated,
+	    just as some <c><anno>Flags</anno></c> values.
+	  </p>
+	</warning>
+      </desc>
+    </datatype>
+    <datatype>
       <name name="posix"/>
       <desc>
         <p>An atom that is named from the POSIX error codes used in Unix,
@@ -324,38 +397,64 @@ fe80::204:acff:fe17:bf38
       <name name="getifaddrs" arity="0"/>
       <fsummary>Return a list of interfaces and their addresses.</fsummary>
       <desc>
-        <p>Returns a list of 2-tuples containing interface names and the
-          interface addresses. <c><anno>Ifname</anno></c> is a Unicode string.
-          <c><anno>Hwaddr</anno></c> is hardware dependent, for example, on
-          Ethernet interfaces
-          it is the 6-byte Ethernet address (MAC address (EUI-48 address)).</p>
-        <p>The tuples <c>{addr,<anno>Addr</anno>}</c>, <c>{netmask,_}</c>, and
-          <c>{broadaddr,_}</c> are repeated in the result list if the interface
-          has multiple addresses. If you come across an interface with
-          multiple <c>{flag,_}</c> or <c>{hwaddr,_}</c> tuples, you have
-          a strange interface or possibly a bug in this function. The tuple
-          <c>{flag,_}</c> is mandatory, all others are optional.</p>
-        <p>Do not rely too much on the order of <c><anno>Flag</anno></c> atoms
-          or <c><anno>Ifopt</anno></c> tuples. There are however some rules:</p>
-        <list type="bulleted">
-          <item><p>Immediately after
-            <c>{addr,_}</c> follows <c>{netmask,_}</c>.</p></item>
-          <item><p>Immediately thereafter follows <c>{broadaddr,_}</c> if flag
-            <c>broadcast</c> is <em>not</em> set and flag
-            <c>pointtopoint</c> <em>is</em> set.</p></item>
-          <item><p>Any <c>{netmask,_}</c>, <c>{broadaddr,_}</c>, or
-            <c>{dstaddr,_}</c> tuples that follow an <c>{addr,_}</c>
-            tuple concerns that address.</p></item>
-        </list>
-        <p>The tuple <c>{hwaddr,_}</c> is not returned on Solaris, as the
-          hardware address historically belongs to the link layer and only
-          the superuser can read such addresses.</p>
-	<warning>
-	  <p>On Windows, the data is fetched from different OS API functions,
-            so the <c><anno>Netmask</anno></c> and <c><anno>Broadaddr</anno></c>
-            values can be calculated, just as some <c><anno>Flag</anno></c>
-            values. Report flagrant bugs.</p>
-	</warning>
+        <p>
+	  Returns a list of 2-tuples containing interface names and
+	  the interfaces' addresses. <c><anno>Ifname</anno></c>
+	  is a Unicode string and
+	  <c><anno>Ifopts</anno></c> is a list of
+	  interface address description tuples.
+	</p>
+        <p>
+	  The interface address description tuples
+	  are documented under the type of the
+          <seealso marker="#type-getifaddrs_ifopts">
+	    <c><anno>Ifopts</anno></c>
+	  </seealso>
+	  value.
+	</p>
+      </desc>
+    </func>
+
+    <func>
+      <name>getifaddrs(Opts) ->
+        {ok, [{Ifname, Ifopts}]} | {error, Posix}
+      </name>
+      <fsummary>Return a list of interfaces and their addresses.</fsummary>
+      <type>
+	<v>
+	  Opts = [{netns, Namespace}]
+	</v>
+	<v>
+	  Namespace =
+	  <seealso marker="file#type-filename_all">
+	    file:filename_all()
+	  </seealso>
+	</v>
+	<v>Ifname = string()</v>
+	<v>
+	  Ifopts =
+	  <seealso marker="#type-getifaddrs_ifopts">
+	    getifaddrs_ifopts()
+	  </seealso>
+	</v>
+	<v>Posix = <seealso marker="#type-posix">posix()</seealso></v>
+      </type>
+      <desc>
+	<p>
+	  The same as
+	  <seealso marker="#getifaddrs/0"><c>getifaddrs/0</c></seealso>
+	  but the <c>Option</c>
+	  <c>{netns, Namespace}</c> sets a network namespace
+	  for the OS call, on platforms that supports that feature.
+	</p>
+	<p>
+	  See the socket option
+	  <seealso marker="#option-netns">
+	    <c>{netns, Namespace}</c>
+	  </seealso>
+	  under
+	  <seealso marker="#setopts/2"><c>setopts/2</c></seealso>.
+	</p>
       </desc>
     </func>
 
