add {active,N} socket option for TCP, UDP, and SCTP

Add the {active,N} socket option, where N is an integer in the range
-32768..32767, to allow a caller to specify the number of data messages to
be delivered to the controlling process. Once the socket's delivered
message count either reaches 0 or is explicitly set to 0 with
inet:setopts/2 or by including {active,0} as an option when the socket is
created, the socket transitions to passive ({active, false}) mode and the
socket's controlling process receives a message to inform it of the
transition. TCP sockets receive {tcp_passive,Socket}, UDP sockets receive
{udp_passive,Socket} and SCTP sockets receive {sctp_passive,Socket}.

The socket's delivered message counter defaults to 0, but it can be set
using {active,N} via any gen_tcp, gen_udp, or gen_sctp function that takes
socket options as arguments, or via inet:setopts/2. New N values are added
to the socket's current counter value, and negative numbers can be used to
reduce the counter value. Specifying a number that would cause the socket's
counter value to go above 32767 causes an einval error. If a negative
number is specified such that the counter value would become negative, the
socket's counter value is set to 0 and the socket transitions to passive
mode. If the counter value is already 0 and inet:setopts(Socket,
[{active,0}]) is specified, the counter value remains at 0 but the
appropriate passive mode transition message is generated for the socket.

This commit contains a modified preloaded prim_inet.beam due to changes in
prim_inet.erl.

Add tests for {active,N} mode for TCP, UDP, and SCTP sockets.

Add documentation for {active,N} mode for inet, gen_tcp, gen_udp, and
gen_sctp.

5 files changed, 17 insertions, 4 deletions

diff --git a/lib/kernel/src/gen_sctp.erl b/lib/kernel/src/gen_sctp.erl
index 0d005eb651..23a698f9b2 100644
--- a/lib/kernel/src/gen_sctp.erl
+++ b/lib/kernel/src/gen_sctp.erl
@@ -36,7 +36,7 @@
 
 -type assoc_id() :: term().
 -type option() ::
-        {active, true | false | once} |
+        {active, true | false | once | -32768..32767} |
         {buffer, non_neg_integer()} |
         {dontroute, boolean()} |
         {high_msgq_watermark, pos_integer()} |
diff --git a/lib/kernel/src/gen_tcp.erl b/lib/kernel/src/gen_tcp.erl
index 96026aa428..bc8ffbe5e3 100644
--- a/lib/kernel/src/gen_tcp.erl
+++ b/lib/kernel/src/gen_tcp.erl
@@ -30,7 +30,7 @@
 -include("file.hrl").
 
 -type option() ::
-        {active,          true | false | once} |
+        {active,          true | false | once | -32768..32767} |
         {buffer,          non_neg_integer()} |
         {delay_send,      boolean()} |
         {deliver,         port | term} |
diff --git a/lib/kernel/src/gen_udp.erl b/lib/kernel/src/gen_udp.erl
index e82b11d2ef..70dceb3679 100644
--- a/lib/kernel/src/gen_udp.erl
+++ b/lib/kernel/src/gen_udp.erl
@@ -26,7 +26,7 @@
 -include("inet_int.hrl").
 
 -type option() ::
-        {active,          true | false | once} |
+        {active,          true | false | once | -32768..32767} |
         {add_membership,  {inet:ip_address(), inet:ip_address()}} |
         {broadcast,       boolean()} |
         {buffer,          non_neg_integer()} |
diff --git a/lib/kernel/src/inet.erl b/lib/kernel/src/inet.erl
index 9cfd3819f0..7261d6486f 100644
--- a/lib/kernel/src/inet.erl
+++ b/lib/kernel/src/inet.erl
@@ -667,6 +667,9 @@ con_opt([Opt | Opts], R, As) ->
 		false ->
 		    {error, badarg}
 	    end;
+        {active,N} when is_integer(N), N < 32768, N >= -32768 ->
+            NOpts = lists:keydelete(active, 1, R#connect_opts.opts),
+            con_opt(Opts, R#connect_opts { opts = [{active,N}|NOpts] }, As);
 	{Name,Val} when is_atom(Name) -> con_add(Name, Val, R, Opts, As);
 	_ -> {error, badarg}
     end;
@@ -733,6 +736,9 @@ list_opt([Opt | Opts], R, As) ->
 		false ->
 		    {error, badarg}
 	    end;
+        {active,N} when is_integer(N), N < 32768, N >= -32768 ->
+            NOpts = lists:keydelete(active, 1, R#listen_opts.opts),
+            list_opt(Opts, R#listen_opts { opts = [{active,N}|NOpts] }, As);
 	{Name,Val} when is_atom(Name) -> list_add(Name, Val, R, Opts, As);
 	_ -> {error, badarg}
     end;
@@ -787,6 +793,9 @@ udp_opt([Opt | Opts], R, As) ->
 		false ->
 		    {error, badarg}
 	    end;
+        {active,N} when is_integer(N), N < 32768, N >= -32768 ->
+            NOpts = lists:keydelete(active, 1, R#udp_opts.opts),
+            udp_opt(Opts, R#udp_opts { opts = [{active,N}|NOpts] }, As);
 	{Name,Val} when is_atom(Name) -> udp_add(Name, Val, R, Opts, As);
 	_ -> {error, badarg}
     end;
@@ -805,7 +814,7 @@ udp_add(Name, Val, R, Opts, As) ->
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %  Currently supported options include:
 %  (*) {mode,   list|binary}	 or just list|binary
-%  (*) {active, true|false|once}
+%  (*) {active, true|false|once|N}
 %  (*) {sctp_module, inet_sctp|inet6_sctp} or just inet|inet6
 %  (*) options set via setsockopt.
 %      The full list is below in sctp_options/0 .
@@ -867,6 +876,9 @@ sctp_opt([Opt|Opts], Mod, R, As) ->
 		false ->
 		    {error, badarg}
 	    end;
+        {active,N} when is_integer(N), N < 32768, N >= -32768 ->
+            NOpts = lists:keydelete(active, 1, R#sctp_opts.opts),
+            sctp_opt(Opts, Mod, R#sctp_opts { opts = [{active,N}|NOpts] }, As);
 	{Name,Val}	-> sctp_opt (Opts, Mod, R, As, Name, Val);
 	_ -> {error,badarg}
     end;
diff --git a/lib/kernel/src/inet_int.hrl b/lib/kernel/src/inet_int.hrl
index 18a4a61b2f..024a5fd3b6 100644
--- a/lib/kernel/src/inet_int.hrl
+++ b/lib/kernel/src/inet_int.hrl
@@ -46,6 +46,7 @@
 -define(INET_PASSIVE, 0).
 -define(INET_ACTIVE,  1).
 -define(INET_ONCE,    2). % Active once then passive
+-define(INET_MULTI,   3). % Active N then passive
 
 %% state codes (getstatus, INET_REQ_GETSTATUS)
 -define(INET_F_OPEN,         16#0001).