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.

1 files changed, 1 insertions, 1 deletions

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} |