actually add libbb/safe_gethostname.c

libbb/safe_gethostname.c

@@ -0,0 +1,53 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Safe gethostname implementation for busybox
+ *
+ * Copyright (C) 2008 Tito Ragusa <farmatito@tiscali.it>
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+/*
+ * SUSv2 guarantees that "Host names are limited to 255 bytes"
+ * POSIX.1-2001 guarantees that "Host names (not including the terminating
+ * null byte) are limited to HOST_NAME_MAX bytes" (64 bytes on my box).
+ *
+ * RFC1123 says:
+ *
+ * The syntax of a legal Internet host name was specified in RFC-952
+ * [DNS:4].  One aspect of host name syntax is hereby changed: the
+ * restriction on the first character is relaxed to allow either a
+ * letter or a digit.  Host software MUST support this more liberal
+ * syntax.
+ *
+ * Host software MUST handle host names of up to 63 characters and
+ * SHOULD handle host names of up to 255 characters.
+ */
+
+#include "libbb.h"
+#include <sys/utsname.h>
+
+/*
+ * On success return the current malloced and NUL terminated hostname.
+ * On error return malloced and NUL terminated string "?".
+ * This is an illegal first character for a hostname.
+ * The returned malloced string must be freed by the caller.
+ */
+char *safe_gethostname(void)
+{
+	struct utsname uts;
+
+	/* The length of the arrays in a struct utsname is unspecified;
+	 * the fields are terminated by a null byte.
+	 * Note that there is no standard that says that the hostname
+	 * set by sethostname(2) is the same string as the nodename field of the
+	 * struct returned by uname (indeed, some systems allow a 256-byte host-
+	 * name and an 8-byte nodename), but this is true on Linux. The same holds
+	 * for setdomainname(2) and the domainname field.
+	 */
+	
+	/* Uname can fail only if you pass a bad pointer to it. */
+	uname(&uts);
+
+	return xstrndup(!*(uts.nodename) ? "?" : uts.nodename, sizeof(uts.nodename));
+}