1/* Copyright (C) 1999-2020 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library 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 GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <assert.h>
19#include <errno.h>
20#include <stdio.h>
21#include <string.h>
22#include <unistd.h>
23#include <sys/socket.h>
24
25/* Return a socket of any type. The socket can be used in subsequent
26 ioctl calls to talk to the kernel. */
27int
28__opensock (void)
29{
30 static int last_family; /* Available socket family we will use. */
31 static int last_type;
32 static const struct
33 {
34 int family;
35 const char procname[15];
36 } afs[] =
37 {
38 { AF_UNIX, "net/unix" },
39 { AF_INET, "" },
40 { AF_INET6, "net/if_inet6" },
41 { AF_AX25, "net/ax25" },
42 { AF_NETROM, "net/nr" },
43 { AF_ROSE, "net/rose" },
44 { AF_IPX, "net/ipx" },
45 { AF_APPLETALK, "net/appletalk" },
46 { AF_ECONET, "sys/net/econet" },
47 { AF_ASH, "sys/net/ash" },
48 { AF_X25, "net/x25" },
49#ifdef NEED_AF_IUCV
50 { AF_IUCV, "net/iucv" }
51#endif
52 };
53#define nafs (sizeof (afs) / sizeof (afs[0]))
54 char fname[sizeof "/proc/" + 14];
55 int result;
56 int has_proc;
57 size_t cnt;
58
59 /* We already know which family to use from the last call. Use it
60 again. */
61 if (last_family != 0)
62 {
63 assert (last_type != 0);
64
65 result = __socket (last_family, last_type | SOCK_CLOEXEC, 0);
66 if (result != -1 || errno != EAFNOSUPPORT)
67 /* Maybe the socket type isn't supported anymore (module is
68 unloaded). In this case again try to find the type. */
69 return result;
70
71 /* Reset the values. They seem not valid anymore. */
72 last_family = 0;
73 last_type = 0;
74 }
75
76 /* Check whether the /proc filesystem is available. */
77 has_proc = __access ("/proc/net", R_OK) != -1;
78 strcpy (fname, "/proc/");
79
80 /* Iterate over the interface families and find one which is
81 available. */
82 for (cnt = 0; cnt < nafs; ++cnt)
83 {
84 int type = SOCK_DGRAM;
85
86 if (has_proc && afs[cnt].procname[0] != '\0')
87 {
88 strcpy (fname + 6, afs[cnt].procname);
89 if (__access (fname, R_OK) == -1)
90 /* The /proc entry is not available. I.e., we cannot
91 create a socket of this type (without loading the
92 module). Don't look for it since this might trigger
93 loading the module. */
94 continue;
95 }
96
97 if (afs[cnt].family == AF_NETROM || afs[cnt].family == AF_X25)
98 type = SOCK_SEQPACKET;
99
100 result = __socket (afs[cnt].family, type | SOCK_CLOEXEC, 0);
101 if (result != -1)
102 {
103 /* Found an available family. */
104 last_type = type;
105 last_family = afs[cnt].family;
106 return result;
107 }
108 }
109
110 /* None of the protocol families is available. It is unclear what kind
111 of error is returned. ENOENT seems like a reasonable choice. */
112 __set_errno (ENOENT);
113 return -1;
114}
115