1 /* Accept a connection on a socket, with specific opening flags.
2 Copyright (C) 2009-2021 Free Software Foundation, Inc.
3
4 This file is free software: you can redistribute it and/or modify
5 it under the terms of the GNU Lesser General Public License as
6 published by the Free Software Foundation; either version 3 of the
7 License, or (at your option) any later version.
8
9 This file is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
16
17 #include <config.h>
18
19 /* Specification. */
20 #include <sys/socket.h>
21
22 #include <errno.h>
23 #include <fcntl.h>
24 #include "binary-io.h"
25 #if GNULIB_MSVC_NOTHROW
26 # include "msvc-nothrow.h"
27 #else
28 # include <io.h>
29 #endif
30
31 #ifndef SOCK_CLOEXEC
32 # define SOCK_CLOEXEC 0
33 #endif
34 #ifndef SOCK_NONBLOCK
35 # define SOCK_NONBLOCK 0
36 #endif
37
38 int
accept4(int sockfd,struct sockaddr * addr,socklen_t * addrlen,int flags)39 accept4 (int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags)
40 {
41 int fd;
42
43 #if HAVE_DECL_ACCEPT4
44 # undef accept4
45 /* Try the system call first, if it exists. (We may be running with a glibc
46 that has the function but with an older kernel that lacks it.) */
47 {
48 /* Cache the information whether the system call really exists. */
49 static int have_accept4_really; /* 0 = unknown, 1 = yes, -1 = no */
50 if (have_accept4_really >= 0)
51 {
52 int result = accept4 (sockfd, addr, addrlen, flags);
53 if (!(result < 0 && errno == ENOSYS))
54 {
55 have_accept4_really = 1;
56 return result;
57 }
58 have_accept4_really = -1;
59 }
60 }
61 #endif
62
63 /* Check the supported flags. */
64 if ((flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK | O_TEXT | O_BINARY)) != 0)
65 {
66 errno = EINVAL;
67 return -1;
68 }
69
70 fd = accept (sockfd, addr, addrlen);
71 if (fd < 0)
72 return -1;
73
74 #if SOCK_CLOEXEC
75 # if defined _WIN32 && ! defined __CYGWIN__
76 /* Native Windows API. */
77 if (flags & SOCK_CLOEXEC)
78 {
79 HANDLE curr_process = GetCurrentProcess ();
80 HANDLE old_handle = (HANDLE) _get_osfhandle (fd);
81 HANDLE new_handle;
82 int nfd;
83
84 if (!DuplicateHandle (curr_process, /* SourceProcessHandle */
85 old_handle, /* SourceHandle */
86 curr_process, /* TargetProcessHandle */
87 (PHANDLE) &new_handle, /* TargetHandle */
88 (DWORD) 0, /* DesiredAccess */
89 FALSE, /* InheritHandle */
90 DUPLICATE_SAME_ACCESS)) /* Options */
91 {
92 close (fd);
93 errno = EBADF; /* arbitrary */
94 return -1;
95 }
96
97 /* Closing fd before allocating the new fd ensures that the new fd will
98 have the minimum possible value. */
99 close (fd);
100 nfd = _open_osfhandle ((intptr_t) new_handle,
101 O_NOINHERIT | (flags & (O_TEXT | O_BINARY)));
102 if (nfd < 0)
103 {
104 CloseHandle (new_handle);
105 return -1;
106 }
107 return nfd;
108 }
109 # else
110 /* Unix API. */
111 if (flags & SOCK_CLOEXEC)
112 {
113 int fcntl_flags;
114
115 if ((fcntl_flags = fcntl (fd, F_GETFD, 0)) < 0
116 || fcntl (fd, F_SETFD, fcntl_flags | FD_CLOEXEC) == -1)
117 {
118 int saved_errno = errno;
119 close (fd);
120 errno = saved_errno;
121 return -1;
122 }
123 }
124 # endif
125 #endif
126
127 #if SOCK_NONBLOCK
128 if (flags & SOCK_NONBLOCK)
129 {
130 int fcntl_flags;
131
132 if ((fcntl_flags = fcntl (fd, F_GETFL, 0)) < 0
133 || fcntl (fd, F_SETFL, fcntl_flags | O_NONBLOCK) == -1)
134 {
135 int saved_errno = errno;
136 close (fd);
137 errno = saved_errno;
138 return -1;
139 }
140 }
141 #endif
142
143 #if O_BINARY
144 if (flags & O_BINARY)
145 set_binary_mode (fd, O_BINARY);
146 else if (flags & O_TEXT)
147 set_binary_mode (fd, O_TEXT);
148 #endif
149
150 return fd;
151 }
152