1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
|
------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- G N A T . S O C K E T S . T H I N . S I G N A L L I N G _ F D S --
-- --
-- B o d y --
-- --
-- Copyright (C) 2001-2008, 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 2, 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. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
-- Boston, MA 02110-1301, USA. --
-- --
-- As a special exception, if other files instantiate generics from this --
-- unit, or you link this unit with other files to produce an executable, --
-- this unit does not by itself cause the resulting executable to be --
-- covered by the GNU General Public License. This exception does not --
-- however invalidate any other reasons why the executable file might be --
-- covered by the GNU Public License. --
-- --
-- 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 GNAT.Sockets.Thin.Signalling_Fds
-- used for platforms that do not support UNIX pipes.
-- Note: this code used to be in GNAT.Sockets, but has been moved to a
-- platform-specific file. It is now used only for non-UNIX platforms.
separate (GNAT.Sockets.Thin)
package body Signalling_Fds is
-----------
-- Close --
-----------
procedure Close (Sig : C.int) is
Res : C.int;
pragma Unreferenced (Res);
-- Res is assigned but never read, because we purposefully ignore
-- any error returned by the C_Close system call, as per the spec
-- of this procedure.
begin
Res := C_Close (Sig);
end Close;
------------
-- Create --
------------
function Create (Fds : not null access Fd_Pair) return C.int is
L_Sock, R_Sock, W_Sock : C.int := Failure;
-- Listening socket, read socket and write socket
Sin : aliased Sockaddr_In;
Len : aliased C.int;
-- Address of listening socket
Res : C.int;
pragma Warnings (Off, Res);
-- Return status of system calls (usually ignored, hence warnings off)
begin
Fds.all := (Read_End | Write_End => Failure);
-- We open two signalling sockets. One of them is used to send data
-- to the other, which is included in a C_Select socket set. The
-- communication is used to force the call to C_Select to complete,
-- and the waiting task to resume its execution.
loop
-- Retry loop, in case the C_Connect below fails
-- Create a listening socket
L_Sock := C_Socket (SOSC.AF_INET, SOSC.SOCK_STREAM, 0);
if L_Sock = Failure then
goto Fail;
end if;
-- Bind the socket to an available port on localhost
Set_Family (Sin.Sin_Family, Family_Inet);
Sin.Sin_Addr.S_B1 := 127;
Sin.Sin_Addr.S_B2 := 0;
Sin.Sin_Addr.S_B3 := 0;
Sin.Sin_Addr.S_B4 := 1;
Sin.Sin_Port := 0;
Len := C.int (Lengths (Family_Inet));
Res := C_Bind (L_Sock, Sin'Address, Len);
if Res = Failure then
goto Fail;
end if;
-- Get assigned port
Res := C_Getsockname (L_Sock, Sin'Address, Len'Access);
if Res = Failure then
goto Fail;
end if;
-- 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);
if Res = Failure then
goto Fail;
end if;
-- Create read end (client) socket
R_Sock := C_Socket (SOSC.AF_INET, SOSC.SOCK_STREAM, 0);
if R_Sock = Failure then
goto Fail;
end if;
-- Connect listening socket
Res := C_Connect (R_Sock, Sin'Address, Len);
exit when Res /= Failure;
if Socket_Errno /= SOSC.EADDRINUSE then
goto Fail;
end if;
-- 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.
pragma Assert (Res = Failure
and then
Socket_Errno = SOSC.EADDRINUSE);
Res := C_Close (W_Sock);
W_Sock := Failure;
Res := C_Close (R_Sock);
R_Sock := Failure;
end loop;
-- 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.
W_Sock := C_Accept (L_Sock, Sin'Address, Len'Access);
if W_Sock = Failure then
goto Fail;
end if;
-- Set TCP_NODELAY on W_Sock, since we always want to send the data out
-- immediately.
Set_Socket_Option
(Socket => Socket_Type (W_Sock),
Level => IP_Protocol_For_TCP_Level,
Option => (Name => No_Delay, Enabled => True));
-- Close listening socket (ignore exit status)
Res := C_Close (L_Sock);
Fds.all := (Read_End => R_Sock, Write_End => W_Sock);
return Thin_Common.Success;
<<Fail>>
declare
Saved_Errno : constant Integer := Socket_Errno;
begin
if W_Sock /= Failure then
Res := C_Close (W_Sock);
end if;
if R_Sock /= Failure then
Res := C_Close (R_Sock);
end if;
if L_Sock /= Failure then
Res := C_Close (L_Sock);
end if;
Set_Socket_Errno (Saved_Errno);
end;
return Failure;
end Create;
----------
-- Read --
----------
function Read (Rsig : C.int) return C.int is
Buf : aliased Character;
begin
return C_Recv (Rsig, Buf'Address, 1, SOSC.MSG_Forced_Flags);
end Read;
-----------
-- Write --
-----------
function Write (Wsig : C.int) return C.int is
Buf : aliased Character := ASCII.NUL;
begin
return C_Sendto
(Wsig, Buf'Address, 1,
Flags => SOSC.MSG_Forced_Flags,
To => System.Null_Address,
Tolen => 0);
end Write;
end Signalling_Fds;
|
