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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- G N A T . S O C K E T S . T H I N . C _ S O C K E T P A I R --
-- --
-- B o d y --
-- --
-- Copyright (C) 2001-2022, AdaCore --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- Portable sockets-based implementation of the C_Socketpair used for
-- platforms that do not support UNIX socketpair system call.
-- Note: this code is only for non-UNIX platforms.
separate (GNAT.Sockets.Thin)
function C_Socketpair
(Domain : C.int;
Typ : C.int;
Protocol : C.int;
Fds : not null access Fd_Pair) return C.int
is
use type C.char_array;
L_Sock, C_Sock, P_Sock : C.int := Failure;
-- Listening socket, client socket and peer socket
Family : constant Family_Type :=
(case Domain is
when SOSC.AF_INET => Family_Inet,
when SOSC.AF_INET6 => Family_Inet6,
when others => Family_Unspec);
Len : aliased C.int := C.int (Lengths (Family));
C_Sin : aliased Sockaddr;
C_Bin : aliased C.char_array (1 .. C.size_t (Len));
for C_Bin'Address use C_Sin'Address;
-- Address of listening and client socket and it's binary representation.
-- We need binary representation because Ada does not allow to compare
-- unchecked union if either of the operands lacks inferable discriminants.
-- RM-B-3-3 23/2.
P_Sin : aliased Sockaddr;
P_Bin : aliased C.char_array (1 .. C.size_t (Len));
for P_Bin'Address use P_Sin'Address;
-- Address of peer socket and it's binary representation
T_Sin : aliased Sockaddr;
T_Bin : aliased C.char_array (1 .. C.size_t (Len));
for T_Bin'Address use T_Sin'Address;
-- Temporary address to compare and check that address and port of the
-- socket equal to peer address and port of the opposite connected socket.
Res : C.int with Warnings => Off;
begin
Set_Family (C_Sin.Sin_Family, Family);
case Family is
when Family_Inet =>
C_Sin.Sin_Addr.S_B1 := 127;
C_Sin.Sin_Addr.S_B4 := 1;
when Family_Inet6 =>
C_Sin.Sin6_Addr (C_Sin.Sin6_Addr'Last) := 1;
when others =>
Set_Socket_Errno (SOSC.EAFNOSUPPORT);
return Failure;
end case;
for J in 1 .. 10 loop
-- Retry loop, in case the C_Connect below fails
C_Sin.Sin_Port := 0;
-- Create a listening socket
L_Sock := C_Socket (Domain, Typ, Protocol);
exit when L_Sock = Failure;
-- Bind the socket to an available port on localhost
Res := C_Bind (L_Sock, C_Sin'Address, Len);
exit when Res = Failure;
-- Get assigned port
Res := C_Getsockname (L_Sock, C_Sin'Address, Len'Access);
exit when Res = Failure;
-- Set socket to listen mode, with a backlog of 1 to guarantee that
-- exactly one call to connect(2) succeeds.
Res := C_Listen (L_Sock, 1);
exit when Res = Failure;
-- Create read end (client) socket
C_Sock := C_Socket (Domain, Typ, Protocol);
exit when C_Sock = Failure;
-- Connect listening socket
Res := C_Connect (C_Sock, C_Sin'Address, Len);
if Res = Failure then
-- In rare cases, the above C_Bind chooses a port that is still
-- marked "in use", even though it has been closed (perhaps by some
-- other process that has already exited). This causes the above
-- C_Connect to fail with EADDRINUSE. In this case, we close the
-- ports, and loop back to try again. This mysterious Windows
-- behavior is documented. See, for example:
-- http://msdn2.microsoft.com/en-us/library/ms737625.aspx
-- In an experiment with 2000 calls, 21 required exactly one retry, 7
-- required two, and none required three or more. Note that no delay
-- is needed between retries; retrying C_Bind will typically produce
-- a different port.
exit when Socket_Errno /= SOSC.EADDRINUSE;
goto Repeat;
end if;
-- Since the call to connect(2) has succeeded and the backlog limit
-- on the listening socket is 1, we know that there is now exactly
-- one pending connection on L_Sock, which is the one from R_Sock.
P_Sin.Sun_Path := (others => C.nul);
P_Sock := C_Accept (L_Sock, P_Sin'Address, Len'Access);
exit when P_Sock = Failure;
-- Address and port of the socket equal to peer address and port of the
-- opposite connected socket.
Res := C_Getsockname (P_Sock, T_Sin'Address, Len'Access);
exit when Res = Failure;
if T_Bin /= C_Bin then
goto Repeat;
end if;
-- Address and port of the socket equal to peer address and port of the
-- opposite connected socket.
Res := C_Getsockname (C_Sock, T_Sin'Address, Len'Access);
exit when Res = Failure;
if T_Bin /= P_Bin then
goto Repeat;
end if;
-- Close listening socket (ignore exit status)
Res := C_Close (L_Sock);
Fds.all := (Read_End => C_Sock, Write_End => P_Sock);
return Thin_Common.Success;
<<Repeat>>
Res := C_Close (C_Sock);
C_Sock := Failure;
Res := C_Close (P_Sock);
P_Sock := Failure;
Res := C_Close (L_Sock);
L_Sock := Failure;
end loop;
declare
Saved_Errno : constant Integer := Socket_Errno;
begin
if P_Sock /= Failure then
Res := C_Close (P_Sock);
end if;
if C_Sock /= Failure then
Res := C_Close (C_Sock);
end if;
if L_Sock /= Failure then
Res := C_Close (L_Sock);
end if;
Set_Socket_Errno (Saved_Errno);
end;
return Failure;
end C_Socketpair;
|
