commit 5a9020eeb27eee88e7839ff5e9cea94892ec90ff
Author: Maciej W. Rozycki <macro@redhat.com>
Date:   Wed Jun 4 16:27:20 2025 +0100

    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 0f5ec07ede2a1949..e2f00b82a81fec6f 100644
--- 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})