@@ -950,20 +1049,29 @@ get_tcpi_sacked(Sock) ->
           </item>
           <tag><c>{mode, Mode :: binary | list}</c></tag>
           <item>
-            <p>Received <c>Packet</c> is delivered as defined by <c>Mode</c>.
+            <p>
+	      Received <c>Packet</c> is delivered as defined by <c>Mode</c>.
             </p>
           </item>
-	  <tag><c>{netns, Namespace :: file:filename_all()}</c></tag>
+	  <tag>
+	    <marker id="option-netns"/>
+	    <c>{netns, Namespace :: file:filename_all()}</c>
+	  </tag>
 	  <item>
-	    <p>Sets a network namespace for the socket. Parameter
+	    <p>
+	      Sets a network namespace for the socket. Parameter
 	      <c>Namespace</c> is a filename defining the namespace, for
 	      example, <c>"/var/run/netns/example"</c>, typically created by
 	      command <c>ip netns add example</c>. This option must be used in
 	      a function call that creates a socket, that is,
 	      <seealso marker="gen_tcp#connect/3"><c>gen_tcp:connect/3,4</c></seealso>,
 	      <seealso marker="gen_tcp#listen/2"><c>gen_tcp:listen/2</c></seealso>,
-	      <seealso marker="gen_udp#open/1"><c>gen_udp:open/1,2</c></seealso>, or
-	    <seealso marker="gen_sctp#open/0"><c>gen_sctp:open/0,1,2</c></seealso>.</p>
+	      <seealso marker="gen_udp#open/1"><c>gen_udp:open/1,2</c></seealso>
+	      or
+	      <seealso marker="gen_sctp#open/0"><c>gen_sctp:open/0,1,2</c></seealso>,
+	      and also
+	      <seealso marker="#getifaddrs/1"><c>getifaddrs/1</c></seealso>.
+	    </p>
 	    <p>This option uses the Linux-specific syscall
 	      <c>setns()</c>, such as in Linux kernel 3.0 or later,
 	      and therefore only exists when the runtime system
diff --git a/lib/kernel/src/inet.erl b/lib/kernel/src/inet.erl
index 5dd68dc285..9f22eb6aaa 100644
--- a/lib/kernel/src/inet.erl
+++ b/lib/kernel/src/inet.erl
@@ -154,6 +154,15 @@
 		 'running' | 'multicast' | 'loopback']} |
       {'hwaddr', ether_address()}.
 
+-type getifaddrs_ifopts() ::
+        [Ifopt :: {flags, Flags :: [up | broadcast | loopback |
+                                    pointtopoint | running | multicast]} |
+                  {addr, Addr :: ip_address()} |
+                  {netmask, Netmask :: ip_address()} |
+                  {broadaddr, Broadaddr :: ip_address()} |
+                  {dstaddr, Dstaddr :: ip_address()} |
+                  {hwaddr, Hwaddr :: [byte()]}].
+
 -type address_family() :: 'inet' | 'inet6' | 'local'.
 -type socket_protocol() :: 'tcp' | 'udp' | 'sctp'.
 -type socket_type() :: 'stream' | 'dgram' | 'seqpacket'.
@@ -321,32 +330,32 @@ getopts(Socket, Opts) ->
 	    Other
     end.
 
--spec getifaddrs(Socket :: socket()) ->
-	{'ok', [string()]} | {'error', posix()}.
-
+-spec getifaddrs(
+        [Option :: {netns, Namespace :: file:filename_all()}]
+        | socket()) ->
+                        {'ok', [{Ifname :: string(),
+                                 Ifopts :: getifaddrs_ifopts()}]}
+                            | {'error', posix()}.
+getifaddrs(Opts) when is_list(Opts) ->
+    withsocket(fun(S) -> prim_inet:getifaddrs(S) end, Opts);
 getifaddrs(Socket) ->
     prim_inet:getifaddrs(Socket).
 
