[PATCH 2/5] virfile: Introduce virCloseFrom()

[Michal Privoznik <mprivozn@xxxxxxxxxx>]

It is handy to close all FDs from given FD to infinity. On
FreeBSD the libc even has a function for that: closefrom(). It
was ported to glibc too, but not musl. At least glibc
implementation falls back to calling:

  close_range(from, ~0U, 0);

Now that we have a wrapper for close_range() we implement
closefrom() trivially.

Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
 src/libvirt_private.syms |  1 +
 src/util/virfile.c       | 21 +++++++++++++++++++++
 src/util/virfile.h       |  1 +
 3 files changed, 23 insertions(+)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 3782f7f3c7..9477a07834 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2269,6 +2269,7 @@ saferead;
 safewrite;
 safezero;
 virBuildPathInternal;
+virCloseFrom;
 virCloseRange;
 virCloseRangeInit;
 virCloseRangeIsSupported;
diff --git a/src/util/virfile.c b/src/util/virfile.c
index 7696910e00..c74bdd1264 100644
--- a/src/util/virfile.c
+++ b/src/util/virfile.c
@@ -265,6 +265,27 @@ virCloseRangeIsSupported(void)
 }
 
 
+/**
+ * virCloseFrom:
+ *
+ * Closes all open file descriptors greater than or equal to @fromfd.
+ *
+ * Returns: 0 on success,
+ *         -1 on error (with errno set).
+ */
+int
+virCloseFrom(int fromfd)
+{
+#ifdef __FreeBSD__
+    /* FreeBSD has closefrom() since FreeBSD-8.0, i.e. since 2009. */
+    closefrom(fromfd);
+    return 0;
+#else /* !__FreeBSD__ */
+    return virCloseRange(fromfd, ~0U);
+#endif /* !__FreeBSD__ */
+}
+
+
 /**
  * virFileDirectFdFlag:
  *
diff --git a/src/util/virfile.h b/src/util/virfile.h
index be0b02fdf0..adc032ba33 100644
--- a/src/util/virfile.h
+++ b/src/util/virfile.h
@@ -64,6 +64,7 @@ static inline void virForceCloseHelper(int *fd)
 int virCloseRange(unsigned int from, unsigned int to);
 int virCloseRangeInit(void);
 bool virCloseRangeIsSupported(void);
+int virCloseFrom(int fromfd);
 
 /* For use on normal paths; caller must check return value,
    and failure sets errno per close. */
-- 
2.41.0