On 6/22/20 7:38 PM, Daniel P. Berrangé wrote:
On Mon, Jun 22, 2020 at 07:26:44PM +0200, Michal Privoznik wrote:
This function offers operating system agnostic way to fetch host
name. It is implemented for both POSIX-like and Windows systems.
Signed-off-by: Michal Privoznik <mpriv...@redhat.com>
---
include/qemu/osdep.h | 10 ++++++++++
util/oslib-posix.c | 32 ++++++++++++++++++++++++++++++++
util/oslib-win32.c | 13 +++++++++++++
3 files changed, 55 insertions(+)
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index ff7c17b857..a795d46b28 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -607,4 +607,14 @@ static inline void qemu_reset_optind(void)
#endif
}
+/**
+ * qemu_get_host_name:
+ * @errp: Error object
+ *
+ * Operating system agnostic way of querying host name.
+ *
+ * Returns allocated hostname (caller should free), NULL on failure.
+ */
+char *qemu_get_host_name(Error **errp);
+
#endif
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 916f1be224..865a3d71a7 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -761,3 +761,35 @@ void sigaction_invoke(struct sigaction *action,
}
action->sa_sigaction(info->ssi_signo, &si, NULL);
}
+
+#ifndef HOST_NAME_MAX
+# ifdef _POSIX_HOST_NAME_MAX
+# define HOST_NAME_MAX _POSIX_HOST_NAME_MAX
+# else
+# define HOST_NAME_MAX 255
+# endif
+#endif
+
+char *qemu_get_host_name(Error **errp)
+{
+ long len = -1;
+ char *hostname;
+
+#ifdef _SC_HOST_NAME_MAX
+ len = sysconf(_SC_HOST_NAME_MAX);
+#endif /* _SC_HOST_NAME_MAX */
+
+ if (len < 0) {
+ len = HOST_NAME_MAX;
+ }
+
+ hostname = g_malloc0(len + 1);
Nitpick, generally qemu prefers g_new0
+
+ if (gethostname(hostname, len) < 0) {
+ error_setg_errno(errp, errno,
+ "cannot get hostname");
+ return NULL;
+ }
According to my man page, it is undefined by POSIX whether there's a
trailing NUL when hostname exceeds the buffer, so the paranoid thing
todo is to add
hostname[len] = '\0';
Isn't this guaranteed by allocating len + 1 bytes? I mean, g_malloc0()
and g_new0() will memset() the memory to zero. And since I tell
gethostname() the buf is only len bytes long I am guaranteed to have 0
at the end of it, aren't I? Maybe I should put a comment just before
g_malloc0() or g_new0() that documents this thought.
Michal
