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
|
------------------------------------------------------------------------------
-- --
-- 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) 2001-2020, 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;
|