--spec getifaddrs() -> {ok, Iflist} | {error, posix()} when
-      Iflist :: [{Ifname,[Ifopt]}],
-      Ifname :: string(),
-      Ifopt :: {flags,[Flag]} | {addr,Addr} | {netmask,Netmask}
-             | {broadaddr,Broadaddr} | {dstaddr,Dstaddr}
-             | {hwaddr,Hwaddr},
-      Flag :: up | broadcast | loopback | pointtopoint
-            | running | multicast,
-      Addr :: ip_address(),
-      Netmask :: ip_address(),
-      Broadaddr :: ip_address(),
-      Dstaddr :: ip_address(),
-      Hwaddr :: [byte()].
-
+-spec getifaddrs() ->
+                        {'ok', [{Ifname :: string(),
+                                 Ifopts :: getifaddrs_ifopts()}]}
+                            | {'error', posix()}.
 getifaddrs() ->
     withsocket(fun(S) -> prim_inet:getifaddrs(S) end).
 
--spec getiflist(Socket :: socket()) ->
-	{'ok', [string()]} | {'error', posix()}.
 
+-spec getiflist(
+        [Option :: {netns, Namespace :: file:filename_all()}]
+        | socket()) ->
+                       {'ok', [string()]} | {'error', posix()}.
+
+getiflist(Opts) when is_list(Opts) ->
+    withsocket(fun(S) -> prim_inet:getiflist(S) end, Opts);
 getiflist(Socket) -> 
     prim_inet:getiflist(Socket).
 
@@ -363,11 +372,19 @@ getiflist() ->
 ifget(Socket, Name, Opts) -> 
     prim_inet:ifget(Socket, Name, Opts).
 
--spec ifget(Name :: string() | atom(), Opts :: [if_getopt()]) ->
+-spec ifget(
+        Name :: string() | atom(),
+        Opts :: [if_getopt() |
+                 {netns, Namespace :: file:filename_all()}]) ->
 	{'ok', [if_getopt_result()]} | {'error', posix()}.
 
 ifget(Name, Opts) ->
-    withsocket(fun(S) -> prim_inet:ifget(S, Name, Opts) end).
+    {NSOpts,IFOpts} =
+        lists:partition(
+          fun ({netns,_}) -> true;
+              (_) -> false
+          end, Opts),
+    withsocket(fun(S) -> prim_inet:ifget(S, Name, IFOpts) end, NSOpts).
 
 -spec ifset(Socket :: socket(),
             Name :: string() | atom(),
@@ -377,11 +394,19 @@ ifget(Name, Opts) ->
 ifset(Socket, Name, Opts) -> 
     prim_inet:ifset(Socket, Name, Opts).
 
--spec ifset(Name :: string() | atom(), Opts :: [if_setopt()]) ->
+-spec ifset(
+        Name :: string() | atom(),
+        Opts :: [if_setopt() |
+                 {netns, Namespace :: file:filename_all()}]) ->
 	'ok' | {'error', posix()}.
 
 ifset(Name, Opts) ->
-    withsocket(fun(S) -> prim_inet:ifset(S, Name, Opts) end).
+    {NSOpts,IFOpts} =
+        lists:partition(
+          fun ({netns,_}) -> true;
+              (_) -> false
+          end, Opts),
+    withsocket(fun(S) -> prim_inet:ifset(S, Name, IFOpts) end, NSOpts).
 
 -spec getif() ->
 	{'ok', [{ip_address(), ip_address() | 'undefined', ip_address()}]} | 
@@ -391,10 +416,14 @@ getif() ->
     withsocket(fun(S) -> getif(S) end).
 
 %% backwards compatible getif
--spec getif(Socket :: socket()) ->
+-spec getif(
+        [Option :: {netns, Namespace :: file:filename_all()}]
+        | socket()) ->
 	{'ok', [{ip_address(), ip_address() | 'undefined', ip_address()}]} | 
 	{'error', posix()}.
 
+getif(Opts) when is_list(Opts) ->
+    withsocket(fun(S) -> getif(S) end, Opts);
 getif(Socket) ->
     case prim_inet:getiflist(Socket) of
 	{ok, IfList} ->
@@ -415,7 +444,10 @@ getif(Socket) ->
     end.
 
 withsocket(Fun) ->
-    case inet_udp:open(0,[]) of
+    withsocket(Fun, []).
+%%
+withsocket(Fun, Opts) ->
+    case inet_udp:open(0, Opts) of
 	{ok,Socket} ->
 	    Res = Fun(Socket),
 	    inet_udp:close(Socket),