Use sysctl CTL_NET.PF_INET6 to check if IPv6 is available or not.

With this sysconf(3) no longer needs the inet pledge.
The kernel has been updated for this for a while now.
OK sthen@ deraadt@

diff --git a/lib/libc/gen/sysconf.c b/lib/libc/gen/sysconf.c
index 7b7647e..de36493 100644 (file)
--- a/lib/libc/gen/sysconf.c
+++ b/lib/libc/gen/sysconf.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: sysconf.c,v 1.27 2020/10/12 19:51:28 deraadt Exp $ */
+/*     $OpenBSD: sysconf.c,v 1.28 2022/07/19 09:25:44 claudio Exp $ */
 /*-
  * Copyright (c) 1993
  *     The Regents of the University of California.  All rights reserved.
@@ -62,7 +62,7 @@ sysconf(int name)
 {
        struct rlimit rl;
        size_t len;
-       int mib[2], value, namelen, sverrno;
+       int mib[3], value, namelen, sverrno;
 
        len = sizeof(value);
        namelen = 2;
@@ -238,12 +238,17 @@ sysconf(int name)
        case _SC_IPV6:
 #if _POSIX_IPV6 == 0
                sverrno = errno;
-               value = socket(PF_INET6, SOCK_DGRAM, 0);
+               mib[0] = CTL_NET;
+               mib[1] = PF_INET6;
+               mib[2] = 0;
+               namelen = 3;
+               value = 0;
+               if (sysctl(mib, 3, NULL, 0, NULL, 0) == -1)
+                       value = errno;
                errno = sverrno;
-               if (value >= 0) {
-                       HIDDEN(close)(value);
+               if (value != ENOPROTOOPT)
                        return (200112L);
-               } else
+               else
                        return (0);
 #else
                return (_POSIX_IPV6);