added sethostname syscall with proper error checks

Change-Id: I4b4e0a7c4035e19d5843b86ee1f714096adcecd2

lib/libc/gen/Makefile.inc

@@ -10,7 +10,7 @@
 .if defined(__MINIX)
 # Unsupported by Minix.
 # 	closefrom.c confstr.c extattr.c getdevmajor.c \
-#	pthread_atfork.c setdomainname.c sethostname.c setproctitle.c \
+#	pthread_atfork.c setdomainname.c setproctitle.c \
 #	sysctl.c sysctlbyname.c sysctlgetmibinfo.c sysctlnametomib.c \
 #	wait3.c
 
@@ -39,7 +39,7 @@ SRCS+= 	_errno.c alarm.c alphasort.c arc4random.c assert.c basename.c clock.c \
 	psignal.c \
 	ptree.c pwcache.c pw_scan.c raise.c randomid.c rb.c readdir.c \
 	rewinddir.c scandir.c seekdir.c \
-	setjmperr.c setmode.c setprogname.c \
+	sethostname.c setjmperr.c setmode.c setprogname.c \
 	shquote.c shquotev.c sighold.c sigignore.c siginterrupt.c \
 	sysctl.c sysctlbyname.c sysctlgetmibinfo.c sysctlnametomib.c \
 	siglist.c signal.c signame.c sigrelse.c \

lib/libc/gen/minix/gethostname.c

@@ -7,20 +7,19 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <minix/paths.h>
 
 #ifdef __weak_alias
 __weak_alias(gethostname, _gethostname)
 #endif
 
-#define HOSTNAME_FILE "/etc/hostname.file"
-
 int gethostname(char *buf, size_t len)
 {
 	int fd;
 	int r;
 	char *nl;
 
-	if ((fd= open(HOSTNAME_FILE, O_RDONLY)) < 0) return -1;
+	if ((fd= open(_PATH_HOSTNAME_FILE, O_RDONLY)) < 0) return -1;
 
 	r= read(fd, buf, len);
 	close(fd);

lib/libc/gen/minix/sethostname.c

@@ -0,0 +1,64 @@
+/* gethostname(2) system call emulation */
+#include <sys/cdefs.h>
+#include "namespace.h"
+
+#include <sys/types.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <minix/paths.h>
+
+#ifdef __weak_alias
+__weak_alias(sethostname, _sethostname)
+#endif
+
+int sethostname(const char *buf, size_t len)
+{
+	int fd;
+	int r;
+	int tmperr;
+	char name[20];
+	strlcpy(name, "/tmp/hostname.XXXXX",sizeof(name));
+	fd = mkstemp(name);
+
+	if (fd == -1)
+		return -1;
+
+	r = fchmod(fd, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+
+	if (r == -1) {
+		tmperr = errno;
+		close(fd);
+		unlink(name);
+		errno = tmperr;
+		return -1;
+	}
+
+	r = write(fd, buf, len);
+	tmperr = errno;
+	close(fd);
+
+	if (r == -1) {
+		unlink(name);
+		errno = tmperr;
+		return -1;
+	}
+
+	if (r < len) {
+		unlink(name);
+		errno = ENOSPC;
+		return -1;
+	}
+
+	r = rename(name, _PATH_HOSTNAME_FILE);
+
+	if (r == -1) {
+		tmperr = errno;
+		unlink(name);
+		errno = tmperr;
+	}
+
+	return 0;
+}