manual: Document error codes missing for 'if_nametoindex'

Add documentation for ENODEV error code returned and refer to 'socket'
for further possible codes from the underlying function call.

While changing the text clarify the description by mentioning 'ifname'.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

diff --git a/manual/socket.texi b/manual/socket.texi
index a6fb6b1b7e2b047362f124ae7bcee0e47f025147..e8285b9200bbfc6d3cb88777512281de5086170f 100644 (file)
--- a/manual/socket.texi
+++ b/manual/socket.texi
@@ -497,7 +497,20 @@ interface name, including its terminating zero byte.
 @c takes a lock, which makes all callers AS- and AC-Unsafe.
 @c  opensock @asulock @aculock @acsfd
 This function yields the interface index corresponding to a particular
-name.  If no interface exists with the name given, it returns 0.
+name specified with @var{ifname}.
+
+The return value is the interface index on success.  On failure, the
+function's return value is zero and @code{errno} is set accordingly.
+The following @code{errno} values are specific to this function:
+
+@table @code
+@item ENODEV
+There is no interface by the name requested.
+@end table
+
+Additionally, since @code{if_nametoindex} invokes @code{socket}
+internally, @code{errno} may also be set to a value listed for the
+@code{socket} function (@pxref{Creating a Socket}).
 @end deftypefun
 
 @deftypefun {char *} if_indextoname (unsigned int @var{ifindex}, char *@var{ifname})