svn commit: r360231 - head/lib/libc/net

[Kristof Provost]

Author: kp
Date: Thu Apr 23 21:16:51 2020
New Revision: 360231
URL: https://svnweb.freebsd.org/changeset/base/360231

Log:
  libc: Shortcut if_indextoname() if index == 0
  
  If the index we're trying to convert is 0 we can avoid a potentially
  expensive call to getifaddrs(). No interface has an ifindex of zero, so
  we can handle this as an error: set the errno to ENXIO and return NULL.
  
  Submitted by:	Nick Rogers
  Reviewed by:	lutz at donnerhacke.de
  MFC after:	2 weeks
  Sponsored by:	RG Nets
  Differential Revision:	https://reviews.freebsd.org/D24524

Modified:
  head/lib/libc/net/if_indextoname.c

Modified: head/lib/libc/net/if_indextoname.c
==============================================================================
--- head/lib/libc/net/if_indextoname.c	Thu Apr 23 20:14:59 2020	(r360230)
+++ head/lib/libc/net/if_indextoname.c	Thu Apr 23 21:16:51 2020	(r360231)
@@ -66,6 +66,11 @@ if_indextoname(unsigned int ifindex, char *ifname)
 	struct ifaddrs *ifaddrs, *ifa;
 	int error = 0;
 
+	if (ifindex == 0) {
+		errno = ENXIO;
+		return(NULL);
+	}
+
 	if (getifaddrs(&ifaddrs) < 0)
 		return(NULL);	/* getifaddrs properly set errno */